基于夹杂-细晶粒区-鱼眼疲劳失效的超长寿命预测模型

本文旨在研究夹杂-细晶粒区-鱼眼诱发疲劳失效的超长寿命预测模型.基于Cr-Ni-W合金钢疲劳试验结果,结合局部应力-寿命法和位错-能量法,分别构建了局部裂纹萌生寿命模型(LCIL)和考虑夹杂及细晶粒区影响的裂纹萌生寿命模型(IFCIL),并与Tanaka-Mura模型(T-M)进行了对比分析.其次,分别对细晶粒区内的小裂纹扩展行为和细晶粒区外鱼眼内的长裂纹扩展行为进行建模,最终形成了包含裂纹萌生和扩展在内的全寿命预测模型.结果表明,考虑夹杂及细晶粒区影响的裂纹萌生寿命模型(IFCIL)有较高的预测精度;对应细晶粒区的裂纹萌生寿命几乎等同于全寿命;裂纹扩展寿命仅占据全寿命很小的一部分;预测结果全部处于2倍偏差以内,即全寿命模型可有效地用于夹杂-细晶粒区-鱼眼诱发失效的超长寿命预测.

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.