Prosthetic socket fitting is achieved by the prosthetist applying artisan techniques which are skill dependent and of subjective nature. This study investigates the use of finite element (FE) modelling techniques to predict the biomechanical behaviour at the residual limb/socket interface for the purpose of obtaining a quantitative evaluation of socket fit. Three dimensional FE models of the residual limb of trans-femoral amputees were generated based on geometrical data obtained using a mechanical digitizer and magnetic resonance (MR) imaging techniques. The inter-segmental loadings at the amputee's hip during standing and walking were applied to the FE models. These were measured with the aid of force platforms and infrared cameras. The material characteristic is introduced to the FE models were obtained by testing the residual limb's soft tissue with a computer controlled mechanical indentor. The FE models were validated by comparing predicted and measured pressures at the inter face between the residual limb and the socket. The majority of the FE prediction erred within 70% of the measured values. Detailed internal geometry of two trans-femoral amputees' residual limb in its natural shape and wearing quadrilateral and ischial containment type sockets was studied using MR imaging techniques. At the ischial level, the maximum difference in cross sectional area between the muscles of the sound limb and the residual limb was approximately 62%. The difference in muscles' size can be attributed to muscle atrophy in the residual limb or an increase in the muscle bulk in the sound limb. At similar level, the cross sectional area of the rectus femoris in the residual limb was reduced by as much as 68% from its natural shape when wearing the quadrilateral socket. Based on the acquired MR images,a two dimensional FE model of a transverse section 30 mm below the ischium was modelled. The model incorporated the interface characteristics between the muscles and intermuscular tissues. The maximum stress was recorded inside the residual limb near muscles/intermuscular tissue interface and at muscles/bone interface. The FE models generated have shown the potential of predicting stresses and deformation at the residual limb.

This thesis presents the results of a study into the mechanics of stresses in adhesive layer and the failure of adhesively bonded lap joints. A brief survey was made of the existing methods on the stress analysis of adhesively bonded lap joints. Following this is a discussion of the mechanics of adhesively bonded lap joints. The existence of stresses and factors affecting these stresses are presented in physical terms. A new method is presented for the determination of bending moments at the ends of the overlap for single lap joints. This method is accurate for joints with either identical or different adherends. A new procedure combining the analytical and numerical methods was proposed to obtain stresses in the adhesive layer accurately and efficiently. The reason why analytical methods yield somewhat hall the real peel stresses in the adhesive layer in double lap joints has been establis'hed. Some improvements in the determination of peel stresses in the adhesive layer in double lap joints have been made. A three dimensional stress analysis was carried out to study the stress distribution across the joint- width. An intuitive and numerical study was made into the mechanics of the longitudinal stresses in the adhesive layer. An elastic-plastic stress and strain analysis. has been performed with FEM on joints bonded with radii adherends to study the effect of the rounding of the adherend corners on the stress distribution in the adhesive layer. Some study into the failure process and failure modes were performed. Tests were made on both double and single lap joints. Finally. the failure criteria concerning strength predictions of adhesively bonded joints were reviewed. A, new criterion was proposed for the prediction of joint strength

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Thesis (Ph.D.)--University of Tulsa, 1990. / Bibliography: leaves 103-106.

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