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National Repository of Grey Literature 2 records found  Search took 0.00 seconds. 
Mechanical behaviour of Strenx steel at high strain rates
 Basler, Matěj ; Forejt, Milan (referee) ; Jopek, Miroslav (advisor)
The thesis is focused on the description of the behaviour of high-strength steel Strenx under quasi-static and dynamic conditions with emphasis on the influence of anisotropy. A compression test was used as a low strain rate test with specimens formed from rolled sheet in the 0, 45 and 90 degree directions relative to the rolling direction. The behaviour of the steel at high strain rates was described using the Taylor impact test, again with specimens oriented with respect to the rolling direction. The contour of the deformed specimens from the dynamic test was measured by image analysis and the dynamic yield strength of Strenx steel was calculated. The test results were compared between the loaded directions and the anisotropic behaviour of the material was described. From the values obtained from the performed experiments, the material constants for Johnson-Cook's material model were determined and its reliability was compared with both quasi-static and dynamic test results. The calculated values using the material model achieved satisfactory accuracy and the developed material model can be considered reliable.
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Optimization of infill selection with an emphasis on maximum dynamic resistance
 Konvalina, Michal ; Svoboda, Petr (referee) ; Jopek, Miroslav (advisor)
The thesis deals with the study of the effect of different wall thicknesses of 3D printed infill patterns at constant cross-sectional area on their final properties under static and dynamic loading. Based on literature study, two experimental methods are chosen. The quasi-static test and the Taylor anvil test. For the experiment, square and hexagonal grid specimens are printed using FDM technology from PLA material. Quasi-static test is used to measure the static properties such as maximum compressive strength, yield stress, modulus of elasticity and to derive material model of Johnson-Cook. The dynamic impact test TAT is used to evaluate different types of patterns at high impact velocities. In ANSYS, the specimens that resisted the highest impact velocities in TAT are simulated and strain rate sensitivity parameter is optimized for the specific velocity. The highest dynamic resistance was achieved by a square infill pattern with wall thickness of 0,4 mm at an impact velocity of 37 ms-1.
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