Finite element modeling and validation of thermomechanical behavior of Ti-6Al-4V in directed energy deposition additive manufacturing

Thermally induced residual stresses and residual distortions in the additive manufactured (AM) parts are two of the major obstacles that are preventing AM technology from gaining wide adoption. In this work, a three-dimensional thermo-elastic-plastic model is proposed to predict the thermomechanical behavior in the laser engineered net shaping (LENS) process of Ti-6Al-4V using Finite Element Method (FEM). It is shown that the computed thermal history and mechanical deformations are in good agreement with the experimental measurements. The main contributions of this study are: (I) in the past, a point-wise comparison between simulation results and experimental measurements is more favored to validate the employed model, where the general picture is lost; rather, to validate the proposed model, the simulated distortion of the bottom surface of a thin substrate is compared with experimental measurements using a 3D laser scanner, in terms of both magnitude and distribution map. (II) Rather few works have been done to show the effectiveness of widely employed quasi-static mechanical analysis in the transient LENS process; as such, both quasi-static and dynamic simulations are performed and compared mechanically to demonstrate the validity of using quasi-static modeling to save computational cost.