Cracking prediction at solid-tooth support interface during laser powder bed fusion additive manufacturing

Abstract

Cracking resulting from residual stress at the solid-tooth support interface frequently occurs in laser powder bed fusion (LPBF) metallic additive manufacturing, and thus it is critical to predict possible cracking and design the support to prevent it. This study employs a combination of computational methods and experiments to predict cracking at the interface and, for the first time, determine the relationship between the critical J-integral and the contact area of the solid-tooth support interface. In particular, the finite element method-based global-local approach is used to perform the modified inherent strain analysis with homogenized material for the entire part (global), which is followed by the fracture mechanics-based J-integral analysis at conjectured vulnerable locations (local). Both numerical and experimental validations are conducted, showing that the local-global approach is accurate and efficient in crack prediction at the interface between the solid and the tooth support in as-built LPBF printed metals. It is found that given the same basic tooth unit design in the support structure, the critical J-integral increases at an approximate linear slope of 2 with a local contact area percentage (∼20–40%) at the solid-support interface. These results will enable support designers the flexibility to design the support contact area to prevent solid-tooth support cracking while ensuring the ease of support removal.