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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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Study of Influence of Strain Rate and Temperature on Formability of Titanium Alloys
Šlais, Miroslav ; Spišák, Emil (referee) ; prof. Ing. Milan Turňa, Ph.D., EWE, IWE (referee) ; Forejt, Milan (advisor)
The PhD thesis deals with the influence of temperature and strain rate on the mechanical behaviour of the Ti-6Al-4V titanium alloy. After verification tests under static loading conditions, the samples were deformed at high strain rates and elevated temperatures, using device for Hopkinson pressure bar test. The result is dependence of stress and strain rate on strain in the temperature range of 20 to 500°C. The deformed shape of specimen from the Taylor anvil test is compared with the results of the simulation in the Ansys – LS Dyna software. The parameters of Johnson-Cook equation were determined from these experiments. Also, the influence of loading conditions on the microstructure was studied. Both optical and scanning electron microscopes were used for the observations. During the research, some adjustments to the experimental devices were made in order to suppress the high-frequency components and noise in the recorded pulses. A functional tensile test adapter for the Hopkinson test was developed; it is registered under No. 2007/008 at the Technology Transfer Office of BUT.
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Manufacturing of composite for ballistic purposes
Majchrák, Aleš ; Gregor, Lukáš (referee) ; Zouhar, Jan (advisor)
The master thesis deals with high-strength fiber composites with a focus on their use in ballistic protection. It’s aim is to manufacture of composite panels and to test their properties. The theoretical part discusses the fiber composites area and ballistic protection. The experimental part consists of the choice of the suitable technologies for the production of the panels of the given materials, the production process itself, the preparation of the samples and their testing. Materials used for production were Twaron from aramides group and Endumax from the UHMWPE group of materials. Panels had three different matrices – epoxide resine, thermoset matrix and thermoplastic matrix. Manufacturing methods consisted of vacuum infusion, hot press and autoclave. Tensile and bending tests were examined, so as ballistic tests on the Taylor anvil test device and in ballistic laboratory. The results confirmed the high strenght of the material and its ability to absorb kinetic energy. During ballistic tests, the amount of material resistence against the ballistic impact was observed with regard to the NIJ 0101.06 standard and the limit thickness within tested samples was defined.
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Study of Influence of Strain Rate and Temperature on Formability of Titanium Alloys
Šlais, Miroslav ; Spišák, Emil (referee) ; prof. Ing. Milan Turňa, Ph.D., EWE, IWE (referee) ; Forejt, Milan (advisor)
The PhD thesis deals with the influence of temperature and strain rate on the mechanical behaviour of the Ti-6Al-4V titanium alloy. After verification tests under static loading conditions, the samples were deformed at high strain rates and elevated temperatures, using device for Hopkinson pressure bar test. The result is dependence of stress and strain rate on strain in the temperature range of 20 to 500°C. The deformed shape of specimen from the Taylor anvil test is compared with the results of the simulation in the Ansys – LS Dyna software. The parameters of Johnson-Cook equation were determined from these experiments. Also, the influence of loading conditions on the microstructure was studied. Both optical and scanning electron microscopes were used for the observations. During the research, some adjustments to the experimental devices were made in order to suppress the high-frequency components and noise in the recorded pulses. A functional tensile test adapter for the Hopkinson test was developed; it is registered under No. 2007/008 at the Technology Transfer Office of BUT.
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