弧形双悬臂梁试样裂纹扩展电测接线点布局研究

(西安科技大学 机械工程学院,陕西 西安 710054)

机械工程; 裂纹扩展监测; 有限元分析; 直流电位降法; 弧形双悬臂梁试样

Wire connection points layout of crack extension electrical measurement of contoured double cantilever beam specimen
NI Chen-qiang,XUE He,ZHAO Ling-yan,CUI Ying-hao,WANG Shuai

(College of Mechanical and Engineering,Xi'an University of Science and Technology,Xi'an 710054,China)

mechanical engineering; crack propagation monitoring; finite element analysis; direct current potential drop method; contoured double cantilever beam specimen

DOI: 10.13800/j.cnki.xakjdxxb.2019.0218

备注

直流电位降法是应用于高温高压水环境下裂纹扩展监测试验的主要方法,弧形双悬臂梁试样是一种应力腐蚀裂纹扩展试验的常用试样。为了寻求被测试样的最优接线点布局方案以提高测试精度和稳定性,论文利用有限元软件建立了弧形双悬臂梁试样三维有限元模型,模拟了多组可选的接线点布局方案,求解得到了试样三维电位场分布及其随裂纹变化的规律,并根据计算结果从信号灵敏度、信号幅度和测点位置误差敏感度3方面对试样电流加载点位置和电位差测量点位置的优化选取进行了分析。研究结果表明,不同位置电位差测点下的灵敏度相对大小关系与电流输入位置无关,电位差测点选在试样缺口侧时可获得较高的信号灵敏度; 电位差测点与电流加载点的距离是信号幅度大小和测点位置敏感度的主要影响因素,较大的距离会导致信号幅度降低,而较小的距离会导致很高的测点位置误差敏感度。提出的寻优依据和分析方法也可应用于其他类型试样,为进一步研究其他测试精度的影响因素奠定了基础。

The direct current potential drop method is the main approach used in crack propagation monitoring test under high temperature and high pressure water environment.The contoured double cantilever beam specimen is commonly used for the stress corrosion crack propagation test.To find the optimal wire connection points layout of the tested specimens,thus improve the test accuracy and stability,a 3D finite element model of contoured double cantilever beam specimen was established using finite element software.Multiple sets of selectable wire connection points layout scheme was simulated,and the 3D potential field distribution of the specimen and its variation with the crack extension were obtained.Then,according to the calculation results the optimized selection of location of the current loading points and potential difference measurement points were analyzed from three aspects of the signal sensitivity,signal amplitude and measurement points position error sensitivity.The results show that the relative magnitude relationship of the potential difference signal sensitivity at different measurement points positions is independent of the current input position,and when the potential difference measurement point is located on the notch side of the specimen,higher signal sensitivity can be obtained; the distance between the potential difference measurement points and the current loading points is the main influential factor on signal amplitude and measurement points position error sensitivity.A larger distance will cause the signal amplitude to decrease,while a smaller distance will lead to a very high measurement point position error sensitivity.The proposed search basis and analysis method can also be applied to other types of specimens,laying the foundation for further research on the influence of other factors on the test accuracy.