Metal additive manufacturing (AM) is capable of producing complex parts, using a wide range of functional metals that are otherwise very difficult to make and involve multiple manufacturing processes. However, because of the involvement of thermal energy in the fabrication of metallic AM parts, residual stress remains one of the major concerns in metal AM. This residual stress has negative effects on part quality, dimensional accuracy, and part performance. This study aims to carry out a comprehensive review and analysis of different aspects of residual stress, including the causes and mechanisms behind the generation of residual stress during metal AM, the state-of-the-art measurement techniques for measuring residual stress, various factors influencing residual stress, its effect on part quality and performance, and ways of minimizing or overcoming residual stress in metal AM parts. Residual stress formation mechanisms vary, based on the layer-by-layer deposition mechanism of the 3D printing process. For example, the residual stress formation for wire-arc additive manufacturing is different from that of selective laser sintering, direct energy deposition, and powder bed fusion processes. Residual stress formation mechanisms also vary based on the scale (i.e., macro, micro, etc.) at which the printing is performed. In addition, there are correlations between printing parameters and the formation of residual stress. For example, the printing direction, layer thickness, internal structure, etc., influence both the formation mechanism and quantitative values of residual stress. The major effect residual stress has on the quality of a printed part is in the distortion of the part. In addition, the dimensional accuracy, surface finish, and fatigue performance of printed parts are influenced by residual stress. This review paper provides a qualitative and quantitative analysis of the formation, distribution, and evolution of residual stress for different metal AM processes. This paper also discusses and analyzes both in situ and ex situ measurement techniques for measuring residual stress. Microstructural evolution and its effect on the formation of residual stress are analyzed. Various pre- and post-processing techniques used to countermeasure residual stress are discussed in detail. Finally, this study aims to present both a qualitative and quantitative analysis of the existing data and techniques in the literature related to residual stress, as well as to provide a critical analysis and guidelines for future research directions, to prevent or overcome residual stress formation in metal AM processes.

The effect of the grinding process for weld flash removal on the surface integrity of the welded joint has not been researched. The surface integrity of the welded joint is essential for the bandsaw blade life and to prevent any premature failure at the weld joint due to fatigue loading (a band saw blade undergoes mainly cyclic bending fatigue during its service). In this study, the effects of using different cutting fluid combinations on the grinding of weld flash in medium carbon alloy steel were carried out. The use of compressed air (CA) as a sustainable solution for grinding weld flash was explored. An experimental investigation of four different cutting fluid applications (dry/no cutting fluid, compressed air, minimum quantity lubricant using vegetable oil, and minimum quantity coolant using water-soluble oil) was carried out. The surface roughness, sub-surface residual stresses, and microhardness of the ground region were measured. This is a first-of-the-kind study on the effect of the flash removal process on the surface integrity of the welded joint. The results show that the surface integrity of the welded joint is significantly influenced by the cutting fluid application used during the grinding process of the flash. Dry grinding, the current industry standard for grinding weld flash in band saw blades, produced surface tensile residual stresses (24.82 MPa), lowest sub-surface microhardness (43.28 HRc), and the highest surface roughness (3.40 µm). In comparison, the air application had the highest surface compressive residual stresses (−289.57 MPa), highest sub-surface microhardness (48.67 HRc), and relatively low surface roughness (1.61 µm). This study provides the road map for selecting the cutting fluid application for grinding weld flash produced by the resistance welding process in the band sawing industry.