Using discretized mechanical constraints to improve the stresses measured by electron backscatter diffraction
Calculation of stresses from high-resolution electron-backscatter diffraction (EBSD) maps has been a quite useful tool for understanding single- and polycrystal deformation. In this research, we used the weak form of a least-squares fit to the experimental measurements together with mechanical constraints in both two- and three-dimensional stresses derived from the cross-correlation technique. This approach serves as a physical filter to achieve realistic stress distributions that closely align with experimental data. The method is applied to the stress maps of unirradiated and irradiated single-crystal indents of pure iron as well as an austenitic stainless steel polycrystal. The method allows for computation of reference point stresses, thereby leading for the first time to computation of actual stresses using the cross-correlation technique. In addition, three-dimensional analysis enables the fulfillment of traction-free conditions, eliminating out-of-plane shear stress at the top surface while maintaining nonzero stress values within the element. The suggested computational approach ensures a uniform correlation of stress profiles with EBSD data, originating from the subsurface because of the diffraction volume that extends several tens of nanometers beneath the surface. The proposed finite element-based residual stress analysis (RSA2D/3D) considerably improves the measured stresses near slip bands, grain boundaries, and hard phases while keeping the stresses physically consistent with mechanical equilibrium and traction-free surfaces