Numerical Simulation Of Propagation Characteristics And Defect Detection Of Bending Mode In Pipeline

Ultrasonic guided waves are widely used in structural non-destructive testing in pressure vessels,aviation industry,oil and gas pipelines,etc.due to their long propagation distance and wide detection range.However,the ultrasonic guided wave has the characteristics of multi-mode and dispersion,especially in the pipeline,and the fluctuation mode is also the most complicated bending mode,which makes the signal identification difficult and error in the detection process.Due to the inherent wave structure properties of the bending mode,it is sensitive to the detection of certain types of defects and the radial stress of the pipe structure,but the bending mode is difficult to control in practical applications.Therefore,the bending mode guided wave single mode excitation method is studied.And the use of curved modal guided waves for non-destructive testing has important practical significance and broad application prospects.In this paper,the propagation characteristics of the bending mode are simulated.The finite element software ABAQUS is used to simulate the propagation characteristics of the bending mode in the pipeline.The propagation characteristics of the bending modes excited by different frequencies in the pipeline and the propagation characteristics of the bending modes in four different sizes of pipelines are numerically simulated.The propagation characteristics and energy attenuation of guided wave modes at different frequencies and receiving points are analyzed.A bending mode excitation frequency suitable for detection and a sensor arrangement distance are obtained.The F(1,1)mode and F(2,1)mode are used to simulate the defect detection of the pipeline.The F(1,1)mode and F(2,1)mode are analyzed for sensitivity of different defects.The results show:A relatively clean single curved mode guided wave can be obtained at a frequency of 50 kHz.After simulating the propagation characteristics of the bending modes at four different receiving points in four different sizes of pipes,it is finally possible to determine the F(1,1)obtained when the pipe size is 10×1 mm,the frequency is 50 kHz,and the receiving point is 600 mm.The mode is a single bending mode;The direction of the defect is longitudinal and lateral,the type is square groove and square groove,the size is 2×6×1.5mm and 1×4×0.5mm,and the bending mode of frequency 50kHz and 85kHz is selected for numerical simulation test.Comparative analysis shows that the F(1,1)mode is more sensitive to defects than the F(2,1)mode when the defect is longitudinal;When the defect is lateral,the F(1,1)mode and the F(2,1)mode have little difference in sensitivity to lateral defects.The simulation results clearly show the location and size of the defect echo;In contrast,the bending mode is more sensitive to lateral defects.The defect signal at the excitation frequency of 50 kHz is significantly stronger than the defect signal at the excitation frequency of 85 kHz.