Phased array ultrasonic testing:Phased Array Ultrasonic Testing,Short name (paut). Its basic principle is to generate and receive ultrasonic beams with multi-element transducers of different shapes. By controlling the different delay time of transmitting (or receiving) pulses of each element in the transducer array, the phase relationship of the sound wave when it reaches (or comes from) a point in the object is changed, and the change of focus and beam direction is realized, so as to realize the scanning, deflection and focusing of ultrasonic beams. Then, mechanical scanning and electronic scanning are combined to realize image imaging. It provides greater ability to determine the shape, size and direction of discontinuities than a single or multiple probe system. Due to the accurate positioning of paut and the fact that the probe does not need to be replaced frequently (wide angle range of angle of angle probe), it is now widely used in chemical industry (wall thickness corrosion detection), manufacturing (weld detection,), nuclear power (valve detection), wind power (composite material detection), railway (rail, bolt detection) and other fields.