引入应变循环损伤的材料裂纹扩展行为预测模型

根据循环载荷下的裂尖循环弹塑性应力应变场分析,结合Manson-Coffin经验关系,定义了基于循环塑性区内材料塑性应变幅值的单位平均损伤；根据Miner疲劳线性累积损伤理论,以裂尖扩展方向的循环塑性区尺寸为裂纹裂尖的单位扩展量,提出了基于低周疲劳损伤预测I型裂纹扩展速率的新预测模型.新模型中给出的参数均有明确的物理意义,不需要人为调试.Cr2Ni2MoV和X12CrMoWVNbN 10-1-1两种转子材料的低周疲劳试验结果表明,新模型对这两种材料裂纹扩展速率的预测结果与试验结果吻合良好.利用相关文献中提供的6种材料的低周疲劳性能数据,进一步验证了新模型用于裂纹扩展速率预测的良好适用性.

Prediction Model of Fatigue Crack Growth Behavior by Introducing Strain Cycle Damage

According to the cyclic elasto-plastic HRR field near the crack tip,the Manson-Coffin theory is applied to define the unit average damage over the plastic strain magnitude of the materials within the cyclic plastic region.Assuming the step size of the crack advancement equals the size of the real cyclic plastic region along the crack growth direction,then following the linear damage accumulation theory-Miner law,a model for predicting the low cycle fatigue crack growth of the opening mode crack is set up.It is noted that every factor in the new model is endowed with clear physical meaning without any human debugging.The prediction results of the low cyclic fatigue crack propagation by the proposed model coincide well with the low cycle fatigue test data of two rotor materials.The good prediction capability of the proposed model is verified by the data of six different materials from literatures.