基于P-ε-N曲线整体推断的涡轮盘寿命可靠性分析

Estimation of LCF life for a turbine disk based on P-ε-N curves

关键词:  涡轮盘  低循环疲劳  异方差回归分析  应变-寿命曲线  置信度  可靠性

Key words:  Turbine disk  Low cycle fatigue  Heteroscedastic regression analysis  Strain-life curve  Confidence  Reliability

摘要:

疲劳寿命符合对数正态分布,并且对数寿命的标准差随弹性应变幅和塑性应变幅的减小而增大。采用基于异方差回归分析的整体推断方法在现有低循环疲劳试验数据的基础上,得到了航空发动机涡轮盘材料GH4133在温度250℃下的P-ε-N曲线;利用P--εN曲线对某涡轮盘进行低循环疲劳寿命可靠性分析,得到置信度0.95,可靠度0.998 7的轮盘寿命为1 866次循环,合683飞行小时,与涡轮盘疲劳试验分析得到的技术寿命接近。整体推断得到的P-ε-N曲线精度较高,利用P-ε-N曲线进行轮盘寿命可靠性设计分析具有计算简便、节约试验成本的优点。

Abstract:

The fatigue life follows log-normal distribution and the standard deviation of logarithmic life increases with reducing elasticity and plasticity strain.The P-ε-N curves of turbine disk material GH4133 in temperature of 250℃ was obtained by the integral estimation method based on heteroscedastic regression analysis of the low cycle fatigue(LCF) test data.The reliability analysis of LCF life for a turbine disk was completed by these P-ε-N curves.The fatigue life with confidence of 0.95 and reliability of 0.998 7 was 1 866 cycles,and it was converted into 683 hours of flight,which fitted well with the technical life based on real turbine disks fatigue test estimation.The precision of the P-ε-N curve obtained by the integral estimation was good enough.The fatigue reliability design and analysis of turbine disks based on P-ε-N curves was simple in computation and could save the cost of fatigue tests.