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Influence of Structure Directionality on Fatigue Properties of Formed Al Alloy.
Jíša, David ; Mazal, Pavel (referee) ; Liškutín, Petr (advisor)
The main goal of this diploma thesis is the examination of the influence of structure directionality on fatigue properties of formed aluminium alloy 6082/T6. The main attention is focused on the study of the influence of structure directionality on kinetics of short fatigue cracks growth. The measurement of short fatigue cracks growth was performed on cylindrical samples. The samples were made in two different directions; one parallel with the forming direction and second perpendicular to the forming direction. Servo hydraulic machine MTS 880 was used for the cyclic loading. The samples were cycled at two different constant stress amplitudes. Cyclic loading was systematically interrupted in order to measure the length of short cracks by a light microscope. Tensile tests, measuring of cycling hardening-softening curves, observation of microstructure, observation of surface relief, measuring of microhardness and fractographical analysis of fracture surfaces were used for further examination of the influence of the structure directionality. Some of these measured characteristics did not show any influence of the structure directionality (microhardness, fatigue life curve, Young modulus). In other cases is this influence measurable, however insignificant (yield stress, ultimate stress, cyclic hardening-softening curves and kinetics of short fatigue cracks growth). It can be summarised that the material, though the directionality of its microstructure is apparent, shows relatively isotropic mechanical behaviour.
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Tensile and Fatigue Testing of Thin Fibres and Foils
Štěrbáček, Jaroslav ; Liškutín, Petr (referee) ; Kruml, Tomáš (advisor)
A testing system MTS Tytron 250 with an original construction was bought at the Institute of Physics of Materials, AVCR v.v.i. The main aim of this diploma thesis was to obtain experiences with the controlling of the system and with its advantages and limitations. The tensile tests were performed on Al fibres with diameters of 125 micrometer, 180 micrometer a 500 micrometer, nylon fibres of 250 micrometer and 500 micrometer and tensile and cyclic tests on Al foil of 77 micrometer in thickness. It was found that the machine is suitable for testing of either subtle specimens with low loading forces or specimens with low stiffness as e.g. polymers or very long metallic or ceramic fibres. On the other side, the Tytrom system is not able to perform tests on specimens with a high stiffness and high loading forces. Material parameters were determined with a high reproducibility. Advantages and limitations of several types of subtle specimen's fixation into the grips were studied too.
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High cycle fatigue of Ti6Al4V titanium alloy
Bártková, Denisa ; Liškutín, Petr (referee) ; Věchet, Stanislav (advisor)
The main goal of this master's thesis is an analysis of high-cycle fatigue of titanium alloy Ti- 6Al- 4V. In the first section of a theoretical part of the thesis, there are summarized current facts about production, properties and aplications of titanium alloys. The second section pursues fatigue behaviour of material. An experimental part consists of metallographic analysis, evaluation of tension and bending tests and mainly analysis of high-cycle fatigue behavior for different assymetry ratios.
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Low cycle fatigue of EN-AW 7075 aluminium alloy
Bártková, Denisa ; Liškutín, Petr (referee) ; Věchet, Stanislav (advisor)
The main goal of this bachelor thesis is analysis of low-cycle fatigue of wrought alluminium alloy EN-AW 7075. In theoretical part of thesis, current facts about alluminium alloys and fatigue behaviour of material are summarized. Practical part contains evaluation of tension tests and analysis of experiments in low-cycle fatigue region. In additional, the microstructure of an alloy was observed.
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Mechanical properties of titanium alloys
Prudíková, Alena ; Liškutín, Petr (referee) ; Věchet, Stanislav (advisor)
This bachelor thesis was created in a form of literary search and it summarizes the basic information of Titanium and its alloys. The most significant features, such as its position in Periodic Table of the Elements, allotropic modifications and their crystal lattices, chemical or physical qualities, are mentioned in the first chapters. The attention was also paid to both the mechanical and the technological qualities of titanium as such, including the effect of impurities that may be very significant. General and summarized information about the history of titanium, as well as current directions in the development of its alloys are discussed in chapter 1.3. As a following, the information about production and the methods used during the production are discussed in chapter 2. Distinct part of the thesis depicts the partition of concrete titanium alloys and the heat treatment of them. The TiAl6V4 alloy was described in details, since it is the most widely used, therefore the most often produced titanium alloy.
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Application of magnesium alloys castings
Pernica, Vítězslav ; Liškutín, Petr (referee) ; Roučka, Jaromír (advisor)
Magnesium alloys are still idle in technical applications because of their properties. The history of metal is not very old, the first application of its alloy started on the beginning of the 20th century. Magnesium is very light. Its weight is about one third less than the weight of aluminum and it is the third most frequented structural metal. However its preparation and processing can be problematical because magnesium has high affinity to oxygen. It causes intensive burning. During the century of stature have been improved both production and alloys. The usage of magnesium alloys took more importance and it is the most used alloy in automotive field sofar. Recently its demand expands mainly in electrotechnics. Next usage we can find in aeronautics, energetics, military and many other branches.
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High cycle fatigue of Ti6Al4V titanium alloy
Bártková, Denisa ; Liškutín, Petr (referee) ; Věchet, Stanislav (advisor)
The main goal of this master's thesis is an analysis of high-cycle fatigue of titanium alloy Ti- 6Al- 4V. In the first section of a theoretical part of the thesis, there are summarized current facts about production, properties and aplications of titanium alloys. The second section pursues fatigue behaviour of material. An experimental part consists of metallographic analysis, evaluation of tension and bending tests and mainly analysis of high-cycle fatigue behavior for different assymetry ratios.
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Influence of Structure Directionality on Fatigue Properties of Formed Al Alloy.
Jíša, David ; Mazal, Pavel (referee) ; Liškutín, Petr (advisor)
The main goal of this diploma thesis is the examination of the influence of structure directionality on fatigue properties of formed aluminium alloy 6082/T6. The main attention is focused on the study of the influence of structure directionality on kinetics of short fatigue cracks growth. The measurement of short fatigue cracks growth was performed on cylindrical samples. The samples were made in two different directions; one parallel with the forming direction and second perpendicular to the forming direction. Servo hydraulic machine MTS 880 was used for the cyclic loading. The samples were cycled at two different constant stress amplitudes. Cyclic loading was systematically interrupted in order to measure the length of short cracks by a light microscope. Tensile tests, measuring of cycling hardening-softening curves, observation of microstructure, observation of surface relief, measuring of microhardness and fractographical analysis of fracture surfaces were used for further examination of the influence of the structure directionality. Some of these measured characteristics did not show any influence of the structure directionality (microhardness, fatigue life curve, Young modulus). In other cases is this influence measurable, however insignificant (yield stress, ultimate stress, cyclic hardening-softening curves and kinetics of short fatigue cracks growth). It can be summarised that the material, though the directionality of its microstructure is apparent, shows relatively isotropic mechanical behaviour.
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Tensile and Fatigue Testing of Thin Fibres and Foils
Štěrbáček, Jaroslav ; Liškutín, Petr (referee) ; Kruml, Tomáš (advisor)
A testing system MTS Tytron 250 with an original construction was bought at the Institute of Physics of Materials, AVCR v.v.i. The main aim of this diploma thesis was to obtain experiences with the controlling of the system and with its advantages and limitations. The tensile tests were performed on Al fibres with diameters of 125 micrometer, 180 micrometer a 500 micrometer, nylon fibres of 250 micrometer and 500 micrometer and tensile and cyclic tests on Al foil of 77 micrometer in thickness. It was found that the machine is suitable for testing of either subtle specimens with low loading forces or specimens with low stiffness as e.g. polymers or very long metallic or ceramic fibres. On the other side, the Tytrom system is not able to perform tests on specimens with a high stiffness and high loading forces. Material parameters were determined with a high reproducibility. Advantages and limitations of several types of subtle specimen's fixation into the grips were studied too.
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