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Abstract

The austenitic steel 316L is a widely used material for additive manufacturing of components that are to be used under severe mechanical conditions, as fatigue, high-temperature fatigue, or thermomechanical fatigue. Since fatigue experiments at high or even alternating temperatures are a complex and time-consuming process, it is important to develop realistic numerical models to predict fatigue behavior and to extrapolate the limited experimental results into a wider range of thermomechanical conditions for the microstructures obtained from additive manufacturing. A micromechanical model has been set up, based on representative volume elements (RVE) that mimic the microstructure of the experimentally tested materials that has been characterized by EBSD analysis. With the help of these RVEs, the temperature and deformation-dependent internal stresses in the microstructure can be simulated in a microstructure-sensitive manner. The material behavior in the elastic regime is described by temperature-dependent anisotropic elastic constants, whereas the plastic behavior is described with a temperature-dependent crystal plasticity model, including the Ohno-Wang relation for kinematic hardening. The material parameters are identified with an inverse procedure, based on experimental data from isothermal fatigue tests at various temperatures. After this, the model is applied to thermo-mechanical fatigue, where temperature and mechanical load, both, vary in a cyclic way. The correctness of the model is validated with independent data from thermomechanical fatigue tests on the same materials. From the comparison of experiment and numerical simulation, conclusions about the prevailing deformation and failure mechanisms under fatigue conditions can be derived.