Dynamic analysis of 2-hydroxy ethyl methacrylate and methyl methacrylate copolymer as an interface material in total hip replacement using finite element methods

Keywords

Finite element method; Total hip replacement

Abstract

The major mode of long-term failure of Total Hip Arthroplasty is prosthetic loosening. The performance of a new copolymer of 2-Hydroxy Ethyl MethAcrylate (HEMA) and Methyl MethAcrylate (MMA) as an interface material used in Total Hip Replacement (THR) under impact was analyzed using an explicit finite element code to see if this copolymer has the potential of eliminating the long term loosening in THR. A finite element model of the copolymer coated structure sample, which consists of two cylindrical steel rods, copolymer layer and bone cement, and the spherical steel balls, which were used to impact the sample, were developed in the LS-INGRID modeling package for impact simulation. The material properties for the copolymer layer were obtained from the experimental tensile test results of the structure sample and the bulk copolymer. The copolymer layer was modeled using isotropic elastic-plastic and piecewise linear plastic material models. LS-DYNA, an explicit nonlinear finite element code, was used for the analysis. Spherical balls delivering the impact were given an initial velocity while the sample was held stationary. The energy absorbed by the structure sample was noted. The composition of the copolymer was varied from 0% HEMA to 60% HEMA so as to show the effect of increase in the percentage of HEMA and also both the dry and the wet samples were analyzed. Experimental analysis was performed on a few compositions of the copolymer to verify the finite element results. Results of the impact analysis without failure indicated that varying the percentage of HEMA in the copolymer does show some difference in the energy absorption below the breaking limit. 40% wet HEMA after silane coating which was concluded as the best composition in static analysis absorbs less energy at break than the 0% wet HEMA. These results indicate that varying the percentage of HEMA in the copolymer appears to improve the performance of the structure sample under impact loading conditions, below the breaking limit. These finite element results were validated against experimental results.

Notes

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Graduation Date

2003

Advisor

Nicholson, David W.

Degree

Master of Science (M.S.)

College

College of Engineering

Department

Mechanical, Materials, and Aerospace Engineering

Format

PDF

Pages

87 p.

Language

English

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Identifier

DP0029112

Subjects

Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic

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