Determination of bi-dimensional normal residual stress distributions in metallic laser-based powder bed fusion parts

Abstract

Disadvantageous complex residual stress distributions are common in parts manufactured by laser-based powder bed fusion metals (PBF-LB/M). Thus, the residual stress state determination is essential for understanding the part’s limitations. One residual stress measurement technique applicable to PBF-LB/M parts is the slitting method. This destructive technique allows through-thickness measurements and copes well with discontinuities in the material, yet is limited to one-dimensional stress profiles. Conversely, other stress measurement techniques, e.g. X-ray diffraction, are restricted to the part’s surface. This article presents an inexpensive and straightforward stress determination approach that combines an implementation of the slitting method with X-ray diffraction measurements to create a continuous two-dimensional residual stress map along a part’s cross-section. The approach was numerically validated using finite element models that simulate, on the one hand, the PBF-LB/M process and, on the other hand, the measuring process; further, it was experimentally tested in PBF-LB/M AlSi10Mg samples. The use of linear elastic fracture mechanics allowed a straightforward formulation of the approach, which enabled a high degree of automation. The accurate stress distribution results and the correlation with the simulations and previous studies demonstrate the approach’s robustness and effectiveness for complex residual stress states determination in two dimensions.