14 research outputs found
Two-dimensional finite element simulation of fracture and fatigue behaviours of alumina microstructures for hip prosthesis
This paper describes a two-dimensional (2D) finite element simulation for
fracture and fatigue behaviours of pure alumina microstructures such as those
found at hip prostheses. Finite element models are developed using actual Al2O3
microstructures and a bilinear cohesive zone law. Simulation conditions are
similar to those found at a slip zone in a dry contact between a femoral head
and an acetabular cup of hip prosthesis. Contact stresses are imposed to
generate cracks in the models. Magnitudes of imposed stresses are higher than
those found at the microscopic scale. Effects of microstructures and contact
stresses are investigated in terms of crack formation. In addition, fatigue
behaviour of the microstructure is determined by performing simulations under
cyclic loading conditions. It is shown that crack density observed in a
microstructure increases with increasing magnitude of applied contact stress.
Moreover, crack density increases linearly with respect to the number of
fatigue cycles within a given contact stress range. Meanwhile, as applied
contact stress increases, number of cycles to failure decreases gradually.
Finally, this proposed finite element simulation offers an effective method for
identifying fracture and fatigue behaviours of a microstructure provided that
microstructure images are available
A Semi-deterministic Wear Model Considering the Effect of Zinc Dialkyl Dithiophosphate Tribofilm
Tribochemistry plays a very important role in the behaviour of systems in tribologically loaded contacts under boundary lubrication conditions. Previous works have mainly reported contact mechanics simulations for
capturing the boundary lubrication regime, but the real mechanism in which tribofilms reduce wear is still unclear. In this paper, the wear prediction capabilities of a recently published mechanochemical simulation approach (Ghanbarzadeh et al. in Tribol Int, 2014) are tested. The wear model, which involves a time- and spatially dependent
coefficient of wear, was tested for two additive concentrations and three temperatures at different times, and the predictions are validated against experimental results. The experiments were conducted using a mini-traction machine in a sliding/rolling condition, and the spacer layer interferometry method was used to measure the tribofilm thickness. Wear measurements have been taken using a white-light interferometry. Good agreement is seen between simulation and experiment in terms of tribofilm thickness and wear depth predictions