Research On Ultrasonic Phased Arrays Detecting System For Pipeline Girth Welding Defect

Automatic Phased Array Ultrasonic Testing (APAUT) system is combined ultrasonic measurement technology with computer technique. Comparing with other ultrasonic testing methods, APAUT is a new non-destructive evaluation (NDE) technology that has the characteristics of high detecting efficiency and can accurately give the image of defect. APAUT system developed in the thesis is mainly used in pipeline grith welding and aimed to evaluate the welding quality of long-distance large-diameter pipeline welded by automatic welding equipment. It has strong ability to test the defect, especially for non-fusing welding interlayers and groove fringe. It can also be used to evaluate the quality of semi-automatic welding in the condiction of corresponding gap fixed.On the basis of ultrasonic theory and pipeline girth welding technique, the mathematic model for phased array ultrasonic testing is bulided in this thesis. Based on the theory calculation and experiment research on ultrasonic focusing, deflection and the near field characteristic, the phased array ultrasonic testing process is formulated. According to the testing standard of welding defect in pipeline construction with girth welding, the software control system with high open source and good adaption is developed, in which the measurement display software in upper computer, Field-Programmable Gate Array (FPGA) technique control programme, the process control programme and data acquisition and transimission software in lower computer are included. Based on the project requirement, the hardware control system is developed and fabricated, in which phased array ultrasonic transimission/reception system, high speed data acquisition system and crawl-scanning system for pipeline girth welding is involved. The welding defect evaluation method for pipeline girth welding is studied and corresponding software is developed. The result of experiment and application shows that the performance of APAUT systme developed in this paper is stable. The innovation of the research include:(1) to establish the mathematic model of phased array ultrasonic testing for long-distance pipeline girth welding with various wall thickness, different groove. (2) based on ultrasonic theory, to conclude the calculation model of phased array ultrasoinic focusing, number of crystal piece and time-delay among the crystal pieces; a series of testing block designed to modulate the focusing, deflecting and near field length corresponging to pipeline girth welding phased array ultrasonic sensors for designing and developing the hardware and software of phased array ultrasonic. (3) According to the non-destructive testing standard of long-distance pipeline girth welding, intelligent defect identification model and classification method established for pipeline girth welding, so as to realize the intelligent identification of defect.