Fatigue Analysis of Polycentric Prosthetic Knee for Trans-Femoral Amputation

Abstract

A prosthetic knee is predominantly subjected to cyclic action leading to fatigue failure during its operation. However, cyclic failure is more severe as it occurs below the yield strength and may happen even without prior indication. This study presents a cyclic structural analysis of an existing polycentric mechanical prosthetic knee by finite element simulation and its experimental validation as per the ISO 10328:2016 standard. The three-dimensional (3D) model is imported to the ANSYS 20.1 workbench to study stress distribution and fatigue life in the knee for ensuring its safety performance. The maximum von-Mises stresses developed at the front and back joint bars made of A390.0-T5 and A390.0-T6 cast aluminium are 100 and 89[Formula: see text]MPa, respectively, in both loading conditions compared to their mechanical fatigue strength of 89[Formula: see text]MPa. The maximum deformation and average number of cycles for fatigue failure are 2.66 and 2.53[Formula: see text]mm and [Formula: see text] and [Formula: see text] for simulation and experimental results, respectively. These results suggest that this polycentric knee unit has poor fatigue strength and thereby does not meet the ISO structural standard. A validation test has been performed with an average error of 4.75% between the simulation and experiments results showing higher reliability.