A conceptual design of residual stress reduction with multiple shape laser beams in direct laser deposition

Residual stress is a major problem in metal parts fabrication with the direct laser deposition (DLD) process due to severe temperature gradient around a molten pool. A three-dimensional finite element analysis (FEA) model with a simplified substrate clamping fixture modeling method is proposed, validated, and then implemented with a novel DLD heat input strategy in Ti-6Al-4V thin-wall structure fabrication, which was applied with multiple beam shapes, including a super-Gaussian beam, Gaussian beam, and inverse-Gaussian beam, to reduce residual stress in the final part. A regression model of the heat input and final part residual stress was obtained via a three-factor two-level full factorial design. An optimized heat input strategy was achieved based on response surface contour plots of the regression model.