Nondestructive Evaluation Of A Polymer Composite Hip Implant Using Lock-In Thermography

Lock-in thermography, combined with finite element analysis and experimental testing, was used to investigate the stress/strain pattern in a novel composite hip implant made of carbon fibre and polyamide 12 (CF/PA12). In this study, the geometry of the hip implant was first modelled and analysed in ANSYS workbench 11. Different virtual loads of 800N, 1400N and 2200N were applied on the finite element model of the hip stem at an adduction angle of 15º, thereby replicating the present experimental setup. The values of strains obtained were confirmed by replicating the experiment by using strain gauges. A Pearson's correlation (R²=0.98) was obtained, which indicated good agreement between the FEA model and experimental hip stem. The hip implant was again subjected to similar loading conditions, and stresses were recorded by using a thermal camera at corresponding vertices. The comparison of results showed good agreement between the values of stress calculated from the strain gauge experiment and stress obtained from thermography. This study showed that it was possible to find stresses in a hip implant reliably by thermography.