A coupled viscoplastic rate-dependent damage model for the simulation of fatigue failure of cement–bone interfaces

Clinical loosening of cemented hip replacements is often associated with mechanical failure of the cement–bone interface. Although different computational models trying to simulate the interface behavior can be found in the literature, plastic deformations have not been considered yet, despite the experimental results available demonstrating their importance. The main purpose of this work is to develop a computational model for bone–cement interfaces able to capture the behavior of the interface under static and cyclic mixed-mode loading, incorporating stiffness degradation (damage) and permanent deformation (plasticity). With this aim, a cohesive zone model that incorporates a coupled damage-viscoplastic constitutive law has been developed. A detailed description of the corresponding mathematical and computational framework is here included. A parameter fitting has been also performed, obtaining a correlation for every parameter with the quantity of interdigitated bone that can be easily obtained from computer tomographies. 3D finite element simulations of several experimental tests for cement–bone specimens have been carried out in order to show the ability of the model to reproduce the initiation and progression of failure as well as fatigue life of the interface. The predicted results are in close agreement with such experimental observations.