Research On Ultrasonic Phased Array Inspection Of Polyethylene Pipe Welded Joints

The polyethylene pipeline that transports oil and natural gas was a key transportation facility for transporting energy media and was considered to be the "blood vessel" of national energy transportation.Compared with traditional metal pipelines,polyethylene pipelines are recognized as "green" pipelines due to their outstanding advantages such as good flexibility,corrosion resistance,long service life,and non-contaminating transmission media.But the defects existing on the end face of the pipe welded joint may seriously affect the quality of the joint.Some traditional non-destructive testing methods do not apply to the detection of polyethylene because of strict requirements on the test object.Ultrasonic phased array inspection technology based on ultrasonic testing can detect the defect signal.Complete collection and 2D imaging are achieved,which greatly improves the detection of polyethylene pipe defects.This paper started with the principle of phased array detection,adopted mathematical modeling method to establish the sound field model,and studies the sound field characteristics through numerical simulation methods.The width of the array element,the number of array elements,the array element frequency,the sound beam direction are studied.Changes in the nature of sound effects on the sound field have found that changes in the width of the array element will cause side lobe effects;in the case of constant depth of focus,an increase in the number of array elements will lead to a narrower bandwidth of the sound beam and stronger directionality of the sound beam.With the decrease of the depth of focus,the number of array elements to be excited decreases accordingly.Otherwise,the side lobe effect will easily occur.The higher the frequency is,the higher the resolution of the image will be,but the number of grating lobes will increase,which is disadvantageous to the discovery of defect signals.When a material with large acoustic attenuation is detected,a low-frequency probe is often selected;under the condition that the same number of elements is excited,the greater the depth of focus,the better the directivity of the acoustic beam.The study of these parameters provides a theoretical basis for the simulation and optimization design of the probe parameters for subsequent ultrasonic phased array detection.Secondly,based on the sound field simulation,using wave3000 software to simulate the defects in the polyethylene material and parameters of the ultrasonicphased array probe,the array element width,the number of array elements,the array element frequency,the sound beam directionality,etc.A simulation study was conducted to verify the effect of various parameter changes on the simulation results.Again,from the simulation-verified experiment,the control variable method was used to obtain the optimal detection sensitivity for the polyethylene defect echo at the change of the parameter factor,and to select the low-frequency probe unit for the simulation of the polyethylene material with large acoustic attenuation.The detection sensitivity will be improved.The increase in the number of array elements and the increase in array spacing will increase the imaging resolution.A reasonable choice of array element width will improve the focusing effect.Finally,related probes are designed based on optimized probe parameter combinations.Several calibration test blocks are designed for polyethylene materials.First,the acoustic parameters of polyethylene materials are measured by a conventional detection method,and then an optimized phased array probe is used.The sound velocity,wedge delay,probe sensitivity,and TCG curve production of the test block were used to calibrate the production.Ultrasound phased array inspection was performed on the various defects of the prepared polyethylene pipe.The test results were referenced to the Shanghai local standard “Gas-use polyethylene pipe”.Welded Joints Phased Array Ultrasonic Testing" Quality grading based on the nature,quantity and closeness of defects.The research results show that the ultrasonic phased array inspection technology can effectively detect the defects in the welded joints of polyethylene pipe joints.