Microdefect detection methodology for beamslab structures
                                      LIN Qiben1, ZHONG Shuncong1,2, FAN Xueteng1, TANG Changming1, FANG Bo1
(1.School of Mechanical Engineering and Automation, Fuzhou University, Fuzhou 350108, China;2.School of Mechatronics Engineering and Automation, Shanghai University, Shanghai 200072, China)

Abstract: Aiming at the problem of identifying multiple microdefects in beamslab structure, modal parameters of beamslab structure were proposed. Defect identification of beamslab structures based on discrete wavelet transform (DWT) and moving mass probing method was employed. It was studied that with the change of moving mass position on the structure surface, the natural frequency of the coupled structure will change, and a weak discontinuity will happen in the frequency shift surface when the moving mass is located at the defect of the structure. The frequency surfaces was obtained by using the natural frequencies at different position of moving mass. However, it is challengeable to extract directly the weak crack information from the frequency surfaces. In the present work, the dynamic characteristics of the coupled structure was probed by changing the position of the moving mass. Subsequently, the microdefect information of the beamslab structure was extracted by the proposed method that the discrete wavelet transform on mode shapes and frequency shift surface was used. The theoretic support was provided for small crack detection of beamslab structures. The results indicate that the method can effectively identify the microdefects of beamslab structure and provide a practical new detection method for engineering applications

Key words: discrete wavelet transform(DWT); beamslab structure; defect detecting; moving mass