Nondestructive Testing And Automatic Defect Detection Of Polyethylene Pipe Joints Based On Ultrasonic Phased Array

Polyethylene(PE)pipe is widely used in pipeline transportation systems,such as gas transport,urban water supply,for its economical and practical,easy installation,corrosion resistance,high toughness,long service life,etc.It is crucial to ensure the safety of PE pipe joints with the rapid spread of PE pipes.The common connection ways to join polyethylene pipes are fusion-jointing and electrofusion-jointing.At present,the ultrasonic phased array is one of the most effective non-destructive testing methods for electrofusion joints.This paper focused on the simulation and experiment of ultrasound phased array imaging and automatic defect detection for PE pipe joints.The main works was as follows:Researching simulation of ultrasound phased array imaging based on Fourier transform,and analyzing the effect of diverse parameters(the spacing and number of array elements).It showed that the simulation was effective under certain conditions,by comparison with the theoretical beam pattern.Its acoustic performance was in keeping with the general rules of ultrasonic phased array imaging.The finite element model was built to simulate ultrasonic response of heating wire in PE pipe electro fusion joints by using multi-physics coupling finite element analysis software COMSOL Multiphysics,the defected PE pipe with drilling hole and electrofusion joints with pore were tested by an ultrasonic phased array imaging system for the verification of the finite element model.The ultrasonic phased array images of defected PE pipe with drilling hole were processed by Richardson-Lucy deconvolution algorithm.T he result of image restoration was well.It proved the feasibility of simulation of ultrasound phased array imaging based on Fourier transform,the simulation of imaging for electrofusion joints was achieved based on it.An automatic defect classification detection method was developed in order to improve efficiency and accuracy.It used digital image processing technologies,such as Otsu algorithm,Mathematical morphology,and considered signal feature of ultrasound phased array imaging for different defects and internal structures in electrofusion joints.It has get remarkably effect in simulation images of electrofusion joints to recognize the Eigen-line of cold welding,heating wire,hole and inclusion near the fusion interface,and the defect detection result in experiment images was acceptable.The researches provide a new technique for nondestructive testing and evaluation of defected PE pipe electrofusion joints and it could be recommended for engineering applications.