Challenges in determination and evaluation of residual stress states in additive manufacturing

Additive manufacturing (AM) processes such as laser- and electron-beam powder bed fusion (PBF-LB/M and PBF-EB/M) as well as laser-based directed energy deposition (DED-LB/M) are used for fabrication of many high-performance parts. Assessment of residual stress states within any kind of part is of utmost importance. Here, it needs to be considered that the shape of the part has not only an influence on the prevailing residual stress state, but also on the local microstructure. In numerous AM materials microstructures established are characterized by coarse, columnar grains and pronounced texture. Furthermore, microstructure gradients are seen across a given section of the part. Fine cellular features with cell walls decorated by segregations and/or precipitates as well as very rough surfaces are further characteristics of AM parts. All these specific features of AM materials and parts, respectively, pose significant challenges to robust and reliable determination of residual stress states. The present paper summarizes all challenges and highlights potential pathways to overcome prevailing issues.