基于声发射和双谱分析的铝合金损伤原位监测研究

In-situ Damage Monitoring of Aluminum Alloy Based on Acoustic Emission and Bispectrum Analysis

以列车车体材料7N01铝合金为研究对象,基于声发射和数字图像技术对7N01铝合金三点弯曲损伤过程进行了监测,采用传统的声发射参数与双谱法分析了7N01铝合金裂纹萌生及失稳扩展的声发射特征。结果表明:声发射能量和质心频率可有效预报7N01铝合金微裂纹的萌生。声发射信号的双谱等高线图显示两个频率成分之间的耦合关系,使得识别7N01铝合金三点弯曲过程中的不同阶段变得相对容易。7N01铝合金试样缺口尖端的损伤演变过程的数字图像监测结果,验证了声发射能量和质心频率对裂纹萌生的预测。实验结果显示声发射监测技术为裂纹演变行为的预测提供了依据。

This work was performed on 7N01 aluminum alloy which used in the body of high-speed train and damage was monitored based on acoustic emission （AE） and digital image technology during three-point bending failure of 7N01 aluminum alloy, conventional AE parameters and bispectrum anal- ysis were used to study the characteristic of AE signals during the crack initiation and unstable propa- gation of 7N01 aluminum alloy. The result shows that AE energy and centroid frequency （CF） were effective indicators to predict the crack initiation of 7N01 aluminum alloy. Bispectrum contour map of AE signals shows the coupling relationship of the two frequency components which makes it easy to identify different stages during three point bending of 7N01 aluminum alloy. The digital images of damage evolution from monitoring the notch tip region of 7N01 sample verify the prediction of AE sig- nals. The results indicate that AE technique provides the basis for predicting the initiation of micro- crack.