Development of a track level thermomechanical model for LPBF with a novel approach for plasticity computation

The Laser Powder Bed Fusion (LPBF) process is characterized by rapid thermal cycles that induce complex thermo-mechanical phenomena such as significant plastic strain accumulation and residual stress formation. Simulation models for the process are gaining popularity due to the limitations of experimental techniques but are often extensive and computationally demanding, limiting their practical application for process optimization. In this study, a thermo-elastoplastic model for simulating the LPBF process at the track level is developed. The model uses a moving Goldak heat source along with temperature-dependent material properties and phase changes to accurately capture transient thermal distributions and is coupled with an elastoplastic model. The model strives for an effective balance between efficiency and accuracy and is compared with other experimentally validated simulation models. A key contribution of this study is the comparative analysis of numerical strategies for plasticity. A conventional fully consistent implicit Newton solver for the nonlinear mechanical problem, is compared against a Quasi-Newton fixed point approach, where nonlinear terms of the tangent stiffness matrix are relocated to the right-hand side of the weak form and treated explicitly. This formulation is designed to maintain accuracy while offering improved computational efficiency. Preliminary runs on simple elastoplastic models in the past have shown good computational improvements by reducing calculation times thus simplifying the computational cost of plastic fidelity.