Distribution characteristics of residual stresses in typical wall and pipe components built by wire arc additive manufacturing

It is of great importance to thoroughly understand residual stress distribution in wire arc additive manufacturing (WAAM) and its relationship with the deposition variables. In this study, stainless steels 308LSi and 304 were used as WAAM feedstock and substrate, respectively, for additive manufacturing of two typical structures, namely wall and pipe structures. A thermomechanical coupling analysis model for WAAM was developed to investigate the formation mechanism of residual stresses in both structures, and their relationship with the deposition height and shape. The validity of the analysis was evaluated by comparing the simulated residual stresses with those measured by the contour method. Regardless of the wall or pipe structure, the tensile longitudinal (or circumferential) residual stress exists on the WAAM top surface and has the largest value (~300 MPa) at the position of several layers below the top surface. The distribution pattern of the longitudinal (or circumferential) residual stress is tensile in the layers near the top surface, compressive in the layers near the substrate surface, and tensile near the bottom surface of the substrate. This distribution pattern reaches a quasi-stable state when the total deposition height is greater than a certain size (~10 mm and 15 mm for wall and pipe structures, respectively). For the pipe structure, however, the residual stress distribution is not symmetric along the height direction. This analysis model can provide guidance for effective tailoring of residual stresses in WAAM components.