Study on the FCG Prediction Model Based on Material’s LCF Damage

Abstract: Based on the cyclic elasto-plastic HRR field near the crack tip under the cyclic loading, combined with the Manson-Coffin theory, a unit average damage over the plastic strain magnitude of the node in the cyclic plastic region was defined. Then, combined with the linear damage accumulation theory-Miner law, the crack was assumed to advance each step of the size of cyclic plastic region along the extending direction. Therefore, a new model for predicting the fatigue crack growth (FCG) of the opening mode crack based on the low cycle fatigue damage was set up. In the new model, a variable factor to calculate the blunting size during the process of crack advancement was applied, and the plastic damages of the material located in the cyclic plastic region along the extending direction were considered. Obviously, the advantage of the new model is that every factor has clearly physical meaning which does not need any human debugging. Based on the low cycle fatigue (LCF) data gained from the laboratory, the predictions of the FCG by the new model is consistent with the test results of X12CrMoWVNbN 10-1-1. What’s more, according to the reference papers, the good predictability of the new model on four materials is also discussed.