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中南大学学报(自然科学版)

Journal of Central South University

第51卷    第5期    总第309期    2020年5月

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文章编号:1672-7207(2020)05-1245-10
偏心切口对棒料裂纹起裂和扩展的影响
张立军1,张军伟1,金永山1,陈先锋1,张德培1,任芋见2,王旱祥1,刘延鑫1

(1. 中国石油大学(华东) 机电工程学院,山东 青岛,266580;
2. 西安交通大学 机械工程学院,陕西 西安,710049
)

摘 要: 为促进棒料裂纹的起裂和缩短裂纹的扩展时间,提出将偏心切口应用于低应力下料技术中。运用有限元分析和ZHENG-HIRT疲劳裂纹扩展速率公式,探讨偏心切口对棒料V型槽应力集中效应和疲劳裂纹扩展时间的影响。研究结果表明:在起裂阶段,偏心切口尖端一周各点的应力集中效应分布不均匀,在偏心切口最深处应力集中效应显著增强,为此处的局部起裂创造了更有利条件;在裂纹扩展阶段,名义切口偏心距e/b在0~0.12范围内,随着e/b增大,疲劳裂纹扩展时间显著下降,但e/b>0.12后,疲劳裂纹扩展时间变化趋势趋于平缓,综合考虑下料时间和偏心切口加工,选取e/b=0.12为最佳值,下料时间随切口偏心距的变化趋势与理论上得到的疲劳裂纹扩展时间随切口偏心距的变化趋势一致。从断面质量而言,并不是e/b越大越好,但从总体看,有偏心切口时的断面质量比没有偏心切口的断面质量好。

 

关键字: 低应力下料;偏心环形切口;二次应力集中;起裂;疲劳裂纹扩展

Influence of eccentric incision on crack initiation and propagation of metal bars
ZHANG Lijun1, ZHANG Junwei1, JIN Yongshan1, CHEN Xianfeng1, ZHANG Depei1, REN Yujian2, WANG Hanxiang1, LIU Yanxin1

1. School of Mechanical and Electronic Engineering, China University of Petroleum(East China), Qingdao 266580, China;
2. School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Abstract:In order to promote the crack initiation and shorten the crack propagation time, the application of eccentric notch in low stress cutting technology was proposed. Using finite element analysis and ZHENG-HIRT fatigue crack growth rate formula, the effects of eccentric notches on the stress concentration effect and fatigue crack propagation time of V-notch in bars were discussed. The results show that during the crack initiation stage, the stress concentration effect at each point of the eccentric incision tip is unevenly distributed, and the stress concentration effect is significantly enhanced at the deepest point of the eccentric incision, which creates more favorable conditions for local cracking here. During the crack growth stage, the nominal notch eccentricity e/b is in the range of 0-0.12, and as e/b increases, the fatigue crack growth time decreases significantly, but when e/b> 0.12, the trend of fatigue crack growth time tends to change gently. After comprehensive consideration of the cropping time and eccentric incision processing, and select e/b = 0.12 as the best value. The changing trend of the cropping time with the eccentric notch and the theoretical fatigue crack propagation time with the eccentric notch is consistent. In terms of section quality, e/b is not the bigger the better. But in general, the quality of the section with eccentric incision is better than that without eccentric incision.

 

Key words: low-stress cropping; eccentric circular notch; secondary stress concentration; crack initiation; fatigue crack growth

中南大学学报(自然科学版)
  ISSN 1672-7207
CN 43-1426/N
ZDXZAC
中南大学学报(英文版)
  ISSN 2095-2899
CN 43-1516/TB
JCSTFT
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