Abstract

Cracking often occurs after Laser Powder Bed Fusion (LPBF) due to residual stresses from the manufacturing process. To mitigate these stresses, post-processing methods like stress relief Heat Treatment (HT) are used. This study combines computational and experimental methods to analyze and predict macro crack behavior in two geometries—dog bone and cruciform—fabricated from LPBF IN738 alloy. The objective is to understand and predict macro crack formation following LPBF and HT to prevent cracking. A coupled thermomechanical analysis was conducted to identify locations and timing of stress concentrations in the geometries. A simulation workflow was developed quantifying residual stresses at various stages of LPBF and HT. Fracture analysis using the stress intensity factor, a parameter in fracture mechanics, was performed to predict crack formation. Both numerical simulations and experimental validations were employed to assess this approach's effectiveness. Results showed that the stress intensity factor at stress concentration sites exceeded IN738's fracture toughness, indicating potential cracks. Despite geometric differences, both geometries showed similar stress peak patterns and crack behavior. High stress concentrations were observed early in the build process, during HT, and after cooling. The study also examined the impact of post-process sequences, such as HT and base plate removal, on geometric accuracy. These findings provide insights for designing geometries to prevent cracking and emphasize the role of geometric features and process sequencing in optimizing additive manufacturing. Understanding the relationship between design, residual stresses, and process sequences aids in developing robust design strategies and post-processing techniques to enhance LPBF component designs.