Material condition monitoring with multiple sensing modes

• US 20050171703A1
• Filed: 01/14/2005
• Published: 08/04/2005
• Est. Priority Date: 01/16/2004
• Status: Active Grant

• Current Assignee: Jentek Sensors, Inc.
• Original Assignee: Jentek Sensors, Inc.
• Inventors: Goldfine, Neil J., Grundy, David C., Schlicker, Darrell E., Washabaugh, Andrew P., Zilberstein, Vladimir A., Lyons, Robert J., Shay, Ian C., Walrath, Karen E., Craven, Christopher A., Weiss, Volker
• Granted Patent: US 7,451,657 B2
• Time in Patent Office: Days
• US Class Current: 702/30
• CPC Class Codes: G01N 27/9013 Arrangements for scanning

Abstract

Methods are described for assessing material condition. These methods include the use of multiple source fields for interrogating and loading of a multicomponent test material. Source fields include electric, magnetic, thermal, and acoustic fields. The loading field preferentially changes the material properties of a component of the test material, which allows the properties of the component materials to be separated. Methods are also described for monitoring changes in material state using separate drive and sense electrodes with some of the electrodes positioned on a hidden or even embedded material surface. Statistical characterization of the material condition is performed with sensor arrays that provide multiple responses for the material condition during loading. The responses can be combined into a statistical population that permits tracking with respect to loading history. Methods are also described for measuring the stress in the material by independently estimating effective electrical properties, such as magnetic permeability or electrical conductivity, using layered models or predetermined spatial distributions with depth that are then correlated with the stress.

Claims

1. A method for measuring a material property comprising:

placing a sensor proximate to a test material having at least two component materials, said sensor providing at least one source field for interrogating the test material;

loading the test material by applying a second source field, the component materials having different material property changes with loading;

measuring a response with a sensor that responds to at least one component property change for each source field; and

converting each response into a test material property.

2. The method as claimed in claim 1 wherein one source field is magnetic.

3. The method as claimed in claim 1 wherein one source field is electric.

4. The method as claimed in claim 1 wherein one source field is temperature.

5. The method as claimed in claim 1 wherein the loading is mechanical.

6. The method as claimed in claim 1 wherein the loading source field is acoustic.

7. The method as claimed in claim 1 wherein the loading source field is thermal.

8. The method as claimed in claim 1 wherein the loading source is a laser.

9. The method as claimed in claim 1 further comprising applying a bias field with one of the source fields.

10. The method as claimed in claim 1 wherein the second source field operates in a transient manner.

11. The method as claimed in claim 1 wherein the second source field operates in a steady-state manner.

12. The method as claimed in claim 1 wherein the second source field operates in a dynamic manner.

13. The method as claimed in claim 1 wherein the test material property is electrical conductivity.

14. The method as claimed in claim 1 wherein the test material property is thermal conductivity.

15. The method as claimed in claim 1 wherein the test material property is dielectric permittivity.

16. The method as claimed in claim 1 wherein the test material property is magnetic permeability.

17. The method as claimed in claim 1 wherein the second source field is also applied by the sensor.

18. A method for monitoring material state comprising:

placing at least one conductor proximate to a test material surface and at least one additional conductor on an opposing hidden material surface, at least one conductor driven with an electric signal to create an interrogating field, at least one of the remaining conductors sensing the response to the interrogating fields;

measuring a sense response;

relating the sense response to material state, and

monitoring said material state changes over time at the same location on the test material.

19. The method as claimed in claim 18 wherein the state is damage.

20. The method as claimed in claim 18 wherein the state is usage.

21. The method as claimed in claim 18 wherein the driven conductor is on an opposing hidden material surface.

22. The method as claimed in claim 21 wherein the sense response is measured at multiple locations over the material surface, with the drive conductors stationary.

23. The method as claimed in claim 18 wherein the driven conductor is placed on the surface.

24. The method as claimed in claim 23 wherein the sense response is measured for multiple driven conductor locations over the material surface, with the sense response conductors stationary.

25. The method as claimed in claim 18 wherein said material and opposing hidden surfaces both contain driven and sense response conductors.

26. The method as claimed in claim 18 wherein the field is magnetic.

27. The method as claimed in claim 18 wherein the field is electric.

28. A method for performing statistical material property characterization comprising:

placing a sensor array on a material surface, the sensor array being driven by an electrical signal to create an interrogating field and having multiple elements for sensing the material response to said field,

monitoring the loads applied to the material,

measuring a response from each sense element, and

converting the sense element responses into a statistical population, and

tracking changes in the statistics of the response population with cumulative loading history.

29. The method as claimed in claim 28 wherein the cumulative loading history is assumed to be proportional to a time based measure.

30. The method as claimed in claim 29 wherein the time based measure is flight hours.

31. The method as claimed in claim 29 wherein the time based measured is number of cycles is a fatigue test.

32. The method as claimed in claim 28 wherein the field is magnetic.

33. The method as claimed in claim 28 wherein the field is electric.

34. The method as claimed in claim 28 wherein the loading is mechanical.

35. The method as claimed in claim 28 wherein the material condition is fatigue.

36. The method as claimed in claim 28 wherein the response is measured during loading.

37. The method as claimed in claim 28 wherein the material property is electrical conductivity.

38. The method as claimed in claim 28 wherein the material property is dielectric permittivity.

39. The method as claimed in claim 28 wherein the material property is magnetic permeability.

40. The method as claimed in claim 28 further comprising tracking changes in the statistics of a subpopulation of responses separated from the main population.

41. A method for characterizing stress in a material:

placing a sensor on a material surface, the sensor having a preferred orientation for measuring a material property and being driven by an electrical signal to create an interrogating field,

measuring a sensor response for at least two orientations and excitation frequencies,

combining the responses with a predetermined model for the spatial material property distribution with distance away from the sensor to estimate a material property value, and

correlating this electrical property value with a material stress.

42. The method as claimed in claim 41 wherein the field is magnetic.

43. The method as claimed in claim 41 wherein the model has at least two component layers.

44. The method as claimed in claim 43 wherein the stress is at an interface between two of the component layers.

45. The method as claimed in claim 41 wherein the stress results from a cold work process.

46. The method as claimed in claim 45 wherein the cold work process is shot peening.

47. The method as claimed in claim 41 wherein the property is an electrical conductivity.

48. The method as claimed in claim 41 wherein the property is magnetic permeability.

49. A method for estimating properties of near surface and hidden material layers comprising:

placing a sensor on a material surface, the sensor being driven by an electrical signal to create an interrogating magnetic field, the material being processed to have a near surface layer and a hidden material layer on a substrate,

modeling each layer with a predetermined and assumed thickness,

estimating the properties of the near surface layer,

using the estimated properties of the near surface layer to estimate the properties of the hidden material layer, and

using the estimated properties to determine the properties of the substrate.

50. The method as claimed in claim 49 further comprising using precomputed databases of responses to estimate the properties.

51. The method as claimed in claim 49 wherein a property is an electrical conductivity.

52. The method as claimed in claim 49 wherein a property is magnetic permeability.

53. The method as claimed in claim 49 wherein the process involves machining.

54. The method as claimed in claim 49 wherein the process involves cold work processing.

55. The method as claimed in claim 54 further comprising measuring the response before and after cold work processing.

56. The method as claimed in claim 55 further comprising normalizing the properties estimated after processing by the properties estimated before processing.

57. The method as claimed in claim 54 wherein the cold work process is shot peening.

58. The method as claimed in claim 54 wherein the cold work process is roller burnishing.

59. The method as claimed in claim 54 wherein the cold work process is low plasticity burnishing.

60. The method as claimed in claim 54 wherein the cold work process is laser shock peening.

61. The method as claimed in claim 54 wherein the sensor is directional.

62. The method as claimed in claim 61 further comprising measuring the response in at least two directions.

63. The method as claimed in claim 62 wherein the response is measured continuously as the direction is changed.