| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for measuring a hardness of a specimen whereby the hardness can be correctly and speedily evaluated in a nondestructive manner even when a thickness of the specimen is unknown or when the thickness of the specimen varies depending on points. SOLUTION: While an ultrasonic probe 10 is moved along a direction in which the specimen 20 is prevented from changing in shape, ultrasonic waves are brought into the specimen 20. At this time, an arrival time difference between front face echoes and bottom face echoes is measured with the use of the ultrasonic probe 10, and a propagation time of the ultrasonic waves reciprocating in the specimen 20 is measured. Then, a sound velocity change rate of the ultrasonic waves propagating in the specimen 20 is obtained from a change of the propagation time along the movement direction of the ultrasonic probe 10.
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