Optimization On Key Parameters Of Phased Array Ultrasonic Testing

The phased array ultrasonic testing technology can flexibly change the beam direction, focus size and position by exciting each element of an ultrasonic array transducer with independent phase delay, which has improved the resolution, sensitivity and signal to noise ratio. Meanwhile, the accessibility, suitability, real-time and intuitive have been enhanced, the accuracy and reliability of the testing results have been improved too, which promoted the application and development of NDT and has become an international research focus in recent years. Phased array ultrasonic testing system is involved in wide domain and has many parameters, and the correlation between those parameters is complicated. Only by optimization the key parameters could we eliminate artifacts and minimize missed defects, thereby obtain a good system characteristics.Based on this, the sound field theory, focus theory and beam control principle were analyzed in the paper, the phase delay mathematical model was established and the experimental study on the optimization of key parameters in phased array ultrasonic testing system was carried out. The influence of key parameters on the imaging resolution was given, and the method for improving the resolution was investigated experimentally. Finally, the ship plate weld was inspected by phased array ultrasonic, the results were compared with X-ray and conventional ultrasonic testing, which had validated the optimizing effect of the key parameters of phased array ultrasonic. The main contents of this paper are summarized as follows:(1) Based on the sound field theory and focus theory, the influence of element spacing d, element wide a, element number N, focus length F and deflection angleθs on phased array ultrasonic was discussed. The optimization methods of key parameters were given by comparing the Sector scanning images ofφ4 horizontal holes on DB-H2 standard test block, with the use of Tomoscan FOCUS LT 128 channel phased array detector.(2) The beam deflection, focus, and dynamic control experiments were carried out with the use of CSK-IA and DB-H1 standard test block. The time delay principle was obtained and the influence of transducer aperture D, focus length F and deflection angleθs on focusing and imaging were analyzed.(3) The lateral resolution, axial resolution and signal to noise ratio at different D and F were measured, the analysis of influence of D and F on imaging resolution were investigated. The results show that lateral resolution, axial resolution and signal to noise ratio improved with the increase of D, other factors such as F also affect the resolution, therefore an integrated optimization of various factors should be carried out.(4) The inspection of slots andφ3 horizontal holes at 35mm thick ship plate weld with phased array ultrasonic was implemented to examine the optimization effect. In addition, the defect found by X-ray and conventional ultrasonic testing was detected by phased array ultrasonic, which had verified the effectiveness of phased array ultrasonic testing.