| 摘要 |
A method and apparatus for sizing a surface-connected planar crack through a gas- or liquid-filled gap. Ultrasonic energy having a frequency equal to the resonant frequency of the gap is emitted toward the crack edge. A first portion of the energy is back-scattered by the crack edge toward the emitter in a detection mode and a second portion is scattered by the crack edge toward a surface to which the crack is connected, which reflects the second portion toward a detector. The difference between the respective times-of-flight from emission to detection of the first and second portions is measured and used to determine the depth of penetration of the surface-connected crack. The paths traveled by the first and second portions of said emitted ultrasonic energy substantially intersect at the gap. A similar method also applies in sizing buried planar cracks across fluid-filled gaps.
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