基于疲劳-蠕变载荷等效转换的涡轮盘载荷谱编制及寿命预测

针对雨流计数法在峰谷值提取时进行等值压缩,忽略保载时间的问题进行了改进,提出了一种基于损伤曲线的疲劳-蠕变载荷等效转换方法。利用非线性疲劳损伤累积函数和损伤等效原则,建立了不同应力水平、不同保载时间下疲劳-蠕变载荷与疲劳载荷之间的等效换算模型。利用涡轮盘材料试验数据,计算了不同循环加载条件下的等效换算比,得到了其随保载时间的变化规律。利用改进的雨流计数法,编制了航空发动机高压涡轮盘载荷谱,并将其与寿命-时间分数预测法相结合,得到了涡轮盘剩余寿命。结果表明,改进的雨流计数法综合考虑了疲劳-蠕变耦合损伤对涡轮盘寿命造成的影响,相比于传统雨流计数法,寿命预测误差降低了15.02%,验证了该方法的有效性。

Load Spectrum Compiling and Life Prediction for Turbine Disc Based on Equivalent Transformation of Fatigue-Creep Load

Aiming at the problem of ignoring the holding time when the rainflow counting method extracts the peak and valley values by equivalent compression, a fatigue-creep load transformation method was proposed based on damage curves. By nonlinear fatigue damage accumulation function and damage equivalent, the model of equivalent transformation between fatigue-creep load and fatigue load under different stress levels and holding time was built. Using the data of turbine disc material test, the equivalent transformation ratio under different cycle loading conditions, and the law of its variation with holding time was obtained. Based on the improved rainflow counting method, the load spectrum of the high-pressure turbine disc was compiled, and combined with the life-time fraction prediction method, the residual life of turbine disc was obtained. The result shows that the influence of fatigue-creep coupling damage on component life is considerd comprehensively by the improved rainflow counting method, and the life prediction error is down by 15.02% compared with the traditional rainflow counting method, which verifies the validity of the method.