Residual Stress Evaluation in 316L WAAM Components Using Neutron Diffraction and the Contour Method

Wire-Arc Additive Manufacturing (WAAM) enables the cost-effective production of large-scale steel structures but introduces significant residual stresses that can compromise structural integrity. This study investigates the residual stress distribution in WAAM-produced 316L stainless steel components using neutron diffraction and the contour method, with particular focus on cross-correlating those two independent techniques. Residual stress measurements from both methods show strong agreement, providing valuable input for finite element models (FEM) of the process. Neutron diffraction enables non-destructive subsurface and bulk measurements, but its accuracy heavily depends on the preparation of stress-free reference samples. A detailed analysis of these reference samples revealed a strong crystallographic texture, though the overall variation remained small across the height of the WAAM component. The contour method, in contrast, is unaffected by texture or chemical composition variations, offering a key advantage over diffraction-based techniques. However, as a destructive method, it is limited to measuring residual stress in a single direction. This study discusses the strengths and limitations of both techniques in the context of WAAM, particularly regarding spatial resolution, reference sample requirements, and applicability to large-scale components. By refining residual stress measurement methodologies and identifying key constraints, this study advances the approach to residual stress assessment of WAAM printed structures and hence contributes to improved process control and enhanced structural reliability of additive manufacturing for civil and structural applications.