Abstract
The exploration of fatigue mechanisms in the VHCF regime is gaining importance since many components have to withstand a
very high number of loading cycles due to high frequency or long product life. In this regime, particular attention is paid to the
period of fatigue crack initiation and thus the localization of plastic deformation. The resonant behavior of a metastable austenitic
stainless steel (AISI304) is studied experimentally in the VHCF regime and shows a distinct transient characteristic. The major
contribution of this work is to obtain a physically-based understanding of this characteristic by modeling the underlying
microstructural mechanisms and their influence on the resonant behavior. Microscopic examinations indicate that AISI304
undergoes deformation-induced martensite formation starting mostly at intersecting shear bands during fatigue. Therefore, a
microstructural shear band model [Hilgendorff et al. (2013)] is extended regarding the mechanism of deformation-induced
martensite formation. The model accounts for the microstructural mechanisms occurring in shear bands as documented by
experimental results, and nucleation of martensite is assumed to occur at intersecting shear bands following the Olsen-Cohen
nucleation model (1972) in combination with the Bogers-Burgers mechanism (1964). The simulation model is numerically
solved using the two-dimensional (2-D) boundary element method. By using this method, a 2-D microstructure can be modeled
considering grain orientations as well as individual anisotropic elastic properties in each grain. The resonant behavior is
characterized by evaluating the force-displacement hysteresis loop. Results show that plastic deformation in shear bands and
deformation-induced martensite formation have a major impact on the resonant behavior in the very high cycle fatigue (VHCF)
regime