Method and apparatus for determining and assessing a characteristic of a material

• US 7,082,833 B2
• Filed: 06/04/2004
• Issued: 08/01/2006
• Est. Priority Date: 06/06/2003
• Status: Expired due to Fees

• Current Assignee: Luna Innovations
• Original Assignee: Luna Innovations
• Inventors: Lynch, John T., Heyman, Joseph S.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): MILLER, ROSE MARY
• Application Number:
  US10/860,636
• Publication Number:
  US 20050072236A1
• Time in Patent Office: 788 Days
• Field of Search: 735/97, 735/98, 735/99, 736/00, 736/02, 735/87, 735/79, 736/18, 736/27, 736/28, 736/29, 737/78, 737/99, 738/01
• US Class Current: 73/598
• CPC Class Codes: G01N 2203/0016 Tensile or compressive
• CPC Class Codes: G01N 2203/0023 Bending
• CPC Class Codes: G01N 2203/0062 Crack or flaws
• CPC Class Codes: G01N 2203/0075 Strain-stress relations or elastic constants
• 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 2291/02881 Temperature
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/048 Transmission, i.e. analysed material between transmitter and receiver
• CPC Class Codes: G01N 2291/2623 Rails; Railroads
• CPC Class Codes: G01N 29/07 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/227 related to high pressure, tension or stress conditions
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects

Abstract

An acoustic energy-based, non-contact or contact testing approach provides low cost, highly accurate, and reliable information to (a) identify flaws and anomalies and (b) assess the integrity of a particular material. This approach is not hindered by surface conditions or impediments, and indeed, looks beneath the surface of the material by propagating an acoustic wave through the material using two differential transducers. A dynamic differential measurement is made of the material under a load condition and an unloaded condition that allows identification and assessment of various characteristics of the material. Multiple “windows” of information may be generated that permit (a) direct detection of flaws, defects, and anomalies using a scattering technique, (b) detection of crack closure and opening used to assess the stability of the material, (c) determination of strain on the material which relates to its performance, and (d) determination of defect dynamics linked to the defect size and stability.

Claims

1. A method for assessing a characteristic of a material, comprising:

(a) propagating an acoustic wave through the material in an unloaded condition;

(b) detecting a reflection or a transmission of the acoustic wave;

(c) determining a parameter of the transmitted acoustic wave or the reflected acoustic wave using first and second sensors mounted on a movable load and separated by a known length;

(d) repeating steps (a)–

(c) with the material in a loaded condition;

(e) determining a parameter difference between the unloaded and loaded conditions; and

(f) determining from the parameter difference the characteristic of the material.

2. The method in claim 1, wherein the parameter is related to a velocity of the transmitted acoustic wave or the reflected acoustic wave and the characteristic is a strain, stress, density or a stiffness of the material.

3. The method in claim 1, wherein the characteristic is a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material.

4. The method in claim 3, further comprising:

determining a change in the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material based on the parameter difference.

5. The method in claim 3, further comprising:

repeating steps (a)–

(f) for different positions along the material and generating therefrom data corresponding to one or more waveforms representing the characteristic of the material with respect to position, and

assessing an effect of the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material based on a detected nonlinearity in the data corresponding to one or more waveforms.

6. The method in claim 5, wherein the data corresponding to one or more waveforms is used to determine one or more of the following relationships:

a strain, stress,

density or stiffness relationship for the unloaded material and the loaded material, a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw detection relationship, and data corresponding to a waveform that shows an effect of the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw on the material.

7. The method in claim 6, further comprising:

determining an amplitude of the transmitted acoustic wave or the reflected acoustic wave for different positions along the material with the material in an unloaded condition;

determining an amplitude of the transmitted acoustic wave or the reflected acoustic wave for different positions along the material with the material in a loaded condition; and

generating data corresponding to one or more waveforms representing the characteristic of the material with respect to position based on the determined amplitudes.

8. The method in claim 3, further comprising:

determining an amplitude of the transmitted acoustic wave or the reflected acoustic wave for different positions along the material with the material; and

generating data corresponding to one or more waveforms representing the characteristic of the material with respect to position based on the determined amplitudes.

9. The method in claim 8, further comprising:

detecting the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw on the material using the one or more waveforms.

10. The method in claim 1, wherein the material is any material through which an acoustic wave can propagate.

11. The method in claim 1, further comprising:

detecting a parameter in an environment of the material and factoring that detected parameter into the material characteristic determination.

12. The method in claim 11, wherein the detected parameter is temperature, pressure, humidity electric field, magnetic field or other environmental condition.

13. The method in claim 1, further comprising:

performing steps (a)–

(f) plural times to determine a stability of the material.

14. The method in claim 1, wherein the acoustic wave is a guided wave or a higher-order guided wave.

15. The method in claim 1, wherein steps (a)–

(f) are performed without contacting the material or by contact to the material.

16. The method in claim 1, further comprising:

moving the movable load over the material to produce both the loaded condition and the unloaded condition.

17. The method in claim 1, wherein the parameter is related to the velocity of the acoustic wave, the method further comprising:

dividing the normalized velocity parameter difference by the load to determine a dividend, and

determining the characteristic based on the dividend.

18. The method in claim 17, wherein the first and second sensors are phase lock loop sensors and the acoustic wave is generated at a first frequency, further comprising:

determining a second frequency of the reflected acoustic wave in an unloaded condition and a third frequency of the reflected acoustic wave in a loaded condition, and

determining a frequency difference between the second and third frequencies,

wherein the velocity difference can be determined from the frequency difference.

19. The method in claim 1, wherein the acoustic wave propagates under a surface layer of the material.

20. The method in claim 1, wherein the acoustic wave is an acoustic surface, guided, shear, compressive, or bulk wave.

21. The method in claim 1, further comprising:

using loaded and unloaded acoustic wave data to determine a dynamic or static crack-opening, a crack-closing, or a changed condition in the material.

22. The method in claim 1, further comprising:

archiving data obtained from any of steps (a)–

(f) for monitoring changes in the material over time.

23. The method in claim 1, further comprising:

transmitting data obtained from any of steps (a)–

(f) by wireless link.

24. A method for assessing a characteristic of a material, comprising:

(a) propagating an acoustic wave through the material in an unloaded condition;

(b) detecting a reflection or a transmission of the acoustic wave;

(c) determining a parameter of the transmitted acoustic wave or the reflected acoustic wave;

(d) repeating steps (a)–

(c) with the material in a loaded condition;

(e) determining a parameter difference between the unloaded and loaded conditions; and

(f) determining from the parameter difference the characteristic of the material, the method further comprising;

repeating steps (a)–

(f) for different positions along the material and generating therefrom data corresponding to one or more waveforms representing the characteristic of the material with respect to position, and

assessing an effect of a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material based on a detected nonlinearity in the data corresponding to one or more waveforms,

wherein the parameter is a velocity of the acoustic wave or the reflected acoustic wave determined for different positions along the material, further comprising;

generating data corresponding to one or more waveforms representing the characteristic of the material with respect to position based on the velocity parameter.

25. A method for assessing a characteristic of a material, comprising:

(a) propagating an acoustic wave through the material in an unloaded condition;

(b) detecting a reflection or a transmission of the acoustic wave;

(c) determining a parameter of the transmitted acoustic wave or the reflected acoustic wave;

(d) repeating steps (a)–

(c) with the material in a loaded condition;

(e) determining a parameter difference between the unloaded and loaded conditions; and

(f) determining from the parameter difference the characteristic of the material, the method further comprising;

using loaded and unloaded acoustic wave data to determine defect stability from acoustic scattering in the material.

26. A method for assessing a characteristic of a material, comprising:

propagating an acoustic wave through the material under different load conditions;

detecting a reflection or a transmission of the acoustic wave under the different load conditions;

processing information related to the detected acoustic wave to detect dynamically or statically crack-opening or closing of a crack in the material,

wherein the processing includes determining a velocity parameter of the detected acoustic wave for unloaded and loaded conditions, determining a velocity difference between the unloaded and loaded velocity parameters, and determining a non-linear characteristic of the velocity difference, and the method further comprising;

determining that a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material likely exists based on the non-linear characteristic of the velocity difference.

27. The method in claim 26, further comprising:

generating a waveform related to the detected acoustic wave under the different load conditions, and

analyzing that waveform to detect dynamically or statically crack-opening or closing of a crack in the material.

28. The method in claim 26, further comprising:

determining a variation in stress, density or a strain in the material from the processing.

29. The method in claim 26, further comprising:

compensating for an effect of temperature in the processing.

30. The method in claim 26, further comprising:

storing some of the processed information in an archive.

31. The method in claim 26, further comprising:

determining that a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material likely exists based on detecting a reflected acoustic wave whose amplitude exceeds a predetermined value.

32. Apparatus for assessing a characteristic of a material, comprising:

a radiation source for propagating an acoustic wave through the material;

a first transducer for detecting a reflection or a transmission of the acoustic wave at a first position in the material under a first load;

a second transducer for detecting a reflection or a transmission of the acoustic wave at a second position in the material under a second load less than the first load;

electronic circuitry configured to determine (1) a parameter of the transmitted acoustic wave or the reflected acoustic wave for the first and second load conditions, (2) a parameter difference between the first and second load conditions, and (3) from the parameter difference, the characteristic of the material,

wherein the first and second transducers are mounted on a movable load and are separated by a predetermined length.

33. The apparatus in claim 32, wherein the parameter is related to a velocity of the transmitted acoustic wave or the reflected acoustic wave and the characteristic is a strain, stress, density or a stiffness of the material.

34. The apparatus in claim 32, wherein the characteristic is a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material.

35. The apparatus in claim 34, the electronic circuitry further configured to determine a change in the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material based on the parameter difference.

36. The apparatus in claim 34, wherein the electronic circuitry further configured to:

repeat (1)–

(3) for different positions along the material and generating therefrom one or more waveforms representing the characteristic of the material with respect to position, and

assess an effect of the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material based on a detected nonlinearity in the one or more waveforms.

37. The apparatus in claim 36, wherein the electronic circuitry is configured to use the one or more waveforms to generate one or more of the following:

a strain, stress, density or stiffness versus position relationship for the unloaded material and the loaded material, a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw detection versus position relationship, and a waveform that shows an effect of the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw on the material.

38. The apparatus in claim 37, wherein the electronic circuitry is configured to:

determine an amplitude of the transmitted acoustic wave or the reflected acoustic wave for different positions along the material with the material in an unloaded condition;

determine an amplitude of the transmitted acoustic wave or the reflected acoustic wave for different positions along the material with the material in a loaded condition; and

generate data corresponding to one or more waveforms representing the characteristic of the material with respect to position based on the determined amplitude.

39. The apparatus in claim 38, wherein the parameter is a velocity of the acoustic wave determined for different positions along the material, wherein the electronic circuitry is configured to:

generate data corresponding to one or more waveforms representing the characteristic of the material with respect to position based on the measured velocity parameter.

40. The apparatus in claim 34, wherein the electronic circuitry is configured to:

determine an amplitude of the transmitted acoustic wave or the reflected acoustic wave for different positions along the material with the material; and

generate data corresponding to one or more waveforms representing the characteristic of the material with respect to position based on the measured amplitudes.

41. The apparatus in claim 40, wherein the electronic circuitry is configured to:

detect the crack, defect, anomaly, microstructure variation, chemistry variation, or flaw on the material using data corresponding to the one or more waveforms.

42. The apparatus in claim 32, wherein the material is any material through which an acoustic wave can propagate.

43. The apparatus in claim 32, further comprising:

a detector for detecting a parameter in an environment of the material,

wherein the electronic circuitry is configured to factor the detected parameter into the material characteristic determination.

44. The apparatus in claim 43, wherein the detected parameter is temperature, pressure, humidity, electric field, magnetic field.

45. The apparatus in claim 32, wherein the electronic circuitry is configured to perform (1)–

(3) plural times to determine a stability of the material.

46. The apparatus in claim 32, wherein the acoustic wave is a guided wave or a higher-order guided wave.

47. The apparatus in claim 32, wherein the first and second transducers do not contact the material.

48. The apparatus in claim 32, wherein the first and second transducers contact the material.

49. The apparatus in claim 32, wherein the movable load is configured to move over a railway track.

50. The apparatus in claim 49, wherein the material is a rail of the railway track, and wherein moving the movable load over the railway track produces the first and second load conditions.

51. The apparatus in claim 50, wherein the electronic circuitry is configured to use acoustic wave data under the first and second load conditions to determine a dynamically or statically crack-opening, a crack-closing, or a changed condition in the rail.

52. The apparatus in claim 50, wherein the electronic circuitry is configured to use acoustic wave data under the first and second load conditions to determine defect stability based on acoustic scattering in the material.

53. The apparatus in claim 50, wherein the parameter is related to the velocity of the acoustic wave, and wherein the electronic circuitry is configured to:

divide the normalized velocity parameter difference by the load to determine a dividend, and

determine the characteristic based on the dividend.

54. The apparatus in claim 53, wherein the first and second sensors are phase lock loop sensors and the acoustic wave is generated at a first frequency, and wherein the electronic circuitry is configured to:

determine a second frequency of the transmitted acoustic wave in the first load condition and a third frequency of the transmitted acoustic wave in the second load condition, and

determine a frequency difference between the second and third frequencies,

wherein the normalized velocity difference can be determined from the normalized frequency difference.

55. The apparatus in claim 32, wherein the acoustic wave propagates under a surface layer of the material.

56. The apparatus in claim 32, wherein the acoustic wave is an acoustic surface, guided, shear, compressive, or bulk wave.

57. The apparatus in claim 32, further comprising:

a transmitter for wirelessly transmitting data obtained from any of (1)–

(3).

58. Apparatus for assessing a characteristic of a material, comprising:

a radiation source for propagating an acoustic wave through the material;

a first transducer for detecting a reflection or a transmission of the acoustic wave without contacting the material at a first position under a first load;

a second transducer for detecting a reflection or a transmission of the acoustic wave without contacting the material at a second position under a second load less than the first load;

electronic circuitry configured to determine (1) a parameter of the transmitted acoustic wave or the reflected acoustic wave for the first and second load conditions, (2) a parameter difference between the first and second load conditions, and (3) from the parameter difference, the characteristic of the material;

a memory for archiving data obtained from (1)–

(3) for monitoring changes in the material over time; and

a global positioning detector for detecting a global position associated with the (1)–

(3),

wherein the electronic circuitry is configured to store associated global position information in the memory.

59. Apparatus for assessing a characteristic of a material, comprising:

a source for propagating an acoustic wave through the material under different load conditions;

a detector for detecting a reflection or a transmission of the acoustic wave under the different load conditions; and

processing circuitry configured to process information related to the detected acoustic wave to detect an opening or closing of a crack in the material.

wherein the processing circuitry is configured to determine a velocity parameter of the detected acoustic wave for less loaded and more loaded conditions, a normalized velocity difference between the less loaded and more loaded velocity parameters, a non-linear characteristic of the velocity difference, and that a crack, defect, anomaly, microstructure variation, chemistry variation, or flaw in the material likely exists based on the non-linear characteristic of the velocity difference.

60. The apparatus in claim 59, further comprising:

generating a waveform related to the detected acoustic wave under the different load conditions, and

analyzing that waveform to detect dynamically or statically an opening or closing of a crack in the material.

61. The apparatus in claim 59, wherein the processing circuitry is configured to determine a stress or a strain in the material.

62. The apparatus in claim 59, wherein the processing circuitry is configured to compensate for an effect of temperature, humidity, pressure, electric field, magnetic field.

63. The apparatus in claim 59, wherein the processing circuitry is configured to storing some of the processed information in an archive.

64. The apparatus in claim 59, wherein the processing circuitry is configured to determine that a flaw in the material likely exists based on detecting a reflected acoustic wave whose amplitude exceeds a predetermined value.