Distortion and Residual Stress in Additive Manufacturing
2025-07-21
Additive manufacturing (AM) has attracted considerable attention and extensive research due to its advantage of producing complex-shaped parts without the need for casting molds. However, deformation is a known problem faced by many additive manufacturing technologies, which can reduce the precision of parts. Similar to welding, localized high energy inputs can generate residual stresses, thus adversely affecting the fatigue properties of additively manufactured parts.
By definition, residual stress is considered as purely elastic stress. When the stress exceeds the yield strength, it induces plastic deformation until the stress is released below the yield strength. This explains why the magnitude of the maximum longitudinal stress is close to the yield strength of the deposited material. Therefore, it can be assumed that the maximum elastic strain and part of the plastic strain occur at the top of the formed part (arm), as shown in Figure (a). After removing the support, the part deforms, as shown in Figure (b). This deformation causes a change in the distribution of elastic strain (or residual stress) and plastic strain in the formed part. Li et al. found that the residual stress decreased by 70% after removing the support. Ding et al. and Khouzani et al., respectively, observed a significant reduction in longitudinal stress after unclamping parts formed by WAAM and SLM.
Distortion and residual stress are two major problems in AM. This work provides an overview towards the mechanisms, evolution, and influencing factors of distortion and residual stresses. Several conclusions can be drawn as follows:
(1) The shrinkage of added deposit that constraint by the previous deposited or surrounding material is the intrinsic cause of distortion and residual stress in AM.
(2) Most of the maximum distortion lie at the far end (or ends) of built part. The longitudinal stresses are distributed as “tensile-compressive-tensile” from top to bottom of built part after cut from the substrate.
(3) The classic temperature gradient mechanism provides a micro perspective towards the evolution of distortion and residual stress. The model of constraining force makes it possible to clarify the influence of structural, material, and processing factors on the distortion and residual stress from a macro perspective.