17 research outputs found
Comparison of compact bone failure under two different loadings rates: experimental and modelling approaches
Understanding the mechanical behaviour of bones up to failure is necesary for
diagnosis and prevention of accident and trauma. As far as we know, no authors
have yet studied the tensile behaviour of compact bone including failure under
dynamic loadings (1m/s). The originality of this study comes from not only the
analysis of compact bone failure under dynamic loadings, the results of which
are compared to those obtained under quasi static loadings but also the
development of a statistical model. We developed a protocol using three
different devices. Firstly, an X-ray scanner to analyse bone density, secondly,
a common tensile device to perform quasi static experiments and thirdly, a
special device based upon a hydraulic cylinder to perform dynamic tests. For
all the tests, we used the same sample shape which took into account the
brittleness of the compact bone. We first performed relaxation and hysteresis
tests followed by tensile tests up to failure. Viscous and plastic effects were
not relevant to the compact bone behaviour so its behaviour was considered
elastic and brittle. The bovine compact bone was three to four times more
brittle under a dynamic load than under a quasi static one. Numerically, a
statistical model, based upon the Weibull theory is used to predict the failure
stress in compact bone
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