Research On Characteristics Of Acoustic Emission Source Of Commonly-Used Steels Of Automobile Crane Based On Wavelet Analysis

This dissertation involves the application research on the Acoustic Emission (AE) testing technology for Non-destructive testing (NDT) of automobile crane. The research in this dissertation is a part of the 863 plan project "The remote maintenance and monitoring systems on the engineering plant" topic three:"The key technical research of automobile crane safety monitoring and warning systems". The main tasks we have done contain:(1)The research of bending testing of W960(WELDOX960) and HG70 steels which are commonly used for materials of automobile crane and characteristic parameters of AE signal. (2)The extracting of the AE signal wave features based on the wavelet analysis. (3)The research on the AE source location method based on the wavelet packet analysis combined with the cross-correlation function.These main conclusions of this dissertation are as follows:(1)Acquiring the AE parameter characteristics of plastic deformation signal through the bending testing of W960 and HG70 steels, which are commonly used steels of automobile crane. The AE parameters include amplitude, energy, counts, rise time and duration.(2)Acquiring the AE parameters characteristics of crack propagation fracture by studying the crack signal from the bending testing of W960 and HG70 steels with welding defect such as gas pore and slag inclusion. And make a comparative analysis on the AE parameters characteristics.(3)Combining with the AE signal of automobile crane commonly used steels' plastic deformation and crack propagation fracture, make use of feather extraction method of AE signal based on Wavelet packet feature energy frequency coefficient to extract the features of different AE signal.(4)The AE location method based on the wavelet packet analysis combined with the cross-correlation function for time difference calculation was researched. By means of experiment, the practical time difference acquired by this method is anastigmatic with the theoretical value.The research of this dissertation make a contribution to enhance the comprehensive understanding of AE sources of automobile crane and conduct to lay a foundation for the method of AE testing and analysis of automobile crane. It is of vitally importance and utility value in promoting the application of AE technology in the field of crane.