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Modelling of metal on metal hip prostheses

Al-Saffar, Ali 2015. Modelling of metal on metal hip prostheses. PhD Thesis, Cardiff University.
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Metal-on-metal (MOM) total hip replacement is an artificial hip joint has been used to replace damaged or diseased natural joints. MOM studies have demonstrated severe complications due to metal wear debris in tissues adjacent to the implants. Reducing the wear rate and operating with full film lubrication could reduce these problems; a better understanding of the lubrication mechanisms is also relevant to other hard bearing materials such as ceramics or new metal alloys. Ball-in-socket MOM contacts were analysed using the Abaqus Finite Element package to simulate dry contact between the acetabular cup and the femoral head. Different cup thicknesses of 4, 6, 8, and 10 mm were considered using a polyurethane foam block support system. Elastohydrodynamic lubrication (EHL) analyses were developed for the contacts using three different approaches to specify the contact. These were (i) A simple model based on the radii of relative curvature, (ii) An equivalent contact model developed so that its dry contact area and maximum pressure replicated the values obtained from the FE analysis, and (iii) A modified version of (ii) that also ensured equivalence of the gap shape outside the contact area. Published in vivo information for the hip joint contact forces over the walking cycle was used to specify the operating conditions for the EHL analysis. III This was achieved by developing techniques to transform the in vivo information to provide load direction and kinematic information relative to the nominal contact point between the components. The analysis method was found to be effective for all points of the walking cycle for cases where the cup thickness exceeded 5 mm and modelling approach (ii) was identified as satisfactory. For a cup thickness of 4 mm, membrane action began to emerge in the FE analyses so that such contacts behaved in a different way.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TJ Mechanical engineering and machinery
Uncontrolled Keywords: Metal-On-Metal Hip Replacement; EHL Lubrication
Date of First Compliant Deposit: 30 March 2016
Last Modified: 15 Oct 2016 04:30

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