Abstract
One of the major factors that control the longevity of implanted artificial hip joint is wear debris of UHMWPE. The wear debris is caused by the transient stress occurring repeatedly at the inner spherical surface and its neighborhood and the change in clearance due to the deformation in UHMWPE acetabular cup. In this study, three-dimensional viscoelastic stress and creep deformation in hemispherical acetabular cup made of UHMWPE are analyzed using integral forms of stress-strain constitutive relations and based on the correspondence principle between the analytic solution of three-dimensional elastic problem subjected to same load in the cup of same shape and the Laplace transformed viscoelastic solution. Analytic solution of three-dimensional elastic problem is formulated by the use of Papkovich-Neuber displacement function, and the Laplace transformed stress of viscoelastic hollow hemisphere is derived based on the correspondence principle from the analytic solution. The inverse Laplace transform of the viscoelastic solution is performed by Hosono's numerical method. Effects of the load distribution applied on the inner surface of the cup on the viscoelastic stress and creep deformation in UHMWPE cup are quantitatively discussed.
