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A Nonlinear Viscoelastic Finite Element Model of Polyethylene

P.C. Chen∗,†, C.W. Colwell, D.D. D’Lima†,‡
Scripps, La Jolla, CA, USA
UCSD, La Jolla, CA, USA
This paper is a tribute to Prof. Pin Tong in honor of his 72th birthday, and edited by Dr. David Lam.

Molecular & Cellular Biomechanics 2011, 8(2), 135-148. https://doi.org/10.3970/mcb.2011.008.135

Abstract

A nonlinear viscoelastic finite element model of ultra-high molecular weight polyethylene (UHMWPE) was developed in this study. Eight cylindrical specimens were machined from ram extruded UHMWPE bar stock (GUR 1020) and tested under constant compression at 7% strain for 100 sec. The stress strain data during the initial ramp up to 7% strain was utilized to model the "instantaneous" stress-strain response using a Mooney-Rivlin material model. The viscoelastic behavior was modeled using the time-dependent relaxation in stress seen after the initial maximum stress was achieved using a stored energy formulation. A cylindrical model of similar dimensions was created using a finite element analysis software program. The cylinder was made up of hexahedral elements, which were given the material properties utilizing the "instantaneous" stress-strain curve and the energy-relaxation curve obtained from the experimental data. The cylinder was compressed between two flat rigid bodies that simulated the fixtures of the testing machine. Experimental stress-relaxation, creep and dynamic testing data were then used to validate the model. The mean error for predicted versus experimental data for stress relaxation at different strain levels was 4.2%. The mean error for the creep test was 7% and for dynamic test was 5.4%. Finally, dynamic loading in a hip arthroplasty was modeled and validated experimentally with an error of 8%. This study establishes a working finite element material model of UHMWPE that can be utilized to simulate a variety of postoperative arthroplasty conditions.

Keywords

Polyethylene, UHMWPE, finite element model, finite element analysis, total joint arthroplasty, hip arthroplasty, knee arthroplasty

Cite This Article

Chen, P., Colwell, C., D’Lima, D. (2011). A Nonlinear Viscoelastic Finite Element Model of Polyethylene. Molecular & Cellular Biomechanics, 8(2), 135–148.



This work is licensed under a Creative Commons Attribution 4.0 International License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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