COUPLED BOUNDARY ELEMENT-FINITE ELEMENT MODEL TO ESTIMATE HUMAN HEEL-PAD ELASTICITY MODULUS

Abstract

The key role of heel-pad in protecting calcaneus bone against excessive local stresses during walking and running is well discussed in the literature. Aiming to obtain a more profound understanding of this soft collagenous load-bearing tissue, material characterization of heel-pad has attracted the attention of many researchers. One way of achieving this goal is to estimate the mechanical properties of heel-pad based on Finite Element (FE) simulation of the indentation experiment which has been conducted by various teams before. During this process, the soft tissue undergoes a relatively large deformation causing the elements in FE Model to be extremely distorted particularly near the vicinity of indenter-heel pad contact making the numerical modeling tedious and significantly increasing the computational cost. The main contribution of the current study is to develop a coupled Boundary Element–Finite Element (BE–FE) plane strain model to improve the deficiency of the conventional numerical methods as the three-node 1 degree-of-freedom BEs eliminate the distortion issue near the deformed heel-pad zone and effectively lower the computational costs which is vital for iterative processes of this kind. Later through iterative post-processing of data, the modulus of elasticity (E) describing the elastic behavior of heel-pad is extracted. E is determined by using the inverse technique to minimize the displacement error between the experimental data and the corresponding numerical results after a considerable number of iterations. Obtained results contribute in design and construction of state-of-the-art prosthetic feet and therapeutic foot wear.