An integrated methodology for separating closure and residual stress effects from fatigue crack growth rate data

To properly interpret the results of standard fatigue crack growth tests it is often necessary to incorporate corrective techniques to the Delta K applied data. This is especially true in the near-threshold regime where long crack data need to be closure corrected to predict small crack behaviour. It is also an issue in the presence of residual stress. A methodology to separate the influence of sample size, geometry, crack length and residual stress from the standard crack growth test data to obtain a true material response is presented. Stress ratio and residual stress contributions from known combinations of assumed crack size, applied stress and residual stress are also addressed and incorporated in the fatigue crack growth behaviour.