Application Of Spectrum Analysis Of Ultrasonic Testing In Pile

In recent pile ultrasonic testing, it is a routine to conduct a time-domain analysis onthe signals received. Important parameters such as sonic time, head wave amplitude,dominant frequency and waveform are used to judge the integrity of piles. However, otherinformation like spectral are not well exploited. The majority of the domestic and oversearesearch works on ultrasonic spectra are based on tests. The validity of the results is stillunsubstantiated due to the variation of test conditions and test methods. Therefore,systematic theoretical analyses and numerical simulation are needed in the application ofultrasonic spectral analysis in pile tests. In this thesis, the ANSYS/LS-DYNA is used toperform the numerical simulation in ultrasonic frequency domain, and an emphasis is puton the frequency domain characteristics of ultrasonic waves.Firstly, the selection of ultrasonic vibration source is discussed, and the spectralcharacteristics of vibration source manipulated by different window function areinvestigated. By analyzing the characteristics of different window function, the reasonablewindow functions are selected. And the way to reduce spectral leakage and improve theresolution of frequency domain is also investigated. Then, the propagation of ultrasonicwave in the pile is simulated using LS-DYNA, and the propagation law of ultrasonic wavein concrete pile is analyzed, and the pile vibration law is also validated by the calculationof wave velocity. Based on the above work, a spectral analysis of signals received atdifferent transactions of pile is conducted. And the spectral information is discussed. Adetailed parametric study is given to investigate the influence of transaction geometry,testing method, test location, test distance and defect on the results, and the correspondentlaws are summarized. Finally, the numerical results are verified by the site test results, andcorrespondent suggestions of practical ultrasonic testing are also given.The application of ultrasonic frequency domain analysis in pile test is analyzed in detail, and the result is of certain application and popularization significance.