Simulation of the VHCF deformation of austenitic stainless steels and its effect on the resonant behaviour

In the context of a project cooperation – consisting of an experimental part (see previous article of this book) and a modelling and simulation part – the characterisation of the cyclic deformation behaviour of austenitic stainless steels during very high cycle fatigue (VHCF) was carried out. Experimental observations indicated clear differences between the VHCF deformation behaviour of a metastable and a stable austenitic stainless steel. In order to provide a more profound knowledge about the individual deformation mechanisms, the experimental study was extended by modelling and simulation. Two-dimensional microstructures consisting of several grains were represented using the boundary element method and plastic deformation within the microstructure was considered by a mechanism-based approach. Specific mechanisms of cyclic plastic deformation in shear bands and deformation-induced martensitic phase transformation – as documented by experimental results and based on well-known model approaches – were defined and implemented into the simulation. Since the plastic deformation depends amongst others on the initial sample temperature, the effect of a moderate increase of temperature is reflected in the model. Simulation results were directly compared with the observed deformation evolution on the real specimen surfaces and a comparison based on the transient resonant behaviour of the specimens and of the modelled microstructures was carried out. Good agreement of results confirms the model assumptions and allowed for assigning certain deformation mechanisms to the specific change of transient resonant behaviour. Finally, a more profound understanding of the VHCF deformation behaviour of both austenitic stainless steels is provided.