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Criteria of Multiaxial Fatigue Life
Blaha, Jakub ; Slámečka, Karel (referee) ; Horníková, Jana (advisor)
Bachelor’s thesis is about fatigue of materials and options of component’s lifetime determination during multiaxial cyclic loading. First it is described mechanism of initiation and grow of fatigue cracks, then the way of determination fatigue life during uniaxial loading and state of stress during multiaxial loading. Then multiaxial fatigue criteria for life time determination are presented. All criteria are based on critical plane and are divided into stress-based, strain-based and energy-based.
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Fatigue Crack Propagation under Combined Load in Selected Polymer and Metal Materials
Slávik, Ondrej ; Klusák, Jan (referee) ; Padovec,, Zdeněk (referee) ; Náhlík, Luboš (advisor)
Material fatigue plays key role in terms of lifetimes of many service parts. Study of fatigue behavior of materials is ongoing from the previous century. To a large degree, the focus is put on studies of fatigue crack growth under uniaxial loading, or the so-called opening mode crack growth. However, in practice there are multiple cases of multiaxially loaded service parts, in which cracks loaded under mixed-mode loading conditions may be present. There is currently not enough knowledge with regards to this topic. This thesis is focused on some of the aspects of fatigue crack growth under combined loading. The aim is to find appropriate experimental specimens for studies regarding these issues and with their help to acquire necessary experimental data. Obtained results were used for simplification of residual fatigue lifetime estimation of parts made of polymer and metal materials. In the thesis it is also noticed about the differences in fatigue fractures between polymer and metal materials loaded by combination of tension and shear loading. These results contribute to better understanding of the processes of fatigue fractures of parts loaded by combined loading. Therefore, the submitted thesis is focused on the studies of fatigue behavior of metal and polymer materials under multiaxial loading.
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Criteria of Multiaxial Fatigue Life
Blaha, Jakub ; Slámečka, Karel (referee) ; Horníková, Jana (advisor)
Bachelor’s thesis is about fatigue of materials and options of component’s lifetime determination during multiaxial cyclic loading. First it is described mechanism of initiation and grow of fatigue cracks, then the way of determination fatigue life during uniaxial loading and state of stress during multiaxial loading. Then multiaxial fatigue criteria for life time determination are presented. All criteria are based on critical plane and are divided into stress-based, strain-based and energy-based.
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Structure life under a multiaxial loading
Svoboda, Jaroslav ; Balda, Miroslav ; Fróhlich, Vladislav
The contribution deals with a problem of fatigue life of structures exposed to a proportional random multiaxial loading in tension - pressure and torsion. Tests proved that a fatigue damage is stronglydependent on the main stress level, while maintaining the corresponding maximum shear stress constant. The obtained fatigue-life curve as a main stress standard deviation as function of the number of loading blocks has the similar character as the S-N curve under harmonic loading.
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Fatigue Properties of Steels Under Multiaxial Loading
Václavík, Martin ; Svoboda, Jaroslav
Study of combined loading influence to fatigue lifetime of smooth polished specimens made by the material 11523.1. Followed are the stress field changes at various rates of shear and normal loading, and the coherence between the level of particular stress components and specimen fatigue lifetime. Three hypotheses for limit stress computations (HMH, Findley´s and Dang Van's)were verified.
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