The role of parameter identification in finite element contact analyses with reference to orthopaedic biomechanics applications.

A finite element model accounting for large sliding frictional contact requires, depending on the type of contact algorithm in use, the definition of many numerical parameters such as contact stiffness, convergence norm and tolerance, compenetration monitoring, over-relaxing factors, etc. All these parameters do not have a physical meaning and thus they cannot be measured experimentally. This makes their identification quite complex. The aim of this study was to investigate the role of parameter identification on the accuracy of results produced by finite element models accounting for bone-implant frictional contact, when the Penalty method is used. The sensitivity analysis of several numerical parameters that may govern the state of results was carried out. Two parameters, contact stiffness and convergence tolerance, were found to play a crucial role in establishing the accuracy of the finite element results. Based on the achieved results it was stated that any numerical-only study involving contact non-linearity and omitting careful qualification of the model limits should be rejected from any peer-reviewed journal.