Compression-Compression Fatigue Behaviour of Triply Periodic Minimal Surface Porous Structures Fabricated by Selective Laser Melting

Abstract

Triply Periodic Minimal Surface (TPMS) porous structures are recognized as the most promising bionic artificial structures for tissue engineering. The fatigue properties of additive manufactured porous structures are essential for long-term use in a dynamical bio-skeletal environment. The aim of this study is to study the compression-compression fatigue behaviour and the underlying fatigue mechanism of Gyroid cellular structures (GCS), a typical TPMS porous structure. The high-cycle fatigue results show that both cyclic ratcheting and fatigue damage phenomena contributes to the failure of GCS during fatigue testing. For most fatigue loading stress, the failure samples have nearly 45° fracture bands along the diagonal surface. The fatigue ratio of GCS reached 0.35 for as-built samples and can be raised to 0.45 after sandblasting treatment. The fatigue ratio values are higher than most of the other bending-dominated lattice structures, suggesting superior fatigue resistance properties of GCSs due to the smooth surface connection between struts. Besides, a systematic investigation of the crack initiation and propagation was conducted by both deformation analysis and finite element method to support experimental phenomena. The results also indicates that the fatigue resistance properties of GCSs are significantly enhanced by sandblasting post-treatment, through removing the adhered powder particles, inducing compressive residual stress on the surface and generating a nanocrystalline zone.

Keywords: Additive manufacturing, Selective laser melting, Triply periodic minimal surface, Porous structure, Fatigue properties, Stainless steel