Simulation of the VHCF deformation behavior of austenitic stainless steelsTuesday (27.09.2016) 14:45 - 15:00 Part of:
In this study a model describing the VHCF deformation behavior of a stable and a metastable austenitic stainless steel is presented and solved within two-dimensional (2-D) morphologies of microstructures by using a boundary element method. In case of the metastable alloy a pronounced localization of plastic deformation in shear bands followed by a deformation-induced martensitic phase transformation determines the cyclic deformation behavior. The stable alloy undergoes only a very limited local plastic deformation in shear bands with almost no phase transformation. Based on experimental observations of the cyclic deformation behavior at stress amplitudes below the VHCF limit a model was developed that can simulate the characteristic mechanisms for plastic deformation in shear bands and for deformation-induced martensitic phase transformation from the γ-austenite to the α’-martensite. Since the deformation-induced martensitic phase transformation depends amongst others on the initial sample temperature, the effect of a moderate increase of temperature is reflected in the model. Simulation results are directly compared to the observed deformation evolution on the real specimen surfaces and a comparison based on the transient behavior of the specimens and of the modeled microstructures is carried out. The transient behavior of the material is characterized by the change in resonance behavior during cyclic deformation, which is experimentally monitored during fatigue tests and evaluated from simulated hysteresis loops. Good agreement of results confirms the model assumptions and, finally, a more profound understanding of the VHCF deformation behavior of both austenitic stainless steels is provided.