应力比对25Cr2Ni2MoV钢焊接接头近门槛值区疲劳裂纹扩展曲线转折点的影响

发布时间：2018-05-06 17:22

本文选题：疲劳裂纹扩展 + 门槛值　；参考：《机械工程学报》2015年08期

【摘要】：在常温下采用逐级降载法进行不同缺口位置、不同应力比下25Cr2Ni2Mo V钢焊接接头的疲劳裂纹扩展试验,研究疲劳裂纹扩展曲线上近门槛值区转折点的变化规律。结果表明,焊接接头的疲劳裂纹扩展曲线在近门槛值区内存在一个转折点,其对应的应力强度范围随应力比的增大而减小,其大小为疲劳门槛值的0.5~0.8。近门槛值区疲劳裂纹扩展转折点前后扩展曲线斜率发生变化表明裂纹扩展机理的改变,热影响区缺口处的转折行为对疲劳裂纹扩展影响较小。应力比R低于0.5时,循环塑性区尺寸总体接近于材料特征组织尺寸;应力比R高于0.5后,两者偏差加大。应力比低于0.5时转折点对应的循环塑性区尺寸同特征组织尺寸接近,驱动力由ΔK控制向Kmax主导的转变是引起转折点随应力比变化的原因。
[Abstract]:The fatigue crack propagation tests of welded joints of 25Cr2Ni2Mo V steel at different notched positions and different stress ratios were carried out at room temperature by means of progressive load reduction method, and the variation law of turning points in the near threshold region of fatigue crack growth curve was studied. The results show that there is a turning point in the fatigue crack propagation curve of welded joints in the near threshold region. The corresponding stress intensity range decreases with the increase of the stress ratio, and its size is 0.5 / 0.8 of the fatigue threshold value. The change of the slope of the fatigue crack growth curve before and after the turning point of fatigue crack growth in the near threshold region indicates the change of the crack growth mechanism, and the transition behavior at the notch in the heat affected zone has little effect on the fatigue crack growth. When the stress ratio R is lower than 0.5, the size of the cyclic plastic zone is close to the characteristic structure size of the material, and the deviation increases when the stress ratio R is higher than 0.5. When the stress ratio is lower than 0.5, the size of the cyclic plastic zone corresponding to the turning point is close to the size of the characteristic structure, and the change of driving force from 螖 K to Kmax is the cause of the change of turning point with the stress ratio.
【作者单位】：华东理工大学机械与动力工程学院;
【基金】：国家杰出青年基金(51325504) 高等学校博士学科点专项科研基金(20120074120010) 上海市晨光计划(12CG33)资助项目
【分类号】：TG407

【参考文献】