Effect of curvature radius on the residual stress of thin-walled parts in laser direct forming

In laser direct forming, part geometry especially the curvature radius has a significant effect on the residual stress of the fabricated parts. But few people have studied the effect of part geometry especially curvature radius on residual stress. Here, a three-dimensional FE model is developed to analyze the temperature and residual stress in laser direct forming. The effect of curvature radius on the circumferential stress and vertical (z direction) stress during the fabrication of thin-walled cylinder parts are studied numerically and experimentally. The simulation results show that the curvature radius has obvious effect on temperature gradients in different directions in the process of laser direct forming. The vertical temperature gradient declines significantly with the increase of curvature radius, which leads to a relatively stable residual stress distribution in vertical directions after a declining tendency in the initial stage. However, the circumferential temperature gradient increases significantly with curvature radius, resulting in a gradually stable vertical residual stress after an increasing tendency in the initial stage. The experimental results show good agreement with the simulation. The results show great significance for process optimization of complex parts fabricated by laser direct forming and provide some guidance for the designation of structure of parts fabricated by this technology.