Method for material property monitoring with perforated, surface mounted sensors

• US 20070120561A1
• Filed: 09/18/2006
• Published: 05/31/2007
• Est. Priority Date: 09/07/1999
• Status: Active Grant

• Current Assignee: Andrew Washabaugh, Darrell Schlicker, Karen Walrath, Neil Goldfine, Vladimir Tsukernik, Vladimir Zilberstein
• Original Assignee: Andrew Washabaugh, Darrell Schlicker, Karen Walrath, Neil Goldfine, Vladimir Tsukernik, Vladimir Zilberstein
• Inventors: Tsukernik, Vladimir, Zilberstein, Vladimir, Schlicker, Darrell, Washabaugh, Andrew, Goldfine, Neil, Walrath, Karen
• Granted Patent: US 7,348,771 B2
• Time in Patent Office: Days
• US Class Current: 324/238
• CPC Class Codes: G01B 7/24 using change in magnetic properties
• CPC Class Codes: G01B 7/34 for measuring roughness or irregularity of surfaces
• CPC Class Codes: G01N 27/20 Investigating the presence of flaws
• CPC Class Codes: G01N 27/72 by investigating magnetic variables
• CPC Class Codes: G01N 27/902 by moving the sensors
• CPC Class Codes: G01R 33/12 Measuring magnetic properties of articles or specimens of solids or fluids involving magnetic resonance G01R33/20

Abstract

Material condition monitoring may be performed by electromagnetic sensors and sensor arrays mounted to the material surface. The sensors typically have a periodic winding or electrode structure that creates a periodic sensing field when driven by an electrical signal. The sensors can be thin and flexible so that they conform to the surface of the test material. They can also be mounted such that they do not significantly modify the environmental exposure conditions for the test material, such as by creating stand-off gaps between the sensor and material surface or by perforating the sensor substrate.

Claims

1. A method for monitoring material properties comprising:

mounting an electromagnetic sensor on a test material surface; and

periodically measuring at least one electrical property of the material under a sensor footprint, with measurements being made at two or more test material temperatures.

2. A method as claimed in claim 1 where the sensor is an eddy-current sensor.

3. A method as claimed in claim 1 where the sensor is a conformable spatially periodic field eddy-current sensor.

4. A method as claimed in claim 3 where the sensor has a periodic primary winding to excite a periodic magnetic field and at least one sensing element to detect variations in the magnetic field related to electrical properties of the material under test.

5. A method as claimed in claim 4 where multiple sensing elements are used to measure absolute electrical conductivity at each sensing element location with at least one primary current excitation frequency.

6. A method as claimed in claim 5 where at least one sensing element is located in a region expected to see less damage than at other elements.

7. A method as claimed in claim 6 where the sensing element at the location of less damage is used as a reference for measurements at other elements.

8. A method as claimed in claim 1 further comprising intentionally varying the temperature of the material under test to verify the proper performance of the sensor.

9. A method as claimed in claim 1 further comprising intentionally varying the temperature of the material under test, recording the temperature variations with a temperature measurement sensor, and recording the sensor data at a plurality of temperature levels.

10. A method as claimed in claim 9 further comprising calibrating the sensor using the sensor data at different temperatures.

11. A method as claimed in claim 9 further comprising assessing the test material condition using sensor data at multiple temperatures.

12. A method as claimed in claim 1 where the sensor is a dielectrometer.

13. A method as claimed in claim 1 where a second sensor is incorporated with the electromagnetic sensor.

14. A method as claimed in claim 13 where the second sensor is a strain gauge.

15. A method as claimed in claim 13 where the second sensor is a temperature gauge.

16. A method for monitoring material condition comprising:

mounting an electromagnetic sensor on a test material surface, where the sensor comprises a drive conductor to carry an applied electric current and at least one sensing element to measure the electrical properties of the material under test; and

periodically measuring at least one electrical property of the material under a sensor footprint, with measurements being made at two or more test material temperatures.

17. A method as claimed in claim 28 where the sensing elements are absolute inductive coils.

18. A method as claimed in claim 28 where the sensing elements are magnetoresistive elements.