Crack Propagation in Additive Manufactured Materials and Structures

Abstract

Additive manufacturing processes gain more and more interest, among others, due to the feasibility for production of lightweight metallic components directly from design data. Selective laser melting (SLM) is a very promising direct manufacturing (DM) technique for fabrication of near net shape components. The reasons for this are the relative high surface quality and bulk density of SLM processed parts. Still, process induced imperfections, i.e. residual stresses upon processing, need to be considered for future applications, in particular in the aerospace and biomedical sectors. Moreover, fatigue loading is a critical scenario for such components and needs to be investigated thoroughly.In this paper, results from fatigue crack propagation tests on biocompatible SLM-materials (titanium alloy Ti-6-4 and stainless steel AISI 316L) will be presented. For that purpose, fracture mechanical analyses were carried out on these materials. For Ti-6-4 various treatments were taken into account. It could be shown, which optimization steps are required in order to achieve fracture mechanical properties that are comparable to the reference material. In case of 316L, crack growth data for different process parameter sets (different build-up rates) were examined and compared to make conclusions about the influence of increased build-up rate on resultant crack growth behavior. Finally, based on the insights deduced from foregoing tests on Ti-6-4 crack growth propagation and the lifetime were simulated numerically by the use of the software ADAPCRACK3D.