Computer simulation of variable amplitude fatigue crack initiation behaviour using a new strain-based cumulative damage model

Computer software for the prediction of fatigue crack initiation has been developed. Based on a model derived from the closure behaviour of microcracks and the intrinsic resistance of metals and alloys to fatigue damage, this software allows predictions to be readily applied to quickly provide fatigue crack initiation life predictions for a wide range of alloys based on inputs of a nominal stress spectrum, a maximum spectrum stress and a net stress concentration factor. While the model had been previously proven successful for a number of material types and load spectra, in the present investigation the software demonstrated the ability to outperform the software package currently used for fatigue life prediction in the F-18 Hornet fighter aircraft during testing with component geometries, materials and load spectra all characteristic of the aircraft itself. Predictions from the newly developed software were both more accurate and more conservative than those provided by the current F-18 software. Such results lend further credit to the applicability of both the software and the model as general tools for the prediction of fatigue crack initiation.