应变比对2．25Cr1 MoV钢高温低周疲劳行为的影响

摘要

利用MTS 810型疲劳试验机,采用轴向应变控制的方法,研究了应变比对2．25Cr1MoV钢高温(455℃)低周疲劳行为的影响.结果表明：在455℃下,2．25Cr1MoV钢呈现明显的循环软化特性；应变比不改变该钢的循环软化特性,但会产生初始平均应力,平均应力在寿命初期阶段随着循环周次增加急剧降低,并趋为0；应变比不改变疲劳裂纹的萌生方式,且对迟滞环的形状和大小没有影响；对称循环和非对称循环的低周疲劳寿命基本一致.%Low-cycle fatigue behavior of 2.25Cr1MoV steel at 455 ℃ were studied by using a MTS 810 fatigue testing system under strain-controlled conditions.The results reveal that the steel exhibited obvious cyclic softening feature.Strain ratio had no influence on cyclic softening feature but resulted in mean tensile stress.The mean stress relaxed to zero in early stage of life with the increase of cycle numbers.Fatigue crack initiation patterns had not changed by strain ratio,and hysteresis loop and fatigue life of the steel were not appreciably affected by the mean strain.The low cycle fatigue life for symmetric cycle was same with that for unsymmetirc cycle.