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System, device and method for measurement of fastener loading

  • US 10,345,173 B2
  • Filed: 05/12/2017
  • Issued: 07/09/2019
  • Est. Priority Date: 06/15/2016
  • Status: Active Grant
First Claim
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1. A method for measuring a fastener load comprising:

  • generating and directing a first laser ultrasonic generation beam to the fastener when the fastener is unloaded;

    generating and directing a first laser ultrasonic detection beam to the fastener when the fastener is unloaded;

    acquiring by an optical sensor a reference ultrasonic signal while the fastener is unloaded;

    loading the fastener;

    generating and directing a second laser ultrasonic generation beam to the fastener when the fastener is loaded;

    generating and directing a second laser ultrasonic detection beam to the fastener when the fastener is loaded;

    acquiring by the optical sensor a loaded ultrasonic signal while the fastener is loaded;

    determining a time difference between a peak identified in the unloaded reference signal and a corresponding peak identified in the loaded ultrasonic signal, wherein the peak identified in the unloaded reference signal and a corresponding peak identified in the loaded ultrasonic signal are the result of a longitudinal wave which reflects several times from the side walls and then mode converts to a shear wave at the last reflection prior to returning to a detection location on an end of the fastener;

    calculating a measured fastener load based at least in part on the time difference.

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