National Repository of Grey Literature 44 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
In-situ compression test of artificial bone foams in controlled environment using X-Ray micro-computed tomography
Glinz, J. ; Kytýř, Daniel ; Fíla, Tomáš ; Šleichrt, Jan ; Schrempf, A. ; Fürst, D. ; Kastner, J. ; Senck, S.
X-RayMicro-computed tomography (XCT) has already become a standard method for investigations of bone and bone replacement materials in medical research. For an in-depth characterization of histomorphometric features, digital volume data acquired by XCT can be processed and visualized three dimensionally to determine parameters such as bone volume fraction, cortical thickness and porosity. In this study, we investigated specimens of artificial bone foams, developed by the research group for surgical simulators at the UAS Linz, which are used to mimic the haptic feedback of physiologic and pathologic bone for more realistic surgery training. Similar specimen of artificial bone foam in a dry state have already been characterized precisely in [1]. However, since physiological bone typically is in a wet state, the main purpose of this study was the investigation of the influence of environmental conditions on artificial bone foams of varying composition. Thus, specimens with two kinds of mineral filler material as well as different amounts of foaming agent were prepared and tested in an in-situ loading stage developed by the ITAM CAS. In this stage, specimens can be immersed in liquid and tested under temperature-controlled conditions. Consequently, a total amount of 12 specimens was subjected to compression loading; half of them immersed in water at 36.5◦C and half in dry condition. Results showed that there is no significant influence of liquid immersion to the compression outcome. However, foams with less amount of foaming agent appeared to have smaller pores resulting in higher compression strength. Different types of mineral filler material also showed no significant influence on compression strength. Furthermore, a time-lapse in-situ investigation with XCT scans in-between the load steps was performed for one specimen immersed in water to investigate behavior during load. Despite of the open porous morphology of the foam, water immersed only partially into the foam, leaving pores closer to the center unfilled. Concluding, the usage of the artificial bone foams investigated is despite their physiologically wet condition also valid in a dry state since environmental differences are nonessential for their mechanical properties.
Deformation response of polydimethylsiloxane substrates subjected to uniaxial quasi-static loading
Martino, F. ; Vinařský, V. ; Šleichrt, Jan ; Kytýř, Daniel
To investigate cellular response of cardiomyocytes to substrate mechanics, biocompatible material with stiffness in physiological range is needed. Polydimethylsiloxane (PDMS) based material Sylgard 184 is used for construction of microfluidic organ on chip devices for cell culture due to ease of device preparation, bonding, and possibility of surface functionalization. However it has stiffness orders of magnitude out of physiological range. Therefore we adapted recently published protocol [1] aiming to prepare substrates which offer stiffness in physiological range 5−100 kPa using various mixtures of Sylgard 527 and Sylagard 184. The inhouse developed loading device with the loading capacity of 3 kN with 1 μm position tracking accuracy and sub-micron position sensitivity was employed for this experimental campaign. The experiments were controlled by the proprietary LinuxCNC software running on the real-time kernel [2]. All batches of the samples were subjected to monotonic compression loading. During the displacement driven experiment with loading rate 10 μm · s−1 the samples with diameter 12.00 ± 0.05mm and height 14 − 16mm were compressed to minimally 50% deformation. Because of high differences in the samples stiffness various load cells with nominal capacity 50N, 10N, and 1N was used for the most reliable force logging. Material properties for all batches were derived from a set of 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 and elastic moduli are estimated as secant up to 10% deformation.
Acta Polytechnica CTU Proceedings
Kytýř, Daniel ; Major, Z. ; Doktor, Tomáš
The 16th symposium continues both the long tradition of this conference series and introduces novel elements. The YSESM 2018 symposium provides a forum for young researchers and engineers, students and PhD students dealing with subjects of experimental mechanics. In addition, the combination of the experimental mechanics with modern numerical methods will be a new focus of this 16th Symposium.
Multi-channel control system for in-situ laboratory loading devices
Rada, Václav ; Fíla, Tomáš ; Zlámal, Petr ; Kytýř, Daniel ; Koudelka_ml., P.
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.
Instrumentation of four-point bending test during 4D computed tomography
Kytýř, Daniel ; Fíla, Tomáš ; Koudelka_ml., Petr ; Kumpová, Ivana ; Vopálenský, Michal ; Vavro, Leona ; Vavro, Martin
High-resolution time-lapse micro-focus X-ray computed tomography is an effective method for investigation of deformation processes on volumetric basis including fracture propagation characteristics of non-homogeneous materials subjected to mechanical loading. This experimental method requires implementation of specifically designed loading devices to X-ray imaging setups. In case of bending tests, our background research showed that no commercial solution allowing for reliable investigation of so called fracture process zone in quasi-brittle materials is currently available. Thus, this paper is focused on description of recently developed in-situ four-point bending loading device and its instrumentation for testing of quasi-brittle materials. Proof of concept together with the pilot experiments were successfully performed in a CT scanner TORATOM. Based on results of the pilot experiments, we demonstrate that crack development and propagation in a quasi-brittle material can be successfully observed in 3D using high resolution 4D micro-CT under loading.
Influence of printing and loading direction on mechanical response in 3D printed models of human trabecular bone
Doktor, Tomáš ; Kumpová, Ivana ; Wroński, S. ; Śniechowski, M. ; Tarasiuk, J. ; Forte, G. ; Kytýř, Daniel
The paper deals with investigation on directional variations of mechanical response in 3D printed models of human trabecular bone. Sample of trabecular bone tissue was resected from human donor and 3D model was obtained by X-ray computed tomography. Then a series of cubical samples was prepared by additive manufacturing technique and tested by uniaxial compression loading mode. Mechanical response was compared in nine different combinations of direction of 3D printing and loading direction. The results show neglectible influence on the deformation response in elastic region (stiffness) and significant changes of the behaviour in plastic region (stress and strain at yield point, strain at full collapse).
Basic biomechanical characterization of polyurethane based artificial cancellous structures
Šleichrt, Jan ; Kytýř, Daniel ; Pithartová, Kateřina ; Senck, S. ; Fürst, D. ; Schrempf, A.
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.
Utilization of image and signal processing techniques for assessment of built heritage condition
Koudelka_ml., Petr ; Koudelková, Veronika ; Doktor, Tomáš ; Kumpová, Ivana ; Kytýř, Daniel ; Valach, Jaroslav
Historical buildings represent invaluable heritage from the past and therefore their protection is a very important task. Assessment of their condition must not cause damage accumulation thus the least possible volume removed from the structure is essential. As many historical buildings in the Czech Republic are built using sandstone that can be considered as a typical heterogeneous system, statistical signal processing is a promising approach for determination of the representative volume element (RVE) dimensions. Such calculations can be carried out on the domain of logical arrays representing binary images of the materials microstructure. This paper deals with processing of image data obtained using SEM-BSE and high resolution flatbed scanner for determination of RVE dimensions. Advanced image processing techniques are employed and results from calculation using grayscale data are presented and compared with results calculated on the basis of color input images.
Acta Polytechnica CTU Proceedings 7
Kytýř, Daniel ; Zlámal, Petr
The International Symposium on Experimental Methods and Numerical Simulation in Engineering Sciences continues the tradition of the Czech-German bilateral symposium founded by prof. Karl-Hans Laermann and prof. Stanislav Holý in 1985. In the following years, the symposium was extensively developed by prof. Josef Jíra. The symposium shall bring together mainly young scientists who are actively involved in experimental solid mechanics, theoretically and practically, in order to exchange experience, to report on the present state-of-art as well as on running research projects, to discuss due questions and problems and to promote the co-operation between individuals as well as between institutions. Therefore in the symposium discussions will play a highly significant role.
Semi-automated assessment of micromechanical properties of the metal foams on the cell-wall level
Krčmářová, Nela ; Šleichrt, J. ; Doktor, T. ; Kytýř, Daniel ; Jiroušek, O.
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 24.465 HV1.019 and average Vickers hardness of ALCORAS was 36.585 HV1.019..

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