Derivation of effective crack growth rate and crack closure data from effective-strain fatigue life data

Methods are presented for deriving the curves of crack growth rate vs, effective strain intensity factor range (da/dN vs. DeltaK(eff)) and crack opening stress vs. maximum and minimum stresses (sigma (op) vs. sigma (max), sigma (min)) from two series of smooth specimen strain-life test data. These methods allow the application of fatigue crack growth analysis to design problems without the expensive, time-consuming measurements typically required to obtain crack growth rate and crack closure data. These methods are demonstrated for a 2024-T351 aluminum alloy, an SAE 1045 steel, and an 'interstitial-free' sheet steel. Crack growth predictions for notched specimens subject to service loading are obtained using these derived data and compared with observations. The types of histories used are 1) a constant amplitude history, 2) a periodic compressive overload history, and 3) the SAE Grapple-Skidder and SAE Log-Skidder histories.