中国机械工程 ›› 2015, Vol. 26 ›› Issue (21): 2963-2970.

• 材料工程 • 上一篇    下一篇

高频谐振载荷作用下Ⅰ型疲劳裂纹尖端力学参数变化规律

高红俐;郑欢斌;刘欢;刘辉   

  1. 浙江工业大学特种装备制造与先进加工技术教育部/浙江省重点实验室,杭州,310014
  • 出版日期:2015-11-10 发布日期:2015-11-06

Variation Law of Mechanics Parameters of Type Ⅰ Fatigue Crack Tip under High Frequency Resonant Loading

Gao Hongli;Zheng Huanbin;Liu Huan;Liu Hui   

  1. Key Laboratory of Special Purpose Equipment and Advanced Manufacturing Technology,Ministry of Education,Zhejiang University of Technology,Hangzhou,310014
  • Online:2015-11-10 Published:2015-11-06

摘要:

为研究高频谐振式疲劳裂纹扩展试验中带有Ⅰ型预制裂纹的紧凑拉伸(CT)试件裂纹尖端力学参数的变化规律,利用动态有限元方法,采用ANSYS和MATLAB软件编写程序,计算了CT试件在高频恒幅正弦交变载荷作用下,在一个应力循环及裂纹扩展到不同长度时裂纹尖端区域的位移、应变场及裂纹尖端的应力强度因子,并分析了其变化规律。在计算裂纹尖端应力强度因子时,首先采用静态有限元方法和理论公式验证了有限元建模和计算的正确性,然后采用动态有限元方法研究了裂纹扩展过程中裂纹尖端应力强度因子的变化规律。最后进行了高频谐振式疲劳裂纹扩展试验,采用动态高精度应变仪测量了裂纹扩展到不同阶段时裂纹尖端点的应变,并对有限元计算结果进行了验证。研究结果表明:在稳态裂纹扩展阶段,高频谐振载荷作用下Ⅰ型疲劳裂纹尖端位移、应变及应力强度因子均为与载荷同一形式的交变量;随着裂纹的扩展,Ⅰ型疲劳裂纹尖端的位移、应变及应力强度因子幅不断增大;静态应力强度因子有限元计算值和理论值的误差为2.51%,裂纹尖端点应变有限元计算结果和试验结果最大误差为2.93% 。

关键词: 高频谐振载荷, 疲劳裂纹尖端, 动态有限元, 位移, 应变场, 应力强度因子

Abstract:

This paper explored the variation law of mechanics parameters at fatigue crack tip of compact tension(CT) specimen with type Ⅰ pre-notch based on dynamic FEM in the high frequency resonant fatigue crack propagation tests. The displacement fields, the strain fields and the SIFs at CT specimen fatigue crack tip in one stress cycle and at different crack lengths under constant amplitude high frequency sinusoidal alternating loading condition were calculated and the related variation laws of mechanics parameters were analyzed. In order to calculate the dynamic SIF at fatigue crack tip, the static SIF was calculated first, the comparing results of the static finite element analysis with the theoretical calculation show that finite element modeling and calculated method and results are accurate. Secondly, the variation law of SIF at crack tip during the process of fatigue crack propagation tests was studied by dynamic FEM. Finally, the high frequency resonant fatigue crack propagation tests were performed, and the dynamic strain gauge was used to measure the strain at crack tip during one stress cycle. The research results show that during crack stable propagation stage, the displacement, strain and SIF at type Ⅰ fatigue crack tip are the same form with the high frequency resonant load, and the displacement, strain and SIF amplitude increase with the crack growth. The error of static SIF between the calculated result by FEM and the theoretical result is as 2.51%. The maximum error of the strain at crack tip between the calculated result by FEM and the experimental result is as 2.93%.

Key words: high frequency resonant load, fatigue crack tip, finite element method(FEM), displacement; strain field, stress intensity factor(SIF)

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