Modelling Fatigue Crack Growth in Porous Metals

Scaffolds are advanced 3D metallic porous structures produced by additive manufacturing that find applications in biomedicine as bone implants. Our previous research has shown that the titanium scaffolds with porous filaments (14 % porosity) exhibited markedly better fatigue resistance than those with compact filaments (5 % porosity). This article presents a first version of the model of fatigue crack growth in porous metallic materials which should reflect the difference between the crack paths in porous and compact filaments and provide an interpretation of their fatigue resistance, particularly based on computed parameters S dr (the developed interfacial area ratio) and R L (the crack path length). S dr -values for the porous material were found to be distinctly higher than those for the compact material, thus indicating higher shielding effects and higher fatigue life of porous filaments compared to the compact ones. The values of S dr previously measured on fracture surfaces of several scaffold filaments fractured under cyclic compression tests correspond well to those predicted by the model. R L -values determined for the porous material are also significantly higher than those computed for the compact material. The calculated values of R L and S dr nearly follow the well-known approximative formula connecting these parameters.