On numerical modeling of equal channel angular extrusion of ultra high molecular weight polyethylene
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(Ed.)
Ultra high molecular weight polyethylene (UHMWPE) is
widely used in biomedical applications, e.g. as a bearing surface
in total joint arthroplasty. Recently, equal channel angular
extrusion (ECAE) was proposed as a processing method to
achieve higher molec ular entanglement and superior mechanical
properties of this material. Numerical modeling can be utilized
to evaluate the influence of such important manufacturing
parameters as the extrusion rate, temperature, geometry of the
die, back pressure and fricti on effects in the ECAE of
polyethylenes.
In this paper we focus on the development of efficient FE
models of ECAE for UHMWPE. We study the applicability of
the available constitutive models traditionally used in polymer
mechanics for UHMWPE, evaluate the importance of the proper
choice of the friction parameters between the billet and the die,
and compare the accuracy of predictions between 2D (plane
strain) and 3D models.
Our studies demonstrate that the choice of the constitutive
model is extremely important for the accuracy of numerical
modeling predictions. It is also shown that the friction coefficient
significantly influences the punch force and that 2D plane strain
assumption can become inaccurate in the presence of friction
between the billet and the extrusion channel.
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