Numerical Study Of Ultrasonic Surface Wave And Defects Detection Of Pipeline Surface

Pipeline transportation is one of the five modes of transport, railways, highways, waterways, aviation and pipeline. Its play an important role in the economic and social development. However, in the process of manufacture and use of the pipeline, pipeline accidents caused by surface cracks caused a huge security risk in the social environment and personal safety. Therefore, detection of surface cracks in the pipe is very important. Ultrasonic surface wave technology as a reliable defect detection method for detecting damage to the specimen surface is a kind of more efficient detection with respect to the other waveform detection methods.Based on the theory of elastic wave propagation in the homogeneous elastic vibration medium, using the finite element method, establishment of a variety of ultrasonic wave on a finite element model for the pipe surface defect detection. Analysis of the phenomenon on the surface of the ultrasonic wave propagation medium interaction with surface defects, verify the surface acoustic waves for detection of surface defects having a well feasibility.First, the basic model of ultrasonic wave propagation in the medium surface is established in the two-dimensional plane, collecting the vibration displacement signal on the medium surface at different points in the vertical direction, The vibration displacement curve of longitudinal waves, shear, then have analysis and calculation the speed of longitudinal wave, shear wave, surface wave, and compared with the theoretical speed. The model shows that ultrasonic surface wave used in the spread of simulation in the pipe surface has excellent feasibility. Then, based on the basic characteristics of the surface wave, using the hierarchical mesh model, the dielectric layer is divided into surface wave and body wave layer, for different wave layer, the grid cell length is divided into different sizes, in order to results in ensuring accurate while greatly reducing the amount of computation and calculation time model, to improve the efficiency of the simulation.Secondly, in the two-dimensional plane, use the finite element analysis simulation software to simulate the phenomenon of defects on the surface and the ultrasonic wave interaction on the medium surface. Then simulated and analyzed the phenomenon of ultrasound surface wave during spread of along the circumferential surface of the pipe, the ultrasonic surface wave interaction with surface defects. Comparative analysis the differences in ultrasonic surface wave spread of in a plane with the surface when spread of circumferential surface.Finally, researched the surface acoustic wave propagation in the surface of objects of 3D model. Established two kinds of sound source model, the point source and line source. And then simulated the model of ultrasonic surface wave in the pipe surface planar dielectric surface and with or without defect propagation in the two sources. Comparative analysis the surface displacement of with or without defect on vibration signals collected on the vertical direction. And comparative analysis of the impact of changes in the position of the defect on the surface of the medium to the same point on the displacement of the vibration signal acquisition.