考虑缺口和体积效应的轮盘等效体积概率寿命分析方法

Equivalent Volume Analysis Method Accounting for Notch Effect and Volume Effect on Probabilistic Fatigue Life Estimation for Disk

关键词:  轮盘  缺口效应  体积效应  韦布尔分布  等效体积

Key words:  Disk  Notch effect  Volume effect  Weibull distribution  Equivalent volume

摘要:

航空发动机轮盘的疲劳破坏多伴有缺口效应和体积效应。为了研究缺口效应和体积效应对疲劳寿命的影响，采用修正Walker模型考虑平均应力的影响，建立能统一描述各应力水平下疲劳寿命分布的三参数Weibull模型，在“等概率寿命、等损伤”的基本思想下，将轮盘大应力区的危险体积转换为具有相同损伤的等效体积，进而利用Weibull最弱环理论可获得具有缺口效应和体积效应的轮盘危险部位在任意失效概率下的疲劳寿命。对两种不同厚度(4mm和6mm)的涡轮盘螺栓孔模拟试件进行概率寿命预估，并与试验结果及应力体方法预估结果进行对比。结果显示，本方法对两种模拟试件的概率寿命预估结果最大误差在30%左右，在中位、高可靠度时的最大预估误差为-23.2%，预估精度高于应力体方法。

Abstract:

The fatigue failure of aero-engine disks is always accompanied by notch effect and volume effect. To study the influence of notch effect and volume effect on fatigue life， the modified Walker model was used to consider mean stress effect， and the uniform three parameter Weibull distribution was established to account for the scatter of fatigue life under various stress levels. Based on the principle of ‘while the probabilistic fatigue lives are the same， the damage contained are equal’， the detrimental volume in the high stress region of disk was transferred to equivalent volume containing equal damage and accumulated. Furthermore， the weakest link theory was occupied to calculate the probabilistic fatigue life of components with notch effect and volume effect under any failure probability. The probabilistic fatigue lives of two simulated bolt-hole specimens of turbine disk with different thicknesses (4mm and 6mm) were investigated by the equivalent volumetric method proposed in this paper. Besides， the results from fatigue test data and the stress volumetric method were also provided for comparison. Through the comparison， it was shown that the prediction error of estimated probabilistic fatigue lives of the two specimens by the equivalent volumetric method were within 30% for all the cases examined， with the maximum prediction error being merely -23.2% for the medium and high reliability cases， providing better accuracy than the stress volumetric method.