Research On Phased Array Ultrasonic Testing System Technology

Ultrasonic phased array technique can help to achieve flexible, controllable synthesized ultrasound beam by exciting each element of an ultrasonic array transducer with independent phase delay. Phased array ultrasonic testing can accomplish dynamic focusing, obtain visual image, inspect component of complex geometry. So it has recently been highly recognized in NDT research domain. The application of industrial ultrasonic phased array detection is still in the introductory stage in China. The key technology is researched and resolving scheme is put forward in the paper.According to the structure of ultrasonic phased array transducer and the character of phased array ultrasonic field, parameters of piezoelectric substrate , probe protecting coating and backing layer are presented in this paper. The conditions of eliminating grid lobe and diminishing of side-lobe are put forward. According to these conditions, sizes of main cells of a transducer are confirmed and industrial phased array transducer is designed.High precision ultrasonic transmission phased delay is the key technology in phased array ultrasonic beams. A new high precision ultrasonic transmission delay method is described in this paper. Both Complex programmable logic device (CPLD) and digital programmable delay line are applied to take place of single device. According to this method, a 8-channel experimental phased array ultrasonic transmission testing system based on CPLD is designed and developed. With the resolution of delay being 1 ns and the max delay time being 25 us, the system can accomplish all kinds of ultrasonic phased array transmission schemes. Preliminary test and study showed that the delay method was higher in resolution of delay, longer in delay time and wider in adjusting range than conventional analogue delay methods.Overall solution scheme of the ultrasonic phased array receiving and electronic focusing system is presented in this paper. According to the digital beam forming algorithm, two focusing scheme, one of which use high speed memorizer and the other use the method of gating A/D sampling clock . As to phased array receiving, a scheme of separating the delay clock and sampling clock is explicated, which effectively enhance the phased receiving delay resolution.