A review on stress determination and control in metal-based additive manufacturing

Metal additive manufacturing(MAM)is an emerging and disruptive technology that builds three-dimensional(3D)components by adding layer-upon-layer of metallic materials.The complex cyclic thermal history and highly localized energy can produce large temperature gradients,which will,in turn,lead to compressive and tensile stress during the MAM process and eventually result in residual stress.Being an issue of great concern,residual stress,which can cause distortion,delamination,cracking,etc.,is considered a key mechanical quantity that affects the manufacturing quality and service performance of MAM parts.In this review paper,the ongoing work in the field of residual stress determination and control for MAM is described with a particular emphasis on the experimental measurement/control methods and numerical models.We also provide insight on what still requires to be achieved and the research opportunities and challenges.

Optimizing Winding Angles of Reinforced Thermoplastic Pipes Based on Progressive Failure Criterion

This paper examines a scheme to optimize the multiple winding angles of reinforced thermoplastic pipes(RTPs)under internal and external pressures.To consider the nonlinear mechanical behavior of the material under changes of winding angle due to deformation,we use three-dimensional(3D)thick-walled cylinder theory with the 3D Hashin failure criterion and theory of the evolution of damage to composite materials,to formulate a model that analyzes the progressive failure of RTPs.The accuracy of the model was verified by experiments.A model to optimize the multiple winding angles of the RTPs was then established using the model for progressive failure analysis and a multi-island genetic algorithm.The optimal scheme for winding angles of RTPs capable of withstanding the maximum internal/external pressure was obtained.The simulation results showed that the ply number of the reinforced layer has a prominent nonlinear effect on the internal and external pressure capacity of the RTPs.Compared with RTPs with a single angle of±55°,the multiple winding angle overlay scheme based on the multi-angle optimization model improved the internal and external pressure capacity of the RTPs,and the improvement in the external pressure capacity was significantly better than the internal pressure carrying capacity.