Hajime Takada and Takahumi Ozeki
Steel Research Laboratory, JFE Steel Corporation, Kawasaki 210-0855
A new ultrasonic testing technique and a new test system using a transducer array have been developed. The test system works as follows: (1) Ultrasonic waves are transmitted from all the ultrasonic transducer elements in the array at the same time; and (2) By additively synthesizing time-converted ultrasound signals transformed from echo signals received by all the ultrasonic transducer elements in the array at the same time, lines of continuously focused receiving beam (receiving needle beam) are closely formed under the transducer array (parallel receiving needle beam). Also, internal flaws in a cross-section are detected at once using the parallel receiving needle beam. The results of experiments using a 50-MHz transducer array and the developed system have proven that ultra-minute internal flaws 20 μm in diameter can be detected at a scan speed of 1000 mm/s. In addition, the focal zone formed is very long as compared with conventional point-focused beam forming. It is concluded that the system is suitable for simultaneous testing of a cross-section of a test object at high scanning speed.
internal flaws, nonmetallic inclusion, transducer array, receiving beam, needle beam
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