变幅载荷下摩擦焊接头疲劳寿命的分布及模拟

Probability Distribution of Fatigue Life of Notched Friction Welded Joints under Variable amplitude Loading and its Simulation

试验研究并分析了 45钢摩擦焊接头切口件恒幅载荷下的疲劳性能 ,表明其疲劳寿命结果可很好地表示为当量应力幅的函数 ,即Ni=C[Δσ2 /( 1+n)eqv - (Δσeqv) 2 /( 1+n)th ]-2 ,表达式中疲劳抗力系数C和疲劳门槛值 (Δσeqv) th 服从对数正态分布。根据C和(Δσepv) th的物理意义及概率分布 ,可知疲劳试件个体间的差异可以由C、(Δσepv) th来区别 ,而疲劳试验结果的随机分散性产生于试件个体间的差异 ,据此提出了一种新的模拟45钢摩擦焊接头切口件变幅载荷下疲劳寿命试验及其分布的方法 ,给出了相应的模拟计算步骤 ,模拟结果与试验结果进行了比较。结果表明 ,45钢摩擦焊接头切口件在变幅载荷下的疲劳寿命分布的模拟结果服从对数正态分布 ,并与试验结果符合得很好。因此该模拟方法可用于摩擦焊接结构的疲劳可靠性分析 ,从而节省大量的人力。

The experimental investigation is first carded out on the fatigue property of notched friction welded joints of 45-carbon steel under constant amplitude loading and the analysis show's that the fatigue life can be expressed as the function of the equivalent stress amplitude δσepv,i.e. Ni=C[δσeqv2/(1+n) -(δσeqv)th2/(1+n)] -2, where C and (δσeqv)th are the fatigue resistant coefficient and threshold respectively. C and (δσepv)th are found to follow the log-normal distribution. According the physical meaning and their probability distribution of fatigue resistant coefficient C and threshold (δσepv)th in the fatigue life expression, the different fatigue specimen are assumed to be distinguished by the different combination of C and (δσepv)th, while the difference between the fatigue specimens leads to the scatter of the fatigue life, so a new method is propiosed to simulate the fatigue test and the probability distribution of fatigue life of notched friction welded joints of 45-carbon steel under the variable amplitude loading and checkedby test results. It is shown that both the simulated fatigue life and the test result of fatigue life of 45 steel notched friction welded joints under the variable amplitude loading follow the log-normal distribution, and the two distributions agree well with each other. Therefore, the proposed simulating method may be applicable in the fatigue reliability assessment of mild carbon nothched friction welded joints under variable amplitude loading.