高强度钢随机载荷下裂纹扩展模型

Crack growth model and testing research of high strength steel under random load

工程结构在全寿命周期内大多都承受随机载荷作用,随机载荷中载荷顺序对裂纹扩展有显著影响.用基于裂纹闭合现象的裂纹扩展模型依次模拟恒幅载荷、过载峰及随机载荷作用下的疲劳裂纹扩展.通过裂纹张开应力反映裂纹闭合效应,将Paris公式计算疲劳裂纹扩展,将有效应力强度因子范围代入Paris公式中计算,并用高强度钢程序块载荷下疲劳实验结果与计算结果比较.结果证明,基于裂纹闭合现象的裂纹扩展模型能很好地模拟随机载荷下的疲劳裂纹扩展,理论计算结果与试验结果相吻合,具有工程实用价值.

Most engineering structures are under random loads during the entire life and the sequences of the loads have remarkable influence on the life of the crack in the structures. The crack growth model based on the crack closure is adopted in this paper, and is used in the calculation of the fatigue life of the crack under constant amplitude loads, overload peaks, and random loads. The crack opening stress is used to reflect the influence of crack closure. The Paris formula is adopted to simulate the growth of fatigue crack. The effective range of stress intensity factor is taken into the calculation of Paris formula. The result of calcula- tion is compared with the fatigue testing result of high strength steel under random load, which shows that the test results tally with the calculation results and that the method used in this paper can simulate the crack growth under random loads correctly. So this method is worthy of practical application.