A VISCOELASTIC SPHERE MODEL FOR THE REPRESENTATION OF PLANTAR SOFT-TISSUE DURING SIMULATIONS

Simulations of human body during locomotion require a realistic repres entation of the foot which is the major interacting part of the body w ith the environment. Most simulation models consider the foot to be a rigid link, and impose unrealistic kinematic conditions. This study ut ilizes a viscoelastic sphere model with realistic properties, which ca n be used to represent the plantar surface of the foot during locomoti on. The mechanical properties of the sphere are identified using exper imental data on heel pads (Valiant, 1984). To check the validity of th e model the results of the experimental study are reproduced by simula ting the impact tests. Sensitivity analyses of the model parameters ar e carried out. The model is found to be insensitive to variations in s tiffness and damping properties. The change in the thickness of the so ft tissue, however, affected the maximum force of deformation proporti onally. ii symmetrical pressure distribution for the sphere during imp act is calculated. It is concluded that the viscoelastic sphere model, presented here, can be incorporated into a foot model to represent th e plantar surface of the foot. (C) 1998 Elsevier Science Ltd. All righ ts reserved.