In-Process Mitigation of Residual Stress in Laser Powder Additive Manufacturing

Residual stress is one of the most critical challenges in laser powder bed fusion (L-PBF), often leading to part distortion, cracking, and degraded mechanical performance. This thesis investigates the in-process mitigation of residual stress in Ti-6Al-4V components fabricated using L-PBF by exploring the role of scanning strategy. A series of experiments were conducted using different scanning strategies—including unidirectional, 45°, and 67° rotated patterns—under both continuous and discontinuous modes. The resulting residual stresses were measured using the X-ray diffraction (XRD) technique. Results showed that scanning strategy significantly affects stress development, with discontinuous 67° rotation yielding the lowest residual stress and continuous unidirectional scanning producing the highest. To complement the experimental study, a thermal–mechanical simulation was developed in Abaqus using a sequentially coupled approach. A moving Gaussian heat source was implemented through a user-defined DFLUX subroutine to simulate the laser scanning process over a single powder layer. The resulting thermal fields were imported into the mechanical step, where a temperature-dependent elastic-plastic material model was used to predict stress evolution. This combined experimental and numerical investigation demonstrates that optimized scanning strategies can serve as an effective in-process method for controlling residual stress in L-PBF, enabling more reliable additive manufacturing of high-performance metal components. Keywords : Additive manufacturing, Residual stress, Formation mechanisms, Measurement methods, heat treatment, Laser-based additive manufacturing (LAM) process parameters, Finite element method, Numerical modeling