Research On Crack Detection Of Slewing Ring Of Cranes Based On Acoustic Emission

The crack of slewing ring is inevitable, since crane often works in harsh environment. Atpresent, vibration diagnostic method, which was more developed for rotating machinery, isdifficult to achieve effective detection for the crack of low speed and heavy load slewing ring,Combined with crack location is usually more subtle, conventional detection techniques cannot effectively detect fault. Against the difficult problems of crane slewing ring in the field offault diagnosis, this paper focuses on the issues, such as the source localization and severityevaluation of crack using acoustic emission technique to detect the crack of crane slewingring, by analyzing the formation mechanism of the early crack, the propagation of acousticemission signal and acoustic emission characteristics of commonly used materials of craneslewing ring. The main contents included in this article as follows:(1) Analysis of crack formation mechanism and the feasibility of acoustic emissiontesting. The formation mechanism of early crack and crack propagation form were studiedwith the aid of fatigue contact theory. The feasibility of crack detection of crane slewing ringby acoustic emission testing was analyzed on the basis of the elastic wave theory and thebasic principles of acoustic emission testing.(2) Research of propagation rules of signal and acoustic emission characteristics ofcommonly used materials. The acoustic emission signal propagation model was established inthe ANSYS/LS-DYNA by used of the explicit algorithm, and the rules of propagation path,dynamic response, energy attenuation of acoustic emission signal were studied in the outerrace of slewing ring. Acoustic emission characteristics of materials commonly used by craneslewing ring were studied with the tensile test and bending test.(3) The source location and severity evaluation of crack based on acoustic emissiontesting. Crack source localization method of slewing ring was established based on linear timedifference. Time difference of arrival (TDOA) based on the threshold was corrected using thesmoothing pseudo Wigner-Ville distribution and the location effects were verified bysimulated experiment. By use of acoustic emission waveform signal obtained from the tensiletest. The recognition model of severity of acoustic emission signal was established based onthe wavelet packet energy spectrum and support vector machine.(4) The experiment investigation and the preliminary attempt of engineering applicationsof crack detection of slewing ring. Slewing ring crack testing was carried out in the testplatform, which verified the feasibility and accuracy of the acoustic emission testing in thecrack detection of slewing ring. The paper tentatively carried out the engineering application study of crack detection of crane slewing ring, which accumulated valuable experience for theengineering application.