Real-time evaluation of change in thermal conductivity across an interface

• US 8,585,283 B1
• Filed: 04/02/2012
• Issued: 11/19/2013
• Est. Priority Date: 04/02/2012
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Doyle, Derek, Hengeveld, Derek
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): WILLIAMS, JAMEL E
• Application Number:
  US13/437,799
• Time in Patent Office: 596 Days
• Field of Search: 374/44, 374/43
• US Class Current: 374/44
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/0425 Parallel to the surface, e.g. creep waves
• CPC Class Codes: G01N 29/2437 Piezoelectric probes
• CPC Class Codes: G01N 29/2475 Embedded probes, i.e. probes incorporated in objects to be inspected

Abstract

A method of using Structural Health Monitoring (SHM) techniques for determining whether changes in thermal conductivity have occurred to a particular interface between two joined structural members is described, which is particularly useful in satellites or other structures ordinarily subjected to vacuum pressure.

Claims

1. A method of using Structural Health Monitoring (SHM) techniques for determining whether changes in thermal conductivity have occurred to a particular interface between two joined structural members, the method comprising:

sending a guided wave through a structure that contains at least two structural members joined at an interface, wherein the guided wave is transmitted across the interface;

measuring the guided wave that has subsequently propagated through the structure and across said interface, thus obtaining a measured result;

comparing the measured result to a baseline result previously obtained for the interface or a substantially equivalent interface, and calculating a quantitative difference between the measured result and the baseline result; and

calculating a change in thermal conductivity across said interface which is equivalent to the quantitative difference between the measured result and the baseline result, using a predetermined algorithm stored in the memory.

2. The method as recited in claim 1, wherein the measuring step is performed using PWAS, which detect and transmit guided wave signals to a digitizer for processing.

3. The method as recited in claim 1, wherein a plurality of PWAS are disposed on each member of said structure for detecting guided wave signals.

4. The method as recited in claim 3, wherein said interface comprises a bolted joint.

5. A method of using Structural Health Monitoring (SHM) techniques for determining whether changes in thermal conductivity have occurred to a particular interface between two joined structural members, the method comprising:

sending a guided wave through a structure that contains at least two structural members joined at an interface, wherein the guided wave is transmitted across the interface;

measuring the guided wave that has subsequently propagated through the structure and across said interface, thus obtaining a first measured result;

sending a second guided wave through the interface of said structure at a point substantially later in time than the first sending step;

measuring the guided wave that has subsequently propagated through the structure and across said interface, thus obtaining a second measured result;

comparing the second measured result to the first measured result and calculating a quantitative difference between the second measured result and the first measured result; and

calculating a change in thermal conductivity across said interface which is equivalent to the quantitative difference between the second measured result and the first measured result, using a predetermined algorithm stored in the memory.

6. The method as recited in claim 5, wherein each measuring step is performed using PWAS, which detect and transmit guided wave signals to a digitizer for processing.

7. The method as recited in claim 5, wherein a plurality of PWAS are disposed on each member of said structure for detecting guided wave signals.

8. The method as recited in claim 7, wherein said interface comprises a bolted joint.