Numerical analysis of thermal stress evolution of pulsed-wave laser direct energy deposition

Residual stresses and deformation in additive manufactured (AM) are two main barriers which hinder its extensive application seriously. In recent years, pulsed laser additive manufacturing has been widely examined for its advantages such as lower finer microstructure, more excellent mechanical properties, and heat accumulation in comparison with continuous-wave laser additive manufacturing. Few researches about residual stress of pulsed laser additive manufacturing, however, have been studied, and the development law of stain and residual stress is not clear. In this work, a three-dimensional (3D) transient uncoupled thermo-elastic-plastic model for pulsed-wave laser additive manufacturing procedure is carried through to examine the residual stress distribution and thermal history in 316L laser cladding. Excellent acceptance between the experimental measurements and the numerical results is obtained. It is discovered that pulsed-wave laser additive that manufactures attributes melt pools with periodic shape changes, the thermal stress evolution process moves like heartbeat periodically, and the residual stress distribution in laser cladding direction is similar to zigzag inhomogeneity. Furthermore, the influence of laser pulse parameters on residual stress distribution has been studied, and the results indicated that decreasing constant duty cycle and laser pulse length reduces the size and stress gradient of maximum stress’ region for x-direction tensile stresses. It provides operation parameters’ optimization choice with guidance to control or reduce residual stress.