作者：王连庆¹, 可进^2,3, 王红缨¹

作者单位：1. 北京科技大学 新金属材料国家重点实验室，北京 100083;
2. 北京科技大学数理学院，北京 100083;
3. 中建三局工程设计有限公司，湖北 武汉 430000

关键词：Ⅰ-Ⅱ复合加载;裂纹扩展路径;裂纹扩展速率;断口形貌

摘要：

为研究7050铝合金在Ⅰ-Ⅱ型复合加载下疲劳裂纹扩展规律，在Amsler HFP5000高频试验机上利用Richard加载装置，完成紧凑拉剪（CTS）试样疲劳裂纹扩展试验，利用有限元对Ⅰ-Ⅱ复合型裂纹进行数值模拟，采用APDL命令流计算不同裂纹长度的应力强度因子，并引入最大周向应力准则计算裂纹扩展角，用有限元计算等效应力强度因子，并绘制不同加载角下的疲劳裂纹扩展速率曲线，在扫描电镜下观察裂纹扩展断口，分析断口形貌。研究结果表明：有限元数值模拟预测Ⅰ-Ⅱ复合型裂纹扩展角与试验值基本一致；引入当量应力强度因子后不同加载角下的I-Ⅱ型裂纹扩展速率曲线与Ⅰ裂纹的曲线基本重合；扫描电镜下疲劳断口为准解理断裂，断口的粗糙度与加载角有关，加载角越小，断口表面越粗糙。

Investigation on mixed mode Ⅰ-Ⅱ fatigue crack of 7050 aluminum alloy
WANG Lianqing¹, KE Jin^2,3, WANG Hongying¹
1. The State Key Lab for Advanced Metals & Materials, University of Science and Technology Beijing, Beijing 100083, China;
2. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China;
3. China Construction Third Bureau Engineering Design Co., Ltd., Wuhan 430000, China
Abstract: In order to investigate the fatigue crack growth of 7050 aluminum alloy under mixed mode Ⅰ-Ⅱ loading, the fatigue tests of crack propagation were carried out on Amsler HFP5000 machine by using CTS test specimens and the Richard loading device. The numerical simulation of mixed mode Ⅰ-Ⅱ fatigue crack was carried out by using the finite element method, the stress intensity factor of different crack length was calculated by using APDL command flow, the crack growth angle was calculated by using the maximum hoop stress criterion, and the curves of fatigue crack growth were drawn. The fracture surface was observed by using SEM, and the fracture morphology was analyzed. It was found that the crack growth angle under mixed mode Ⅰ-Ⅱ loading calculated by using FEM numerical simulation is basically consistent with the experimental value. The curves of crack growth rate under different loading angles are basically coincident with that of type Ⅰ crack after introducing the equivalent stress intensity factor. The fatigue fracture is quasi-cleavage fracture under SEM, the roughness of fracture is related to the loading angle, and the smaller the loading angle is, the rougher the fracture surface is.
Keywords: mixed mode I-Ⅱ loading;crack growth path;crack growth rate;fracture morphology
2021, 47(1):139-146  收稿日期: 2020-03-18;收到修改稿日期: 2020-06-24
基金项目: 国家自然科学基金委大科学装置联合基金培育项目（U2032121）
作者简介: 王连庆(1967-),男,黑龙江安达市人,高级工程师,博士,主要从事材料疲劳断裂测试与研究
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