| 摘要 |
PURPOSE:To detect a defect in a short distance sound field, with very high accuracy, by forming an electrode shape on the surface of a vibrator contacting with a material to be inspected, on the surface encircled by a Gaussian curve being symmetrical to X and Y axes of orthogonal coordinate. CONSTITUTION:A metal is vapor-deposited on the contact surface of a vibrator whose section forms a circle having a radius R0. Its shape is formed to that which is shown by expression 1, 2 and is encircled by curves I-IV in four sectors respectively, which are formed by dividing equally by orthogonal coordinate of X-Y, in order that each part of the vibrator becomes a Gaussian distribution. In this case, a value r0 is decided by a maximum flaw detection distance (l) and ultrasonic wavelength lambda to a material to be inspected, and is made a value for satisfying r0>R0 and also r0<=(l<lambda>/A) (A in the expression shows a value 2-3). A plane being nearly like a bobbin, which has been encircled by said each curve I-IV is made an electrode part 2, by which a Gaussian vibrator is formed. In this way, mutual interference of acoustic waves is prevented, and also axial acoustic pressure in the direction of ultrasonic oscillation is made maximum, by which only one peak appears in the scanning graphic form. |
