Aprediction model for the very high cycle fatigue life for inclusion-FGA (fine granular area)-fisheye induced fatigue failure

A prediction model for the very high cycle fatigue life for inclusion-fine granular area (FGA)-fisheye-induced failure was studied in this work. Combined with the experimental results of Cr-Ni-W alloy steel, a local crack initiation life model (LCIL) and an inclusion-FGA based crack initiation life model (IFCIL) were developed on the basis of the local stress-life method and the dislocation-energy method, respectively. Using the Tanaka-Mura model as a reference, the fitting results of LCIL and IFCIL models were analyzed. Based on the respective modeling of the small crack growth within the FGA and the long crack growth outside the FGA within the fisheye, the total life model involving crack initiation and growth was established. As a result, combined with the results of three crack initiation life models, the IFCIL model exhibits the highest prediction precision, and the predicted crack initiation life associated with the FGA size is nearly equivalent to the total life. Conversely, the crack growth life only occupies a fine fraction of the total life. Between the predicted and experimental results, the agreement is fairly good within the factor-of-two boundaries. In short, the established total life model can be effectively used to predict the very high cycle fatigue life for the inclusion-FGA-fisheye induced failure.