Modelling of high cycle fatigue strength and cyclic crack propagation behaviour of steels

  Scheme of the model approach for the high cycle fatigue determination IEHK Scheme of the model approach for the high cycle fatigue determination (left to right): RVE of the steel 38MnSiV5; histogram of the extreme values of the accumulated plastic strain (grey columns), extracted from the simulation set with R=-1 and σ_a=402 MP

Within the RFCS project “Freqtigue” a material database of different steel grades for the automotive industry with fatigue parameters and crack growth data is generated for testing frequencies ranging from 25 to 20 000 Hz. The use of ultrasonic testing equipment allows the determination of fatigue parameters in the ultra-high cycle fatigue regime with several billions of cycles leading to information in a reasonable time for the component assessment of a lifetime of not less than a century. One focus here is the modeling of the service life under cyclic loading with commercial calculation software. For this purpose, a bridging approach is used. With the use of several representative volume elements of the microstructure and a crystal plasticity constitutive model, local plasticity and thus material damage can be calculated depending on the microstructure. The approach takes the statistical spread of these indicators into account. With this approach fatigue parameters can be calculated as well as the lifetime predicted.