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THERMAL AND MECHANICAL PROPERTIES OF TUNGSTEN COMPACTS PREPARED BY SPS
Nevrlá, Barbara ; Vilémová, Monika ; Matějíček, Jiří
Tungsten is a promising candidate material for use in the tokamak device aimed at future production of nuclear fusion power. Here, tungsten is intended for the application in the part called first wall,with the function of a heat-resistant plasma facing armor.In the present work,two fractions of tungsten powder (2 and 4 μm) were used to prepare two consolidated samples by spark plasma sintering (SPS),using a combination of pressure,temperature and electric power.This sintering technique produces samples of near theoretical density which is positive for the application.Tungsten compacts were then studied to determine some basic thermal and mechanical properties, namely thermal conductivity using the laser-flash method and hardness by Vickers test.The measurements were focused on thermal conductivity of the compacts because high thermal conductivity is crucial for the material of tokamak first wall,loaded by high heat flux from the plasma.High hardness is desirable for good resistance
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Semiautomatic Surface Reflectance Measurement for Monitoring of Material Weathering
Kocour, Vladimír ; Valach, Jaroslav
We present a device for measurement of surface reflectance in dependence on incidence angle and reflectance angle. This measurement enables us to quantitatively determine how much the surface is glossy or matt. The device is programmable, which enables us to choose non-equidistant steps of angles, and study special situations more in detail. It can be used for monitoring of material weathering or other types of degradation as weathering usually causes that the surface becomes more matt.
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Determination of drift distortion in SEM micrographs acquired at different magnifications and acquisition times
Petráňová, Veronika ; Koudelka_ml., Petr ; Valach, Jaroslav
In the experimental mechanics wide variety of optical methods including measurement of deformation at reduced length scales using combination of computer vision and scanning electron microscopy (SEM) have been recently applied. One of suitable methods for in-plane measurement of displacements and deformations in the micrographs obtained by SEM is the 2D digital image correlation. In contrast to images obtained in visible spectrum by classical optical devices temporally-varying distortions known as drift distortion are present in the SEM micrographs. These distortions are caused by positional errors of electron beam during scanning process. Magnitude of this effect decreases with higher conductivity of the sample and is also influenced by magnification and scanning time. For this purpose measurement of distortion was performed on a series of micrographs of conductive samples acquired at different magnifications and acquisition times. Surface of each sample was covered with liquid silver to ensure adequate contrast pattern necessary for determination of distortion’s magnitude and distortion magnitudes were assessed.
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On the modelling of compressive response of closed-cell aluminium foams under high-strain rate loading
Koudelka_ml., P. ; Zlámal, Petr ; Fíla, Tomáš
Porous metals and particularly aluminium foams are attractive materials for crash applications where constructional elements have to be able to absorb considerable amount of deformation energy while having as low weight as possible. Compressive behaviour for medium impact velocities can be experimentally assessed from a series of droptower impact tests instrumented with accelerometer and high-speed camera. However to predict such behaviour a proper modelling scheme has to be developed. In this paper droptower impact tests of Alporas aluminium foam were used for development of a material model for explicit finite element simulations of high-strain rate deformation process using LS-DYNA simulation environment. From the material models available low density foam, Fu-Chang’s foam, crushable foam and modified crushable foam models were selected for simulations using smoothed-particle hydrodynamics and solid formulations respectively. Numerical simulations were performed in order to assess constitutive parameters of these models and identify material model describing deformation behaviour of Alporas with the best accuracy.
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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.
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Proceedings of 13th Youth symposium on experimental solid mechanics
Kytýř, Daniel ; Zlámal, Petr ; Růžička, M.
Proceedings of the 13th Youth Symposium on Experimental Solid Mechanics held in Decin, Czech Republic. The symposium is focused on experimental methods and numerical simulation in engineering sciences. The proceedings capture the trends in development of experimental methods in mechanics of structures and materials (regardless to the material and structure type, covering fields from civil and mechanical engineering to biomechanics) as well as deployment of particular solution for measurement and automation systems for evaluation of experimental data.
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