FATIGUE-CRACK GROWTH-BEHAVIOR OF METALLIC BIOMATERIALS IN A PHYSIOLOGICAL ENVIRONMENT

Fatigue crack propagation (FCP) in Ringer's solution has been studied on four metallic biomaterials, i.e. pure titanium (TP35H), stainless s teel(SUS304), dual-phase stainless steel(SUS329J4L), and titanium allo y (Ti-6Al-4V). For TP35H and SUS329J4L, the crack growth characteristi cs in Ringer's solution were almost the same as those in room air in t he entire Delta K region examined, and thus the effect of Ringer's sol ution was not observed. The crack growth rates of SUS304 were enhanced in Ringer's solution in the region of Delta K greater than or equal t o 25 MPa root m as compared ro room air, while below this Delta K leve l they were similar in both environments. Also in Ti-6Al-4V, similar c rack growth behaviour in Ringer's solution was found. From the compari son among the da/dN-Delta K relationships of the four materials in Rin ger's solution, TP35H exhibited the fastest growth rates and then Ti-6 Al-4V, SUS304, SUS329J4L in the order of decreasing growth rate. On th e contrary, if the data were plotted in terms of Delta K-eff/E, Ti-6Al -4V and TP35H showed superior crack growth resistance to the stainless steels.