Ultrasonic method to verify the interference fit of fasteners

• US 8,973,441 B1
• Filed: 10/07/2013
• Issued: 03/10/2015
• Est. Priority Date: 10/15/2009
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Nelson, Karl E., Georgeson, Gary E., Rutherford, Paul S., McKenna, Mark
• Primary Examiner(s): SAINT SURIN, JACQUES M
• Application Number:
  US14/047,925
• Time in Patent Office: 519 Days
• Field of Search: 736/02, 735/98, 736/27, 737/61
• US Class Current: 73/602
• CPC Class Codes: G01L 5/246 using acoustic waves
• CPC Class Codes: G01N 2291/0422 Shear waves, transverse waves, horizontally polarised waves
• CPC Class Codes: G01N 2291/0428 Mode conversion
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/2691 Bolts, screws, heads
• CPC Class Codes: G01N 29/041 on the surface of the material, e.g. using Lamb, Rayleigh or shear waves
• CPC Class Codes: G01N 29/043 in the interior, e.g. by shear waves

Abstract

Embodiments of techniques and technologies to verify the interference fit of fasteners are disclosed. In one embodiment, a transducer is positioned to transmit a shear ultrasonic signal through a region of a fastener which is subject to stress when the fastener experiences an interference fit. The shear ultrasonic signal is transmitted through a region of the fastener subject to the stress. As the transmitted ultrasonic signal encounters the region, it is mode converted corresponding to a degree of interference which the fastener is experiencing. A return ultrasonic signal from the fastener is received with the transducer. From the return ultrasonic signal, a processor determines the degree of interference fit which the fastener is experience and outputs an indication of the same.

Claims

1. A system comprising:

an ultrasonic transducer;

a processor in communication with the ultrasonic transducer; and

a memory in communication with the processor and storing computer readable instructions which when executed by the processor cause the processor to perform operations, the operations comprising;

transmitting a shear wave ultrasonic signal via the ultrasonic transducer, wherein when the ultrasonic transducer is aligned with a fastener through a shear wave propagating gel couplant interface, the ultrasonic transducer transmits the shear wave ultrasonic signal through a region of the fastener subject to stress when the fastener experiences an interference fit;

receiving, via the ultrasonic transducer and when the ultrasonic transducer is aligned with the fastener, a return ultrasonic signal from the fastener, the return ultrasonic signal having undergone a mode conversion while traveling through the region subject to stress and corresponding to a degree of interference fit which the fastener is experiencing;

determining, from the mode conversion of the return ultrasonic signal, the degree of interference fit which the fastener is experiencing; and

outputting an indication of the degree of the interference fit.

2. The system of claim 1, wherein determining the degree of interference includes comparing a first amount of energy of a longitudinal wave component and a second amount of energy of a shear wave component of the return ultrasonic signal.

3. The system of claim 1, wherein the interference fit is between the fastener and a material selected from the group consisting of a metallic material and a composite material.

4. The system of claim 1, wherein the return ultrasonic signal is reflected from an end surface of a shank of the fastener.

5. The system of claim 1, further comprising a display including a graphical user interface including an indicator to indicate a go/no-condition of the fastener based on the degree of the interference fit.

6. The system of claim 1, further comprising a fixture to align the ultrasonic transducer and the fastener.

7. The system of claim 1, further comprising a fixture to apply the ultrasonic transducer to the fastener with a selected force.

8. The system of claim 1, further comprising a shear wave propagating gel couplant through which the shear wave ultrasonic signal is propagated from the transducer and into the fastener, and through which the return ultrasonic signal is transmitted from the fastener to the transducer.

9. The system of claim 1, further comprising a rail on which the ultrasonic transducer is movably mounted.

20. The system of claim 1, wherein determining the degree of interference fit includes determining a ratio of a first amplitude of a mode converted component of the return ultrasonic signal to a second amplitude of a non-mode converted component of the return ultrasonic signal.

10. A non-transitory computer readable storage medium storing computer readable instructions which when executed by a processor cause the processor to perform operations, the operations comprising:

transmitting a shear wave ultrasonic signal via an ultrasonic transducer, wherein when the ultrasonic transducer is aligned with a fastener, the ultrasonic transducer transmits the shear wave ultrasonic signal through a region of the fastener subject to stress when the fastener experiences an interference fit;

receiving, via the ultrasonic transducer and when the ultrasonic transducer is aligned with the fastener, a return ultrasonic signal from the fastener, the return ultrasonic signal having undergone a mode conversion while traveling through the region subject to stress and corresponding to a degree of interference fit which the fastener is experiencing;

determining, from the mode conversion of the return ultrasonic signal, the degree of interference fit which the fastener is experiencing; and

outputting an indication of the degree of the interference fit.

11. The non-transitory computer readable storage medium of claim 10, wherein determining the degree of interference fit includes determining a ratio of a first amplitude of a mode converted component of the return ultrasonic signal to a second amplitude of a non-mode converted component of the return ultrasonic signal.

12. The non-transitory computer readable storage medium of claim 10, wherein determining the degree of interference fit includes comparing a first amount of energy of a longitudinal wave component and a second amount of energy of a shear wave component of the return ultrasonic signal.

13. The non-transitory computer readable storage medium of claim 10, wherein the interference fit is between the fastener and a material selected from the group consisting of a metallic material and a composite material.

14. The non-transitory computer readable storage medium of claim 10, wherein the return ultrasonic signal is reflected from an end surface of a shank of the fastener.

15. The non-transitory computer readable storage medium of claim 10, wherein the operations further include displaying a graphical user interface including an indicator to indicate a go/no-condition of the fastener based on the degree of the interference fit.

16. The non-transitory computer readable storage medium of claim 10, wherein a fixture aligns the ultrasonic transducer and the fastener.

17. The non-transitory computer readable storage medium of claim 10, wherein a fixture applies the ultrasonic transducer to the fastener with a selected force.

18. The non-transitory computer readable storage medium of claim 10, wherein the shear wave ultrasonic signal is propagated through a shear wave propagating gel couplant from the transducer and into the fastener, and through which the return ultrasonic signal is transmitted from the fastener to the transducer.

19. The non-transitory computer readable storage medium of claim 10, wherein the ultrasonic transducer is movably mounted on a rail.