Crack Initiation and Propagation Simulations for ManTen and RQC100 Steel Keyhole Notched Specimens Tested by the Fatigue Design & Evaluation Committee of SAE 2020-01-0191

In the 1970s the Fatigue Design and Evaluation Committee of SAE tested 57 "Keyhole" notched specimens with three different variable amplitude(VA) histories using two materials; a lower strength ManTen steel and a higher strength boron steel RQC-100. Recordings were made of not only initiation and final fracture cycles but also a record of the advance of the cracks during the propagation phase. In this work the initiation fatigue life is predicted using the usual method of plasticity correction at the notch followed by a Palmgren-Miner summation of damage with mean stress correction. The emphasis of the study is on simulating the crack propagation results. For that phase the ASME da/dN vs. DeltaK lines augmented by Hasegawa et al's lines and thresholds for negative R ratios, were used specifically to help predict the propagation for one of the VA histories that had a significant negative mean. The open source crack propagation simulation program applied a material memory model to determine the crack advance on a reversal by reversal basis. The resulting crack advance plots are compared with the experimental observations. Results are presented for the constant amplitude tests and for all three VA histories used to test the two materials.