北京航空航天大学学报 ›› 2018, Vol. 44 ›› Issue (1): 187-195.doi: 10.13700/j.bh.1001-5965.2016.0985

• 论文 • 上一篇    下一篇

孔边倒角裂纹当量初始缺陷尺寸的确定方法

孙晓娜1, 贺小帆1, 李玉海2   

  1. 1. 北京航空航天大学 航空科学与工程学院, 北京 100083;
    2. 中国航空工业集团有限公司, 北京 100022
  • 收稿日期:2017-01-03 修回日期:2017-03-10 出版日期:2018-01-20 发布日期:2017-04-13
  • 通讯作者: 贺小帆 E-mail:xfhe@buaa.edu.cn
  • 作者简介:孙晓娜,女,硕士研究生。主要研究方向:结构耐久性;贺小帆,男,博士,副教授。主要研究方向:疲劳/断裂、结构可靠性与耐久性、腐蚀条件下使用寿命评定。

Determination method of equivalent initial flaw size for crack initiated at hole chamfering

SUN Xiaona1, HE Xiaofan1, LI Yuhai2   

  1. 1. School of Aeronautic Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China;
    2. Aviation Industry Corporation of China, Ltd., Beijing 100022, China
  • Received:2017-01-03 Revised:2017-03-10 Online:2018-01-20 Published:2017-04-13

摘要: 孔边倒角裂纹是含孔下陷细节的常见裂纹形态,为进行含孔下陷细节的经济寿命评定,需要确定倒角裂纹的原始疲劳质量(IFQ)。首先,为探究倒角对裂纹前缘应力强度因子的影响,进行了有、无倒角2种情况下应力强度因子的有限元分析。计算表明倒角对相对小裂纹的应力强度因子影响显著。其次,为合理表征该种裂纹的IFQ,将初始缺陷当量为萌生于倒角和试件表面交点,前缘为圆弧的初始裂纹,以萌生点到裂纹前缘沿孔径向的距离作为裂纹特征尺寸。最后,采用相对小裂纹扩展方程描述倒角裂纹的扩展规律,反推得到倒角裂纹的当量初始缺陷尺寸(EIFS)分布。统计分析表明,采用本文定义的裂纹特征尺寸得到的EIFS分布参数与应力水平无关。

关键词: 原始疲劳质量(IFQ), 应力强度因子, 有限元, 裂纹扩展方程, 当量初始缺陷尺寸(EIFS)

Abstract: Cracks often initiate at the chamfering for sagging holes. The initial fatigue quality (IFQ) of this type of crack needs to be determined prior to economic life assessment. Firstly, finite element models with and without chamfering are developed so as to investigate the effect of chamfering on the stress intensity factors at the crack front. The results show that the chamfering imposes great influence on the stress intensity factors of relatively small crack. Secondly, in order to characterize the IFQ of sagging holes, a circular-front crack initiated at the intersection of the chamfering and specimen surface is taken as the initial flaw, with the radial distance of crack front from the initiation site as the crack size. Finally, the crack growth equation for relatively small cracks is employed to characterize the crack growth behavior, and the equivalent initial flaw size (EIFS) distribution is obtained through back-extrapolation. Statistical analyses show that the EIFS distribution parameters obtained by using the proposed crack size definition are independent of stress levels.

Key words: initial fatigue quality (IFQ), stress intensity factor, finite element, crack growth equation, equivalent initial flaw size (EIFS)

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