工程科学学报，第40卷，第12期：1510-1517,2018年12月 Chinese Journal of Engineering,Vol.40,No.12:1510-1517,December 2018 DOI:10.13374/j.issn2095-9389.2018.12.009;http://journals.ustb.edu.cn A7085铝合金I-Ⅱ复合型疲劳裂纹扩展及其数值模拟 宋彦琦)，李向上)四，李名) 1)中国矿业大学（北京）力学与建筑工程学院，北京1000832)北京航空航天大学航空科学与工程学院，北京100083 ☒通信作者，E-mail:2360620184@q4.com 摘要为探究不同加载角度下A7085铝合金I~Ⅱ复合型疲劳裂纹扩展机理，在MTS疲劳试验机上采用紧凑拉伸剪切试件 (CTS)对A7085铝合金进行不同加载角度的疲劳实验：用有限元分析计算不同裂纹扩展长度的裂纹尖端应力强度因子，通过 七点递增多项式法对数据进行处理，计算出A7085铝合金Ps公式中的参数C和m.结果表明不同加载角度的裂纹基本沿 着与外载荷垂直的方向扩展，裂纹扩展路径近似为一条直线，裂纹扩展角测量结果基本符合最大环向拉应力理论；【-Ⅱ复合 型裂纹一旦发生扩展，Ⅱ型应力强度因子K,所占比例急剧减小，I型应力强度因子K,不断增大，此后K,远远小于K,,有效 应力强度因子(K,和K,的组合)基本等于K,,相当于裂纹扩展主要受I型应力强度因子控制，研究结果有助于对I一Ⅱ复合 型疲劳裂纹扩展机理的理解 关键词A7085铝合金：I-Ⅱ复合型疲劳裂纹；有限元分析：应力强度因子：裂纹扩展路径 分类号TG146.2 I-II mixed-mode fatigue crack propagation of A7085 aluminum alloy and its numeri- cal simulation SONG Yan-qi),LI Xiang-shang,LI Ming?) 1)School of Institute of Mechanics and Architecture Engineering,China University of Mining Technology Beijing),Beijing 100083,China 2)School of Aeronautic Science and Engineering,Beihang University,Beijing 100083,China Corresponding author,E-mail:2360620184@qq.com ABSTRACT Compared with other types of aluminum alloys,A7085 aluminum alloy has a series of excellent properties such as high strength,high toughness,and high fatigue resistance.These advantages meet the requirements of aircraft performance;thus,A7085 aluminum alloy is widely used for fabricating aircraft components.The shell cracks in aeronautical structures are often mixed-mode cracks,i.e.,comprising open type and sliding type,and they are also known as the I-II compound crack.It has been found that fa- tigue fracture is the main reason for the failure of most specimens.At present,most studies on fatigue crack are focused on mode I crack,but the load on the specimen is usually not a single pure type I.II,or II mode.It is usually a combination of these three kinds of loads.When the crack is subjected to I-II mixed-mode loads,its crack growth rate and crack growth path are affected by the loading conditions.To investigate the mechanism of I-II mixed-mode fatigue crack growth of A7085 under different loading an- gles,mixed-mode (I-II)fatigue crack growth tests were performed on compact tension shear (CTS)specimens using a servo-hy- draulic fatigue testing machine.The stress intensity factor of the crack tip was calculated by finite element analysis.Furthermore,C and m in the Paris law were calculated using seven-point incremental polynomial methods.The results show that when under different loading angles,cracks will extend along the vertical direction of the external load.Moreover,the path seems to be a straight line.The results of experiments agree with the maximum tensile stress theory.Once the crack expands,type II stress intensity factor K basical- 收稿日期：2018-03-22 基金项目：国家自然科学基金资助项目(41430640)：中国矿业大学（北京）国家重点实验室开放基金资助项目(SKLGDUEK1728)工程科学学报,第 40 卷,第 12 期:1510鄄鄄1517,2018 年 12 月 Chinese Journal of Engineering, Vol. 40, No. 12: 1510鄄鄄1517, December 2018 DOI: 10. 13374 / j. issn2095鄄鄄9389. 2018. 12. 009; http: / / journals. ustb. edu. cn A7085 铝合金玉鄄鄄域复合型疲劳裂纹扩展及其数值模拟 宋彦琦1) , 李向上1) 苣 , 李 名2) 1) 中国矿业大学(北京)力学与建筑工程学院, 北京 100083 2) 北京航空航天大学航空科学与工程学院, 北京 100083 苣通信作者, E鄄mail: 2360620184@ qq. com 摘 要 为探究不同加载角度下 A7085 铝合金玉鄄鄄域复合型疲劳裂纹扩展机理,在 MTS 疲劳试验机上采用紧凑拉伸剪切试件 (CTS)对 A7085 铝合金进行不同加载角度的疲劳实验;用有限元分析计算不同裂纹扩展长度的裂纹尖端应力强度因子,通过 七点递增多项式法对数据进行处理,计算出 A7085 铝合金 Paris 公式中的参数 C 和 m. 结果表明不同加载角度的裂纹基本沿 着与外载荷垂直的方向扩展,裂纹扩展路径近似为一条直线,裂纹扩展角测量结果基本符合最大环向拉应力理论;玉鄄鄄域复合 型裂纹一旦发生扩展,域型应力强度因子 K域 所占比例急剧减小,玉型应力强度因子 K玉 不断增大,此后 K域 远远小于 K玉 ,有效 应力强度因子(K玉 和 K域 的组合)基本等于 K玉 , 相当于裂纹扩展主要受玉型应力强度因子控制,研究结果有助于对玉鄄鄄域复合 型疲劳裂纹扩展机理的理解. 关键词 A7085 铝合金; 玉鄄鄄域复合型疲劳裂纹; 有限元分析; 应力强度因子; 裂纹扩展路径 分类号 TG146郾 2 收稿日期: 2018鄄鄄03鄄鄄22 基金项目: 国家自然科学基金资助项目(41430640);中国矿业大学(北京)国家重点实验室开放基金资助项目(SKLGDUEK1728) 玉鄄鄄域 mixed鄄mode fatigue crack propagation of A7085 aluminum alloy and its numeri鄄 cal simulation SONG Yan鄄qi 1) , LI Xiang鄄shang 1) 苣 , LI Ming 2) 1)School of Institute of Mechanics and Architecture Engineering, China University of Mining & Technology (Beijing), Beijing 100083, China 2)School of Aeronautic Science and Engineering, Beihang University, Beijing 100083, China 苣Corresponding author, E鄄mail: 2360620184@ qq. com ABSTRACT Compared with other types of aluminum alloys, A7085 aluminum alloy has a series of excellent properties such as high strength, high toughness, and high fatigue resistance. These advantages meet the requirements of aircraft performance; thus, A7085 aluminum alloy is widely used for fabricating aircraft components. The shell cracks in aeronautical structures are often mixed鄄mode cracks, i. e. , comprising open type and sliding type, and they are also known as the 玉鄄鄄域 compound crack. It has been found that fa鄄 tigue fracture is the main reason for the failure of most specimens. At present, most studies on fatigue crack are focused on mode 玉 crack, but the load on the specimen is usually not a single pure type 玉, 域, or 芋 mode. It is usually a combination of these three kinds of loads. When the crack is subjected to 玉鄄鄄域 mixed鄄mode loads, its crack growth rate and crack growth path are affected by the loading conditions. To investigate the mechanism of 玉鄄鄄域 mixed鄄mode fatigue crack growth of A7085 under different loading an鄄 gles, mixed鄄mode (玉鄄鄄域) fatigue crack growth tests were performed on compact tension shear (CTS) specimens using a servo鄄hy鄄 draulic fatigue testing machine. The stress intensity factor of the crack tip was calculated by finite element analysis. Furthermore, C and m in the Paris law were calculated using seven鄄point incremental polynomial methods. The results show that when under different loading angles, cracks will extend along the vertical direction of the external load. Moreover, the path seems to be a straight line. The results of experiments agree with the maximum tensile stress theory. Once the crack expands, type 域 stress intensity factor K域 basical鄄