Fatigue Experimental of AS-CAST Ti-6Al-7Nb Implemented on Designed Femoral Stem for Indonesian People Through Finite Element Analysis

Abstract

This study aims to evaluate the durability of as-cast Ti-6Al-7Nb in femoral stem application using fatigue analysis. As-cast Ti-6Al-7Nb rod specimens were tested experimentally with load range of 120%, 100%, 90%, 80%, 70%, 50%, 30%, and 20% relative to the yield strength. The fatigue limit was identified on a range of 141 - 211 MPa, represented by two run-out specimens running until high fatigue cycle (HFC) of 107 without failure. ProFatigue contributed to expose the estimation of the expected failure cycle on fatigue limit stress of as- cast Ti-6Al-7Nb based on Weibull modelling. It was predicted by probability failure (Pfail) of 50%. The failure cycles were revealed at 2.144 x 107 and 2.823 x 109 cycles on amplitude stress of 211 and 141 MPa, respectively. The reliability of the designed femoral stem for Indonesian people has been analyzed under ISO 7206 configuration through finite element analysis by adopting the material properties of as-cast Ti-6Al-7Nb. The static linear analysis demonstrated the maximum stress concentration of 136 MPa occurring over the medial region of the femoral stem, showing lower stress levels compared to the fatigue limit of as-cast Ti-6Al-7Nb. Furthermore, the lifetime analysis computed that the design could withstand cyclic loading until 2.51 x 109 cycles with fatigue safety factor and damage factor in 1.763 and 0.398, respectively. Results concluded that the investment casting is evident to become an alternative manufacturing method of femoral stem made of Ti-6Al-7Nb.