基于模态振型和平稳小波变换的悬臂梁微小缺陷识别研究

Research on small damage detection in cantilever beam based on vibration mode and stationary wavelet transform

结构损伤识别方法有很多种,通常结构振动模态振型对缺陷的损伤识别较为敏感,振型体现结构的固有属性及结构局部的特征,可以用于检测缺陷的存在及其位置。但是缺陷比较微小时,仅仅通过振型难以进行损伤识别。因此本文通过对振型进行平稳小波变换处理来检测悬臂梁的微小缺陷。通过有限元模态分析获得含不同缺陷深度、不同缺陷宽度、不同缺陷位置的悬臂梁模型的振型并利用平稳小波变换进行分析处理。结果表明:该方法可以准确判断缺陷的存在及其位置,并且平稳小波细节系数突变峰值随着缺陷深度增大而增大,随着缺陷宽度增大而增大;另外,该方法受振型节点影响,在工程实际应用时应综合前几阶次振型进行缺陷识别。

Many methods can be used to detect structural defects. In general, vibration modes are very sensitive to the existence of defects. The information of modes includes the local feature information of investigated structure and the inherent properties, so it can be used to detect the presence of defects and to identify their locations. However, when the defects are small, it is difficult to determine the existence of the defects by relying on the vibration modal shapes. A new method is proposed to detect the weak defect information in cantilever beam by using the Stationary Wavelet Transform(SWT) method to analyze the vibration modal shapes. Finite element modal analysis is employed to mimic the modal shape of a cracked cantilevered beam with various defect depths, widths and positions. SWT is applied to obtain the first four modal shapes. Results obtained demonstrate that the proposed method can be used for the identification of small defects. Meanwhile, the peak of stationary wavelet detail coefficient curve would increase with the increase of the defect depth and defect width. Furthermore, in the engineering applications, it is suggested to integrate several vibration modal shapes to identify defects to minimize the vibration node effect.