Experimental Studies and the Model of Anisotropic Plasticity for Additively Manufactured Stainless Steel with Stress State Dependent Properties

In this study the mechanical anisotropy of laser powder bed fusion (LPBF) 316L stainless steel under tensile, compressive, and shear loading in different orientations with respect to the build direction is investigated. Experimental analysis revealed a moderate degree of anisotropy, which is mainly attributed to the build direction. In addition, the mechanical properties were seen to be dependent on the stress state, as evidenced by the tension-compression asymmetry. The anisotropy and asymmetry can be explained by various microstructural factors with texture orientation being one of the most significant. To incorporate such material behavior in structural analysis, a phenomenological model for anisotropic plasticity and tension-compression asymmetry was proposed and calibrated for additive 316L steel. The flexibility of the model allows it to be applied using a mechanical test set on uniaxial loading, and further enhancements may rely on data for combined stress state. The model was calibrated based on FEA of samples loading and fit well all experimental curves, though factors such as residual stresses and test imperfections could introduce some discrepancies.