(V) Studies on Residual Stress and Structural Distortion of Structures Fabricated using Metal Deposition

Tuesday, September 14, 2021: 10:00 AM
230 (America's Center)
Prof. Rakesh K. Kapania , Virginia Tech, Blacksburg, VA
Mr. Mohcine Harrach , Virginia Polytechnic Institute and State University, Blacksburg, VA
Dr. Wei Zhao , Virginia Tech, Blacksburg, VA
Dr. Pinar ACAR , Virginia Polytechnic Institute and State University, Blacksburg, VA
The paper studied the thermo-mechanical responses including residual stress and structural distortion that are often observed during metal deposition during Additive Manufacturing (AM). Finite Element Analysis software package, ABAQUS/Standard, is employed to simulate the additive manufacturing process. We studied a solid-state AM process, which is similar to the stir friction welding. To simulate the real model of the metal AM process, several numerical models with increasing degrees of complexity were developed. The first model considers adding a hot layer on top of a layer that is at room temperature and the top layer cools down to room temperature. The heating and cooling were studied, the thermo-mechanical induced curvature of the layers and the substrate are computed. The results compared relatively well to those available in the literature. Next, we developed a model where we simulated the hot material that was being deposited. We also implemented the heat conduction considering radiative and convective cooling. An accurate plasticity model along with two different boundary conditions on the substrate are considered: (1) free edges and (2) fixed edges. We found out that the substrate boundary conditions play an important role in the residual stresses and the overall deformation of the fabricated panel. When fixing the edges of the substrate, a large stress was observed in the printed part, which could lead to breaking of the printed structure. When one substrate’s edge is fixed, the residual stresses become lower but the substrate gets more distorted. The material of the substrate is found to influence the thermo-mechanical response of the printed structure (compared to the deposition material). In addition, the deposition temperature, the speed of the deposition, and the general dimensions of the whole system, are all studied to investigate their effects on the 3D printed part thermo-mechanical responses including structural distortion and residual stress.