| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately measure crack depth regardless of the depth of the crack. <P>SOLUTION: A crack depth measuring device comprises: a heating laser unit 1 for heating a surface of a structure S in an exposing manner; a first detecting laser unit 2 for detecting an elastic wave, which occurs at the structure S, at a detection position at a predetermined distance from a position for heating by exposure; a second detecting laser unit 3 for measuring signal intensity of a reference signal 9 when the elastic wave is transmitted from the position for heating by exposure to the position at the predetermined distance through a section without a crack C; and an arithmetic unit 10 for deriving crack depth from results of the detection by the both detecting laser units 2 and 3. The arithmetic unit 10 derives the crack depth from a time difference Δt between a measurement signal 8 detected by the both detecting laser units 2 and 3 and a reference signal 9 or from a signal decay ratio r. Since the derivation is executed on the basis of different parameters as above, the reliability of the derived value is improved. <P>COPYRIGHT: (C)2013,JPO&INPIT |
