Three-dimensional transient finite element analysis for residual stresses in the laser aided direct metal/material deposition process

Despite immense advances in the laser aided direct metal/material deposition (DMD) process many issues concerning the adverse effects of process parameters on the stability of variety of properties and the integrity of microstructure have been reported. Comprehensive understanding of the transport phenomena and heat transfer analysis including phase transformations are essential to predict the effects of thermally induced residual stresses and distortions in the deposited materials. A complete model that provides a quantitative relationship between process parameters, cooling rates, and desired material properties is highly desirable. This model, which aims at predicting the residual stress history and the type of microstructure in the material, would reduce the long and cumbersome experimental route to compile sufficient data to predict the material behavior under similar loading conditions. Due to the complexity and nonlinearity of laser aided DMD process, analytical solutions to this process can rarely address the practical manufacturing process. This article is an attempt towards a methodology of finite element analysis for the prediction of macroscopic and microscopic residual stresses in the laser aided DMD process. The computer simulation which is based on the metallothermomechanical theory and finite element analysis for uncoupled temperature, phase transformation, and stress/strain fields can prove to be a very useful tool in predicting the material behavior and optimizing the process parameters to obtain the best material quality and dimensional accuracy. The significance of including phase transformation effects in the process has been demonstrated by a thorough comparison of residual stresses in the material with and without the phase transformation kinetics.