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25Cr2Ni2MoV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DK控制向Kmax主导的转变是引起转折点随应力比变化的原因。
Near-threshold fatigue crack growth tests are conducted at various stress ratios and different pre-cracking locations of a 25Cr2Ni2MoV welded joint by using load-shedding procedure at room temperature to investigate the transition behavior of fatigue crack growth curve. Results show that there exists a transition point in the fatigue crack growth curve in the near-threshold regime, and the stress intensity range at the transition point which is 0.5 to 0.8 times of the fatigue threshold decreases with the increasing of stress ratio. The different slope values of the fatigue crack growth curve before and after the transition point indicates the change of crack propagation mechanisms. The transition behavior with pre-cracks in the heat-affected zone shows slight influence on the fatigue crack growth behavior. The cyclic plastic zone size at the transition point is found close to the characteristic microstructure size when load ratio is below 0.5. It is indicated that the transition of crack growth driving force from stress intensity rangeDK to maximum stress intensity Kmax is responsible for the load ratio influence on the transition point.
出处
《机械工程学报》
EI
CAS
CSCD
北大核心
2015年第8期44-49,共6页
Journal of Mechanical Engineering
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
关键词
疲劳裂纹扩展
门槛值
应力比
焊接接头
fatigue crack growth
transition point
stress ratio
welded joint
作者简介
杜彦楠，男，1987年出生，博士研究生。主要研究方向焊接结构的疲劳与断裂。E—mail：yndu@mail．ecust．edu．cn
朱明亮，男，1984年出生，博士。主要研究方向为机械结构疲劳、断裂及其可靠性。E-mail：mlzhu@ccug．edu．cn
轩福贞（通信作者），男，1970年出生，博士，教授，博士研究生导师。主要研究方向为机械结构完整性技术。发表SCI收录论文130篇，Ei收录论文210篇，获省部级奖励4项。E-mail：fzxuan@ecust．edu．cn
