National Repository of Grey Literature 60 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
High strain-rate compressive testing of filling materials for inter-penetrating phase composites
Doktor, T. ; Fíla, T. ; Zlámal, Petr ; Kytýř, Daniel ; Jiroušek, O.
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.
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..
Book of abstracts. International symposium on experimental methods and numerical simulation in engineering sciences 2016
Kytýř, Daniel ; Zlámal, Petr ; Jiroušek, O.
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.
Mechanical properties of 3D auxetic structures produced by additive manufacturing
Jiroušek, O. ; Koudelka_ml., Petr ; Fíla, Tomáš
Three distinct auxetic structures were produced by direct 3D printing based on parametric CAD models. Mechanical properties of the structures were established by static compression tests where strain fields on the surface of the specimens was measured by non-contact optical method. Parametric finite element (FE) model of each structure was then subjected to a virtual compression test and mechanical properties obtained from the FE simulations were compared to the experimentally assessed values. After verification, the parametric FE models were used to establish relationships between various design parameters (porosity, rod thickness, internal angles, etc.) and overall mechanical properties (particularly stiffness).
On the X-ray micro-tomography measurements of biological samples under compressive loading
Fíla, T. ; Kumpová, Ivana ; Zlámal, Petr ; Kytýř, Daniel ; Koudelka_ml., Petr ; Doktor, Tomáš ; Jiroušek, Ondřej
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.
Investigation of deformation behaviour of aluminium foam under high-strain rate loading and comparison with conventional energy absorbing material
Zlámal, P. ; Fíla, Tomáš ; Jiroušek, O. ; Králík, V.
The aim of this study is proper description of stress-strain behaviour of the metal foam structure Alporas under high-strain rate loading. Stress-strain response of Alporas specimens is measured during an impact test using a drop tower experiment. Strain of the specimens is evaluated by two independent approaches: i) double numerical integration of acceleration data and ii) digital image correlation technique. Thus, experimental setup is equipped with triaxial accelerometer and high speed camera. Resulting stress-strain curves are compared with behaviour of polystyrene material samples (polystyrene material is commonly used as a shock absorber) obtained from the same testing procedure and with stress-strain function determined from Alporas quasi-static compression testing.
Experimental evaluation of strain fields in the vicinity of V-notch in ductile metal
Jandejsek, Ivan ; Jiroušek, Ondřej ; Vavřík, Daniel
This work deals with the experimental measurement of full-field displacements and strains evaluation on the surface of flat high-ductile aluminum specimens in the vicinity of the V-notch during loading. Two different specimen geometry configurations, boundary and middle notch, are tested and compared in terms of deformation constraint. The enhanced Digital Image Correlation method in conjunction with strain gage measurement is employed for the precise full-field strain evaluation.
Experimental study on size effect in quasi-static compressive behavior of closed-cell aluminium foams
Koudelka_ml., Petr ; Zlámal, Petr ; Kytýř, Daniel ; Fíla, Tomáš ; Jiroušek, Ondřej
The size effect in compressive deformation behaviour of commercially available aluminium closed-cell foam Alporas was studied under quasi-static loading conditions with different boundary conditions. Dimensions of the specimen’s cross-section were selected to match those of sufficient representative volume element (RVE) obtained by spectral analysis of the macroscopic structure whereas different heights of specimens were tested to examine size-scaling factor. Mechanical properties were derived from three different data sources: I) using data captured by load-cell, II) by digital image correlation (DIC) of displacement of contact faces, III) by DIC of the specimen’s structure. Mechanical testing was performed in custom-built loading device as well as in Instron 4301 electromechanical testing system with custom computer control software.
Comparative study on numerical and analytical assessment of elastic properties of metal foams
Koudelka_ml., Petr ; Jiroušek, Ondřej ; Doktor, Tomáš ; Zlámal, Petr ; Fíla, Tomáš
Recently, titanium metal foams are being considered as a suitable replacement for substituting trabecular bone microstructure especially for their similar pore distribution. The most common methods for determination of compressive effective elastic properties of such materials involve different approaches based on finite element analysis (FEA) of their microstructure. The internal geometry is usually modeled by two different methods - directly on the basis of a series of CT scans or using one of discretization schemes. However, all these techniques require highly specialized hardware, software and significant amount of computational time. In this paper, the effective elastic properties of the metal foam are instead obtained by analytical modulus-porosity relations and results are compared with previous FE based analysis.
Design and use of novel compression device for microtomography under applied load
Fíla, Tomáš ; Zlámal, Petr ; Koudelka_ml., Petr ; Jiroušek, Ondřej ; Doktor, Tomáš ; Kytýř, Daniel
This paper deals with modification and usage of custom-designed compression device, that allows real time X-ray tomography scanning of specimen under applied pressure. In this case microtomography is used to obtain data required to determine specimens morphology and to develop 3D material model (especially for cellular materials such as bones, metal foams and quasi-brittle materials or particle composites such as concrete or cementitious composites). Important design changes were made in the existing device frame to increase its load capabilities, stiffness and to accomodate a larger specimen. Finally device displacement measurements were conducted and calibration experiment was carried out.

National Repository of Grey Literature : 60 records found   1 - 10nextend  jump to record:
See also: similar author names
1 Jiroušek, O.
28 Jiroušek, Ondřej