Plastic Strain-Based Method for Fast Predictions of Residual Stress and Distortion on Additive Manufactured Parts

Most of additive manufacturing (AM) processes for metals involve highly localized heating and rapidly cooling which induces residual stress and deformation in the built parts. Numerical investigations based on finite elements methods (FEM) have been used to predict residual stress and distortion for optimizing the AM processes. The size of simulated parts is strongly limited by the required calculation times which are in the range of hours up to days, weeks or even months. In order to enable a practical usage of a FEM based method for AM process simulation, a plastic strain-based modeling method was developed which can dramatically reduce the computational time. The modeling method included local models and a global model. Each local model representing a part of simulated geometry is analyzed with a transient moving heat-source modeling method to predict plastic strains. The global model created by meshing a full-sized part is analyzed with an elastic or elastic-plastic analysis to predict deformation by mapping the predicted plastic strains from the local models. This modeling method has been applied to simulate the arc-based and laser-based AM process on several geometries. The model prediction had a reasonable agreement with the measured deformation. This paper presents the theory and application of this modeling method on two complex parts to predict residual stress and distortion. One was built with arc-based AM method and another was built with laser-based AM modeling method.