Fatigue fracture of the stem-cement interface with a clamped cantilever beam test.

A clamped cantilever beam test was developed to determine the fatigue crack propagation rate of the CoCr alloy/PMMA cement interface at high crack tip phase angles. A combination of finite element and experimental methods was used to determine the fatigue crack growth rates of two different CoCr alloy/PMMA cement surfaces. A crack tip phase angle of 69 deg was found, indicating that loading at the crack tip was mixed-mode with a large degree of in-plane shear loading. The energy required to propagate a crack at the interface was much greater for the plasma-sprayed CoCr surface when compared to the PMMA-precoated satin finish (p < 0.001). Both interface surfaces could be modeled using a Paris fatigue crack growth law over crack propagation rates of 10(-4) to 10(-9) m/cycle.