P92钢在蠕变-疲劳交互作用下的初始循环特性

Initial Cyclic Characteristics of P92 Steel Under Creep-Fatigue Interaction

在不同温度(500~675℃)和不同应变速率(5×10^(-6)~1×10^(-4)s^(-1))下对P92钢进行了单周期应变控制蠕变疲劳试验,研究了该钢在蠕变-疲劳交互作用下的初始循环特性,并建立相应的本构方程对其循环过程进行描述。结果表明:在保载阶段P92钢出现明显的应力松弛现象,当温度为500~650℃时,应力下降率相差较小,而当温度为675℃时,随着应变速率的增加,应力下降率增大;除675℃,1×10^(-5)s^(-1)条件外,用由幂函数推导出的应力松弛模型模拟得到真应力和应力松弛值随保载时间的变化曲线与试验结果相吻合,相对误差小于4.28%。在加载和卸载阶段,在应变速率一定条件下,当温度不高于550℃时,温度对应力变化率的影响可以忽略,而当温度高于550℃时,温度的影响较大,当试验温度相同时,应变速率的影响不大;用Ramberg-Ostgood模型模拟得到真应力-真应变曲线和真应力-时间曲线与试验结果吻合,相对误差小于10.37%。

Single-period strain controlled creep-fatigue tests were carried out on P92 steel at different temperatures(500-675℃)and strain rates(5×10^(-6)-1×10^(-4)s^(-1)).The initial cyclic characteristics of the steel under creep-fatigue interaction were studied,and the corresponding constitutive equations were established to describe the cycling process.The results show that at load retention stage there was obvious stress relaxation phenomenon in P92 steel;the stress reduction rate had a small difference at 500-650℃,and increased with strain rate at 675℃;the curves of true stress and stress relaxation with holding time simulated by stress relaxation model derived from the power function were in good agreement with test results except the condition of 675℃,1×10^(-5)s^(-1),and the relative error was less than 4.28%.At loading and unloading stage,when the strain rate was the same and the temperature was not higher than 550℃,the effect of temperature on stress change rate could be ignored;when the temperature was higher than 550℃,the effect of temperature was great;when the temperature was the same,the effect of strain rate was insignificant.The true stress-strain curve and true stress-time curve simulated by Ramberg-Ostgood model were in good agreement with the test results,and the relative error was less than 10.37%.