基于塑性应变能的中低周疲劳概率寿命模型

由于材料、尺寸以及载荷等的分散性,涡轮盘疲劳寿命存在较大的分散性。在充分考虑材料加卸载应力、应变及应力比对疲劳寿命影响的基础上,提出了一种适用于中低周疲劳的塑性应变能概率寿命模型。该模型在考虑材料、尺寸和载荷等导致寿命分散的因素的基础上,重点考虑了循环应力应变曲线的分散性,结合根据应力比的二次插值,获得了插值范围内任意应力比下的塑性应变能损伤参量与疲劳寿命的关系。运用所提概率寿命模型结合响应面法与蒙特卡洛法对某涡轮盘螺栓孔模拟试件进行了概率寿命分析。结果显示,模拟试件的计算结果与试验结果的中位寿命仅相差022%,寿命分散系数相差581%,说明本概率寿命模型概率寿命预估精度高。 

Probabilistic fatigue life model for medium and low cycle fatigue based on plastic strain energy

The fatigue life of turbine disk may show large scatter duo to the variability of parameters such as material properties, geometrical features, load and some other factors. Taking into full account the influence of factors on the fatigue life, such as stress, strain and stress ratio in the loading and unloading process, a probabilistic fatigue life model based on plastic strain energy was proposed for medium and low cycle fatigue. Besides, the factors commonly used to calculate the scatter of fatigue life, like material property, geometry size and load, the randomness of the cyclic stress strain curve, were also considered. With the method of quadratic interpolation for stress ratio, the relation of plastic strain energy damage parameter and fatigue life under various stress ratios could be obtained. Using the plastic strain energy probabilistic fatigue life model in conjunction with the response surface method and Monte Carlo method, the probabilistic fatigue life of a simulated bolt hole specimen of a turbine disk was analyzed. The results showed that the calculated median fatigue life of the simulated specimen was just 022% less than the median test life, while the fatigue life scatter factor was just 581% less than that of the test result, showing high accuracy of the proposed model for probabilistic fatigue life prediction.