基于断裂力学的材料低温疲劳寿命估算模型改进研究

Reserarch of the Improvement of Materials Fatigue Life Estimation Model Based on Fracture Mechanics in Low Temperature Environment

针对低温疲劳裂纹扩展速率模型中工程材料疲劳极限难以测定的问题,考虑裂纹扩展应力强度因子门槛值,将屈服强度、抗拉强度及环境温度引入疲劳极限的计算,分别采用热激活模型和引入温度敏感因子对疲劳极限进行修正,并基于断裂力学方法构建低温疲劳寿命改进模型。根据桥梁常用钢材Q345qD母材及对接焊缝在不同低温环境下的试验数据,对改进疲劳寿命模型估算能力进行验证。结果表明:在低温环境下,估算效果较好,所需参数较少且易测得,便于在实际工程中分析及应用。

In view of the difficulty in determining the material fatigue limit in the fatigue crack growth rate model under the low temperature environment,considering the influence of factors such as the threshold value of the crack growth stress intensity factor,the yield strength,tensile strength and ambient temperature are introduced into the calculation of the fatigue limit,the thermal activation model and the temperature sensitive factor are respectively used to correct the fatigue limit,and the improvement model of the fatigue life in low-temperature is constructed based on the fracture mechanics method.According to the experimental data of Q345qD base material and butt welds in different low temperature environments,the estimation ability of the improved fatigue life model is verified.The results show that the improved estimation model of the fatigue life has good estimation effect,it requires fewer parameters which are easy to measure,so it is convenient for analysis and application in practical engineering.