Research On Erosion Defect Detection Of Bent Pipe Based On Flexural Mode Guided Waves

In the field of oil and gas transportation,pipeline transportation plays a very important role.In the process of long-term service,pipeline will be constantly eroded by internal fluid,resulting in erosion pits on the inner wall of the pipeline,which is the most serious phenomenon at the elbow of the pipeline.Therefore,developing a method to timely detect the health of the inner wall of the pipeline has become an increasingly urgent demand in engineering practice.Among the commonly used nondestructive testing methods,magnetic particle testing,X-ray testing and other methods are limited by testing conditions,testing costs and other problems,and cannot achieve a more accurate detection of the internal health state of the pipeline.In recent years,ultrasonic guided wave has been applied more and more widely in the field of nondestructive testing of pipelines.The ultrasonic guided wave detection method has a large detection range,a long propagation distance,and does not need to peel off the outer coating layer of the pipeline in the detection process,which is widely used in the non-destructive testing of pressure vessels,oil and gas pipelines and other fields.This paper carried out numerical simulation and experimental research on the propagation law of ultrasonic guided wave under different defect depths in pipeline elbow,and studied the change of the propagation law of ultrasonic guided wave under the condition that the two ends of the pipe elbow are connected with flanges.The dispersion curve is drawn when the cross section diameter of the pipeline is116 mm,the wall thickness is 8mm,and the bending radius is 158 mm.The amplitude of the guided wave signal at different frequencies is analyzed.Through the analysis,it is concluded that the amplitude of the signal received by the pipeline at 120 kHz is the maximum.After Hanning window modulation,the five-period signal with a frequency of 120 kHz was selected as the excitation signal.The propagation law of ultrasonic guided wave in the pipeline is numerically simulated.By analyzing the guided wave signal,it is determined that the guided wave propagates in the pipe in the form of bending mode F(1,2).The propagation law of guided wave in the curved pipe under different defect depths is simulated.The variation of guided wave propagation rule is studied when the two ends of the pipe are connected with flanges.The numerical simulation results show that the energy value of the signal received by the upper end of the pipe sensor is the largest,and the signal changes with the depth of the defect is the most obvious.With the deepening of the internal defects of the pipeline,under the influence of erosion defects,the propagation law of guided wave becomes more and more chaotic,and the energy of the signal at the receiving end generally decreases.When the two ends of the pipe are connected with flanges,the guided wave propagates more dispersed in the pipe,and the energy of the signal received at the same position is lower than that without flanges.An experimental platform for ultrasonic guided wave detection was built.Through the analysis of the experimental data,it was proved that guided wave propagated in the bending mode of F(1,2).By calculating the signal energy received by each sensor,combined with the actual situation,it was proposed that in the actual detection,the summing of the signal energy of each position to detect the internal defects of the pipeline has better anti-interference performance.