基于应变的疲劳可靠性分析新方法

NEW METHOD FOR STRAIN-BASED FATIGUE RELIABILITY ANALYSIS

应用随机循环应变载荷－强度干涉模型，建立了基于应变的疲劳可靠性分析新方法。新考虑了材料循环应力－应变响应的分散性。与现有方法不同，材料常数视为非独立随机变量，来自于试验数据的回归结果。随机循环应力－应变行为和循环应变－寿命关系分别采用概率曲线来描述。循环应变载荷和强度的概率密度函数可显式分别由这些曲线求得。方法可方便拓展到如现有方法确定性循环应力－应变模型情形。核工程材料？１Ｃｒ１８Ｎｉ９Ｔｉ不锈钢管道焊缝金属的试验结果分析说明了方法的有效性。

A new method for strain-based fatigue reliability analysis is constructed by considering interference between the random fatigue strain applied and capacity histories. Recently found scatter of the cyclic stress-strain (CSS) responses of a nuclear engineering material,1Cr18Ni9Ti stainless steel pipe-weld metal,is taken into account. Different from the existent methods that took the material constants in the Coffin-Manson cyclic strain-life (CSL) relation as independent random variables,present work treats the material constants in the Ramberg-Osgood CSS and Coffin-Manson CSL relations as dependent random variables from the fits of test data. These relations are approximated by the probability-based CSS and CSL curves,respectively. Probability density functions of the random fatigue strain applied and capacity histories are analytically obtained from the probability-based curves. This method can be applied in practice by a form of reliability-stress-life curves and extrapolated conveniently to the case of deterministic CSS relation as the existent methods did. Availability of this method is indicated by an analysis of the material test results.