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Title: Computational and theoretical contact modelling of hip implant devices with the application of wear simulations
Author: Ali, Murat
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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Contact mechanics, wear and tribology of hip implant devices have been studied since early implantations and the performance of the devices are becoming increasingly important. Wear and surface damage of these bearing surfaces occur through normal gait loading conditions. However, in addition to this, stripe wear patterns are observed on patient implant retrievals and following hip simulator studies. Novel computational and theoretical methods were used and developed based on advanced computer aided engineering techniques and the finite element method. Hip joint modelling and numerical methodologies of mechanical wear simulations were studied through a newly proposed scripting method. Shakedown theory and maps were referred to for studying the biotribology and contact mechanics of hip resurfacing devices under cyclic normal, severe and edge loading conditions. Through implicit and explicit finite element modelling lateral displacement and laxity based microseparation models were developed. The contact pressure under edge loading conditions was at least a factor of 2 larger than under normal loading conditions. The wear rates of both the femoral head and acetabular cup during the bedding-in period were between 1-3 mm3/mc (million cycles) and 80-110 mm3/mc based on a steady-state wear coefficient. Results showed that modelling and verifying the contact and stress results under edge loading conditions required more careful computational modelling than for normal loading conditions. The high contact pressures observed during simulations of microseparation models were consistent with the high level of wear and surface damage observed in experimental simulator studies and from patient retrievals. These methods can therefore be used as a technique to simulate wear of hip implant devices. Shakedown assessments showed that under normal, as well as edge loading and severe loading conditions the hip device remained below the elastic shakedown region of a rolling and sliding shakedown map, which is ideal for minimal surface contact and subsurface damage.
Supervisor: Not available Sponsor: Engineering and Physical Sciences Research Council (EPSRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: R Medicine (General) ; TA Engineering (General). Civil engineering (General)