Effect of subsequent yield surface on residual stress in 3D numerical simulation of laser cladding process

Laser cladding (LC) is an advantageous surface modification technique. However, in the case of a thin substrate or a large process area to substrate, large thermal distortions could be generated, which can affect the dimensional accuracy of machinery parts. A substrate fixation method in the manufacturing process can mitigate thermal distortion. However, this fixation may induce residual tensile stress in the LC layer. Therefore, a simulation technique is required for scenarios with and without substrate fixation during laser cladding. In this study, models of a cantilevered plate (Cl) and a plate fixed at both ends (Fix) were developed. A 3D coupled thermo-mechanical analysis was performed using the element birth-death technique. Isotropic and kinematic hardening laws were also applied to the Cl and Fix models to compare the simulation results of thermal distortion and residual stress distribution. The Cl model with the isotropic hardening law achieved a higher simulation accuracy, while the model with the kinematic hardening law overestimated the thermal distortion. Conversely, the kinematic hardening law closely matched the experimental results in the Fix model. In addition, the comparison of normal stress-plastic strain diagrams revealed large compressive plastic strains repeatedly induced in the substrate regions below the interface in the Fix model due to substrate fixation during LC. The repeated plastic deformation induced the Bauschinger effect, which increased the simulation accuracy with the kinematic hardening law. These findings are crucial for accurately predicting residual stresses and thermal distortions in LC processes with substrate fixation.