| 摘要 |
A method and apparatus for measuring tensile stress in a fastener already in place. This method capitalizes on the discovery that a longitudinal wave will travel roughly twice as fast as a transverse wave and the times-of-flight of the two waves are affected to different degrees by tensile stress. Longitudinal and transverse ultrasonic signals are applied to a first end of the fastener. The longitudinal and transverse signals are detected at this same first end of the fastener after they are reflected off of the second end of the fastener. The time-of-flight for each of the longitudinal and transverse waves is measured. The tensile stress, T, in the fastener is then determined by applying substantially the following equation: <IMAGE> where v10 and v20=the velocities of the longitudinal and transverse signals, respectively, in a similar fastener not under stress; k=the length of the unstressed portion of the fastener; lambda and mu =Lame' constants for the fastener material; and D1 and D2=material constants for the fastener representing a simplified combination of second and third order elastic material constants.
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