TY - EJOU
AU - Chen, P.C.
AU - Colwell, C.W.
AU - Dâ€™Lima, D.D.
TI - A Nonlinear Viscoelastic Finite Element Model of Polyethylene
T2 - Molecular \& Cellular Biomechanics
PY - 2011
VL - 8
IS - 2
SN - 1556-5300
AB - 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.
KW - Polyethylene
KW - UHMWPE
KW - finite element model
KW - finite element analysis
KW - total joint arthroplasty
KW - hip arthroplasty
KW - knee arthroplasty
DO - 10.3970/mcb.2011.008.135