A Review on Distortion and Residual Stress in Additive Manufacturing

Additive manufacturing (AM) has gained extensive attention and tremendous research due to its advantages of fabricating complex-shaped parts without the need of casting mold. However, distortion is a known issue for many AM technologies, which decreases the precision of as-built parts. Like fusion welding, the local high-energy input generates residual stresses, which can adversely affect the fatigue performance of AM parts. To the best of the authors' knowledge, a comprehensive review does not exist regarding the distortion and residual stresses dedicated for AM, despite some work has explored the interrelationship between the two. The present review is aimed to fill in the identified knowledge gap, by first describing the evolution of distortion and residual stresses for a range of AM processes, and second assessing their influencing factors. This allows us to elucidate their formation mechanisms from both the micro- and macro-scales. Moreover, approaches which have been successfully adopted to mitigate both the distortion and residual stresses are reviewed. It is anticipated that this review paper opens many opportunities to increase the success rate of AM parts by improving the dimension precision and fatigue life.