拉—拉变幅载荷下45钢切口件疲劳寿命的分布及其模拟

根据45钢切口件疲劳寿命表达式中疲劳抗力系数和疲劳门槛值物理意义及概率分布，提出了一种新的模拟45钢切口件变幅载荷下疲劳寿命实验及其分布的方法，并与拉－拉变幅载荷下的实验结果进行了比较，结果表明，45钢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，并与实验结果符合得很好。

Probability Distribution of Fatigue Life of Notched Mild Carbon Steel under Tension-Tension Variable-Amplitude Loading and Its Simulation

In the present study, the fatigue tests under tension-tension variable amplitude loading (VAL) are carried out on 45 carbon steel, which is similar to the AISI 1045 steel, to investigate the probability distribution of fatigue life under VAL and investigate the validity of a new simulation model proposed in the paper for the fatigue test and the probability distribution of fatigue life under VAL. The fatigue life of notched 45 steel bar can be expressed as the function of equivalent stress amplitude. The fatigue resistant coefficient and the fatigue threshold in the fatigue life expression are found to follow the log normal distribution and to be material constants. Therefore this distribution of the fatigue resistant coefficient and threshold can be used to represent the distribution characteristics of fatigue properties of the material. Based on the above results and the assumption that the scatter of the fatigue life results from the difference of the fatigue specimens (different specimens can be distinguished by different combinations of the fatigue resistant coefficient and threshold), a new model and procedures are proposed to simulate the fatigue test and the probability distribution of fatigue life of notched 45 carbon steel under tension tension VAL and checked by test results. Statistical analyses show that both the simulated fatigue life and the test result of fatigue life of notched bar of 45 carbon steel under VAL follow the log normal distribution, and the two distributions agree well with each other, which indicate that the proposed simulation model is of practical value in the design and reliability assessment of mechanical elements when the fatigue test under VAL is very difficult, expensive and time consuming.