This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

The stress at the interface between foot and insole (i.e., plantar stress) is known to play an important role in development of foot ulcers in diabetic patients. A specific shoe design can potentially reduce the plantar stress and therefore provide more comfort for the patients. The objective of the study was to examine the effect of insole-to-midsole heel height on the plantar stress using a finite element (FE) model.
A nonlinear axisymmetric two-dimensional model of a human heel-shoe consisting of calcaneus bone, heel pad, insole, midsole and a floor was developed in Abaqus/CAE. Non-linear foam material was assigned to the insole and midsole geometries. The total thickness of the insole-midsole was assumed a fixed number. The insole thickness was varied using Isight, while a representative average bodyweight was applied to the bone. A room temperature of 23°C was considered in this study. The plantar stress was estimated by measuring the predicted maximum contact pressure between the heel and the insole.
The maximum contact pressure reduced by 10% from a thin to thick sole. Our model predictions showed that: 1) the contact pressure varies as a function of the insole-to-midsole heel height; therefore, an optimum ratio needs to be defined in designing a shoe and 2) under the room temperature condition, increasing the insole thickness can reduce the plantar stress (i.e., contact pressure between the heel and the insole). It is known that the foam material is temperature depended, therefore simulation of various thermal conditions needs to be considered next.
The FE model was successfully used to perform a parametric optimization of the shoe dimensions with a view to predict the plantar stress. Development of a FE model allowed the automation of such design tasks which could otherwise be quite complicated due to the complexity of the physical problem and the range of usage conditions.