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研究了定向凝固合金DZ125U型平板缺口试样在850℃下的缺口疲劳行为,进行了理论应力集中因子分别为1.91,3.01和4.35下的疲劳试验,原位观察了疲劳裂纹的萌生位置和扩展方向,并进行了疲劳寿命分析和裂纹萌生与扩展分析.结果表明:理论应力集中因子关联缺口疲劳寿命.随着名义应力的增加,缺口疲劳寿命对理论应力集中因子更敏感,而在低应力范围内,正好相反.通过原位观测技术,试验中还发现缺口疲劳裂纹的萌生和扩展并没有在最大轴向应力的缺口根部,而是缺口附近最大主应力位置.
The notched fatigue behavior at 850 ℃ of DZ125U flat notch specimens of directional solidification alloy was investigated. The fatigue tests at theoretical stress concentration factors of 1.91, 3.01 and 4.35 were carried out respectively. The in-situ fatigue crack initiation and propagation directions , And fatigue life analysis and crack initiation and propagation analysis are carried out.The results show that the theoretical stress concentration factor is related to the notched fatigue life.With the increase of nominal stress, the notched fatigue life is more sensitive to the theoretical stress concentration factor, while in the low stress range , The opposite is true.From the in situ observation, it is found that the initiation and propagation of notched fatigue cracks are not at the root of the maximum axial stress but at the location of the maximum principal stress near the notch.