随机恒幅循环载荷疲劳可靠度异量纲干涉模型

Dissimilar-dimension Interference Model of Fatigue Reliability Under Uncertain Cyclic Load

用于与时间无关的失效模式(例如静强度失效)的失效概率或可靠度计算的'应力—强度干涉模型'已很成熟,但要将干涉分析的概念与方法应用于与时间相关的失效模式(例如疲劳、磨损和腐蚀等)还存在许多困难,即使对于存在不确定性的恒幅循环载荷下的疲劳可靠性问题,目前也还没有像静强度应力—强度干涉模型那样简单、直接、有效的方法及数学模型。在概率统计平均的意义上重新解释传统的两个随机变量干涉分析的基本概念及模型,将干涉模型解释为载荷加权平均模型。具体地讲,就是将应力—强度干涉模型解释、拓展为强度超越(载荷)概率的(载荷)统计加权平均模型,或给定应力下的条件失效概率的随机载荷加权平均模型。这样,传统上只能应用于相同量纲随机变量(例如应力与强度)的干涉模型就可以拓展应用于具有不同量纲随机变量(例如应力与寿命)的情形,例如随机载荷下的疲劳失效概率(寿命小于指定值的概率)或可靠度(寿命大于指定值的概率)计算。应用这样的模型,可以很方便地根据几个确定性恒幅循环载荷下的疲劳寿命分布,预测随机恒幅循环载荷作用下的疲劳失效概率或可靠度。

The stress-strength interference model for static strength failure is well developed, while difficulties still exist when use the concept of stress-strength interference to calculate the reliability of time-dependent failure modes such as fatigue, abrasion, corrosion, etc. There is not yet a straight forward and effective model such as stress-strength interference model even for fatigue under constant amplitude cyclic stress with uncertainty in stress amplitude. Traditional stress-strength interference model is interpreted as that to express the statistical average of the probability that strength is greater than stress, or vice versa. Thus, the same model format, which traditionally can only be used for the situation of the parameters （load and stress） of the same unit, can be applied to more general situation. In other words, the traditional model was extended to the situation of any two variables, as long as one of the variables can be expressed as a function of the other. By such a model, fatigue failure probability/reliability can be calculated with known load distribution and fatigue life distribution.