| 摘要 |
PURPOSE:To quickly and accurately detect the internal flaw of a metallic material, etc., by adjusting the focus of a probe whenever the probe is moved and correcting the deviation between a gate and the focal point of the probe based on each movement, etc., of the probe. CONSTITUTION:When a probe is lowered by DELTAZ (mm) while a gate is fixed, the interval between the gate and a surface echo increases by beta, since the echo approaches the surface by beta. When the sound velocity v1 in a medium (water) is smaller than the sound velocity v2 in a sample(v1<v2), the probe is focused a position (x+alpha) (where, x is the initial position of the gate), since the focal distauce in the sample becomes shorter than that in water. Namely, the position of the gate becomes x+beta instead of its true position x-alpha. Therefore, when the position of the gate is returned by beta-alpha whenever the probe is lowered by DELTAZ, the position of the gate always becomes coincident with the focal point of the probe and clear cross-sectional images are obtained. The returning amount G of the gate becomes G=2DELTAZ (v2<2> --1<2>/v2.v2<2>)mus. Namely, when the position of the gate is returned to the surface side whenever the probe is lowered by DELTAZmm, the position of the gate always becomes coincident with the focal point of the probe. |
