DIRECTIVITY CONTROL METHOD FOR ULTRASONIC BEAM AND ULTRASONIC FLAW DETECTOR

摘要

PROBLEM TO BE SOLVED: To enhance the accuracy and efficiency of inspection by fixing the directivity (azimuth resolution) of receiving ultrasonic beam in the depth direction. SOLUTION: An ultrasonic focus beam 3 is generated using an array probe 1 and an electronic scanner 6 driving the array probe 1. Focal position of the ultrasonic focus beam 3 at the part of an object 5 is controlled at a focal position control section 8. In the vicinity of focal position, the ultrasonic beam width increases as the beam is shifted from the focal point. The receiving signal is thereby selected by means of a time gate 9 including the focal position, a time gate 10 including a position shallower than the focal position, and a time gate 11 including a position deeper than the focal position. Frequency components higher than the resonance frequency are extracted from the frequency components included in the time gates 9-11 to produce a receiving signal. Consequently, the ultrasonic beam width of each receiving signal in the depth direction of object 5 can be set substantially equal to the beam width from the focal position and the defect can be evaluated at a constant azimuth resolution.