| 摘要 |
PURPOSE:To make it possible to detect internal defects along the weld line of a seam welded pipe highly accurately by transmitting an ultrasonic wave which is vertically inputted in to positions which are separated by a depth interval of a constant pitch along the weld line from an array probe. CONSTITUTION:Delay time T=d.sin theta/C, where (d) is the pitch for a piezoelectric transducer, C is the sound speed in a medium and theta is the deflecting direction of the ultrasonic wave, is imparted to driving timing of each piezoelectric transducer. Then, the phases of the ultrasonic waves transmitted from the piezoelectric transducers become the same phase along a line A-A' in the figure. A wave front can be synthesized in the direction of theta. The delay time can be controlled so that the synthesized wave front is gradually focused. Since the ultrasonic wave is vertically inputted into a defect, the reflected wave from the defect can be accurately captured. Thus, the internal defect along the weld line of the seam welded pipe can be detected highly accurately. |
