| Hot melt bonding of 3PE polymer material to the pipeline body to form a cladding structure is an important measure for anticorrosion of key parts such as pipeline welds.However,due to insufficient preparation quality or poor use environment,the cladding structure of the pipeline is prone to debonding defects,which seriously affects its anticorrosion effect.Therefore,there has been a strong demand for using advanced nondestructive testing technology to monitor the debonding defects for the pipeline cladding structure.At present,although a variety of nondestructive testing methods have been developed,ultrasonic imaging testing technology has become one of the most widely used and potential methods due to its unique advantages such as high security,high reliability and strong adaptability.However,the pipeline cladding structure is a cylindrical laminated structure,its acoustic wave propagation characteristics are complex,and the detection for debonding defects puts forward higher requirements for the resolution of ultrasonic imaging.In addition,the existing artificial means can not meet the application needs of the cladding structure detection with wide distribution.It can be seen that there are still many challenges in the ultrasonic imaging detection technology for the effective monitoring of the debonding defects for the pipeline cladding structure.On the basis of the above background,the research on the key technologies of automatic full-matrix ultrasonic imaging inspection for pipeline cladding structure is proposed in this paper.On the basis of understanding the domestic and foreign relevant technologies with status and trend,the technical scheme of the automatic full-matrix ultrasonic imaging and testing system for pipeline cladding structure is defined,and the two key technologies of full-matrix ultrasonic data acquisition and processing,and full-matrix ultrasonic imaging and defect detection for pipeline cladding structure are mainly broken through.At the same time,the design,manufacture and system integration of the automatic ultrasonic imaging scanning device for pipeline cladding structure were completed,and the relevant experimental research was carried out,which proved that the technology in this paper is feasible and effective.The main research contents of this paper are as follows:In Chapter 1,it discusses that the significance of the research on the automatic ultrasonic imaging inspection technology for the pipeline cladding structure.The status and trend of the related technologies such as the ultrasonic nondestructive inspection for the adhesive structure,the phased array ultrasonic full-matrix imaging and the automatic scanning of the pipeline ultrasonic imaging are summarized systematically.The existing problems of the current automatic full-matrix ultrasonic imaging inspection technology of the pipeline cladding structure are analyzed,and the research content and framework of the paper are defined.In Chapter 2,by solving the wave equation in the cylindrical coordinate system,the ultrasonic propagation mechanism and the ultrasonic signal model in the pipeline cladding structure are studied,and the basic principles of the phased array ultrasonic full-matrix data acquisition and related imaging algorithms are analyzed.The theoretical basis of the pipeline cladding structure full-matrix ultrasonic imaging detection is established.At the same time,the functional objectives of the automatic full-matrix ultrasonic imaging inspection system for pipeline cladding structure are determined,and the overall technical scheme of the system is designed.Also,the key technologies that need to be solved are summarized.In Chapter 3,the acquisition and processing technology of phased array ultrasonic full-matrix data for pipeline cladding structure is studied.An automatic ultrasonic imaging scanning device for pipeline cladding structure is designed by adopting the circumferential and axial compound motion forms and the modularization strategy,which lays the key module foundation for comprehensive and high-fidelity acquisition of phased array ultrasonic full-matrix data.At the same time,on the basis of establishing the convolution model of the ultrasonic reflected echo signal of the pipeline cladding structure,the wavelet analysis method is used to realize the subband decomposition of the ultrasonic reflected echo signal,and the subband signal with strong correlation is adaptively determined as the reference signal for deconvolution based on the correlation coefficient.The reflected echo signal is subjected to Wiener filtering,which effectively separates the overlapping interface echo signals.Noise in the signal is eliminated.In Chapter 4,the phased array ultrasonic full-matrix imaging and defect detection technology for pipeline cladding structure are studied.Based on the sound field propagation characteristics and the phase shift principle of the laminated structure,the frequency domain reconstruction of the full-matrix ultrasonic transmitting and receiving sound field is realized,the virtual focusing of each imaging point in the axial direction of the pipeline is realized according to the frequency of domain imaging conditions.The circumferential focusing is realized by using the frequency of domain synthetic aperture algorithm,and thereby completing the axial and circumferential compound focusing imaging of the debonding defects for the pipeline cladding structure.At the same time,through linear interpolation,threshold segmentation,edge tracking and other image processing methods,the number of pixels in the debonding area is obtained,and then the area of debonding defects is calculated,which realizes the quantitative ultrasonic nondestructive detection of debonding defects in the pipeline cladding structure.The simulation and experimental results show that this technology has high imaging resolution and real-time performance for debonding defects for pipeline cladding structure.In Chapter 5,based on the research work in the above chapters,the design,development and manufacturing of relevant hardware and software parts are completed,and the system integration is carried out,and a set of automatic full-matrix ultrasonic imaging inspection system for pipeline cladding structure is made.In the meantime,the system is used to carry out experimental research on ultrasonic imaging scanning motion control,full-matrix ultrasonic imaging and quantitative ultrasonic nondestructive testing for pipeline cladding structure,which proved that the technology in this paper is feasible and effective.In Chapter 6,it summarizes the research contents and innovative achievements of the paper and looks forward to the further research work. |
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