ULTRASONIC FLAW DETECTION METHOD AND DEVICE BY TOFD METHOD

PROBLEM TO BE SOLVED: To provide an ultrasonic flaw detection method and device by a TOFD method, capable of remarkably increasing an SN ratio of diffracted waves from foreign matter (for example cracks) by remarkably reducing noise generated inside a test body or on a surface layer thereof.SOLUTION: (1) By a sector scanning of a phased array probe 15b, the direction of an incident ultrasonic wave beam (incident wave S1) is changed, intersecting axes point depth D from the surface of a test body 3 at intersecting axes point X where central axes of ultrasonic wave beams of a transmission-side probe 12 and a reception-side probe 14 are intersected with each other is sequentially changed, and a plurality of diffracted waves S2 corresponding to a plurality of intersecting axes point depths D are received by the reception-side probe 14. (2) A combined waveform S3 of the diffracted waves S2 are created by overlapping a plurality of diffracted waves with one another.