Lidé na fakultě
doc. Ing. Daniel Kytýř, Ph.D.

rozklikni NABÍDKU

Publikace

informace pocházejí z univerzitní databáze V3S

Autoři:
Bc. Blanka Žaloudková; Koudelka, P.; Frýdlová, P.; Drozdenko, M.; Šleichrt, J.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2024, Acta Polytechnica CTU Proceedings, Praha, České vysoké učení technické v Praze)
Anotace:
The aim of this work is to develop an experimental method suitable for the mechanical testing of highly non-standard biological samples such as snake skin with osteoderms. The objective of the method is to determine, whether the osteoderms provide a protective function for the animal in its natural environment. For this purpose, a simulation of rodents biting the skin based on uni-axial compressive loading using a synthetic tooth as a penetrator was developed with an emphasis on integration with X-ray scanners to facilitate in-situ testing. To identify and characterise the structure of snake skin and to prove the protective function of osteoderms, all samples were subjected to high resolution X-ray computed tomography. The results of the experiments are presented in the form of stress-strain curves and a map of the tangent modulus.
DOI:
10.14311/APP.2024.48.0061
Typ:
Stať ve sborníku z prestižní konf. (Scopus)

Autoři:
Ing. Nela Krčmářová; Ing. Jan Šleichrt, Ph.D.; Ing. Jan Falta; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Čítek, D.; Ing. Tomáš Fíla, Ph.D.
Publikováno:
2024, Emergent Materials, 2024, ISSN 2522-5731
Anotace:
Excellent mechanical properties of ultra high performance concrete make it suitable for use in special applications, where the material is subjected to dynamic phenomena such as impacts, explosions, or earthquakes. This paper presents a novel experimental approach that integrates a Split Hopkinson Pressure Bar with a flash X-ray system and high-speed optical imaging to investigate the dynamic behavior of steel fiber reinforced UHPC under high strain rate uni-axial compression. In-situ Flash X-ray radiography emerges as a particularly effective tool, providing clear visualization of deformation response and overcoming challenges associated with flying debris encountered in optical inspection. Moreover, computed tomography and scanning electron microscopy appear as a vital technique for analyzing micro-structure and fiber distribution and orientation. The combined approach offers a promising method to study the dynamic behavior of steel fiber reinforced ultra high performance concrete and also holds promise for analyzing more complex modes of deformation and material interactions, providing valuable insights for enhancing the design and performance of critical infrastructure subjected to dynamic loading events.
DOI:
10.1007/s42247-024-00893-w
Typ:
Článek v periodiku excerpovaném databází Scopus

Autoři:
Ing. Veronika Drechslerová; Ing. Jan Falta; Ing. Tomáš Fíla, Ph.D.; Ing. et Ing. Radim Dvořák; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2023, Vol. 42 (2023): 18th Youth Symposium on Experimental Solid Mechanics, Praha, České vysoké učení technické v Praze), p. 1-5), ISBN 978-80-01-07237-0, ISSN 2336-5382
Anotace:
This paper focuses on stereolithography (an additive manufacturing technology working on the principle of curing liquid resins layer by layer using ultraviolet radiation) and the effect of aging on the mechanical properties of the material and printed samples. The aging of the material could be a problem for its subsequent use as the stability of the mechanical properties would not be maintained and unwanted deterioration of the material could occur. As part of the research, sets of samples were printed and subjected to different aging methods and subsequently subjected to quasi-static and dynamic uni-axial load tests. From the data obtained, the basic mechanical properties of the material were calculated and compared with each other. The aim of this paper was to investigate whether aging process causes significant changes in the mechanical properties of the materials used, which could have a consequential impact on their use in different industries.
DOI:
10.14311/APP.2023.42.0001
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
Bc. Blanka Žaloudková; Sekorová, Š.; Kopecká, B.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2023, Vol. 42 (2023): 18th Youth Symposium on Experimental Solid Mechanics, Praha, České vysoké učení technické v Praze), p. 94-97), ISBN 978-80-01-07237-0, ISSN 2336-5382
Anotace:
Long-term stability of the tissue product in terms of mechanical parameters is a key factor for its expiration date. For the investigation of storage effects on the cartilage tissues the experimental mechanical loading test combined with XCT scanning for the irregular shape inspection was performed. The samples were preserved according to three different protocols using the deep-freezing and two types of saline solution preservation. The stability of the biomechanical parameters was tested within annual intervals. All samples were subjected to uni-axial compression loading using the in-house developed compact table top loading device in displacement-driven mode. Based on the measurements, the results are represented in the form of stress-strain curves and quantified as elastic modulus and ultimate compression stress. It can be concluded that no significant difference was found in neither the mechanical properties of the samples nor in the effects of each preservational method.
DOI:
10.14311/APP.2023.42.0094
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
Hasn, S.; Vavřík, D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2023
Anotace:
X-ray computed tomography (CT) is extensively used for non-destructive industrial analysis to study the internal structure of materials and complex objects. In the microelectronics industry, X-ray computed tomography has proven useful for quality analysis and defect detection. However, inspecting electronic devices with standard CT is challenging due to the presence of many metals neighboring light materials causing various types of artifacts that affect the quality of computed tomography. This thesis presents new techniques and data processing approaches in the field of energy-sensitive computed tomography, which are used to characterize materials and to study defects in electronic devices. Energy-sensitive computed tomography utilizes energy information from the projection data obtained by energy-sensitive methods. Several standard CT techniques were also tested and compared with the newly presented techniques. The results showed that the standard techniques are inefficient when the scanned samples, electronic components, have high metal content. The work also addresses the spectroscopic performance of photon counting detectors in computed tomography after correcting the threshold mismatch between pixels. This new correction methods have helped to increase the energy resolution and improve the ability of the detector to discriminate materials with similar attenuation properties. Such correction is useful for applications that require high resolution at high energy spectra where the mismatch between pixels increases due to the invalidity of standard calibration methods. The thesis mainly focuses on the inspection of epoxy underfill process for electronic devices by implementing data fusion of multiple computed tomography scans as an alternative method to reduce artifacts. To this end, the work presents a methodology of performing successful computed tomography that enable the inspection of light materials (epoxy) for samples with high metal that cannot be achieved using standard CT techniques. In addition, the work presents the first results of the epoxy underfill inspection for real samples from the industrial field, placing the X-ray inspection as an option for defect detection in the microelectronics industry.
Typ:
Disertační práce (PhD)

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Doktor, Ph.D.
Publikováno:
2023, ISBN 978-80-01-07237-0, ISSN 2336-5382
Typ:
Sborník z mezinárodní konf. v češtině

Autoři:
Novak, N.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Václav Rada; Ing. Tomáš Doktor, Ph.D.; Al-Ketan, O.; Rowshan, R.; Vesenjak, M.; Ren, Z.
Publikováno:
2022, Materials Science and Engineering A - Structural Materials: Properties, Microstructure and Processing, 852 (5), ISSN 0921-5093
Anotace:
One of the most promising options for future crashworthiness applications is thin-walled tubes filled with various cellular materials (e.g. metal foam). Of higher interest are the shell-based lattices, which have lately gained popularity due to their superior qualities over strut-based lattices. In this work, we investigate the mechanical response of foam-filled tubes where the tube's core was represented by Triply Periodic Minimal Surface (TPMS) diamond lattices. Samples made of stainless steel 316L comprising the diamond lattice core, empty tubes, and in-situ TPMS-filled tubes were additively manufactured and mechanically tested under compressive loading. As-fabricated welded tubes and ex-situ TPMS-filled tubes were also analysed and compared. Under the axial loading, the ex-situ and in-situ TPMS-filled tubes showed very similar behaviour. Enhanced energy absorption up to 21% and 44% compared to the sum of empty tubes and the core responses was noted. The energy absorption enhancement of 12% in the case of transversal loading is limited to in-situ TPMS-filled tubes, where the connection between the tube and core prevents the tube's walls from buckling. Computational models with homogenised core were developed and validated based on the experimental data. These straightforward, fast, and accurate computational models can be efficiently used for large-scale real-life applications, e.g. crash and impact.
DOI:
10.1016/j.msea.2022.143680
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Jan Šleichrt, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; Adorna, M.; Ing. Jan Falta; doc. Ing. Petr Zlámal, Ph.D.; Glinz, J.; Ing. Michaela Jurko; Ing. Tomáš Doktor, Ph.D.; Mauko, A.; doc. Ing. Daniel Kytýř, Ph.D.; Vesenjak, M.; Duarte, I.; Ren, Z.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2021, Materials Science and Engineering A - Structural Materials: Properties, Microstructure and Processing, 800, ISSN 0921-5093
Anotace:
Light-weight cellular solids, such as aluminium foams, are promising materials for use in ballistic impact mitigation applications for their high specific deformation energy absorption capabilities. In this study, three different types of aluminium alloy based in-house fabricated cellular materials were subjected to dynamic penetration using the in-house experimental setup to evaluate their deformation and microstructural response. Two-sided direct impact Hopkinson bar apparatus instrumented with two high-speed cameras observing the impact area and the penetrated surface of the specimens was used. Advanced wave separation technique was employed to process strain-gauge signals recorded during penetration. Images captured by one of the cameras were processed using an in-house Digital Image Correlation method with sub-pixel precision, that enabled validation of the wave separation results of the strain-gauge signals. The second camera was used to observe the penetration into the tested specimens for correct interpretation of the measured signals with respect to derived mechanical and microstructural properties at different impact velocities. Differential X-ray computed tomography of selected specimens was performed, which allowed for an advanced pre- and post-impact volumetric analysis. Results of performed experiments and elaborate analysis of the measured experimental data are shown in this study.
DOI:
10.1016/j.msea.2020.140096
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Glinz, J.; Ing. Jan Šleichrt, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ayalur-Karunakaran, S.; Zabler, S.; Kastner, J.; Senck, S.
Publikováno:
2021, Journal of Materials Science, 56 (16), p. 9712-9727), ISSN 0022-2461
Anotace:
In this work, we present a multimodal approach to three-dimensionally quantify and visualize fiber orientation and resin-rich areas in carbon-fiber-reinforced polymers manufactured by vacuum infusion. Three complementary image modalities were acquired by Talbot–Lau grating interferometer (TLGI) X-ray microcomputed tomography (XCT). Compared to absorption contrast (AC), TLGI-XCT provides enhanced contrast between polymer matrix and carbon fibers at lower spatial resolutions in the form of differential phase contrast (DPC) and dark-field contrast (DFC). Consequently, relatively thin layers of resin, effectively indiscernible from image noise in AC data, are distinguishable. In addition to the assessment of fiber orientation, the combination of DPC and DFC facilitates the quantification of resin-rich areas, e.g., in gaps between fiber layers or at binder yarn collimation sites. We found that resin-rich areas between fiber layers are predominantly developed in regions characterized by a pronounced curvature. In contrast, in-layer resin-rich areas are mainly caused by the collimation of fibers by binder yarn. Furthermore, void volume around two adjacent 90°-oriented fiber layers is increased by roughly 20% compared to a random distribution over the whole specimen.
DOI:
10.1007/s10853-021-05907-0
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Doktor, Ph.D.; Gutermann, M.; Rusnáková, S.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2020
Anotace:
The thesis deals with the investigation of the mechanical behaviour of cellular materials at higher strain-rates and enhancement of their energy absorption capabilities. Three types of cellular solids were tested: closed- and open-cell aluminium foam and SLS printed auxetic lattices. To induce a strain-rate sensitive response in open-cell structures, different types of polymeric fillers were tested (polyurethane putty, polyurethane foam and ordnance gelatin) to form Interpenetrating- phase composites (IPCs). At the micro level, the tests were performed using an in-house apparatus in conjunction with the optical strain measurement using Digital Image Correlation (DIC). At the macro-level, for the investigation of the cellular structure a time-lapse X-ray tomography of the compression test was performed. Two types of impact tests were used to cover a broader range of the strain-rates, drop tower and Hopkinson bar (SHPB). A strain-rate sensitive response was observed at moderate strain-rates in the ordnance gelatin and IPC, while the response of unfilled aluminium foam remained unchanged. The SHPB tests showed a strain-rate sensitivity in the energy absorption for all the tested materials. The DIC strain measurement of the SHPB impact tests of the polymer-filled auxetics showed a reduction in the auxetic nature with the filling.
Typ:
Disertační práce (PhD)

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.
Publikováno:
2019, ISBN 978-80-86246-45-1
Typ:
Sborník z mezinár. konf. cizojazyčně

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2019, 17th YOUTH SYMPOSIUM ON EXPERIMENTAL SOLID MECHANICS, Praha, Česká technika - nakladatelství ČVUT), p. 17-20), ISBN 978-80-01-06670-6, ISSN 2336-5382
Anotace:
Presented paper deals with experimental study on compressive properties of auxetics with controlled stiffness of strut joints. The variable strut joints properties were simulated by adding extra amount of material in the struts’ intersection regions. Four groups of inverted honeycomb structures were prepared by multi-jet 3D printing and tested in quasi-static compression. The structure collapsed gradually, however after the first collapse, failure in entire cross-section occurred due to the brittle nature of the base material. The behavior up to the first collapse was consistent among the specimens within each group, while differed slightly subsequently. With higher reinforcement in the joints, results showed increasing stress at the first collapse (ultimate compressive stress) while the strain at the first collapse remained unchanged. The auxetic behaviour became less significant with increasing joints’ reinforcement.
DOI:
10.14311/APP.2019.25.0017
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2019, 17th YOUTH SYMPOSIUM ON EXPERIMENTAL SOLID MECHANICS, Praha, Česká technika - nakladatelství ČVUT), p. 21-24), ISBN 978-80-01-06670-6, ISSN 2336-5382
Anotace:
In this study behavior of the selected types of filling material for the inter-penetrating phase composites was tested in compressive loading mode at low and high strain-rates. Three types of the filling material were tested, (i) ordnance gelatin, (ii) low expansion polyurethane foam, and (iii) polyurethane putty. To evaluate their impact energy absorption bulk samples of the selected materials were tested in compression loading mode at strain-rates 1000 s−1 to 4000 s−1 . The high strain-rate compressive loading was provided by Split Hopkinson Pressure Bar (SHPB) which was equipped with PMMA bars to enable testing of cellular materials with low mechanical impedance. Based on the comparative measurement response to compression at both low and high strain-rates was analysed. The results show a significant strain-rate sensitivity of the ordnance gelatin and of the polyurethane putty, while strain-rate effect in the polyurethane foam was not observed.
DOI:
10.14311/APP.2019.25.0021
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Doktor, Ph.D.
Publikováno:
2019, ISBN 978-80-01-06670-6, ISSN 2336-5382
Typ:
Sborník z mezinár. konf. cizojazyčně

Autoři:
Ing. Jan Šleichrt, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Pithartová, K.; Senck, S.; Fürst, D.; Schrempf, A.
Publikováno:
2018, 16th Youth Symposium On Experimental Solid Mechanics, Praha, Česká technika - nakladatelství ČVUT, ČVUT v Praze), p. 28-31), ISBN 978-80-01-06474-0, ISSN 2336-5382
Anotace:
The main goal of this study is to validate elementary mechanical parameters of a newly designed open-cell foam. The purpouse for investigating artificial material is to approach the properties of the human bone in the case of its adequate replacement. Investigated material can be also used as an artificial bone to train surgical procedures and to improve the skills of the surgeons. Four sets of the foam with different chemical composition were subjected to an uniaxial quasi-static loading to describe basic mechanical behaviour of these samples. Based on these experiments, the stress-strain diagrams were created as a comparative tool including calculation of the effective Young’s modulus. The acquired knowledges will be used as input parameters of a follow-up study aimed at describing the morphology of presented structures and their response to mechanical experiments. A distortion effect of porosity on the results is not considered in this study.
DOI:
10.14311/APP.2018.18.0028
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2018
Anotace:
The main goal of the work presented is aimed at demonstrating modern radiological methods for an investigation of the deformation behaviour of bone scaffolds. Bone scaffold is an artificial structure used for the repairs of trabecular bones damaged by injuries or degenerative diseases. In bone-tissue engineering a proper description of its deformation behaviour is one of the most important assessment characteristics of biocompatibility and bone-integration characteristics of the proposed structure intended to be used as a bone scaffold. Bioactive-glass-reinforced gellan-gum (GG-BAG) with low specific stiffness and simultaneous low attenuation to X-rays makes both the mechanical and imaging parts of the deformation experiments difficult. Therefore, a unique combination of X-ray imaging technigues and experimental procedures was developed to evaluate the full-field microstructure deformation response. The digital volumetric correlation method was applied on the reconstructed data from micro CT measurements to evaluate not only the effective mechanical characteristics but also to enable a detailed inspection of the specimens’ internal structure, particularly the deformation modes of the individual struts and joints. The calculated volumetric strain fields demonstrate the suitability of such experimental methodology and devices to assess both the microscopic and macroscopic characteristics of the investigated complex GG-BAG microarchitectures.
Typ:
Docentská habilitační práce

Autoři:
Ing. Tomáš Doktor, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Jan Šleichrt, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2018, 16th Youth Symposium On Experimental Solid Mechanics, Praha, Česká technika - nakladatelství ČVUT, ČVUT v Praze), p. 44-47), ISBN 978-80-01-06474-0, ISSN 2336-5382
Anotace:
An experimental study on energy absorption capabilities and strain rate sensitivity of ordnance gelatine was performed. Strain energy density under quasi static compression and moderate strain rate impact tests was compared. In the study two types of material were tested, bulk ordnance gelatine and polymeric open-cell meshwork filled with ordnance gelatine. From the results a significant strain-rate effect was observed in terms of ultimate compressive strength and strain energy density. In comparison of the deformation behaviour under quasi static conditions and drop weight test the difference was very significant, however slight increase in both strength and strain energy density was observed even between different impact energies and velocities during the impact testing. The peak acceleration was significantly reduced in polymer meshwork filled by gelatine in comparison to the bulk gelatine.
DOI:
10.14311/APP.2018.18.0044
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
Ing. Václav Rada; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Petr Koudelka, Ph.D.
Publikováno:
2018, 16th Youth Symposium On Experimental Solid Mechanics, Praha, Česká technika - nakladatelství ČVUT, ČVUT v Praze), p. 15-19), ISBN 978-80-01-06474-0, ISSN 2336-5382
Anotace:
In recent years, open-source applications have replaced proprietary software in many fields. Especially open-source software tools based on Linux operating system have wide range of utilization. In terms of CNC solutions, an open-source system LinuxCNC can be used. However, the LinuxCNC control software and the graphical user interface (GUI) could be developed only on top of Hardware Abstraction Layer. Nevertheless, the LinuxCNC community provided Python Interface, which allows for controlling CNC machine using Python programming language, therefore whole control software can be developed in Python. The paper focuses on a development of a multi-process control software mainly for in-house developed loading devices operated at our institute. The software tool is based on the LinuxCNC Python Interface and Qt framework, which gives the software an ability to be modular and effectively adapted for various devices.
DOI:
10.14311/APP.2018.18.0015
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
Ing. Tomáš Fíla, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Jan Falta; Ing. Tomáš Doktor, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Adorna, M.; Luksch, J.; Ing. Michaela Jurko; Valach, J.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2018, EPJ Web of Conferences - Volume 183 (2018) - DYMAT 2018 - 12th International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading, Les Ulis Cedex A, EDP Sciences - Web of Conferences), p. 1-6), ISBN 978-2-7598-9053-8, ISSN 2100-014X
Anotace:
In this paper, a split Hopkinson pressure bar (SHPB) was used for impact loading of an auxetic lattice (structure with negative Poisson’s ratio) at a given strain-rate. High strength aluminum and polymethyl methacrylate bars instrumented with foil strain-gauges were used for compression of an additively manufactured missing-rib auxetic lattice. All experiments were observed using a high-speed camera with frame-rate set to approx. 135.000 fps. High-speed images were synchronized with the strain-gauge records. Dynamic equilibrium in the specimen was analyzed and optimized pulse-shaping was introduced in the selected experiments. Longitudinal and lateral in-plane displacements and strains were evaluated using digital image correlation (DIC) technique. DIC results were compared with results obtained from strain-gauges and were found to be in good agreement. Using DIC, it was possible to analyze in-plane strain distribution in the specimens and to evaluate strain dependent Poisson’s ratio of the auxetic structure.
DOI:
10.1051/epjconf/201818302045
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Major, Z.
Publikováno:
2018, ISBN 978-80-01-06474-0, ISSN 2336-5382
Typ:
Sborník z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2018
Anotace:
The main goal of the work presented is aimed at demonstrating modern radiological methods for an investigation of the deformation behaviour of bone scaffolds. Bone scaffold is an artificial structure used for the repairs of trabecular bones damaged by injuries or degenerative diseases. In bone-tissue engineering a proper description of its deformation behaviour is one of the most important assessment characteristics of biocompatibility and bone-integration characteristics of the proposed structure intended to be used as a bone scaffold. Bioactive-glass-reinforced gellan-gum (GG-BAG) with low specific stiffness and simultaneous low attenuation to X-rays makes both the mechanical and imaging parts of the deformation experiments difficult. Therefore, a unique combination of X-ray imaging technigues and experimental procedures was developed to evaluate the full-field microstructure deformation response. The digital volumetric correlation method was applied on the reconstructed data from micro CT measurements to evaluate not only the effective mechanical characteristics but also to enable a detailed inspection of the specimens’ internal structure, particularly the deformation modes of the individual struts and joints. The calculated volumetric strain fields demonstrate the suitability of such experimental methodology and devices to assess both the microscopic and macroscopic characteristics of the investigated complex GG-BAG microarchitectures.
Typ:
Habilitační přednáška

Autoři:
Hos, J.; Ing. Nela Krčmářová; Jíra, A.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2017
Anotace:
Zkoušky určování povrchové tvrdosti představují jedny z nejpoužívanějších zkoušek materiálů. Výhodou tohoto typu testu je jeho minimální destruktivnost, nízké náklady na jeho provádění a relativně jednoduché vyhodnocení. Tato diplomová práce se zabývá vytvořením automatizované procedury měření povrchové tvrdosti porézních materiálů. Tyto poznatky jsou využity pro napsání programu pro určování nejvhodnějších lokací pro indentaci. Vstupy pro vytvořený program jsou fotografie porézního materiálů. Složením těchto snímků je vytvořen pracovní obraz na němž jsou následně prováděny procedury sloužící k identifikaci nejvhodnějších lokací pro indent. Výstupem skriptu je G-kód pro CNC proceduru. Vytvořený G-kód je použit pro experimentální měření tvrdosti. Vytvořené indenty jsou nafoceny, poté jsou změřeny velikosti jejich úhlopříček, které poslouží jako základ pro výpočet tvrdosti podle Vickerse.
Typ:
Diplomová práce

Autoři:
Ing. Nela Krčmářová; Ing. Jan Šleichrt, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2017, ExNum 2016, Praha, CESKE VYSOKE UCENI TECHNICKE V PRAZE), p. 29-32), ISBN 978-80-01-06070-4, ISSN 2336-5382
Anotace:
The paper deals with investigation of deformation behaviour of gellan gum (GG) based structures prepared for regenerative medicine purposes. Investigated material was synthesized as porous spongy-like scaffold reinforced by bioactive glass (BAG) nano-particles in different concentrations. Deformation behavior was obtained employing custom designed experimental setup. This device equipped with bioreactor chamber allows to test the delivered samples under simulated physiological conditions with controlled flow and temperature. Cylindrical samples were subjected to uniaxial quasistatic loading in tension and compression. Material properties of plain GG scaffold and reinforced scaffold buffered by 50wt% and 70wt% BAG were derived from a set of tensile and compression tests. The results are represented in form of stress-strain curves calculated from the acquired force and displacement data.
DOI:
10.14311/APP.2017.7.0029
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; Ing. Jan Šleichrt, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; Gantar, A; Novak, S
Publikováno:
2017, Acta Polytechnica, 57 (1), p. 14-21), ISSN 1210-2709
Anotace:
This study is focuses on an investigation of the reinforcement effect of the bioactive glass nano-particles in the gellan gum (GG) scaffolds used in bone tissue engineering. The investigated material was synthesized as the porous spongy-like structure improved by the bioactive glass (BAG) nano-particles. Cylindrical samples were subjected to a uniaxial quasi-static loading in tension and compression. Very soft nature of the material, which makes the sample susceptible to damage, required employment of a custom designed experimental device for the mechanical testing. Moreover, as the mechanical properties are significantly influenced by testing conditions the experiment was performed using dry samples and also using samples immersed in the simulated body fluid. Material properties of the pure GG scaffold and the GG-BAG reinforced scaffold were derived from a set of tensile and compression tests under dry and simulated physiological conditions. The results are represented in the form of stress-strain curves calculated from the acquired force and displacement data.
DOI:
10.14311/AP.2017.57.0014
Typ:
Článek v periodiku excerpovaném databází Scopus cizojaz.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.
Publikováno:
2017, ISBN 978-80-01-06070-4, ISSN 2336-5382
Typ:
Sborník z mezinár. konf. cizojazyčně

Autoři:
Ing. Tomáš Fíla, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Ing. Jan Falta; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Jaroslav Valach, Ph.D.
Publikováno:
2017, Advanced Engineering Materials, 19 (10), ISSN 1438-1656
Anotace:
In this paper, impact testing of auxetic structures filled with strain rate sensitive material is presented. Two dimensional missing rib, 2D re-entrant honeycomb, and 3D re-entrant honeycomb lattices are investigated. Structures are divided into three groups according to type of filling: no filling, low expansion polyurethane foam, and ordnance gelatine. Samples from each group are tested under quasi-static loading and dynamic compression using Split Hopkinson Pressure Bar. Digital image correlation is used for assessment of in-plane displacement and strain fields. Ratios between quasi-static and dynamic results for plateau stresses and specific energy absorption in the plateau are calculated. It is found out that not only the manufactured structures, but also the wrought material exhibit strain rate dependent properties. Evaluation of influence of filling on mechanical properties shows that polyurethane increases specific absorbed energy by a factor of 1.05–1.4, whereas the effect of gelatine leads to increase of only 5–10%. Analysis of the Poisson's function reveals influence of filling on achievable (negative) values of Poisson's ratio, when compared to unfilled specimens. The results for the Poisson's function yielded apparently different values as the assessed minima of quasi-static Poisson's ratio in small deformations are constrained by a factor of 15.
DOI:
10.1002/adem.201700076
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2017, 25th INTERNATIONAL CONFERENCE ON MATERIALS AND TECHNOLOGY - PROGRAM AND BOOK OF ABSTRACTS, Ljubljana, Inštitut za kovinske materiale in tehnologije), p. 52-52), ISBN 978-961-94088-1-0
Anotace:
In this study behavior of selected types of filling material were tested in compressive loading mode at high strain rates. Four types of filling material were tested, (i) ordnance gelatin, (ii) low expan sion polyurethane foam, (iii) thixotropic polyurethane putty and (iv) silicon putty. To evaluate their contribution to the impact energy absorption in IPC bulk samples of selected materials were subjected to high strain rate compression. The high strain ra te compressive loading was provided by Split Hopkinson Pressure Bar (SHPB) which was adjusted to be able to test cellular and soft materials. From the tests stress - strain diagrams of investigated materials were obtained, which provided relevant mechanical properties (plateau stress and strain, strain energy density).
Typ:
Abstrakt ve sborníku z mezinár. konf.

Autoři:
Ing. Nela Krčmářová; Ing. Jan Šleichrt, Ph.D.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2017, ExNum 2016, Praha, CESKE VYSOKE UCENI TECHNICKE V PRAZE), p. 72-75), ISBN 978-80-01-06070-4, ISSN 2336-5382
Anotace:
Metal foams are innovative porous material used for wide range of application such as deformation energy or sound absorption, filter material, or microbiological incubation carrier. To predict mechanical properties of the metal foam is necessary to precisely describe elasto–plastic properties of the foam on cell–wall level. Indentation with low load is suitable tool for this purpose. In this paper custom designed instrumented microindentation device was used for measurement of cell-wall characteristics of two different aluminium foams (ALPORAS and ALCORAS). To demonstrate the possibility of automated statistical estimation of measured characteristics the device had been enhanced by semi-automatic indent positioning and evaluation procedures based on user-defined grid. Vickers hardness was measured on two samples made from ALPORAS aluminium foam and one sample from ALCORAS aluminium foam. Average Vickers hardness of ALPORAS foam was 24.465HV1.019 and average Vickers hardness of ALCORAS was 36.585HV1.019.
DOI:
10.14311/APP.2017.7.0072
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; doc. Ing. Petr Zlámal, Ph.D.; Kumpová, I.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; Gantar, A.; Novak, S.
Publikováno:
2017, Materials and Technology, 51 (3), p. 397-402), ISSN 1580-2949
Anotace:
The presented work is aimed at a demonstration of modern radiological methods for an investigation of the deformation behaviour of bone scaffolds. Bone scaffold is an artificial structure used for the repairs of trabecular bones damaged by injuries or degenerative diseases. In bone-tissue engineering a proper description of its deformation behaviour is one of the most important characteristics for an assessment of the biocompatibility and bone-integration characteristics of the proposed structure intended to be used as a bone scaffold. According to recent studies bioactive-glass-reinforced gellan-gum (GG-BAG) is a promising material for bone-scaffold production. However, its low specific stiffness and simultaneous low attenuation to X-rays makes both the mechanical and imaging parts of the deformation experiments difficult. As a result a state-of-the-art experimental setup composed of high-precision micro-loading apparatus designed for the X-ray observation of deformation processes and an advanced radiographical device is required for such experiments. High-resolution time-lapse micro-focus X-ray computed tomography (micro CT) under loading in three different imaging modes was performed to obtain a precise structural and mechanical description of the observed deforming GG-BAG scaffolds.
DOI:
10.17222/mit.2015.237
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Adorna, M.; Fisher, C.; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2017
Anotace:
Předložená práce se zabývá vyhodnocováním dynamických experimentů prováděných na instrumentovaném zařízení SHPB modifikovaném pro měření materiálů s nízkou mechanickou impedancí. V rámci práce je navržena a implementována metodika předzpracování zaznamenaných experimentálních dat, vytvořena sada softwarových nástrojů umožňující konzistentní a přesné vyhodnocení. Celé řešení je implementováno v modulárním uživatelském rozhraní, které umožňuje automatizované, rychlé a spolehlivé vyhodnocení zaznamenaných experimentálních dat. Navržené řešení je ověřeno v rámci vyhodnocení experimentů provedených na auxetické struktuře a na vzorku porézní polymerní pěny. Výsledky získané s použitím navrženého řešení jsou konzistentní a odpovídají již dříve publikovaným hodnotám. Výsledkem práce je soubor softwarových řešení implementovaný v uživatelském prostředí, který značně usnadňuje a zrychluje proces vyhodnocení experimentů provedených na SHPB.
Typ:
Diplomová práce

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; Ing. Tomáš Doktor, Ph.D.; Kumpová, I.; Koudelková, V.; Nepomucká, K.; Šepitka, J.; Gantar, A.
Publikováno:
2017, 25th INTERNATIONAL CONFERENCE ON MATERIALS AND TECHNOLOGY - PROGRAM AND BOOK OF ABSTRACTS, Ljubljana, Inštitut za kovinske materiale in tehnologije), ISBN 978-961-94088-1-0
Anotace:
The microtomography inspection was performed using the patented (European patent no. EP2835631) in-house designed modular radiographical imaging device equipped with scintillators, large single photon counting and spectroscopic detectors. From reconstructed volumetric data internal microarchitecture, porosity, cell-wall thickness and BAG distribution was derivated. The results were compared with the results of the planar analysis of thin scaffold layers prepared by cryosection.
Typ:
Abstrakt ve sborníku z mezinár. konf.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.
Publikováno:
2016, ISBN 978-80-01-06009-4
Typ:
Sborník z mezinárodní konf. v češtině

Autoři:
Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Hos, J.; Ing. Jan Šleichrt, Ph.D.
Publikováno:
2016, Materials and Technology, 50 (3), p. 413-417), ISSN 1580-2949
Anotace:
Composite materials with a polymeric matrix reinforced by carbon fibres are nowadays widely used as high-tech structural materials with excellent mechanical properties (particularly their stiffness and strength). The application of this type of composite to structural parts exposed to thermal loading has recently been proposed. Such an application requires an investigation and analysis of the mechanical behaviour under long-term exposure to simultaneous thermal and mechanical loading. In this paper the measurements and results of the creep behaviour of a composite with a polyphenylene sulphide matrix reinforced with chopped poly-acrylonitrile carbon fibres (C/PPS) are presented. The measured compound is proposed for use as a structural material for a jet-engine frame in the aerospace industry and the internal parts of aircraft with possible thermal loading. A custom experimental device designed for the creep measurements of composite materials was used for measurements of the developing strain at a constant tensile stress and temperature. Short-term creep tests with continuous strain monitoring were performed at a constant stress level at several elevated temperatures below and above the glass-transition temperature of the matrix. The strain was measured using the digital image correlation (DIC) method. The measured data were processed to find the strain-to-time dependency and the creep-compliance-to-time dependency. The creep-compliance-to-time data were also fitted using Findley's creep law for polymers to evaluate the model parameters and to analyse the applicability of the model for a PPS polymer reinforced with chopped carbon fibres.
DOI:
10.17222/mit.2014.208
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.
Publikováno:
2016, Materials and Technology, 50 (3), p. 301-305), ISSN 1580-2949
Anotace:
The study aims at mechanical testing of an artificial bone structure in the form of a scaffold for the application in the repairs of trabecular bones after wounds or degenerative diseases. Such artificial construct has to conform to many requirements including biocompatibility, permeability properties and bone-integration characteristics. Recently, self-degradable bone scaffolds suitable for natural-bone-tissue ingrowth optimized with respect to mechanical properties and body-fluid flow have been considered as an alternative to allografts and autografts. Here, an analysis of deformation behaviour of a scaffold with a morphology identical to the natural bone is the first step in this task. In this work, the geometry and morphology of scaffold specimens produced with direct 3D printing were based on a 3D model derived from the X-ray-computed micro-tomography measurement of a real trabecular bone. The geometrical model was upscaled four times in order to achieve the optimum ratio between its resolution and the resolution of the 3D printer. For its biocompatibility and self-degradability, polylactic acid was used as the printing material. The mechanical characteristics were obtained from a series of uniaxial compression tests, with an optical evaluation of the strain field on the surfaces of the specimens. The acquired stress-strain curves were compared with the characteristics of a real trabecular bone obtained with time-lapse microtomography measurements, evaluated with the digital volumetric correlation method. The results show good correspondence of the stiffness values for both the natural and artificial bone specimens.
DOI:
10.17222/mit.2014.190
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Adorna, M.; Ing. Michaela Jurko; Ing. Jan Šleichrt, Ph.D.; Ing. Nela Krčmářová; Gantar, A; Novak, S
Publikováno:
2016, Engineering Mechanics 2015, Zurich, TRANS TECH PUBLICATIONS LTD), p. 665-670), ISSN 1662-7482
Anotace:
This work presents deformation behaviour of gellan gum and gellan gum - bioactive glass composites as novel hydrophilic materials for production of scaffolds in the field of bone-tissue engineering. According to recent studies such materials are attractive for personalized design of implants thanks to their biocompatibility and wide range of available fabrication methods. Batch of samples was subjected to uni-axial compression loading in a custom designed loading device to obtain their elastic and plastic characteristics. However the testing procedure was challenging because of very low stiffness of the material acquired results show a significant reinforcement effect of bioactive glass and its influence to the elastic modulus.
DOI:
10.4028/www.scientific.net/AMM.821.665
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Petr Koudelka, Ph.D.; Ing. Michaela Jurko; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2016, Engineering Mechanics 2015, Zurich, TRANS TECH PUBLICATIONS LTD), p. 428-434), ISSN 1662-7482
Anotace:
In this work parametric modelling was utilized to design and produce two types of porous microarchitectures with auxetic compressive properties suitable for deformation energy mitigation applications such as blast and bullet protection. The samples were directly produced from acrylic amaterial using a high resolution 3D printer and their compressive mechanical characteristics were tested. Two different structures exhibiting in-plane negative strain dependent Poisson’s ratio were selected for the analysis: i) two-dimensional inverted (re-entrant) honeycomb and ii) two-dimensional cut missing-rib. Stress-strain relationships were established from a set of quasi-static compressional experiments where the strain fields were evaluated using digital image correlation applied to measure the full-field displacements on the samples' surface. From the displacement fields true strain – true stress curves were derived for each sample and relative elastic moduli were evaluated.
DOI:
10.4028/www.scientific.net/AMM.821.428
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Nela Krčmářová; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jan Šleichrt, Ph.D.; Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Fíla, Ph.D.
Publikováno:
2016, Book of Abstracts of International Symposium on Experimental Methods and Numerical Simulation in Engineering Sciences 2016, Praha, katedra mechaniky a materiálů), ISBN 978-80-01-06009-4
Anotace:
This study is focused on investigation of the reinforcement effect of the nano-particles in gellan gum (GG) scaffolds used in bone tissue engineering. This hydrophilic polysaccharide-based material is attractive for personalized design of implants thanks to its biocompatibility and wide range of available fabrication methods. Material properties of pure GG scaffold and GG-BAG reinforced scaffold were derived from set of tensile and compression tests under dry and simulated physiological conditions. The results are represented in form of stress-strain curves calculated from acquired force and displacement data. It can be concluded that significant reinforcement effect of BAG was observed only during the compressive loading.
Typ:
Abstrakt ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Jan Šleichrt, Ph.D.; Ing. Nela Krčmářová; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2016, Book of Abstracts of International Symposium on Experimental Methods and Numerical Simulation in Engineering Sciences 2016, Praha, katedra mechaniky a materiálů), ISBN 978-80-01-06009-4
Anotace:
This work presents deformation behaviour of cost effective chopped fiber composites. Use of chopped fibre is advantageous for manufacturing however complex shape parts production technology could be challenging. Batches of samples with different fibres composition were subjected to uni-axial tensile loading to obtain overall materials properties and inspection of proper manufacturing based on local deformation inhomogeneities. Deformation behaviour of chopped fibre composites represented by stress-strain curves and strain maps was described based on optical measurement of standard tensile test. Local strain concentrations predicting failure area was identified.
Typ:
Abstrakt ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; Šperl, M.
Publikováno:
2016, XIVth Youth Symposium on Experimental Solid Mechanics, Praha, ČVUT v Praze, Česká technika - nakladatelství ČVUT), p. 35-38), ISBN 978-80-01-05885-5, ISSN 2336-5382
Anotace:
In this study high resolution thermography is used for identification of damaged zones in Carbon fiber/polyphenylene sulfide (C/PPS) long fiber composite specimens with induced impact damage subjected to tensile fatigue loading. Image processing techniques were applied on thermographs from all loading cases to obtain segmented images of the damaged location that were then used for calculation of the heated area. Results show that the considered method can be used to identify heated area in the vicinity of damage with high confidence at low number of cycles where no significant fatigue effect is present in the material.
DOI:
10.14311/APP.2016.3.0035
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
Ing. Nela Krčmářová; doc. Ing. Daniel Kytýř, Ph.D.; Petráňová, V; Šepitka, J.; Lukeš, J.; Gantar, A; Novak, S
Publikováno:
2016, Program and book of abstracts, Ljubljana, IMT Ljubljana), ISBN 978-961-94088-0-3
Anotace:
Regeneration of human bone tissue damaged by injuries or by degenerative diseases using biodegradable bone scaffold is one of the promising alternatives to the established treatment methods. This paper is focused on monitoring of BAG particles distribution and material properties mapping employing scanning electron microscopy (SEM) observation and nanoindentation measurement.
Typ:
Abstrakt ve sborníku z mezinár. konf.

Autoři:
Ing. Jan Šleichrt, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Keršner, Z.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2016
Anotace:
Pokročilé experimentální metody v mechanice vyžadují vývoj vlastních experimentálních zařízení, jejichž nezbytnou součástí je řídicí systém. V této práci je popsán návrh a realizace modulární řídicí jednotky poskytující otevřené řešení pro ovládání experimentálních zařízení. Navržená jednotka umožňuje ovládat zařízení s polohováním pracujícím na principu krokového motoru, popř. servo-motoru včetně bezpečnostních prvků, ovládat periferie a vyčítat veličiny měřené během experimentu (signál typu mV/V). V rámci práce byly rovněž vytvořeny softwarové nástroje pro implementaci řídicí jednotky do stávajících ovládacích aplikací pracujících na principu OS Linux s real-time jádrem a jeho speciálním modulem pro řízení LinuxCNC. V závěru byl proveden pilotní experiment s instrumentovaným mikroindentorem, který potvrdil funkčnost navrženého řídicího systému.
Typ:
Diplomová práce

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; Ing. Jan Šleichrt, Ph.D.; Hos, J.
Publikováno:
2016
Anotace:
SEM inspection, EDX analysis, hardness testing and grain structure analysis of delivered rectangular hollow structural section performed using in-house developad evaluation procedures.
Typ:
Výzkumná zpráva cizojazyčně

Autoři:
Major, Z; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2016, ISBN 978-80-01-05885-5, ISSN 2336-5382
Typ:
Sborník z mezinár. konf. cizojazyčně

Autoři:
Adorna, M.; doc. Ing. Daniel Kytýř, Ph.D.; Šperl, M.
Publikováno:
2015
Anotace:
Předložená práce se zabývá měřením deformační odezvy kompozitních materiálů při zkoušce pevnosti v tahu a creepové zkoušce. K řešení byla použita metoda optické korelace obrazu a pole deformací byla vyhodnocována v průběhu experimentu. Byla provedena celá série těchto testů na vzorcích několika různých typů, měření bylo doplněna o tenzometrické měření. Byla vytvořena sada vyhodnocovacích scriptů ve výpočetním prostředí Matlab. Pro analytický popis průběhu tečení byl jako nejlépe odpovídající použit Findleyho model. Dále byl sledován vliv úpravy výrobní technologie a geometrie vzorků na konzistentnost naměřených dat a mechanické vlastnosti materiálu. Výsledky této práce tak ukazují možnost využití tohoto materiálu v leteckém průmyslu v méně zatěžovaných částech konstrukce.
Typ:
Diplomová práce

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Šepitka, J.; Lukeš, J.
Publikováno:
2015, Proceedings of the 11th Conference on Local Mechanical Properties, Uetikon-Zurich, Trans Tech Publications), p. 129-133), ISBN 978-3-03835-555-7, ISSN 1013-9826
Anotace:
This paper deals with evaluation of mechanical properties of human trabeculae in the interconnection area. Local changes in the trabecular connections were evaluated using both quasi-static nanoindenation and modulus mapping technique. Connecting point of two trabeculae was revealed by precise grinding and polishing. A rectangular region in the interconnection was selected and inspected by modulus mapping procedure. Moreover several quasi-static indentation measurements using cube-corner indenter were performed along distinct lamellae. The obtained elastic properties were then compared with the values of the rod-like trabeculae. The comparison does not indicate significant differences in elastic properties between the trabecular rods and interconnections.
DOI:
10.4028/www.scientific.net/KEM.662.129
Typ:
Stať ve sborníku z prestižní konf. (Scopus)

Autoři:
Ing. Michaela Jurko; Ing. Petr Koudelka, Ph.D.; Jandejsek, I.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2015
Anotace:
Předkládaná bakalářská práce se zabývá vývojem experimentální metody pro studium deformačního chování auxetických struktur (porézních materiálů vykazujících záporné Poissonovo číslo) při kvazi-statickém zatěžování. Vzhledem k charakteru odezvy zkoumaných mikrostruktur na tlakové zatížení jsou mechanické charakteristiky odvozovány z vysoce přesného měření síly během experimentů a optického vyhodnocení deformace na povrchu vzorků s použitím metody digitální korelace obrazu (2D-DIC) se subpixelovou přesností. V práci byly zkoumány vzorky tří druhů auxetických mikrostruktur s analyticky dobře popsanou deformační odezvou a teoretickým průběhem Poissonovy funkce (závislosti Poissonova čísla na deformaci) v uspořádáních odpovídajících jak rovinnému, tak volumetrickému charakteru auxetických vlastností. Pro výrobu vzorků byl využit přímý 3D tisk metodou mnohatryskového modelování s vysokým rozlišením. Z naměřených dat byly s použitím vlastního softwarového nástroje vytvořeného v programovacím prostředí Matlab stanoveny závislosti skutečné napětí - skutečná deformace, Poissonovo číslo - skutečná deformace, poměrný Youngův modul pružnosti a hustota pohlcené deformační energie. Bylo ukázáno, že předkládaná metoda je vhodná pro studium mechanických vlastností auxetických materiálů na makroúrovni, což umožní verifikaci analytických a numerických optimalizačních procedur sloužících pro návrh auxetické mikrostruktury přizpůsobené pro konkrétní aplikaci.
Typ:
Diplomová práce

Autoři:
Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; Šepitka, J.; Lukeš, J.
Publikováno:
2015, Proceedings of the 11th Conference on Local Mechanical Properties, Uetikon-Zurich, Trans Tech Publications), p. 138-141), ISBN 978-3-03835-555-7, ISSN 1013-9826
Anotace:
Bone implants in form of artificial scaffolds manufactured from poly-lactic acid (PLA) represent an attractive alternative to traditional surgical treatments of defective bones (i.e. autografts and allografts). In this work factors influencing biocompatibility and primary stability of implants manufactured from PLA using direct 3D printing were assessed using nanoindentation. For this reason bulk sample of the PLA material and a printed object were subjected to nanomechanical measurement. Quasi-static nanoindentation was employed to identify elastic modulus and hardness distribution on surface and within volume of the samples. Moreover mechanical properties along scanning direction and interlayer characteristics were also assessed. Gradients in mechanical properties have been identified within volume of the material, within the printing layers and at contact between individual layers.
DOI:
10.4028/www.scientific.net/KEM.662.138
Typ:
Stať ve sborníku z prestižní konf. (Scopus)

Autoři:
Lukeš, J.; Šepitka, J.; Berg, M.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2015, ESB 2015 – Book of Extended Abstracts, Praha, České vysoké učení technické v Praze, Fakulta strojní), ISBN 978-80-01-05777-3
Anotace:
Artificial bone scaffolds represent an attractive alternative to autografts and allografts used in orthopedic repairs of bone defects. Bone and bone microstructure adapted stiffness properties to their load bearing function; hence effective elastic properties of proposed bone scaffold should be similar enough to provide bone’s primary function of human body support. As an alternative to widely used bone autografts and allografts, artificial bone scaffolds have to exhibit similar bone integration properties in terms of tissue ingrowth, to allow nutrients to pass through the bone marrow and also to preserve high rates of bone regeneration. 3D printing of polylactic acid (PLA) can be successfully used for production of porous 3D structure that mimics bone tissue. However, final scaffold needs to be inspected for potential impurities and mechanical gradients due to hot rapid manufacturing process. Nanoindentation can effectively serve as a quality control tool at microscale.
Typ:
Abstrakt ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Nela Krčmářová; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Šepitka, J.
Publikováno:
2015
Anotace:
Předložená práce se zabývá návrhem, výrobou a zprovozněním indentačního zařízení schopného indentace při nízkém zatížení metodou Vickers. Za tímto účelem byly navrženy dva způsoby zatěžování, první mód pro zatěžování konstantní silou při osazení indentoru závažím a druhý mód pro zatěžování řízené silou. Pro řízení indentačního zařízení technologií CNC byl vybrán modul LinuxCNC verze 2.6.4. Pro oba způsoby zatěžování vzniklo vlastní uživatelské rozhraní. Pro kontrolu správné funkce indentoru a vyhodnocovacích procedur bylo provedeno měření na referenční tvrdoměrné destičce. Toto měření dokázalo plnou funkčnost indentačního zařízení při nízkých zatěžovacích silách. Chyba měření byla mnohem menší, než chyba předepsaná normou.
Typ:
Diplomová práce

Autoři:
Ing. Tomáš Doktor, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2015, Materials and Technology, 49 (4), p. 597-600), ISSN 1580-2949
Anotace:
This paper deals with an experimental study of deformation response of open-cell aluminium foams under a moderate strain-rate compressive loading. Generally, porous metals show a promising potential in energy-absorption applications. However, the low strength of open-cell metal foams is a limiting parameter for such applications. Furthermore, the strain-rate sensitivity of mechanical properties is typically observed in closed-cell metal foams. On the other hand, open-cell foams provide a better control over the morphological parameters of a cellular structure. To enhance the properties of an open-cell microstructure an aluminium open-cell foam cured with polymeric filling was comparatively tested against the deformation-energy-absorption capabilities of the šas-delivered’ foam under a moderate strain-rate compressive loading. Prismatic samples with square cross-sections were prepared from the open-cell aluminium foam and a selected set of the samples was then filled with the thixotropic polyurethane putty. The specimens were tested with quasi-static compression, using a custom drop tower at several levels of the impact energy. The drop tests were instrumented with a tri-axial accelerometer and a high-speed camera to measure the mechanical response and the strain evolution during the impact. The comparison of the quasi-static behaviour with the results of the dynamic tests showed insignificant changes in the deformation curves in the case of the šas-delivered’ open-cell foam and an increasing energy-absorption capacity in the case of the samples equipped with the polymeric filling.
DOI:
10.17222/mit.2014.195
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
doc. Ing. Tomáš Mičunek, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Ing. Michal Frydrýn, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Drahomír Schmidt, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Zdeněk Svatý, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Luboš Nouzovský, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Lenková, A.; Ing. Petr Koudelka, Ph.D.; Ing. Bc. Kateřina Mičunková; Ing. Michaela Jurko; Hájková, B.; Ing. Jan Šleichrt, Ph.D.; Adorna, M.; Hos, J.; Ing. Jan Falta; Ing. Nela Krčmářová
Publikováno:
2015
Anotace:
Předmětem díla je porovnání neoriginálního náhradního dílu s originálním dílem kapoty Škoda Fabia II z pohledu bezpečnosti dopravy. Dále je předmětem díla zjištění zda neoriginální náhradní díly jednoho výrobce mají stejné mechanické vlastnosti.
Typ:
Výzkumná zpráva v češtině

Autoři:
Hos, J.; Ing. Tomáš Doktor, Ph.D.; Kostelecká, M.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2015
Anotace:
Tato bakalářská práce se zabývá určováním orientace vláken v krátkovláknových kompozitních materiálech za pomoci analýzy obrazových dat. Orientace vláken velkou měrou ovlivňuje vlastnosti kompozitních materiálů. Zatímco u dlouhovláknových kompozitů může být orientace snadno kontrolována při výrobě, v případě krátkovláknových kompozitů je takováto kontrola velice obtížná. Práce se zabývá vlastnostmi kompozitních materiálů a základní teorií z oblasti zpracování obrazů. Těchto poznatků je následně využito při tvorbě softwarového nástroje pro určení orientace vláken. Vstupem do programu jsou obrazová data pořízená elektronovým mikroskopem, výstupem jsou histogramy četností orientací jednotlivých vláken.
Typ:
Diplomová práce

Autoři:
Ing. Jan Šleichrt, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Šperl, M.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2014, Proceedings of 13th Youth Symposium on Experimental Solid Mechanics, Praha, České vysoké učení technické v Praze, Fakulta dopravní), p. 124-127), ISBN 978-80-01-05556-4
Anotace:
Carbon-fibre composite is very popular material in aircraft industry. Application of this material is limited by low fragility and low impact resistance. In flight airplane can be initialy damaged by hailstorm or bird strikes. The vibrations of the engine and turbulence during flight can be expansion of this damage. This study testing laser profilometry to investigation post damage under cycling loading.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Jan Šleichrt, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Šperl, M.
Publikováno:
2014, Materials and Technology, 48 (5), p. 777-780), ISSN 1580-2949
Anotace:
Carbon fibre in polyphenylene sulfide composites (C/PPS) became a popular material in the aircraft industry but its fragility and low impact resistance limits its application in primary aircraft structures. This study is focused on damage propagation in the laminated composites reinforced with carbon fibres. The damage may be inflicted during the ground maintenance, by an inflight bird strike or during a flight in severe meteorological conditions (heavy storms). The initial damage was created by a drop-weight out-of-plane impact using a spherical indenter. The response of the material was analysed by monitoring the impacted zones and their propagation history. The influenced area and specimen thickness in the centres of indents were chosen as the degradation parameters. The post-impact damage propagation induced by cyclic loading was assessed using a custom-designed computer-controlled laser-profilometery device. Both the upper and lower profiles of the specimen were scanned during the interruptions of the fatigue test. Global deformation was described with an analytically determined centroidal-axis curve. Local topography changes were obtained with a subtraction of this curve. Surface-deformation maps were created and used for a demonstration of the damage propagation in the specimen.
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Hos, J.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Petráňová, V.
Publikováno:
2014, Proceedings of 13th Youth Symposium on Experimental Solid Mechanics, Praha, České vysoké učení technické v Praze, Fakulta dopravní), p. 48-51), ISBN 978-80-01-05556-4
Anotace:
This paper deals with calculation of fibre orientation distribution (FOD) in fibre reinforced composite. The calculation was based on image analysis algorithm applied on image acquired by scanning electron microscope. A composite with oriented fibres was selected to be enable calibration of the algorithm by comparison of the obtained results with FOD declared by the manufacturer.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; Kumpová, I.; doc. Ing. Petr Zlámal, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2014, Book of abstract of 7th World Congress of Biomechanics, p. 597-597)
Anotace:
Micromechanical testing at the level of individual trabeculae is fundamental for proper description of deformation behaviour of a complex bone structure. This study is focused on influence of various X-ray microradiography procedures, loading procedures and tracking algorithms on accuracy of strain evaluation of loaded human trabeculae. Displacement controlled three-point bending test in both incremental and continual loading modes were carried out. To acquire best quality images two different X-ray imaging setups were used. Large area scintillator and high resolution single photon counting silicon detector WidePix with microfocus X-rays source were employed. Different voltages and target currents were tested to obtain optimal signal to noise ratio in the radiograms. Two different methods were used for displacement tracking: i) digital image correlation (DIC) and ii) tracking of artificial markers attached to the samples. In case of DIC sample inhomogeneity allowed for displacement measurement using Lucas-Kanade tracking algorithm. Gold coated borosilicate glass micro-spheres were used as the markers for displacement tracking in the second method. Here circular Hough transform was used to locate and track the positions of the markers in the loading sequence. Linearisation of the attenuation range was employed to improve contrast in the radiograms and to increase precision of the employed tracking algorithms. Stress-strain characteristics of individual trabeculae were obtained and reduction of thickness in loaded specimens correlating with strain localization was observed.
Typ:
Abstrakt ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Nela Krčmářová; Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Tomáš Fíla, Ph.D.
Publikováno:
2014, 9th International Conference on Local Mechanical Properties, Zürich, Transtech Publications), p. 257-260), ISBN 978-3-03785-876-9, ISSN 1013-9826
Anotace:
The paper presents application on digital image correlation (DIC) and microindentation for investigation of plastic flow under Brinell ball indenter applied on steel specimen made of two screwed together parts. Specimens in two different material state (a) as delivered (b) annealed were investigated. This approach enables internal surface to act as the external one and to be examined by mentioned methods. Results obtained by application of DIC on scanning electron microscope (SEM) images are compared to microhardness maps and agreement is demonstrated.
DOI:
10.4028/www.scientific.net/KEM.586.257
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Králík, V.; Němeček, J.
Publikováno:
2014, Local Mechanical Properties X, Zurich, TRANS TECH PUBLICATIONS LTD), p. 39-42), ISBN 978-3-03835-062-0, ISSN 1013-9826
Anotace:
This study is focused on detection and characterisation of influenced zones in micro-scale specimens of aluminium foam after thermal and mechanical loading induced by preparation process for three-point bending test. Two cell-wall specimens were prepared from a slab of aluminium foam and influences of preparation process (machining) and thermal load on local mechanical properties were investigated using nanoindentation. Although the nanoindentation is powerful method for investigation of material properties of small zones, it can be reliably used only to obtain information about elastic properties. Due to limitation of the nanoindentation for reliable measurement of inelastic properties, plastic properties were determined using a set of indirect finite element simulations of nanoindentation tests. The procedure is based on fitting numerical results to experimentally measured force-depth curves.
DOI:
10.4028/www.scientific.net/KEM.606.39
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Šepitka, J.; Lukeš, J.
Publikováno:
2014, Local Mechanical Properties X, Zurich, TRANS TECH PUBLICATIONS LTD), p. 245-248), ISBN 978-3-03835-062-0, ISSN 1013-9826
Anotace:
This study is focused on inspection of damage extent induced into C/PPS composite material by fatigue and impact loading. Initial damage to specimens was induced by drop-weight out-of-plane impact damage. Several levels of damage states (intact specimen, fatigued and impacted specimen, ruptured specimen) were inspected using modulus mapping (MM) technique. Quantification of the damage level was based on comparison of results from MM obtained in distinct locations on the specimens. Regions of interest were selected in order to determine magnitude of damage after impact and to assess remaining loading capabilities of the material. For this purpose, material maps provided information about location where matrix had been inflicted by the damage. Results show that impact loading has no measurable influence on mechanical properties of the matrix. However, gradient in mechanical properties was detected in the vicinity of crack. Results were validated using quasi-static nanoindentation and constant strain rate continuous measurement that showed depth profile of mechanical properties.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Petr Koudelka, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Koudelková, V.; Lukeš, J.; Ing. Tomáš Doktor, Ph.D.; Ing. Jaroslav Valach, Ph.D.
Publikováno:
2014, Key Engineering Materials, Zurich, TRANS TECH PUBLICATIONS LTD), p. 186-189), ISBN 978-3-03785-876-9, ISSN 1013-9826
Anotace:
In the case of material parameters required for evaluation of built heritage preservation state, knowledge of the least possible volume of removed sample is essential in order to minimize damage accumulation to the buildings. These requirements lead to determination of representative volume element (RVE) that was in this paper calculated using combination of image and signal processing techniques. Then, a detailed map of material properties was created using nanoindentation to evaluate local characteristics of the material. Furthermore, atomic composition of samples was quantified by energy dispersive spectrometry (EDX) detector for scanning electron microscopy (SEM) device. Presented method based on combination of SEM, EDX and nanoindentation techniques demonstrates possibility of effective testing in the field of historical buildings preservation.
DOI:
10.4028/www.scientific.net/KEM.586.186
Typ:
Stať ve sborníku z prestižní konf.

Autoři:
Ing. Tomáš Fíla, Ph.D.; Kumpová, I.; doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Doktor, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2014, Proceedings of 13th Youth Symposium on Experimental Solid Mechanics, Praha, České vysoké učení technické v Praze, Fakulta dopravní), p. 32-35), ISBN 978-80-01-05556-4
Anotace:
In this paper, compact loading device for micro-CT measurements under applied load was used in a series of instrumented compressive test of bone sample. Tested bone samples were loaded in several deformation steps and micro-CT scanning was carried out in each step. Reconstructed three-dimensional data of intact bone sample were used to develop 3D model of the specimen. Data from each deformation step were processed by DVC method for identification of displacement and strain fields and thus for evaluation of deformation response of human trabecular bone sample.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Růžička, M.
Publikováno:
2014, ISBN 978-80-01-05556-4
Typ:
Sborník z mezinár. konf. cizojazyčně

Autoři:
Ing. Petr Koudelka, Ph.D.; Jandejsek, I.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Drdácký, M.; Zíma, P.Z.
Publikováno:
2014, Journal of Instrumentation (9), ISSN 1748-0221
Anotace:
In order to ensure sustainability if historic buildings their technical state has to be inspected on regular basis. Damage assessment has to be preferably carried out using non-destructive methods otherwise damage accumulation may occur during life-cycle of the constructions. According to character of detected damage appropriate intervention measures (i.e. strengthening, consolidation, etc.) have to be then efficiently applied. Among other factors significantly influencing life span of constructions weathering agents (rain, erosion, dissolution, etc.) may cause rapid degradation of mechanical properties. In this paper X-ray radiograhical imaging was used to describe fluid penetration process in porous Maastricht limestone that is commonly used for restoration purposes. The imaging was performed in custom radiography device simulating practical in-situ measurements using microtube device. This device is a modified Karsten tube capable of determining absorbed volume and its speed even on inclined surfaces. However actual fluid penetration process in terms of saturation depth/volume ratio and shape of fluid wave propagating through microstructure is indeterminable using microtube. For this purpose real-time radiography imaging of fluid saturation process was performed to investigate behaviour of fluid in the material. Furthermore X-ray computed microtomography was performed to develop finite element model for simulation of fluid flow in the porous microstructure. Using the real-time imaging relations between penetration speed, penetration depth and penetrated volume were assessed. These results can be used to validate results from microtube measurements including nonlinear regions present when semi-spherical wave propagates through the material. Using a set of finite element simulations of the microtube experiment fluid velocity distribution in the material together with effective Darcy's flux were calculated and results were compared to those from real-time imaging.
DOI:
10.1088/1748-0221/9/05/C05040
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2014
Anotace:
The present study is focused on the investigation of mechanical behaviour of cellular materials at higher strain rates and optimisation of the material to enhance the energy absorption capabilities. The study encounters micromechanical testing, time-lapse tomography under compressive loading and moderate strain-rate loading using drop tower. Three types of material are investigated, open- and closed-cell aluminium foam and interpenetrating phase composite (IPC). The results show increase in strain energy density absorbed by IPC.
Typ:
Kandidátské minimum

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Kumpová, I.
Publikováno:
2014, XIVth Bilateral German/Czech Symposium - Experimental Methods and Numerical Simulation in Engineering Sciences, Wuppertal, Bergische Universität), p. 66-69)
Anotace:
Deeper understanding of the relationship between morphology, micro-mechanical properties at the bone tissue level and overall mechanical properties of the bone is important for assessment of bone physiological and pathological behaviour. Modern radiological methods (e.g. computed micro-tomography) are powerful instruments for investigation of the internal structure. Using the time-lapse tomography enabled assessment of deformation response to the applied loading and monitoring of damage propagation. Different custom based set-ups of high resolution micro-focus X-ray computed tomography equipped with scintillator or single-photon counting detector were used for imaging at both meso and micro levels.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Tomáš Fíla, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Petr Koudelka, Ph.D.; Ing. Jaroslav Valach, Ph.D.
Publikováno:
2013, Proceedings of 12th Youth Symposium on Experimental Solid Mechanics, Bari, Politecnico di Bari)
Anotace:
Evaluation of natural frequencies‘ shift during thermal loading of carbon fibre/polyphenylene sulphide (C/PPS) composites used in aircraft industry is described in this paper. Values of natural frequencies were chosen as indicators of changes in material properties. Custom-designed experimental device suitable for determination of specimen's natural frequencies was developed according to operation in thermal chamber. During the experiment steel pellets were dropped on specimen. Overall acoustic response of the impact was recorded by microphone. Two characteristic natural frequencies were evaluated using spectral analysis of recorded sound. Series of measurements at different temperatures were performed nearly up to the temperature of PPS glass-transition. Obtained results show strong correlation between natural frequency shift and temperature of the specimen’s surface.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Nela Krčmářová; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Petr Koudelka, Ph.D.
Publikováno:
2013, Proceedings of 12th Youth Symposium on Experimental Solid Mechanics, Bari, Politecnico di Bari)
Anotace:
Presented article is focused on plastic strain distribution assessed by microindentation technique. If the nature of the specimen is unsuitable for radiological inspection destructive sample preparation is inevitable to describe its inner state. Two mutually perpendicular planes in deformed zone were manufactured by electrical discharge machining and polishing. One of the planes was created prior the loading procedure and during the loading the parts were connected by screws. In the perpendicular plane the specimen was cut after the loading. Specimens prepared using this procedure were then subjected to microindentation testing. Each set of indents consisted of approximately 150 Vickers microindents covering area of 0.5 mm2. Images of imprint arrays on the specimens surface were acquired by scanning electron microscope. Diagonals of indents were determined and then Vickers hardness values were calculated. Map of hardness distribution was created using cubic interpolation method.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Dammer, J.; Krejčí, F.
Publikováno:
2013, Journal of Instrumentation, 8 (2), ISSN 1748-0221
Anotace:
This study presents an improved radiographic method for strain measurement in very small samples of a single trabeculae. X-ray micro-radiography was used to track the deformation behaviour of individual trabecula during mechanical loading. As the X-ray micro-radiography images of a single trabecula show no significant features applicable for digital image correlation (DIC) a random pattern of markers was created on the surfaces of the samples to improve the accuracy of tracking. Metal plated borosilicate glassmicro-spheres (mean diameter 10um) were used as the markers for trabecular displacement tracking. Two different X-ray imaging setups were used for this purpose. The specimens of isolated trabeculae were loaded by amicro-mechanical testing device developed with respect to radiographical observation. This compact device enables a high precision three-point bending measurement. The specimen was continuously irradiated during the loading procedure by amicro-focus X-ray source. The radiographs were acquired by a single-photon counting silicon pixel detector and s flat panel sensor with CsI flipped scintillator plate. Circular Hough transform was used to locate positions of the spherical markers in the sequence of acquired radiographs and to calculate the strain in the loaded sample. The gold-coated micro-spheres provide clearly visible features in the sequence of radiographs after beam hardening correction, which in conjunction with pattern recognition algorithm enables to substantially improve the accuracy of strain measurements.
DOI:
10.1088/1748-0221/8/02/C02041
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2013, UPB Scientific Bulletin, Series D: Mechanical Engineering, 75 (1), p. 161-170), ISSN 1454-2358
Anotace:
During the last decades, there has been much effort on the determination of effective elastic properties of porous metals. In this paper, the overall elastic moduli of reference aluminium foam Alporas are assessed using predictive methods based on definition of compliance contribution tensor. Surface of the foam is captured using flatbed scanner and such data is subjected to image and signal processing routines in order to obtain dimensions of the sufficient representative volume element and calculation of structural characteristics for analytical homogenization. It is shown that from all considered homogenization models only the Mori-Tanaka scheme gives results reasonably close to nominal values.
Typ:
Článek v periodiku excerpovaném databází Scopus

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Šperl, M.
Publikováno:
2013, UPB Scientific Bulletin, Series D: Mechanical Engineering, 75 (2), p. 157-164), ISSN 1454-2358
Anotace:
Carbon fibre in polyphenylene sulfide composites became popular ma- terial in aircraft industry but its fragility and low resistance against impact load- ing limits the application of these composites in aircraft primary structures. The article deals with experimental investigation of the mechanical response of dam- aged composite. Material degradation of intact and damaged specimens during fatigue tests was investigated. The changes in natural frequencies, ultrasound wave propagation and bending stiffness were chosen as damage parameters. The entire fatigue life of intact and damaged specimens was studied in the article by all the presented methods. The accuracy and reliability of assessment of damage parameters were compared. Comparison of accuracy and reliability of presented method for assessment of damage parameters is also given.
Typ:
Článek v periodiku excerpovaném databází Scopus

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Fíla, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2013, Proceedings of 12th Youth Symposium on Experimental Solid Mechanics, Bari, Politecnico di Bari)
Anotace:
This paper is focused on evaluation of the micro‐scale tests of isolated cell‐walls of aluminium foam. To derive mechanical properties at the level of single cells, three point bending tests were carried out. There are several ways to obtain mechanical properties from the measured data (i) manufacturing of prismatic beam, (ii) testing of a curved beam and simplification of the beam shape by an equation of a curve, (iii) indirect determination of mechanical properties using inverse finite element analysis (FEA). Due to the dimensions and complex shape of the cells there is a high risk of plastic deformation caused by specimen preparation as well as very low dimensions of resulting sample. Hence testing of a curved specimen was performed with a special attention paid to the specimen preparation. A volumetric model enabling utilization of inverse FEA was developed.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.
Publikováno:
2013, Acta Technica CSAV, 58 (2), p. 157-171), ISSN 0001-7043
Anotace:
The aim of the paper is to develop a procedure for determination of elasto-visco-plastic constitutive model with damage for human single trabecula. The procedure is suited for indirect establishing of material model based on nanoindentation and three-point bending test. Constants of the material model are identified by Finite Element (FE) simulations and curve fitting using an algorithm based on least squares fitting of the experimental curves. In the case of nanoindentation, the penetration depth of tip during the FE analyses (FEA) is fitted to experimental nanoindentation curves. In the case of three-point bending, displacements of nodes are compared with displacements of markers observed during the experiment using digital image correlation.
Typ:
Článek v periodiku excerpovaném databází Scopus cizojaz.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Jandejsek, I.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Drahomír Schmidt, Ph.D.
Publikováno:
2013, Proceedings of the Fourteenth International Conference on Civil, Structural and Environmental Engineering Computing, Stirling, Civil-Comp Press Ltd), ISBN 978-1-905088-57-7, ISSN 1759-3433
Anotace:
The possibility of using microstructural finite element models of whole bones to inversely calculate their mechanical properties is described in this paper. In this study, L2 vertebra of a Wistar rat were used to numerically determine its stiffness and the results are compared with the experimentally obtained value. The results demonstrate the possibility of using these large-scale finite element simulations to predict the overall bone stiffness. The micro-structural models used in this study are voxel-based, i.e. each finite element represents one spatial pixel (called a voxel). The micro-structural models are developed from a series of micro-CT images. The resolution of the input image data which is needed to capture the complex microstructure of trabecular bone in sufficient detail is discussed. Tissue material properties are based on our previous nanoindentation study. This paper is focused on the parallel solution strategy employed to solve the large-scale finite element models utilizing existing open-source programs. Because of the high resolution of the microtomographic images the resulting finite element model of the vertebra is composed of approximately 9 million of hexahedral elements. To solve this large problem a parallel strategy must be employed. The main aim was to demonstrate the scalability of selected solvers (the preconditioned conjugate gradient and multifrontal massively parallel sparse direct solver) for these large voxel finite element models. Two architectures are tested: i) distributed memory system, and ii) shared memory system. The results show, that the estimated overall stiffness of the vertebral body is not greatly influenced by the resolution of micro-CT images (albeit it must well capture the micro-structural characteristics of the trabecular bone) provided that the tissue material properties (elastic modulus and Poissons ratio at the level of individual trabeculae) are known.
DOI:
10.4203/ccp.102.105
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Jandejsek, I.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Drahomír Schmidt, Ph.D.
Publikováno:
2013, Proceedings of the Fourteenth International Conference on Civil, Structural and Environmental Engineering Computing, Stirling, Civil-Comp Press Ltd), ISBN 978-1-905088-57-7, ISSN 1759-3433
Anotace:
The possibility of using microstructural finite element models of whole bones to in- versely calculate their mechanical properties is described in this paper. In this study, L2 vertebra of a Wistar rat were used to numerically determine its stiffness and the results are compared with the experimentally obtained value. The results demonstrate the possibility of using these large-scale finite element simulations to predict the over- all bone stiffness. The micro-structural models used in this study are voxel-based, i.e. each finite element represents one spatial pixel (called a voxel). The micro-structural models are developed from a series of micro-CT images. The resolution of the input image data which is needed to capture the complex microstructure of trabecular bone in sufficient detail is discussed. Tissue material properties are based on our previous nanoindentation study. This paper is focused on the parallel solution strategy employed to solve the large-scale fi- nite element models utilizing existing open-source programs. Because of the high res- olution of the microtomographic images (≈5µm3) the resulting finite element model of the vertebra is composed of approximately 9 million of hexahedral elements. To solve this large problem a parallel strategy must be employed. The main aim was to demonstrate the scalability of selected solvers (the preconditioned conjugate gradient and multifrontal massively parallel sparse direct solver) for these large voxel finite element models. Two architectures are tested: i) distributed memory system, and ii) shared memory system. The results show, that the estimated overall stiffness of the vertebral body is not greatly influenced by the resolution of micro-CT images (albeit it must well capture the micro-structural characteristics of the trabecular bone) provided that the tissue material properties (elastic modulus and Poisson’s ratio at the level of individual tra- beculae) are known.
DOI:
10.4203/ccp.102.105
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Jaroslav Valach, Ph.D.; Žďárský, M.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2013, Proceedings of 30th Danubia - Adria Symposium on Advances in Experimental Mechanics, Zagreb, Croatian Society of Mechanics), p. 43-44), ISBN 978-953-7539-17-7
Anotace:
In this paper, application of laser profilometry is demonstrated for surface geometry measurement and compared to results obtained by active thermography as a reference method for damage detection and assessment. Specimens made of eight-ply carbon fiber reinforced PPS matrix laminate in the form of strips 25mm wide, 250mm long and 2mm thick were subjected to simulated impact damage. Both mothods are capable to detect impacts, which is first sign of incurred damage of material. Therefore this methods are suitable for monitoring of damage accumulation during fatigue process.
Typ:
Abstrakt ve sborníku z mezinár. konf.

Autoři:
Žďárský, M.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Šperl, M.; Ing. Tomáš Fíla, Ph.D.
Publikováno:
2013, Proceedings of 12th International Workshop on Advanced Infrared Technology and Applications, Politecnico di Torino), p. 217-219)
Anotace:
The presented work summarizes first results on hi-speed thermography analysis of cyclic loading of carbon fibers reinforced thermoplastic matrix composite. Opportunity to record and analyze minute changes of temperature is shown as well as detailed documentation of energy dumping on gradual increase of mean temperature of the specimen. Demonstrated sensitivity of the thermoanalysis is prerequisite for future investigation of impact damage as discussed in conclusions.
Typ:
Abstrakt ve sborníku z mezinár. konf.

Autoři:
Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2013, Proceedings of the Fourteenth International Conference on Civil, Structural and Environmental Engineering Computing, Stirling, Civil-Comp Press Ltd), ISBN 978-1-905088-57-7, ISSN 1759-3433
Anotace:
This paper describes the determination of the elasto-plastic properties of base material of aluminium foam Alporas. Three point bending experiments at the micro-scale level in conjunction with inverse finite element simulation were performed. In the cellular structure cell-walls with planar shape were identified and vicinity of such walls was extracted. Harvestedmaterial was embedded into transparent rosin to avoid plastic deformation during the manipulation and the selected wall was extracted. The specimens were finalized by grinding and polishing to achieve approximately rectangular shape. Three projections were acquired using a scanning electron microscope (SEM) and a volumetric model of the samples was developed using a semiautomatic image processing tool. Amicro-scale three-point bending test of semi-prismatic specimens extracted from the cell-wall was performed using a custom designed loading device. Loading was provided using a preloaded lead screw with precise travel. Applied force was measured using a high-accuracy load cell with a loading capacity of 2.25N. Strains were measured optically using the digital image correlation method. The volumetric model developed from the set of SEM projections was discretised using tetrahedral elements with quadratic shape functions. In the simulated bending test the elasto-plastic material model with the von Misses yield criterion and bilinear isotropic hardening was used. Boundary conditions consistent with the experimental oneswere prescribed in the simulation. Themeasured force was sampled at 50Hz and applied to the finite elementmodel. Based on themeasured displacements, parameters of the material model were varied to obtain a best fit to the experimental data (load- deflection curve). Elastic and plasticmaterial constants of the constitutivemodel were identified: (i) Young’smodulus of elasticity, (ii) yield stress and (iii) tangentmodulus.
DOI:
10.4203/ccp.102.104
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; Jandejsek, I.; Vavřík, D.
Publikováno:
2013, Journal of Instrumentation, 8 (2), ISSN 1748-0221
Anotace:
Time-lapse X-ray computed microtomography was employed to quantify the deformation behaviour of closed-cell aluminium foam. The specimen was incrementally loaded and tomographically scanned using a custom X-ray tomographic device to capture the deforming microstructure. Because of the very small thickness of the cell walls and the high ratio between pore size and cell wall thickness cone-beam reconstruction procedure was applied. A finite element (FE) model was developed based on the reconstructed three-dimensional data. The FE model was used for two purposes: i) the nodal points were used for tracking the displacements of the deforming structure, ii) verification of the material model for description of the foam's deformational behaviour. Digital volumetric correlation (DVC) algorithm was used on data obtained from the time-lapse tomography to provide a detailed description of the evolution of deformation in the complex structure of aluminium foam. The results from DVC demonstrate the possibility to use the complex microstructure of the aluminium foam as a random pattern for the correlation algorithm. The underlying FE model enables easy comparison between experimental results and results obtained from numerical simulations used for evaluation of proposed constitutive models.
DOI:
10.1088/1748-0221/8/02/C02012
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Minster, J.; Kostelecká, M.
Publikováno:
2012, Chemické listy, 106 (s3), p. 399-400), ISSN 0009-2770
Anotace:
The article deals with monitoring of degradation of carbon fibre reinforced polymer (CFRP) under cyclic loading. The investigated material is composed of polyphenylensulfid matrix and carbon fibres. Four specimens were subjected to repeated cyclic loading. During the fatigue loading surface of tested specimens was observed by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) to obtain surface roughness characteristics and micrographs of surface morphology. With increasing number of cycles the measured surface characteristics showed increasing surface roughness indicating at the level of micromechanics detachment of matrix from the fibers and also changes in the matrix structure itself.
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Fíla, Ph.D.; Urushadze, S.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Šperl, M.
Publikováno:
2012, Engineering Mechanics 2012, Prague, Institute of Theoretical and Applied Mechanics, AS CR), p. 231-237), ISBN 978-80-86246-39-0
Anotace:
Assessment of degradation rate of material can be carried out by many experimental techniques differing in complexity and sophistication. A relatively simple method based on acoustic analysis is described in this contribution. Degradation of material's properties due to fatigue loading is detectable in decrease of their modulus of elasticity that can be derived from natural frequencies of specimens, which were acquired by the presented method. These measurements utilize self-designed device capable of specimen excitation and acquisition of its vibration. The recorded signal is then processed by spectral analysis enabling determination of natural frequencies. Usefulness of the above mentioned acoustic method can be seen in the fact that the measured changes of material's parameters are comparable to those obtained by laser vibrometry, which is by several orders more expensive technique.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Šepitka, J.; Lukeš, J.; prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.
Publikováno:
2012, Chemické listy, 106 (S3), p. 523-524), ISSN 0009-2770
Anotace:
The leech's sucking apparatus is an amazing instrument - it has 3 jaws and 300 teeth made for easily cut into the skin of the host animal. In this study, we used nanoindentation and atomic spectroscopy to reveal composition and material properties of leeches' teeth. Five samples of leech's jaws obtained from adult subjects of Hemopis sanguisuga were investigated. Main constituents of leeches' teeth have been identified. The tooth is composed mainly of calcium (41.9%), oxygen (41.2%) and carbon (11.4%), other constituents are present in small quantities (F, Na, P, 0 and S), therefore, a substance typical for mineral component in bones hydroxyapatite is likely present in the teeth among other substances. Material properties, which are independent on indentation depth, examined by nanoindentation provided average reduced modulus Er = 27.54 +/- 3.71GPa
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Jaroslav Valach, Ph.D.; Žďárský, M.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Šperl, M.
Publikováno:
2012, Chemické listy, 106 (S3), p. 551-554), ISSN 0009-2770
Anotace:
The paper presents enhanced method for study of severe plastic deformation by hardness mapping utilizing portable hardness tester, flatbed scanner and software processing tool. This technique can be advantageous in situations, where crude information is not only sufficient, but also preferred, especially when it concerns testing on-site and on medium to large scale specimens and construction. Validity of the approach is supported by a comparison of hardness mapping results to the results obtained by an independent method based on evaluation of plastic strains from thermograms. It is shown that both methods determined similar shape and the extent of the plastic zone of the studied specimens.
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2012, Proceedings of 11th Youth Symposium on Experimental Solid Mechanics, Brašov, Universitate Transilvania Brasov), p. 88-91), ISBN 978-1-63439-432-1
Anotace:
This paper deals with development of the volume model of irregular specimens using optical projections. A s equence of 360 projections of the specimen was acquired and processed using a custom set of procedures developed in MatLab environment. The projections were segmented, filtered and smoothed. A semiautomatic procedure was used to calibrate scale of the projections and to remove eccentricity of axis of rotation of the specimen. The volume model was obtained using inverse Radon transform. Additional procedures were developed to o btain cross- section characteristics required for e valuation of corresponding micromechanical test. For verification of the developed procedure volume models of known shaped objects were estimated and compared.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Tomáš Fíla, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Minster, J.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2012
Anotace:
Tato práce se zabývá nedestruktivním testováním uhlíkového kompozitu s polymerní matricí C/PPS. Za tímto účelem byla zvolena metoda určování degradace materiálu pomocí akustických charakteristik. Tato metoda byla významně upravena, bylo zkonstruováno vlastní experimentální zařízení a vyvinut vlastní software pro měření a vyhodnocování dat. Pomocí těchto nástrojů byly evaluovány vlastní frekvence vzorku a jejich logaritmický dekrement útlumu. Měřené změny těchto veličin byly následně použity jako indikátory poškození materiálu únavovou degradací.
Typ:
Diplomová práce

Autoři:
Ing. Petr Koudelka, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2012, Proceedings of 11th Youth Symposium on Experimental Solid Mechanics, Brašov, Universitate Transilvania Brasov), p. 244-250), ISBN 978-1-63439-432-1
Anotace:
During the last decades, there has been much effort on the determination of effective elastic properties of porous metals. In this paper, the overall elastic moduli of reference aluminium foam Alporas are assessed using predictive methods based on definition of compliance contribution tensor. Surface of the foam is captured using flatbed scanner and such data are subjected to image and signal processing routines in order to obtain dimensions of the sufficient representative volume element and calculation of structural characteristics for analytical homogenization. It is shown that only the Mori-Tanaka scheme gives results close to nominal values.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Petr Koudelka, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Němeček, J.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2012
Anotace:
Thesis is aimed at the determination of effective mechanical properties of foam materials with concentration on metal foams. Elastic constants are investigated using numerical homogenization method. As a input data, 2-D macrostructure of the reference foam Alporas captured by high resolution flatbed scanner was used. The acquired image is segmented to binary one that is subjected to spectral analysis in order to assess dimensions of the representative volume element sufficient for characterization of the random microstructure of the foam. The real form of the microstructure is substituted by equivalent Voronoi diagram that is consequently transformed to finite element model. The model is used in a set of simulated mechanical tests in ANSYS software leading to determination of searched elastic constants. Obtained results are compared with the experimental ones assessed using tension test performed with the Alporas specimen.
Typ:
Diplomová práce

Autoři:
Ing. Tomáš Fíla, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.
Publikováno:
2012, Proceedings of 11th Youth Symposium on Experimental Solid Mechanics, Brašov, Universitate Transilvania Brasov), p. 92-95), ISBN 978-1-63439-432-1
Anotace:
Abstract: This paper deals with investigation of acoustic material degradation indicator (natural frequency) of carbon fibre C/PPS composite obtained by a custom-built experimental device. The specimen's sound was emitted during the impact of steel pellet in acoustic measurement experimental device. Acoustic signals were recorded and analyzed using spectral and regression analysis. Specimens were repetitively measured after designated number of loading cycles. The decreases of natural frequencies were determined for given number of natural modes. Relations between natural frequency values and their decreases were investigated. To conclude, the data assessed using acoustic measurements are suitable for evaluation of material degradation.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Žďárský, M.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2012, e-Journal of NDT, 17 (10), ISSN 1435-4934
Anotace:
In this paper the application of quantitative thermography analysis on strains is presented on the study dealing with evaluation of material's behavior during plastic deformation of specimen in two thermodynamically different states. The analysis of plastic deformation and thermal phenomena processes is demonstrated on compact-tension steel specimens both in theoretical and experimental way. The experiments proved different temperature response to external loading and dependence of plastic deformation development on material's state. These results support claim that thermography can be used for non-destructive investigation of internal state of materials.
Typ:
Článek v odborném recenzovaném periodiku

Autoři:
Jiroušek, O.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2012, ISBN 978-80-01-05062-0
Typ:
Sborník z mezinár. konf. cizojazyčně

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Nela Krčmářová; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.
Publikováno:
2012, Experimental Methods and Numerical Simulation in Engineering Sciences, Proceedings of XIIIth Bilateral Czech/German Symposium, Praha, České vysoké učení technické v Praze, Fakulta dopravní), p. 31-34), ISBN 978-80-01-05062-0
Anotace:
This paper deals with evaluation of hardness fields using Vickers indentation device and a semi-automatic software tool for local hardness distribution mapping. Specimens from low carbon pipeline steels were investigated. Dense grids of Vickers imprints were created on the specimens' surface. Image data of the surface were acquired by a high resolution flatbed scanner with resolution 6400dpi. The imprints were measured using an custom-developed image processing tool, and from the obtained geometrical characteristics local hardness values were derived. From the local hardness values and their coordinates the hardness field in the whole specimen was interpolated.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.
Publikováno:
2012, Engineering Mechanics 2012, Prague, Institute of Theoretical and Applied Mechanics, AS CR), p. 1611-1620), ISBN 978-80-86246-40-6
Anotace:
The aim of the paper is to develop a procedure for determination of elasto-visco-plastic constitutive model with damage for human single trabecula. The procedure is suited for indirect establishing of material model based on nanoindentation and three-point bending test. Constants of the material model are identified by Finite Element (FE) simulations and curve fitting using an algorithm based on least squares fitting of the experimental curves. In the case of nanoindentation, the penetration depth of tip during the FE analyses (FEA) is fitted to experimental nanoindentation curves. In the case of three-point bending, displacements of nodes are compared with displacements of markers observed during the experiment using digital image correlation.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Tomáš Fíla, Ph.D.; Urushadze, S.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Šperl, M.
Publikováno:
2012, Experimental Methods and Numerical Simulation in Engineering Sciences, Proceedings of XIIIth Bilateral Czech/German Symposium, Praha, České vysoké učení technické v Praze, Fakulta dopravní), p. 35-38), ISBN 978-80-01-05062-0
Anotace:
This paper deals with investigation of acoustic material degradation indicator (attenuation decrement drop of selected natural frequency) measured by a custom-built experimental device. Samples of C/PPS fibre composite material were analyzed. Acoustic signals were recorded and processed using spectral analysis and sound signal regression. Data measured by this method were verified by comparative experiment. Specimens were simultaneously measured using both acoustic experimental device and laser vibrometer. Modal analysis of the specimen were carried out prior to the experiment. This enabled assessment of specimens natural modes and therefore the best impact zone. In total, 10 measurements were performed for each specimen at the same level of degradation. Measured data were then processed and compared. The specimens were repetitively measured after designated number of loading cycles. To conclude, the data assessed using acoustic measurements are comparable in terms of precision, reproducibility and reliability with results from laser vibrometer and the method is suitable for evaluation of material degradation.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Fíla, Ph.D.; Ing. Petr Koudelka, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2012, Proceedings of 11th Youth Symposium on Experimental Solid Mechanics, Brašov, Universitate Transilvania Brasov), p. 263-266), ISBN 978-1-63439-432-1
Anotace:
From a mechanical point of view the most important ability of metal foam is absorption of large amounts of strain energy. This advantage is based on the cellular structure with high ratio of porosity (75-95%). The aim of this study is determination of stress-strain measurement protocol for closed-cell aluminium metal foam Alporas during a compression test using in-house loading device. Changes in structure were observed and strain was calculated based on Digital Image Correlation (DIC) technique. For the assessment of overall compression elastic modulus a new software tool based on the Matlab toolkit was developed.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2012, Journal of Biomechanics, 45 (S1), p. 479-479), ISSN 0021-9290
Anotace:
The single trabecula is basic beam-shaped element of bone structure. To improve knowledge of deformation behaviour of cancellous bone a mechanical tests at the level of single trabecula were performed. Elasto-plastic material properties (Young's modulus and yield point) of single trabecula, assumed as an isotropic material, were assessed from three-point bending tests. Three-point bending test was simulated using Finite Element (FE) analyses and results were compared with experimental ones for determination of suitable material model for single trabecula.
DOI:
10.1016/S0021-9290(12)70480-3
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Kostelecká, M.; Kolísko, J.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2012, 11th Youth Symposium on Experimental Solid Mechanics - book of abstrakt, Brasov, Transilvania University of Brasov), p. 126-127), ISBN 978-606-19-0079-4
Anotace:
The subject of the article is a set of results from series of tests carried out on nine mixture formulas. Asbestos-free plates bonded by hydro-silicate matrix and reinforced by organic fibres were produced from these mixture formulas.
Typ:
Abstrakt ve sborníku z mezinár. konf.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Šepitka, J.; Lukeš, J.
Publikováno:
2012, Chemické listy, 106 (s3), p. 442-445), ISSN 0009-2770
Anotace:
This study aims to investigate the local variations in material properties of single human trabecula in its cross-section. Thin and straight trabeculae were located in a thin slice of trabecular bone extracted from proximal femur. Tensile and three-point bending tests were performed to determine elastic modulae, yield strains and yield stresses. To determine local variations in elastic properties in trabecula's cross-section, modulus mapping (MM) technique was applied in samples' undamaged parts. Using MM the storage and loss modulae are determined. Correlation between average elastic properties in cross-section and properties from micromechanical tests was found for all tested samples.
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Jiroušek, O.
Publikováno:
2011, Engineering Mechanics 2011, Praha, Ústav termomechaniky AV ČR), p. 355-358), ISBN 978-80-87012-33-8
Anotace:
Changes of mechanical properties, namely of modulus of elasticity, often play a role of damage accumulation indicators in the framework of fatigue behaviour of composite materials. In order to improve the reliability of these indicators for identification of material degradation process it is necessary to eliminate the influence of external loading and volume forces associated with thermal expansion of heterogeneous material at various temperatures. Therefore the paper deals with description of experimental assessment of relation between external load and material stiffness and also studies the dependency of material stiffness on temperature. For the monitoring of degradation process ultrasonic measurement was used. Obtained results are discussed with respect to fatigue testing of material and also interpreted from the micromechanical point of view.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Sekyrová, K.; Králík, V.; Němeček, J.
Publikováno:
2011, Chemické listy, 105 (17), p. 729-732), ISSN 0009-2770
Anotace:
The presented paper outlines experimental investigation that is a part of an extensive research plan of study of fatigue properties of aerospace industry grade CRFP laminates. These materials are relatively novel and their long-term behavior and degradation are not yet completely described. Deterioration of this complex material in cyclic loading conditions is to be evaluated by several criteria based on evolution of certain of mechanical properties. Among the criteria is a decrease of modulus of elasticity. In order to reliably detect the changes in this property sensitive three point bending experimental setup was prepared, calibrated and compared to the results of the independent ultrasound method yielding the dynamical modulus of elasticity. Simultaneously, the local mechanical properties were studied by nanoindentation in order to set a reference point for a successive measurement after fatigue tests.
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Němeček, J.
Publikováno:
2011, 10th Youth Symposium on Experimental Solid Mechanics, Chemnitz, Technische Universität Chemnitz), p. 127-128), ISBN 978-1-63439-434-5
Anotace:
Knowledge of trabecular bone behaviour under loading is very important for the bone quality assessment. For investigation of deformation behaviour of trabecular bone a combination of computational and experimental method was used. In this study suitable visco-elasto/plastic material model for single trabeculae was established from numerical simulation of nanoindentation test. The visco-elasto/plastic model with von Mises yield criterion and bilinear isotropic hardening with implicit creep was chosen. Pure elastic material constants can be determined directly from nanoindentation test by Oliver-Pharr method. Other constants determining the plastic and creep behaviour of the model have to be identified indirectly by fitting the load-displacement curve to results from the Finite Element (FE) simulation of nanoindentation test. For statistically significant fitting procedure a multiple indents (10um grid size) with different loading rates, holding times and peak loads were performed.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Jiroušek, J.; doc. Ing. Petr Zlámal, Ph.D.; Kostelecká, M.
Publikováno:
2011, 10th Youth Symposium on Experimental Solid Mechanics, Chemnitz, Technische Universität Chemnitz), p. 71-72), ISBN 978-1-63439-434-5
Anotace:
Article deals with describing of the pre-testing procedure for the uniaxial testing, nanoindentation and finite element modeling of single trabeculae. The first part is focused on the specimen resection, delipidation and fixation in a novel high precision experimental device which enables to measure the strains optically using a high-resolution CCD camera. The second part deals with the development of the volumetric model of the trabecula required for numerical analysis. The last part is dedicated to optimization of polishing procedure used sample surface preparation for nanoindentation. Effect of the grain size, load and duration time of the grinding on final surface roughness was analyzed. Change in the surface roughness was monitored during the preparation process using a confocal microscope. Optimized procedure of sample preparation for micro-mechanical testing with satisfactory results is presented in the paper.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2011
Anotace:
The aim of the research was to investigate the cemented bone-implant interface behavior with emphasis on the imaging techniques suitable to detect early defects in the cement layer. To simulate in vivo conditions a polyethylene acetabular cup was implanted into the human pelvic bone using commercial polymethacrylate bone cement. The implanted cup was then loaded in a custom hip simulator to initiate fatigue crack propagation in the bone cement. The pelvic bone was then scanned repetitively in a micro-tomography device. The reconstructed tomography images showed failure processes that occurred in the cement layer during the first 250,000 cycles. A failure in cemented acetabular implant-debonding, crumbling and smeared cracks -- was found at the bone--cement interface. The use of micro-focus source and large high resolution flat panel detector allowed to reconstruct the micro-structural models suitable for investigation of migration, micromotions and consecutive loosening of the implant.
Typ:
Disertační práce (PhD)

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Jiroušek, O.; doc. Ing. Petr Zlámal, Ph.D.; Pokorný, D.
Publikováno:
2011, Frattura ed Integrita Strutturale, 5 (15), p. 5-13), ISSN 1971-8993
Anotace:
The quality of bonding between the acetabular cup and pelvis bone plays a key role in total hip replacement stability. One of the source of potential loss of the primary stability is the cement layer degradation. The aim of the research was to investigate the cemented bone-implant interface behavior. The main problems (cement layer degradation and bone-cement interface debonding) during physiological loading conditions have been investigated using a custom hip simulator. The experimental setup was designed to allow cyclic loading of the sample of pelvic bone with implanted cemented acetabular component. The process of damage accumulation in cement fixation was monitored by repeated scanning using high resolution micro Computed Tomography. Use of microfocus source and large high resolution flat panel detector allows investigation of structural changes as well as development of full-scale micro-structural models.
DOI:
10.3221/IGF-ESIS.15.01
Typ:
Článek v odborném recenzovaném periodiku

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Jiroušek, O.; Dammer, J.
Publikováno:
2011, Journal of Instrumentation, 1 (C01038), p. 1-5), ISSN 1748-0221
Anotace:
The aim of the research was to investigate the cemented bone-implant interface behavior (cement layer degradation and bone-cement interface debonding) with emphasis on imaging techniques suitable to detect the early defects in the cement layer. To simulate in vivo conditions a human pelvic bone was implanted with polyurethane acetabular cup using commercial acrylic bone cement. The implanted cup was then loaded in a custom hip simulator to initiate fatigue crack propagation in the bone cement. The pelvic bone was then repetitively scanned in a micro-tomography device. Reconstructed tomography images showed failure processes that occurred in the cement layer during the first 250,000 cycles. A failure in cemented acetabular implant - debonding, crumbling and smeared cracks - has been found to be at the bone-cement interface. Use of micro-focus source and high resolution flat panel detector of large physical dimensions allowed to reconstruct the micro-structural models suitable for invest
DOI:
10.1088/1748-0221/6/01/C01038
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Jiroušek, O.; Kostelecká, M.
Publikováno:
2011, 10th Youth Symposium on Experimental Solid Mechanics, Chemnitz, Technische Universität Chemnitz), p. 45-46), ISBN 978-1-63439-434-5
Anotace:
This article is focused on assessment of pore size distribution of a porous material. Improvements of the analysis procedure and of the software tools are presented. For the comparison of reliability of the presented method specimena of various origins were tested. As representatives of biological materials specimena of human and porcine trabecular bone were tested, as representatives of artificial materials synthetic pumice and frit glass were used. Images required for the image analysis were captured using a CCD camera, a high resolution flatbed scanner and a confocal microscope. The different methods used to acquire the images are discussed regarding to the range of the pore size, dimensions of the available specimen and properties of the specimen surface. Used image processing algorithms were tested and improved regarding to the variable shape of the voids present in the material structure.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Tomáš Fíla, Ph.D.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Šperl, M.
Publikováno:
2011, Experimentální analýza napětí 2011, Brno, Brno University of Technology), p. 49-55), ISBN 978-80-214-4275-7
Anotace:
The article deals with assessment of fatigue degradation of C/PPS composites using simple acoustic measurement technique. Changes in natural frequency and attenuation decrement were chosen as indicators of fatigue damage accumulation in the studied composite material. New testing device was developed for acoustic measurement. The experimental setup was designed to chime the specimen by repeatable force of stiff striker exciting a specific natural mode of vibration and to record the acoustic response of the specimen to the impact simultaneously. From the power spectral density of the signal the natural frequency was obtained. Using the same signal, the attenuation decrement was estimated from regression of the its envelope. Presented high precision non-destructive method allows to conclusively measure the natural frequency and its change with a deviation smaller than a few tenths per cents.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Dudíková, M.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Jiroušek, O.
Publikováno:
2011, Chemické listy, 105 (S), p. 790-791), ISSN 0009-2770
Anotace:
Article deals with monitoring and optimization of roughness reduction procedure used for preparation of samples for nanoindentation tests. The aim of the research was to measure roughness reduction effect of various combination of grindstones, polishing time, pressure and speed. Suitable procedure with respect to time and cost for three different materials was proposed. For porous materials trabecular bone was chosen, fibre composite as and asbestos-free plates compact ones. Roughness measurement was performed by contactless method using a confocal microscope. Number of grinding steps was reduced and optimal forces and times of grinding were estimated.
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Jiroušek, O.; Němeček, J.; doc. Ing. Daniel Kytýř, Ph.D.; Kunecký, J.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Doktor, Ph.D.
Publikováno:
2011, Chemické listy, 105 (17), p. 668-671), ISSN 0009-2770
Anotace:
The published mechanical properties of human trabecular bone vary between 1GPa and 15GPa. The cause of this broad discrepancy in results might be in sample preparation, different testing protocols or anisotropy and asymmetry of the micro-samples. The article deals with a comparison between the properties assessed using nanoindentation and properties measured using uniaxial testing of single trabeculae. A novel experimental device was developed for high precision loading control. The strains at the surface of the sample are measured using a high-resolution CCD camera. The strain field is evaluated by precise DIC algorithm applied to whole surface of the loaded sample. The mechanical properties measured on micrometer-sized specimens using both methods (nanoindentation and micro-mechanical testing) are prescribed to FE model. The sample is then loaded according to the experimental procedure. The response of the FE model (stress-strain curve) is compared to results from the tensile test.
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Ing. Tomáš Doktor, Ph.D.; Ing. Jaroslav Valach, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Jiroušek, O.
Publikováno:
2011, Engineering Mechanics 2011, Praha, Ústav termomechaniky AV ČR), p. 115-118), ISBN 978-80-87012-33-8
Anotace:
This paper deals with pore size distribution assessment of trabecular structure of human proximal femur. Two distinct methods for estimation of the pore size distribution histograms are tested, mercury intrusion porosimetry and image analysis. For the image analysis two-dimensional images of crosssections of the specimens were used and the pore size distribution was estimated using a stereological calculation method based on the geometrical properties of an idealized pore. Comparison of the results of both methods is presented. Suitability of both methods for biological materials is discussed regarding to mechanical properties of these materials, characteristics of pores and range of pore sizes present in the structure.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Tomáš Doktor, Ph.D.; Jiroušek, O.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; Jandejsek, I.
Publikováno:
2011, Journal of Instrumentation, 6 (11), p. 1-6), ISSN 1748-0221
Anotace:
X-ray microradiography was used to quantify the strains in loaded human trabecula. Samples of isolated trabeculae from human proximal femur were extracted and glued in a loading machine specially designed for testing of small specimens. The samples were tested in tension and three-point bending until complete fracture occured. Real-time microradiography in conjunction with digital image correlation has been used. The samples were irradiated continuously by X-rays. Radiographs were acquired using 0.25s exposure time with hybrid single-photon counting silicon pixel detector Medipix2. Designed loading device enables for precise control of the applied displacement which is important for the post-yield behavior assessment. Tested experimental setup enables to combine micromechanical testing of the basic building block of trabecular bone with time-lapse X-ray radiography to assess the mechanical properties of single human trabecula and capture the softening curve with sufficient precision.
DOI:
10.1088/1748-0221/6/11/C11007
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Jiroušek, O.; doc. Ing. Daniel Kytýř, Ph.D.; Kunecký, J.; doc. Ing. Petr Zlámal, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Němeček, J.
Publikováno:
2011, Proceedings of the Thirteenth International Conference on Civil, Structural and Environmental Engineering Computiing, Edinburgh, Civil-Comp Press), p. 1-12), ISBN 978-1-905088-46-1, ISSN 1759-3433
Anotace:
The paper presents a comparison between mechanical properties of single human trabeculae obtained by micromechanical testing and those assessed by nanoindentation. Compact uniaxial tension/compression device has been developed for this purpose. The strains at the surface of the sample are measured optically using a high-resolution CCD camera. The strain field is evaluated using image correlation technique. Local micromechanical properties were assessed using nanoindentation. From obtained nanoindentation curves material parameters for elasto-plastic constitutive model with isotropic hardening are identified in a FE simulation of the indentation process. The unknown parameters are identified in a large set of parametric studies in which the response of the model is best-fitted to the experimental curve. Validation of the material model obtained from nanoindentation is presented in simulation of the tensile test of single trabecula.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Jiroušek, O.; doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Kroupa, M.
Publikováno:
2011, Nuclear Instruments and Methods in Physics Research, Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, 633 (Supp. 1), p. S148-S151), ISSN 0168-9002
Anotace:
A micro-radiographic system composed of microfocus X-ray tube and a large flat panel detector has been adapted for imaging complicated internal microstructure of trabecular bone under applied deformation. To capture the deforming microstructure a load was applied in small increments while the sample was tomographically scanned. Reconstruction of the internal structure is provided using backprojection algorithm for equiangular cone-beam projection data. From the reconstructed cross-sections a finite element (FE) model of the microstructure was developed and loaded according to the experiment. Deformation behavior of the FE model was compared to the experimentally determined response of the sample.
DOI:
10.1016/j.nima.2010.06.151
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
Kostelecká, M.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.
Publikováno:
2011, 10th Youth Symposium on Experimental Solid Mechanics, Chemnitz, Technische Universität Chemnitz), p. 61-62), ISBN 978-1-63439-434-5
Anotace:
Results from series of tests carried out on nine mixture formulas are the main data set. Asbestos-free plates bonded by hydro-silicate matrix and reinforced by organic fibers were produced from these mixture formulas. Within the scope of this project, the following activities were carried out: finding out the dimensional and weight characteristics of the plates, bending strength under normal conditions, the influence of frost on bending strength, the influence of putting the plates into hot water on bending strength, the impermeability of plates and measurement of change of length in the direction along and across the fibers.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Ing. Tomáš Doktor, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; Jiroušek, O.
Publikováno:
2010, 9th Youth Symposium on Experimental Solid Mechanics, Trieste, University Trieste), p. 155-157), ISBN 978-88-95940-30-4
Anotace:
Article deals with pore size distribution assessment of porous materials using image analysis. Test samples used in the study were prepared from metal foams and porcine trabecular bone. Two- and threedimensional images were obtained by SEM (scanning electron microscopy) and a high resolution flatbed scanner. For the pore size distribution assessment various methods were used, depending on input data properties (method of obtainig image data) and on pores characteristics (different approach should be used for closed or opened pores). For pore size evaluation using 2D images 25F Association method [5] was used. For verification of the developed algorithms MIP (mercury intrusion porosimetry) measurements were performed, but only in case of trabecular bone samples, because opened pores are necessary for these measurements. Presented algorithms were verified using artificial data structures.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2010, Proceedings of the Seventh IASTED International Conference, Innsbruck, IASTED), p. 67-71), ISBN 978-0-88986-827-4
Anotace:
The paper deals with investigation of the trabecular bone behaviour during compression test. Paper describes loading test of trabecular bone specimen using real-time Computer Tomography scanning and its simulation by Finite Element Method. Model for the Finite Element simulation was obtained using the reconstruction from tomographic projections of the zero deformation state. Deformation states were reconstructed to assess the three-dimensional strain field in the microstructure and compared with results from FE simulations. Assessment of the material model was based on nanoindentation experiment. The nanoindentation test of the trabecular bone sample was performed and the material model was identified from FE simulation of the nanoindentation test.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Tomáš Doktor, Ph.D.; Jiroušek, O.; Zlámal, P.; Pokorný, D.
Publikováno:
2010, 9th Youth Symposium on Experimental Solid Mechanics, Trieste, University Trieste), p. 151-154), ISBN 978-88-95940-30-4
Anotace:
The quality of bonding between the acetabular cup and pelvis bone plays a key role in total hip replacement stability. One of the source of potential loss of the primary stability is the cement layer degradation. The aim of the research was to investigate the cemented bone-implant interface behavior. The main problems (cement layer degradation and bone-cement interface debonding) during physiological loading conditions have been investigated using a custom hip simulator. The experimental setup was designed to allow cyclic loading of the sample of pelvic bone with implanted cemented acetabular component. The process of damage accumulation in cement fixation was monitored by repeated scanning using high resolution micro Computed Tomography. Use of microfocus source and large high resolution flat panel detector allows investigation of structural changes as well as development of full-scale micro-structural models.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Jiroušek, O.; doc. Ing. Petr Zlámal, Ph.D.; Pokorný, D.; Dammer, J.
Publikováno:
2010, Proceedings of 9th International Symposium on Computer methods in Biomechanics and Biomedical Engineering, Valencia, Universidad Politécnica de Valencia), p. 467-471), ISBN 978-0-9562121-3-9
Anotace:
The aim of the research was to investigate the cemented bone-implant interface behavior. The main problems (cement layer degradation and bone-cement interface debonding) during physiological loading conditions have been investigated using a custom hip simulator. The experimental setup was designed to allow cyclic loading of a sample of pelvic bone with implanted cemented acetabular component. The most unfavorable activity (downstairs walking) was simulated in two million cycles with 4Hz frequency. The process of damage accumulation in cement fixation was monitored by repeated scanning using high resolution micro-focus X-ray Computed Tomography. Use of micro-focus source and large high resolution flat panel detector allows investigation of structural changes as well as development of full-scale micro-structural models. 3D high resolution finite element model was reconstructed from the microCT data. The FE model is suitable for prediction of bone-implant interface behaviour.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Jiroušek, O.; prof. Ing. Josef Jíra, CSc.; Hrdlička, O.; Kunecký, J.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jan Vyčichl, Ph.D.; Ing. Tomáš Doktor, Ph.D.
Publikováno:
2010, Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 224 (4), p. 259-267), ISSN 0954-4097
Anotace:
This article deals with finite-element (FE) modelling of the reinforcing effect of the geosynthetic material used in the construction of a ballasted track. Various different designs of geosynthetic material are studied and their reinforcing effects are evaluated in terms of the total settlement reduction. Three-dimensional FE models of the reinforced railway superstructure are compared to a reference FE model with no reinforcement. Each geosynthetic material is modelled respecting its material properties, and the interaction with the ballast material is simulated according to its primary function.
DOI:
10.1243/09544097JRRT319
Typ:
Článek v periodiku excerpovaném SCI Expanded

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Jiroušek, O.; Dammer, J.
Publikováno:
2010, Experimental methods and numerical simulation in engineering sciences, Wuppertal, Bergische Universität Wuppertal), p. 64-65)
Anotace:
Aseptic loosening is one of the most frequent reasons of failure of total hip joint replacement. The aim of the research was to investigate the processes playing role during cement degradation. To determine the degradation caused by cyclic mechanical loading radiological investigation have been used. The main problem of loosening - cement layer degradation and bone-cement interface debonding - have been investigated using a custom hip simulator. Image data from high resolution micro-focus X-ray Computed Tomography were used to reconstruct the complex geometry of the inner structure of the trabecular bone and the interface between the pelvic bone and the implant. Visualisation of trabecular bone structure and cement layer changes provided information about implant instability progress.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
Jiroušek, O.; Jandejsek, I.; doc. Ing. Daniel Kytýř, Ph.D.; Dammer, J.
Publikováno:
2010, Experimental methods and numerical simulation in engineering sciences, Wuppertal, Bergische Universität Wuppertal), p. 66-69)
Anotace:
Digital Volume Correlation method is used to establish the spatial displacement and strain fields in a loaded sample of trabecular bone. The displacements are evaluated at the nodal points of underlaying FE mesh which is used to calculate the strains in each tetrahedral element. Precision of the method is evaluated using artificial image data.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; Horníček, L.; prof. Ing. Josef Jíra, CSc.; Kunecký, J.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jan Vyčichl, Ph.D.
Publikováno:
2009, Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing, Stirling, Civil-Comp Press Ltd), ISBN 978-1-905088-31-7, ISSN 1759-3433
Anotace:
This paper deals with numerical and experimental investigation of ballasted track under cyclic loading. The experimental part deals with measurement of settlements of different track bed designs under repetitive load. The designs are tested in laboratory conditions in a small-scale box filled with ballast material reinforced with different type of geosynthetics. Different thickness of the ballast and subballast layers are tested and results in terms of measured settlements at different locations are compared with FE models.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; Horníček, L.; prof. Ing. Josef Jíra, CSc.; Kunecký, J.; doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jan Vyčichl, Ph.D.
Publikováno:
2009, Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing, Stirling, Civil-Comp Press Ltd), p. 69-69), ISBN 978-1-905088-30-0, ISSN 1759-3433
Anotace:
Paper deals with numerical and experimental investigation of ballasted track under cyclic loading. The experimental part deals with measurement of settlements of different track bed designs under repetitive load. The designs are tested in laboratory conditions in a small-scale box filled with ballast material reinforced with different type of geosynthetics. Different thickness of the ballast and subballast layers are tested and results in terms of measured settlements at different locations are compared with FE models.
Typ:
Abstrakt ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jaroslav Valach, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; prof. Ing. Josef Jíra, CSc.; Frankeová, D.
Publikováno:
2009, 8th Youth Symposium on Experimental Solid Mechanics, Budapešť, Scientific Society of Mechanical Engineers), ISBN 978-963-9058-26-2
Anotace:
Article deals with investigation of physical and mechanical properties of trabecular bone. Non-destructive ultrasonic tests and heat measurements were used to determine the modulus of elasticity of each sample. The velocity of longitudinal ultrasonic waves' propagation depends on the mechanical properties of the material, so the Young's modulus can be obtained from the formula coupling elasticity modulus, wave velocity and bone density.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Vavřík, D.
Publikováno:
2009, Engineering Mechanics 2009 - Book of Extended Abstracts, Praha, Ústav teoretické a aplikované mechaniky AV ČR), p. 166-167), ISBN 978-80-86246-35-2
Anotace:
The paper deals with microstructure investigation of trabecular bone in acetabular region. Trabecular bone microstructure is the main factor of the bone quality and mechanical propertites at macroscopic level. Data from high resolution micro Computed Tomography can be used to reconstruct the complex geometry of the trabecular bone inner structure and interface between bone and implant. The data are usable as for micro-FE modeling as well as for experimental loading tests evaluation.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
prof. Ing. Ondřej Jiroušek, Ph.D.; doc. Ing. Petr Zlámal, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; Kroupa, M.
Publikováno:
2009, Book of Abstracts 11th International Workshop on Radiation Imaging Detectors, Praha, Institute of Experimental and Applied Physics,ČVUT), p. 49-49), ISBN 978-80-01-04378-3
Anotace:
To explore the possibilities of modern X-ray detectors an experimental setup with trabecular bone sample under uni-axial load in special loading device enabling time-lapse tomography was used. The load was applied gradually and after complete tomographic scanning the deformed shape was reconstructed. Collected 3-D images help to study the deformation process of the micro-structure where collapsing of individual trabeculae can be observed and compared to finite element simulations.
Typ:
Abstrakt ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Micka, M.
Publikováno:
2008, Proceedings of Workshop 2008, Praha, Czech Technical University in Prague), p. 428-429), ISBN 978-80-01-04016-4
Anotace:
The most common problem that may happen soon after hip hemiarthroplasty surgery is migration of the head of the acetabulumreplacement. In the operation records of the Orthopaedic Clinic of the 3rd Faculty of Medicine of the Charles University in Prague, the implants that migrated in different ways in the course of several months were retrieved and evaluated. There are two dominant directions of the replacement head migration: median migration into pelvis minor or migration in acetabular labrum direction. The aim of this research work is to analyse the migration of the replacement head in pelvic bone under various types of loading and shapes of acetabulum.
Typ:
Stať ve sborníku Workshop ČVUT

Autoři:
Kunecký, J.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2008, New trends in experimental methods together with advanced numerical modelling, Praha, České vysoké učení technické v Praze, Fakulta dopravní), p. 49-52), ISBN 978-80-86246-34-5
Anotace:
For a good design of protective helmet, a determination of its protective properties is needed, especially relation between construction and acceleration history underwent by head.Usually the helmet is made of polystyrene and e.g. polycarbonate layer. The dynamic response of the system is crucial. In the article, numerical analysis of FE model of sendwich model is decribed, as well as comparison with experiments.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Jan Vyčichl, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.
Publikováno:
2008, The Present and Future of Modern Transport, Praha, Czech Technical University in Prague), p. 333-336), ISBN 978-80-01-04056-0
Anotace:
The article deals with problem of interaction between pelvic bone and cemented acetabular component in light of contact stress distribution in subchondral bone. To solving this problem was creating two EF models. First models is inaccurate implanted in pelvic bone and this model is compared with model with ideal position of acetabular component in the pelvic bone.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Kunecký, J.; doc. Ing. Daniel Kytýř, Ph.D.
Publikováno:
2008, The 7th Youth Symposium on Experimental Solid Mechanics, Wroclaw, Oficyna Wydawnicza Politechniki Wroclawskiej), p. 47-47), ISBN 978-83-7493-386-5
Anotace:
For the research of protective devices, the understanding of the relationship between stiffness of the protective liner, impacting mass and the resulting protective properties is needed. If so, one is able to interpret the physical meaning of the acceleration history of a dummy head embedded in protective helmet during a drop test. The paper is focused on comparison of experimental and numerical approaches in testing of XPS brick (simulating protective liner) with polycarbonate layers of different thicknesses (simulating shell) impacted by metal hammer. Piezoelectric accelerometer is used for the acceleration history measurement.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.; Žák, O.
Publikováno:
2008, New trends in experimental methods together with advanced numerical modelling, Praha, České vysoké učení technické v Praze, Fakulta dopravní), p. 53-54), ISBN 978-80-86246-34-5
Anotace:
Article deals with material properties of spongy bone assessed by optical identification based on surface texture registration.Strains at the specimen surface were measured using high-resolution CCD camera and optical identification method was used to trace their position during deformation. Centres of gravity of the markers are then considered to be vertices of connected triangles for which fields of displacement and strain are calculated. The assessed displacements of the structure of trabecular bone are used to obtain strain-stress diagram.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Žák, O.; doc. Ing. Daniel Kytýř, Ph.D.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2008, The 7th Youth Symposium on Experimental Solid Mechanics, Wroclaw, Oficyna Wydawnicza Politechniki Wroclawskiej), p. 90-90), ISBN 978-83-7493-386-5
Anotace:
Article deals with material properties and failure criteria of trabecular bone assessed by optical identification based on surface texture registration. Trabecular bone samples of cylindrical shape are loaded in Instron 3382 loading machine. Tension and compression tests are recorded by high resolution CCD camera. Captured images are processed using Visualization ToolKit (VTK). The map is reduced to control points like ends, centres and crossing. Allocation of control points at filtered structure in every image gives information about deformation of tested sample.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Ing. Jan Vyčichl, Ph.D.; doc. Ing. Jitka Jírová, CSc.; prof. Ing. Josef Jíra, CSc.
Publikováno:
2008, Proceedings of the Sixth International Conference on Engineering Computational Technology, Stirling, Civil-Comp Press Ltd), p. 160-160), ISBN 978-1-905088-26-3
Anotace:
The paper deals with numerical analysis of hip joint surgery that effects changes of stress field in acetabulum area. Pelvic bone geometry was obtained from computer tomography by automatic generation. Material properties of trabecular bone were obtained from experiments by the optical identification method. The numerical analysis compares shapes and peak values of stress field in the acetabulum area and the cement layer. Ultimate values of first principal stress, third principal stress and total displacements were used as reference magnitudes.
DOI:
10.4203/ccp.89.160
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.; Ing. Jan Vyčichl, Ph.D.
Publikováno:
2007, From Horse-drawn Railway to High-speed Transportation Systems, Praha, Czech Technical University in Prague), p. 143-146), ISBN 978-80-01-03699-0
Anotace:
The paper deals with numerical analysis of hip joint surgery effect to changes of acetabulum stress field and implant migration in acetabulum area. Pelvic bone geometry was obtained from computer tomography by semi-automatic generation. There are two main input parameters for the stress analysis. CE angle detailing the shape of acetabulum. Direction of loading substitute the femoral replacement. The numerical analysis compare shapes and peak values of stress field in acetabulum area. Ultimate values of first principal stress, third principal stress and total displacements were used as reference magnitudes. This ultimate values predict probable migration process. Numerical analysis results correspond well with after surgery clinical reports.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
Ing. Jan Vyčichl, Ph.D.; doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.; prof. Ing. Josef Jíra, CSc.
Publikováno:
2007, Engineering Mechanics 2007, Praha, Ústav termomechaniky AV ČR), p. 321-322), ISBN 978-80-87012-06-2
Anotace:
The article deals with contact stress analysis of pelvic bone after implantation of cemented acetabular component with imperfections of cemented layer. 3D high resolution FE model of pelvic bone was created from the sequence of CT-slices. Boolean operations were used for inserting the spherical cemented component. Cemented component was eccentrically inserted into the pelvic bone and that created imperfection as non-uniform cement layer. Two contacts were defined in the FE model. The first contact is defined between the cement layer and the pelvic bone and the second one is between the cement layer and the polyethylene cup. The model was loaded by quasi-static joint forces, representing the maximum value of stance phase of gait [Bergmann et al., 2001]. The FE model was used to ascertain the contact stress conditions in the underlying subchondral bone.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.; Ing. Jan Vyčichl, Ph.D.; prof. Ing. Josef Jíra, CSc.
Publikováno:
2007, Engineering Mechanics 2007, Praha, Ústav termomechaniky AV ČR), p. 151-152), ISBN 978-80-87012-06-2
Anotace:
In general all orthopaedic operations may cause the change of muscle balance. This dysbalance various not only range of movement but also the loading vector during the movement. In case of hemiarthroplasty when the new joint is created by femoral replacement and intact acetabulum could be the dysbalance very dangerous. Migration of the implant head after hemiarthoplasty is the problem which observed to nearly at all patients. Muscle dysbalance and shape of acetabulum are the two main problems solved by numerical analysis of hip joint FE model.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.; prof. Ing. Josef Jíra, CSc.; Micka, M.
Publikováno:
2007, Finite Element Modelling in Biomechanics and Mechanobiology, Dublin, Trinity Centre for Bioengineering), p. 173-174), ISBN 0-9548583-1-X
Anotace:
Hip joint replacement is the only way for millions of patients to recover their mobility. Hemiarthroplasty is a surgical procedure which replaces one half of the joint with an artificial surface and leaves the other part in its natural (pre-operative) state, which article deals with. There are volumetric models used for analysis. Pelvic bone geometry was obtained from computer tomography using semi-automatic generation. Model was solved in various loading directions with loading direction from -45° to 10°. The stress and displacement fields show that primary migration of the replacement head follows the direction of loading.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Donati, M.; Stagni, R.
Publikováno:
2006, 2st Students' Scientific Conference of Biomechanics, Wroclaw, Oficyna Wydawnica Politechniki Wroclawskiej), p. 93-94), ISSN 1732-0240
Anotace:
The ultrasound technique, as other modern medical scanning techniques, is used for the development of geometric models of human organs. The combination of both ultrasound and motion capture seems to be a promising reconstruction system. This article proposes a calibration method of the aforementioned system to obtain the transformation matrix between its components, which is necessary for obtaining a correct reconstruction.
Typ:
Stať ve sborníku z mezinár. konf.

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; Kunecký, J.; prof. Ing. Ondřej Jiroušek, Ph.D.; Zelenková, K.; doc. Ing. Jitka Jírová, CSc.
Publikováno:
2006, 14th ANSYS Users´Meeting, Brno, SVS FEM), p. 21-24), ISBN 80-239-7764-4
Anotace:
Article deals with cancellous bone material properties determination comparing to results of FE model based on CT scanning. Speciments are gained from fresh pig's heads of femur. Speciments are drilled in dorection of main loading and in other two normal direction. There were Instron 3382 loading machine for tension test and Nicon camera for optical dentification method at experiment set up. Results of those experiments are displayed on standard stress-strain graph and Young modulus is determined. Young modulus results are suited for biomechanicel FE models and the experimental method could be used for human testing.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.; Micka, M.; prof. Ing. Josef Jíra, CSc.
Publikováno:
2006, Engineering Mechanics 2006, Praha, Ústav teoretické a aplikované mechaniky AV ČR), p. 212-213), ISBN 80-86246-27-2
Anotace:
Migration of the implant head after hemiarthoplasty is a problem which appertain to nearly all patients. Article deals with development and utilization of parametrical FE model of the hip joint for numerical analysis of implant head migration. There are two main input parameters for the stress analysis. CE angle representing the shape of acetabulum and direction of the femoral replacement loading. To assess the influence of selected parameters on the implant migration and to enable easy comparison to patients X-Ray scanning, the analysis was carried out as axially symmetric 2D and 3D contact problem. Ultimate values of first principal stress, third principal stress and sum of displacements were used as a reference magnitude.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.; prof. Ing. Ondřej Jiroušek, Ph.D.
Publikováno:
2005, Engineering Mechanics 2005, Praha, Ústav termomechaniky AV ČR), p. 193-194), ISBN 80-85918-93-5
Anotace:
Methods for fully-automatic generation of FE model are shortly discussed in the paper. There are two basic principles of reconstruction, voxel-based and volume-based methods. The voxel model generation is based on checking all pixel values and defining voxels by means of the selected pixels. Development of the volume model is usually divided into three procedures: tissue segmentation, contour model definition and surface area definition. Three FE models of femur were considered: (i) cortical model (ii) spongio-cortical model with homogeneous cancellous tissue (iii) spongio-cortical model with heterogeneous cancellous tissue. These models were compared in a simple stress analysis. FE analyses results of all these models are compared with results of experiments conducted using fresh cadaver femur and strain-gauge measurement.
Typ:
Stať ve sborníku z mezinár. konf. cizojazyčně

Autoři:
doc. Ing. Daniel Kytýř, Ph.D.; doc. Ing. Jitka Jírová, CSc.; Micka, M.
Publikováno:
2005, 13. ANSYS User´s Meeting, Brno, SVS FEM), p. 333-338), ISBN 80-239-5675-2
Anotace:
Článek popisuje využití parametrického modelu pro analýzu migrace hlavice kloubní náhrady objevující se u všech pacientů po implantaci cervikokapitálni endoprotézy. Je zde provedena analýza napětí v pánvi v závislosti na změnách velikosti střísky kyčelní jamky a směru zatížení. Pro provedení analýzy s parametrickými vstupy bylo použito načítání parametrů v cyklech definovaných přímo se zápisem výsledků do souboru a také využitím v ANSYSu odsažené pravděpodobnostní analýzy. Problém je řešen jako osově symetrická rovinná kontaktní úloha.
Typ:
Stať ve sborníku z lokální konf. česky