There have already been some techniques to decrease residual stress in composites. As a result, misinterpretation may occur in characterizing the mechanical properties of composites. Such stresses are often ignored or neglected in the design of composites. Residual stress in composites has resulted from the high contraction of the polymeric matrix in comparison with fibers during the curing and cooling processes of fabrication. Ahad Daneshvar, in Residual Stresses in Composite Materials (Second Edition), 2021 12.5 Conclusions and future trends Reduction of residual stresses in polymer composites using nano-additives Mechanical control method can balance out the high tensile residual stress by introducing an in-situ compressive pressure, such as laser shock peening or rolling. Different materials and different dwell time would also affect the residual stress. Higher residual stress, although can hardening the metal parts, is most likely to cause bending of parts. The formation of residual stress can be concluded due temperature gradient mechanism (TGM) model and cool-down phase model. A smaller scan island size and increased length energy density would result in a reduced residual stress field. Most of the bending and distortion in AM are caused by residual stress due to rapid heating-cooling thermal cycle in almost all AM processes. Residual stress is an important parameter to indicate whether the quality and geometry accuracy of additive manufacturing parts are good. Wei Li, in Quality Analysis of Additively Manufactured Metals, 2023 12 Residual stresses Quality of AM parts in automotive application: Design-process-property relation for automotive parts For example, the residual stresses in DED Inconel 718 samples with yield strength of ~1100 MPa are ~1.5 times higher than that in DED AISI 316 stainless steel specimens with yield strength of ~450 MP. The materials with higher yield strength can generate a higher magnitude of residual stresses. The magnitude of residual stresses is closely related to that of the yield strength of printed materials. If the local residual stresses are beyond the ultimate tensile stress of printed materials, it may induce cracking within the printed parts. When residual stresses are higher than yield stress of materials, warping or plastic deformation may take place. Metallic AM components usually retain excessive residual stresses with high magnitudes. Hence, it leads to a spatially varied thermal distribution, as well as nonuniform expansion and contraction during printing. This is because metallic AM products experience repeated rapid melting/solidification and heating/cooling processes. Residual stresses are an inherent characteristic in metallic AM products, especially in PBF and DED metallic products. Residual stresses are stresses that are remained in the components after the completion of mechanical processes. Read moreĬhao Cai, Kun Zhou, in Digital Manufacturing, 2022 7.5.1.1 Excessive residual stresses It concludes with some suggestions to carry out research both experimentally and computationally to improve understanding of RS and its mitigation. A commentary on computational methods in relation with RS in FSW has been included to provide a good insight into state of RS research. Computational methods have become indispensable tool in studying RS. Additionally, a conceptual framework has been put forth to understand the origin of RS in friction stir welding. Apart from summarizing this aspect, this book very succinctly puts forth the factors which can help reduce RS and resulting distortions. A great deal of research has gone into understanding the influence of RS on quasi-static and dynamic mechanical properties along with stress-corrosion cracking behavior of these alloys. Majority of alloys used for RS studies have been Al-based alloys. A large number of variables affect the origin of RS and these are discussed in this book. Friction stir welding (FSW) also leads to the introduction of RS in welded structures. It may result in distortion of the weldments which can lead to fitting issues and/or failures. Residual stresses (RS) are results of complex thermal-mechanical-metallurgical interactions during welding. Baumann, in Residual Stresses in Friction Stir Welding, 2014 Summary, Conclusions, and Future Direction