Part-Scale Model for Fast Prediction of Thermal Distortion in DMLS Additive Manufacturing Part 2: A Quasi-Static Thermomechanical Model
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The direct metal laser sintering (DMLS) additive manufacturing process can quickly produce complex parts with excellent mechanical properties. However, thermal stress accumulated in the layer-by-layer build cycles of DMLS may induce part distortion and even cause the failure of the whole build process. This paper is the second part of two companion papers that present a part-scale model for fast prediction of temperature history and part distortion in DMLS. In this paper, a quasi-static thermomechanical (QTM) model is built to estimate the thermal distortion of entire parts in DMLS. Firstly, the thermal contraction in each build cycle is modeled as a quasi-static loading process; the final thermal stress accumulated in the parts is the superposition of thermal stress generated in each build cycle. Secondly, the stress relaxation process after the parts are cut off from the substrate is modeled, and final distortion of the parts is predicted with thermal stress calculated from the thermal contraction processes. In comparison to existing transient thermomechanical models, the QTM can predict thermal distortion in DMLS with much faster computational speed, and a comparison against experiment shows less than 10% error.