Load distribution and damage evolution in bending and stretch dominated Ti-6Al-4V cellular structures processed by selective laser melting

Abstract

Cellular structures produced by additive manufacturing techniques, such as selective laser melting, enable for realizing parts of high specific strength and stiffness. In dependence of the prevalent deformation mechanism, i.e. bending or stretch dominated behavior, differences in the mechanical performance are observed. However, predictability of the mechanical behavior by current analytical and numerical approaches is limited, as local phenomena, such as process related geometrical inaccuracies and/or the local microstructure, are not incorporated in respective models. Thus, little knowledge on the actual load distribution and the damage evolution within cellular structures is available, although a high dependency of the structural performance on these aspects can be expected.The current work aims at closing this gap. By means of digital image correlation profound insights into the local strain distribution and damage evolution on the level of individual struts were obtained and correlated to the phenomena observed on the macroscopic scale under quasi-static and cyclic loading. By contemplating as-built as well as heat treated Ti-6Al-4V structures revealing fundamentally different mechanical performance, the observations made are not only related to the geometrically induced deformation mechanism, but also to process induced material characteristics, such as pronounced brittleness and the presence of residual stresses in the as-built condition.