基于循环应变特征的疲劳-蠕变寿命预测方法

为研究非对称加载下疲劳-蠕变交互作用对粉末高温合金涡轮盘寿命的影响，开展了550 ℃时不同应力水平及保载时间下FGH96粉末高温合金的低周疲劳-蠕变试验，得到了材料的循环应变响应及疲劳-蠕变寿命随保载时间的变化规律。在此基础上，结合材料的循环软化特征，以循环应变范围作为损伤控制参量，将其与保载时间和动态循环次数相关联，提出了一种基于循环应变特征的疲劳-蠕变寿命预测方法。该模型综合考虑了载荷历程和保载时间对材料疲劳-蠕变损伤的影响，能够实现不同应力水平、不同保载时间下FGH96粉末高温合金疲劳-蠕变寿命预测以及消耗寿命的动态跟踪。通过与工程上常用的几种模型进行对比，发现新模型具有较高的预测精度，且预测结果分散性较小，寿命预测结果基本位于±2.5倍寿命分散带之内，预测标准差小于0.4。

Fatigue-creep life prediction based on cyclic strain characteristics

To investigate the effect of fatigue-creep interaction on the life of Powder Metallurgy (P/M) superalloy turbine disks under asymmetric loading, low cycle fatigue-creep tests of the P/M FGH96 superalloy are conducted at 550℃ at different stress levels and holding time, obtaining its cyclic strain response and the variation of fatigue-creep life. A fatigue-creep life prediction method based on cyclic strain characteristics is proposed. The new model takes the cyclic strain range as the damage control parameter which correlates with the load holding time and the dynamic cycles. The influences of the load history and holding time on the fatigue-creep damage are comprehensively considered, and the fatigue-creep life prediction and dynamic tracking of consuming life for FGH96 at different stress levels and within different holding time can be realized. Compared with other life prediction models, the new model owns high prediction accuracy with small dispersion of prediction. The life prediction results are mostly within ±2.5 times of the scatter band, and the standard deviation is less than 0.4.