The effect of stress ratio on the fatigue behavior of additively manufactured porous biomaterials

Abstract

Meta-biomaterials are porous biomaterials created by additive manufacturing techniques such as Selective Laser Melting. These materials are built up form a repeating unit cell, resulting in a porous structure that can be applied for bone implants or prosthetics. The mechanical properties of these meta-biomaterials can be tailored by variations in unit cell type and strut thickness, resulting in different porosity values. This makes it possible to create a material with mechanical properties similar to bone, which prevents negative side effects of conventional bone implants such as stress shielding. The fatigue behavior of these meta-biomaterials has been studied before, but only at a single stress ratio of R=0.1 This study investigates the fatigue behavior at different stress ratios which result in an increased mean stress. A cylindrical porous structure that is built up from a diamond unit cell is tested at stress ratios of R=0.1, R=0.3, R=0.5, R=0.7 and R=0.8. Two samples types are made of Ti-6Al-4V ELI powder, resulting in a theoretical porosity of 80% and 10%. Also an experimental DIC method is developed, to visualize the deformation behavior during the fatigue tests.