![]() ![]() It also allows distinguishing very early whether the specimen will become a runout or if it will fail at a given amplitude. Based on these results a prediction of the fatigue life can be made at a very early stage of the fatigue experiment. By determining the dissipated energy per fatigue cycle, which was derived from the power input of the ultrasonic fatigue machine, it is possible to account for the amount of irreversibility during one loading pulse. In order to assess quantitatively the contribution of irreversible plastic deformation a new method was developed. The accumulation of irreversible plastic deformation in the ferrite grains and the strength of microstructural barriers in the vicinity of the plastically deformed grains are mainly determining the total fatigue life. During further cyclic loading plastic deformation accumulates in those grains and finally leads to crack initiation and fatigue failure. ![]() ![]() With decreasing stress amplitudes plastic deformation becomes more and more localized in particular ferrite grains. The ferrite grains deform plastically under cyclic loading. Due to the different carbon contents the ratio of ferrite to pearlite decreased from C15E to C60E. For this purpose, the steels C15E, C45E and C60E, with different ferritic-pearlitic microstructures were investigated. The fatigue behaviour and damage evolution in body centered cubic low alloyed steels in the high cycle and very high cycle fatigue regimes (HCF/VHCF) were in focus of this work. ![]()
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