Research On Flaw Detection Technology Of Ultrasonic Phased Array For T-weld

Recently the T-weld inspection has been paid more and more attention. The technologies of the conventional testing are the magnetic particle testing, the penetrative testing, the radiographic testing, the conventional ultrasonic testing and ultrasonic phased array(UPA) testing,ect.. Among them, the UPA technology has many incomparable advantages: high efficiency, high sensitivity, and harmlessness,ect. However, the scheme of the UPA technology for the T-weld inspection is relatively weak. Based on the special structure of the T-weld and the principle of UPA, this thesis studies the scheme of the T-weld inspection and the improvement of the phase-controlled accuracy.Firstly, according to the characteristics of the ultrasonic field and the structural feature of T-weld, the wave type, the work mode and the principle of choosing probe are determined. Then, the inspection scheme is designed for the three parts of T-weld: the root part,the groove part and the central part. The scheme contains the best surface for testing, the probe and wedge, scanning mode and the steering angle,ect. After the simulation by the CIVA software and the analysis of the simulation results, the feasibility of the scheme is proved.The optimal scheme is applied to the experiment of the T-weld inspection. After analyzing the results, the location and size of the flaws are estimated.And the types of flaws are assessed through empirical analysis. At last, the scheme is proved reliable by comparing the experimental results to the actual specimen.Based on the wavelet packet,the energy features of the flaw signals are extracted and the energy feature histograms are obtained. The energy spectra are composed of the relatively large energies. By comparing the energy features of the flaws, the energy distribution of each echo signal is analyzed. Finally,the distinctions of their energy features are demonstrated.The phase-controlled accuracy is very important to the quality of the inspection results. Low phase-controlled accuracy in the UPA system is a problem in our nation. The phase-controlled design of high accuracy using FPGA is made in this thesis. And through the design of the phase-controlled transmitter with 2.5ns accuracy, the simulation and the experiment are carried out. Form the result, the design improving the phase-controlled accuracy is proved feasible. Therefore, the design has some significance to our nation in this respect.