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Pore Size Distribution of Human Trabecular Bone - Comparison of Intrusion Measurements with Image Analysis
Doktor, Tomáš ; Valach, Jaroslav ; Kytýř, Daniel ; Jiroušek, Ondřej
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.
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Assessment of C/PPS composites degradation indicators using acoustic measurement
Kytýř, Daniel ; Valach, Jaroslav ; Doktor, Tomáš ; Jiroušek, Ondřej
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.
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Deformační analýza trabekulární kosti za použití mikrotomografie v čase
Jiroušek, Ondřej ; Zlámal, Petr ; Kytýř, Daniel ; Kroupa, M.
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.
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Kalibrace konstitutivního modelu trabekulární kosti na základě nanoindentace
Zlámal, Petr ; Jiroušek, Ondřej ; Němeček, J.
The paper deals with investigation of a trabecular bone behaviour during nanoindentation test. Behavior of trabecular bone is investigated using real nanoindentation and finite element simulation. Two different plasticity criteria for material model of trabeculae are tested, namely von Mises and Drucker-Prager. Von Mises criterium is extended bilinear isotropic hardening. Constants needed for numerical material model are obtained from fitting procedure of a experimetal load-displacement curve.
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Zjišťování mikrostrukturálních vlastností acetabula lidské pánve pomocí mikro-CT
Kytýř, Daniel ; Jiroušek, Ondřej ; Vavřík, Daniel
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.
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MKP analýza únosnosti vícevrstvého železničního podloží
Jiroušek, Ondřej ; Kunecký, Jiří ; Jíra, J. ; Horníček, L.
Numerical investigation of bearing capacity of railway substructure using finite element method and laboratory experiments is presented. A set of parametric FE models is built and unified approach for assessment of bearing capacity of the construction presented. Results are presented in terms of design graphs, where for every type of substructure design resulting bearing capacity is evaluated. Presented methodology is easily extensible for reinforcing effects of layer inclusion, geogrid placement or use of cemented layers.
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MKP analýza poranění hlavy během dopravní nehody
Kunecký, Jiří ; Jiroušek, Ondřej
The work is based on the Visible Human Project. Impact acceleration history is taken from MADYMO accident simulation. For the solution LS-DYNA software is used.The paper shows possibility to use detailed finite element model of human head to predict or describe injuries during mechanical loading as in this case of a traffic accident. The possibility of using combination of rigid body modeling of the whole situation together with detailed FE model of the region of interest is highly advantageous. However, the model should be verified in large number of reconstructions.
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Zjišťování materiálových vlastností houbovité kostní tkáně optickou metodou
Kytýř, Daniel ; Jiroušek, Ondřej ; Žák, Ondřej
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.
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