Quantitative Characterization Method And Three-dimensional Imaging Of Pipeline Defects Based On Laser Ultrasonic

With the popularization and development of natural gas pipelines,domestic pipelines have gradually entered the age of accident-prone.It is necessary to regularly detect and maintain existing pipelines.Therefore,the research on non-destructive detection technology of pipelines has been highly valued.Laser-based ultrasonic nondestructive testing can usually detect the approximate location of metal defects,but the research of this technology used to detect pipeline crack defects is very few.Quantitative characterization of pipeline crack defects only stays at the location,and visualization of cracks needs further study.Therefore,in order to optimize the repair and maintenance technology of pipeline cracks,a pipeline crack based on laser-based ultrasound is developed.Quantitative characterization and three-dimensional imaging methods are particularly important.In this paper,a quantitative characterization and three-dimensional imaging method for crack defects of X80 pipeline steel is designed on the basis of using laser ultrasonic technology to detect metal defects at home and abroad for reference.Through theoretical analysis,finite element analysis and experimental research,the process of laser ultrasonic propagation in two-dimensional pipeline is explored,and the influence of pipeline defects on the process of ultrasonic propagation is analyzed.The quantitative characterization relationship between pipeline defects and ultrasound is established.The three-dimensional digital matrix is constructed by ultrasonic signals,and the three-dimensional imaging of Pipeline Defects Based on Qt and PCL is completed.(1)A quantitative characterization method of Pipeline Defects Based on laser ultrasonic signal was designed.By studying the different excitation modes of laser ultrasound,the causes and propagation modes of longitudinal wave,shear wave and surface wave under thermoelastic mechanism are analyzed,and the propagation characteristics of laser point source and linesource are compared based on theoretical modeling.The physical model of two-dimensional pipeline is established by finite element method,and the actual pipeline surface cracks are replaced by rectangular grooves on the two-dimensional model.Defects are simulated to simulate the propagation process of Laser-induced Ultrasonic Wave in the pipeline.By analyzing the time when different waveforms reach the receiving point,the transformation of various ultrasonic shapes in the propagation process is simulated.Through this quantitative characterization method,the specific depth,location and angle of pipeline crack defects can be detected.(2)Based on the simulation analysis,a crack detection system for different pipelines was designed and built.The crack defects of different height,width and angle were studied by experiments,and the influence of different defect parameters on ultrasonic wave was analyzed.Based on the quantitative characterization method of pipeline crack,the information of crack location,depth and angle was obtained.The experimental results show that the proposed quantitative characterization method of crack defects has high quantitative accuracy,and the results are in good agreement with the results of finite element simulation,which further verifies the correctness of the method.(3)A three-dimensional imaging method for pipeline cracks is designed.A three-dimensional digital matrix is constructed based on the ultrasonic signal.Point cloud data with three-dimensional space coordinates are established by detecting pipeline cracks at different angles.A point cloud imaging system is built based on Qt and PCL.The three-dimensional image of pipeline defects is established by the obtained point cloud data.The results show that the three-dimensional image can be easily observed and analyzed.The research in this paper provides theoretical and experimental basis for quantitative characterization of pipeline defects and 3D imaging,and contributes to the further development of laser ultrasonic technology.