Research On Phased Array Imaging Testing For Curved Components

Curved components has been widely used to in some key equipments of important industrial fields, such as aerospace, transportation, power, medical apparatus. Ultrasonic phased array can achieve flexible, controllable beam by controlling the delay time, and it has high resolution, high efficiency, high-percision, among others. As curved components have complex geometry characteristics, There are hotpot of ultrasonic nondestructive testing to improve imaging quality, qualitative analysis on the defect in recent years. This dissertation is focused on the problems of the low quality of ultrasonic phased array inspection imaging and the difficulties of defect extraction and quantification because of complex ultrasonic propagation in curved components. Some problems in relation to the imaging parameters optimization and detection image processing were systematically studied in this dissertation.In chapter 1 the background and significance of the paper were expounded. related research and the existing problems were analyzed from detection method of curved component, phased array technology, simulation of curved surface component. And the dissertation contents and chapters arrangement were extracted.In chapter 2 the basic principle and key technology of phased array were described. The principle of ultrasonic phased array and beam control were expounded, phased array deflection and focusing model were analyzed, Calculation method of sound beam delay control, The foundation that phased array detection deflection and focusing for curved component was laid.In chapter 3 to solve the problem of phased array detection and low imaging, The principle sound pressure characteristics of phased array transducer were explained. The influence on detecting imaging quality of the number of element, characteristics of sound field center axis pressure characteristic, interface, pulse width and other parameters were all analyzed. The surface structure of phased array sound field was simulated by using the software of WAVE2000 based on finite difference time domain method. and influence on the quality of imaging element number, element spacing and array element width and other geometry parameters were analyzed. Finally, Parameter optimization results were obtained.In chapter 4 the ultrasonic phased array testing on the wheel rim test block and RB-3 test block was carried out through controlling variable method. The experimental data were detailed analysis combining with theoretical analysis, And the correctness of parameter optimization results was verified.In chapter 5 the Combining iterative method and mathematical morphology according to the low detection of image quality and difficulties of defect extraction were put forward.Effect of the defect feature such as defect area, perimeter and the length of the shaft by using the traditional iterative method, Otsu method, Bernsen method and different aperture in this method were comparative analyzed. The results that combining iterative method and mathematical morphology was better defect extraction and quantization precision were showed. And The relative error of the defect quantification was reduced with the increases of aperture.Finally, the main results and conclusions of this dissertation summarized, the prospects and study emphases of the future research work were discussed and forecast.