Numerical Evaluation of Fatigue Crack Growth Rate of Hot-Rolled 16Mn Steel Based on Compliance Method

摘要

Reliable evaluation of the fatigue crack growth rates in different kinds of specimen is necessary for the design of engineering components working in fatigue-load conditions. In this study, a new numerical model for evaluation of the fatigue crack growth rate in a three-point-bend specimen was proposed on the basis of compliance method. A three-point-bending fatigue test machine with a displacement-controlled loading system was developed to measure decrease of the fatigue load due to increase of the compliance of the specimen caused by crack growth. Evaluation of the fatigue crack growth rates of hot-rolled 16Mn steel was carried out using the test machine and the numerical model. The analysis results of the crack growth rates revealed different tendencies of slope for the former and latter processes of the subcritical propagation. Paris's constants of hot-rolled 16Mn steel for the former process were obtained as c=1.17x10-9 and m=4.47, whereas the same parameters for the latter process were obtained as c '=3.09x10-5 and m '=0.84. The threshold value of the stress-intensity factor range for the material was determined as Delta Kth=10.8 MPa root m.