Determination of the mechanical properties of Bionate 80A and Bionate 75D for the stress analysis of cushion form bearings.
Two biomedical grade polyurethanes, currently under investigation as an alternative tibial bearing for a total knee replacement, are analysed. Extensive mechanical testing has been performed on these materials to determine the mechanical properties in terms of strain energy density functions for use in the finite element package MSC. Marc 2001 that do not rely on linear elasticity. A variation in Poisson's ratio in the fourth decimal place can lead to significant errors in the magnitude and distribution of stresses in a linear elastic analysis. As large variations in this parameter (up to the first decimal place) were determined experimentally, it is concluded that a linear elastic approach to the stress analysis of these materials is not valid.
Nic An Ghaill
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Department of Mechanical and Aeronautical Engineering, University of Limerick, Castletroy, Limerick, Ireland. natalie.nicanghaill@ul.ie
Little
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