三种疲劳蠕变交互作用寿命预测模型的比较及其应用

COMPARISON AMONG THREE FATIGUE-CREEP INTERACTION LIFE PREDICTION MODELS AND THEIR APPLICATIONS

对疲劳蠕变交互作用寿命预测方法进行简单回顾,并分别介绍从能量耗竭、韧性耗竭、延性耗竭角度提出的三种应力控制疲劳蠕变寿命预测方法。通过文献试验数据和1.25Cr0.5Mo钢520℃应力控制、梯形波加载试验数据对上述三种模型的优缺点和适用范围进行评价。三种方法的预测精度都大大高于传统的频率分离法和应变能频率分离法;能量模型对应力应变控制模式都适用,延性耗竭模型预测精度最高,平均应变速率模型形式最简单,适用于应力控制下纯蠕变、纯疲劳或疲劳蠕变交互作用下的各种失效组合模式,拓宽了Monkman-Grant经验关系式的应用范围,因此具有重要的工程应用价值和应用前景。最后阐述平均应变速率模型的应用步骤。

Life prediction methods of fatigue-creep interaction are beriefly reviewed. Three fatigue-creep life prediction models .for stress controll mode are introduced, which are based on energy exhaustion, toughness exhaustion, and ductility exhaustion theory respectively. Data from literatures and stress controlled fatigue-creep interaction test of 1.25Cr0.SMo steel with trapezium waveform at 520 ℃ are used to comment on these models and their applicability. The predicting precisious of three models are greatly improved comparing with traditional frequency separation teclmique（FS） and strain energy flequency modified approach（SEFS）. The energy model is applicable to not only stress controll mode, but also strain controll mode. The ductility exhaustion model has the best life prediction precision. The mean strain rate model has very simple form, and can be applied to all stress controlled failure modes, including pure creep, pure fatigue and fatigue-creep interaction. The mean strain rate model extends the applicability of Monkman-Grant relation, and has important engineering value. At last, the application precedure of mean strain rate model is discussed.