The inherent strain rate method for thermo‐mechanical simulation of directed energy deposition additive manufacturing

Abstract

AbstractTo reduce the computational time of thermo‐mechanical simulation of additive manufacturing by directed energy deposition, a new method is proposed, consisting in linearizing the transient standard thermomechanical simulation, by taking advantage of the strong concentration of strain rates around the deposition zone. In practice, a predictor/corrector algorithm is developed. The predictor step consists of a linearized mechanical resolution, which is obtained by considering the scalar generalized viscoplastic strain rate as an inherent strain rate, deduced from resolutions performed during previous time steps. The corrector step consists of a local (e.g., in each finite element) reconstruction of the effective stress field by solving a local nonlinear scalar equation. This predictor/corrector strategy is employed to deal with the dynamic evolution of strain rates and stress, during the distinct stages of the process: deposition, inter‐layer dwell time, and final cooling. With the proposed method, a time gain of around 5 is obtained for both a single wall and a curved turbine blade mock‐up, while the results (distortion and stress) of the full nonlinear thermomechanical resolution are replicated with an excellent accuracy. This makes the new inherent strain rate method a very promising tool for additive manufacturing simulation.