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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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Tube Flaring Technology under Dynamic Conditions
Macháček, David ; Forejt, Milan (referee) ; Peterková, Eva (advisor)
This master thesis is divided into three main parts. In first part is more closely described the method of tube flaring. Tube flaring was chosen for analysis of biaxial stress, in this thesis particularly in the presence of high strain rate. In the second part is more closely described influence of high strain rate on the forming process. There is described influence of high strain rate on behavior of the material, hardening, change of quasi-static yield strength to the dynamic yield strength, influence of high strain rate on the microstructure and more. During the description of these processes there is effort to describe the cause of these changes as well. For this task was used domestic and foreign literature, as well as peer review papers whose authors study intensively this problematic. Besides all of the above there is also derived the velocity of elastic and plastic wave. In the end is evaluated experiment, in which was done tube flaring, which is part of this master thesis. Results from the 3D optical system ARAMIS are interpreted with the help of Microsoft Excel, where the chosen results were used as the input to the equations modified for the dynamic loading.
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Dynamic Tensile Test – Material Parameters Determination
Sismilich, Vladimír ; Hadraba, Hynek (referee) ; Severa, Martin (advisor)
The purpose of the work is to summarise todays existing methods of testing materials at high strain rates and techniques of evaluation acquired experimental data. There are shown the most important dynamic materials characteristics, by which is able to describe material behaviour at high strain rates. Dynamic tensile test on Eurofer’97 steel at loading rate 1m/s was conducted experimental data were analysed and evaluated. In the evaluation The most important strain and stress properties of this steel were determined.
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Influence of strain rate on stress-strain dependencies of aortic tissues
Slažanský, Martin ; Fuis, Vladimír (referee) ; Burša, Jiří (advisor)
The thesis deals with the influence of strain rate on stress-strain dependencies of aortic tissues to estimate the error of hyperelastic models, which are neglecting the viscoelastic effects that are typical for soft biological tissues. It was found by the experiment and the subsequent evaluation that in the range of the strain rate from 0,167 to 5,000 mm/s the influence of strain rate on stress-strain dependencies is negligible. The deviation by transition from experimental data to a constitutive model was significantly larger than the deviation between the data sets varying at different strain rates, which means that the use of stress-strain curves varying at different strain rates in given range of the strain rate has no effect on the resulting model. The best of analysis models that were examined in this thesis appears to be the Yeoh hyperelastic model using the FEM.
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Development of an impactor for the Taylor anvil test
Müller, Samuel ; Forejt, Milan (referee) ; Jopek, Miroslav (advisor)
The Master Thesis describes the differences between quasi-static and dynamic material tests and discusses the effect of strain rate in forming processes. It contains a detailed description of Split Hopkinson pressure bar test, Split Hopkinson tensile bar test and Taylor anvil test. The thesis contains a basic theory of ballistics and the history of the development of the material sample carrier for the Taylor test and the analysis of its current state. A new sample carrier was developed for the adjusted diameter of the Taylor test equipment. The shape of the carrier was designed, based on simulations in ANSYS software and practical testing. The carrier was made by 3D printing technology, FDM method. Samples of aluminum alloy 2024-T3 were tested using the new samples carriers. Dynamic flow stress was determined, and the strain rate constant was optimized for specifics impact velocities.
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Development of an impactor for the Taylor anvil test
Müller, Samuel ; Forejt, Milan (referee) ; Jopek, Miroslav (advisor)
The Master Thesis describes the differences between quasi-static and dynamic material tests and discusses the effect of strain rate in forming processes. It contains a detailed description of Split Hopkinson pressure bar test, Split Hopkinson tensile bar test and Taylor anvil test. The thesis contains a basic theory of ballistics and the history of the development of the material sample carrier for the Taylor test and the analysis of its current state. A new sample carrier was developed for the adjusted diameter of the Taylor test equipment. The shape of the carrier was designed, based on simulations in ANSYS software and practical testing. The carrier was made by 3D printing technology, FDM method. Samples of aluminum alloy 2024-T3 were tested using the new samples carriers. Dynamic flow stress was determined, and the strain rate constant was optimized for specifics impact velocities.
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Tube Flaring Technology under Dynamic Conditions
Macháček, David ; Forejt, Milan (referee) ; Peterková, Eva (advisor)
This master thesis is divided into three main parts. In first part is more closely described the method of tube flaring. Tube flaring was chosen for analysis of biaxial stress, in this thesis particularly in the presence of high strain rate. In the second part is more closely described influence of high strain rate on the forming process. There is described influence of high strain rate on behavior of the material, hardening, change of quasi-static yield strength to the dynamic yield strength, influence of high strain rate on the microstructure and more. During the description of these processes there is effort to describe the cause of these changes as well. For this task was used domestic and foreign literature, as well as peer review papers whose authors study intensively this problematic. Besides all of the above there is also derived the velocity of elastic and plastic wave. In the end is evaluated experiment, in which was done tube flaring, which is part of this master thesis. Results from the 3D optical system ARAMIS are interpreted with the help of Microsoft Excel, where the chosen results were used as the input to the equations modified for the dynamic loading.
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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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