考虑尺寸效应的结构振动疲劳寿命评估方法

Evaluation method of vibration fatigue life of structures considering size effect

为提高振动环境下液体火箭发动机关键结构振动寿命评估精度,通过裂纹萌生特征体积假设和危险区域体积细分串联模型,将尺寸效应引入振动疲劳寿命分析,提出了一种振动疲劳体积寿命模型,并建立了其数值模型。在关键结构模拟件振动试验数据基础上,识别了典型材料小尺度振动疲劳特性参数,并利用仿真与试验寿命数据极大似然对裂纹萌生特征长度进行优化取值。利用关键结构模拟试验件振动疲劳试验对提出的模型进行验证,结果表明:对两种状态模拟件,模型预测各量级振动寿命分布均覆盖试验数据,且原状态平均寿命在试验1.5倍分散带内、改进状态在试验2倍分散带内,提出的方法具有准确性及适用性。

In order to improve the evaluation precision of vibration life of key structure of liquid rocket engine under vibration environment,the size effect was introduced into vibration fatigue life analysis by using crack initiation characteristic volume hypothesis and dangerous volume subdivision series model,and the vibration fatigue volume life model was put forward,and its numerical model was established.Based on the vibration test data of key structural simulators,the small-scale vibration fatigue characteristic parameters of typical materials were identified,and the life data maximum likelihood of simulation and test was used to optimize the crack initiation characteristic length.The model was verified by the vibration fatigue test of the key structure simulators.It is found that for the two simulators,the distribution of vibration life of each load order covers the test data,and the average life of the original state is within 1.5 times the dispersion band of the test,and the improved state is within 2 times the dispersion band of the test.The accuracy and applicability of the method were proved.