Ultrasonic Method to Verify the Interference Fit of Fasteners

• US 20090031811A1
• Filed: 08/03/2007
• Published: 02/05/2009
• Est. Priority Date: 08/03/2007
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Georgeson, Gary E., Lee, James H., Nelson, Karl E.
• Granted Patent: US 7,730,784 B2
• Time in Patent Office: Days
• US Class Current: 73/588
• CPC Class Codes: G01L 5/246 using acoustic waves
• CPC Class Codes: G01N 2291/02491 Materials with nonlinear acoustic properties
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft parts
• CPC Class Codes: G01N 29/043 in the interior, e.g. by shear waves
• CPC Class Codes: G01N 29/075 by measuring or comparing phase angle measuring frequencies or phase angles per se G01R23/00, G01R25/00
• CPC Class Codes: G01N 29/223 Supports, positioning or alignment in fixed situation mounting transducers per se G10K11/004
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00
• CPC Class Codes: G01N 29/4427 with stored values, e.g. threshold values

Abstract

Embodiments of techniques to verify the interference fit of fasteners are disclosed. In one embodiment, a method includes aligning a probe proximate a fastener, the fastener being disposed within a material. A dynamic stress signal is generated from the probe using a low frequency transducer, and the dynamic stress signal is interrogated after it passes between the fastener and the material. An interference fit is then determined based on the interrogated dynamic stress signal.

Claims

1. A method, comprising:

aligning a probe proximate a fastener, the fastener being disposed within a material, generating a dynamic stress signal from the probe using a low frequency transducer;

interrogating the dynamic stress signal after it passes between the fastener and the material; and

determining an interference fit parameter between the fastener and the material based on the interrogated dynamic stress signal.

2. The method of claim 1, wherein generating a dynamic stress signal using a low frequency transducer includes using a dynamic wave generator.

3. The method of claim 1, wherein interrogating the dynamic stress signal includes interrogating at least a portion of an area adjacent to the fastener.

4. The method of claim 1, wherein interrogating the dynamic stress signal includes using a high frequency ultrasonic testing (HFUT) transducer.

5. The method of claim 4, wherein the HFUT transducer is powered by an ultrasonic pulser receiver system.

6. The method of claim 4, wherein determining an interference fit includes determining at least one of a phase shift and a velocity shift of an ultrasonic signal generated by the HFUT transducer.

7. The method of claim 1, wherein determining an interference fit based on the interrogated dynamic stress signal includes comparing the interrogated dynamic stress signal to a threshold value.

8. A method of determining an interference fit of a fastener, comprising:

transmitting a low frequency stress wave through at a first portion of a structure, the structure including a material secured with a fastener;

monitoring an ultrasonic signal transmitted through a second portion of the structure, the second portion being separated from the first portion by an interference portion defined between the fastener and the material;

measuring a phase shift from the ultrasonic signal; and

determining an interference fit from the measured phase shift.

9. The method of claim 8, wherein the first portion is proximate the fastener and the second portion is proximate the material.

10. The method of claim 8, wherein determining an interference fit from the measured phase shift of the ultrasonic signal includes comparing the measured phase shift to a threshold value.

11. The method of claim 8, wherein the ultrasonic signal is generated by a high frequency ultrasonic testing (HFUT) transducer.

12. The method of claim 11, wherein the HFUT transducer generates a back echo with a frequency of substantially equal to or between 0.5 MHz to 10 MHz.

13. The method of claim 8, wherein measuring the phase shift from the ultrasonic signal includes measuring the ultrasonic signal with an ultrasonic pulser receiver.

14. The method of claim 8, wherein the first portion is proximate the material and the second portion is proximate the fastener.

15. A method of verifying an interference fit, comprising:

aligning a probe to a fastener;

activating the probe, the probe transmitting low frequency stress waves into a first portion of a structure and measuring the stress waves with an ultrasonic signal at a second portion of the structure, the first and second portions of the structure being separated by an interference between a fastener and a material proximate the fastener;

calculating an interference fit between the fastener and the material from the measured stress waves; and

determining if the interference fit is within a threshold range.

16. The method of claim 15, wherein the first portion is proximate the material and the second portion is proximate the fastener.

17. The method of claim 15, wherein activating the probe includes activating a low frequency transducer to generate low frequency stress waves and activating a high frequency ultrasonic testing (HFUT) transducer to generate high frequency ultrasonic signals.

18. The method of claim 15, wherein calculating the interference fit between the fastener and the material includes outputting a value for the interference fit.

19. The method of claim 15, wherein the fastener includes a straight shank, a head, and a threaded portion to receive a bolt.

20. The method of claim 15, wherein the material is fiber reinforced composite material.