Signal Image Reconstruction Method Of Weld Defect For Pressure-carrying Small-hole-pipes Using Phased Array Inspection Technique

Pressure-carrying small-hole-pipes are widely applied in the forms of oil and chemical pipeline and steam hot water boiler to transfer fluid medium.They always works in the tough environment of high temperature,high pressure etc.Therefore,their welding defects at butt welds are easy to induce some harsh disasters,such as leakage and explosion.Hence,it is very important to inspect the weld quality of these small pipes during manufacturing.Nowadays,ultrasonic phased array inspection(UPAI)technique is a hot research topic of nondestructive testing(NDT)methods,it is faster and more sensitive than conventional pulse ultrasonic technique during testing.In actual use,the device of the UPAI characterize welding defects basing on its A-SCAN waveform,which is obtained by the graphical results of C-SCAN,line-SCAN,and fan-SCAN.line-SCAN.On the view of signal processing perspective,the ultrasonic phased array inspection technique is an imaging method in the time domain.Generally,due to the structure limitation of small pipes,there are always numerous noise signals generated during detection process,which easily affect the quality of signal images,thereby inducing significant detection detection errors.In this work,the imaging method of UPAI technique was investigated.The working principle and digital signal processing method of UPAI technique were analyzed,and some key techniques of UPAI were discussed,such as phase delay,dynamic focusing,acoustic performance and signal denois,As such,the UPAI process of small pipes was investigated using the CIVA simulation software,As a result,the distribution of the probe sound field,dynamic focusing and fan scan imaging were obtained,which provided the basis for actual detection.To validate the applicability of UPAI,some small pipes with classic weld defects were artificially made,and an UPAI device(SUPOR-32p)was employed to check out these defects.First,numerous original data were recorded during test.Second,A-SCAN wave form was deduced.Third,these wave forms were wavelet reconstructed and denoised in time domain using the MATLAB software.Forth,with the experience mode decomposition method,the intrinsic mode function was extracted to restructure data.Lastly,the signal reconstruction of weld defects was completed.On the whole,a signal processing method for UPAI was presented.It can do denoise and smooth of detection signals,remove noise,then reconstruct original signals.This method helps to make the comparison between the initial and as-processed signals more easily.Therefore,this work is of great significance for timely detection of potential defects and improving detection quality of the weld area of pressure-carrying small pipes.