Three-dimensional fatigue cracking under elastic–plastic deformation

Aircraft engine structures can contain small cracks, which have developed from defects induced during material processing. Advanced structural materials such as nickel-based superalloys undergo extensive plastic deformation prior to failure, therefore, these small cracks can be subjected to localized damage with significant amount of plasticity. We have conducted a combined computational/experimental study of fatigue crack growth at room temperature and at 260°C. The experimental results have been correlated with three-dimensional finite element calculations. Material constitutive equations and a computational procedure to calculate energy release rate along the crack front are developed. It is shown that the fatigue crack growth rate is related to a power function of Jmax.