Research On Ultrasonic Composite Array Detection Method For Pipeline Defect Based On Sparse Sampling Data

Pipeline is one of the important means of energy transportation and occupies an important position in the national economy.However,in the long period of service,the influence of environmental stress will produce different kinds of defects in pipeline,which will make the formation of leakage hazards and lead to the occurrence of accidents.Therefore,it is necessary to regularly detect the health status of the pipeline.Ultrasonic array detection is one of the common detection methods of pipeline defects.However,most of the existing equipment using a single beam incident mode,cannot meet the detection requirements of different kinds of defect in pipeline.In addition,in order to improve the detection efficiency and accuracy of the defect,the ultrasonic sensor often works at high frequency.Then according to conventional methods of data acquisition will have a huge amount of data,which restricts the application of this technology.Because of these problems,this thesis has studied the ultrasonic composite array detection method for pipeline flaw based on sparse data.An ultrasonic composite transducer array structure with three acoustic beam incidence modes is developed in this study.This array can scan the pipeline with three kinds of incidence modes at the same time,so as to improve the detection rate of different defects,especially the cracks.The finite rate of innovation(FRI)sparse data acquisition system based on Lab VIEW is also designed,and the FRI sparse data is obtained directly through the experiment,reducing the amount of detection data.The method of characteristic parameter extraction from the sparse data obtained directly is studied,and obtained the amplitude and delay parameters of ultrasonic echo signal.The spatial coordinate model and the defect imaging model of the composite array structure are established,and the visual image of the defect is obtained.The main research work of this thesis is as follows:(1)A structure of ultrasonic composite transducer array with vertical incidence,axial oblique incidence and circumferential oblique incidence is designed.The acoustic field distribution of composite array in the pipeline is analyzed,and the spatial coordinate model of the composite array is also established.(2)According to the FRI sampling hardware circuit made by the laboratory,a sparse data acquisition system of composite array based on LabVIEW is designed.Then the test platform of pipeline defect ultrasonic composite transducer array detection is established.Six different types of defect are tested with this test platform,and the sparse data of the detection signal are obtained directly.(3)The method of obtaining the characteristic parameters of ultrasonic echo signal from sparse sampling data is studied.The annihilating filter algorithm based on Cadzow de-noising method is used to extract the characteristic parameters of the measured pipeline ultrasonic signal.The delay and amplitude parameters of the echo signal are obtained and the errors are analyzed.(4)According to the analysis of the characteristics of traditional ultrasonic imaging methods,a pipeline defect ultrasonic imaging method based on sparse sampling data is proposed.The pipeline defect imaging model is also established to realize the visualization of pipeline defects.The imaging results of different defects are compared and analyzed under the conditions of conventional sampling data and sparse sampling data.The experimental results show that the visible image of the same resolution can still be obtained with the data volume of about 5.5% of conventional data.