Acoustic structural integrity monitoring system and method

• US 20090070048A1
• Filed: 01/12/2007
• Published: 03/12/2009
• Est. Priority Date: 07/15/2004
• Status: Active Grant

• Current Assignee: Ultra PCS Limited
• Original Assignee: Ultra Electronics Limited (Ultra Electronics Holdings PLC)
• Inventors: Dargle, Andrew, Stothers, Ian McGregor
• Granted Patent: US 8,060,319 B2
• Time in Patent Office: Days
• US Class Current: 702/39
• CPC Class Codes: G01N 2291/103 one emitter, two or more receivers
• CPC Class Codes: G01N 2291/106 one or more transducer arrays
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft parts
• CPC Class Codes: G01N 29/045 by imparting shocks to the workpiece and detecting the vibrations or the acoustic waves caused by the shocks measuring resonant frequency G01H13/00; measuring strength properties by application of mechanical stress G01N3/00
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00

Abstract

A method and system is disclosed for detecting structural damage in a structure by detecting acoustic emissions from damage in a structure to obtain acoustic emission data, and processing the acoustic emission data in accordance with a model characterising acoustic paths.

Claims

1. A method of building a model of the effect of acoustic paths in a structure for use in the detection of a plurality of types of structural damage at each of a plurality of locations in said structure, the method comprising:

inducing a plurality of types of acoustic emissions at each of a plurality of positions on said structure, said plurality of types of acoustic emissions corresponding to a respective plurality of types of structural damage;

detecting said acoustic emissions using at least three sensors arranged on said structure;

processing the detections for each type of acoustic emission for each position to determine model data characterising effects on each type of acoustic emission from each position of acoustic paths between said positions and said sensors; and

storing said determined model data.

2. The method of claim 1, wherein said acoustic emissions are induced at each position sequentially.

3. The method of claim 1, wherein said induced acoustic emissions comprise bursts of acoustic emissions at each position.

4. The method of claim 1, wherein said model is for use in identifying structural damage in a structure, and said acoustic emissions are induced in one or more regions where structural damage is likely.

5. The method of claim 1, wherein the determined said model data comprises at least one of differences in times of arrival of said acoustic emissions at said sensors, emission duration, wave-shape information, amplitudes of said acoustic emissions and rise times of said acoustic emissions.

6. The method of claim 1, further comprising determining whether the acoustic emissions from each position enable each position to be uniquely identified and only storing said determined model data if the acoustic emissions enable each position to be uniquely identified.

7. The method of claim 6, further comprising adding sensors to said structure and/or moving at least one of said sensors from a first position on said structure to a second position on said structure if each position cannot be uniquely identified, and repeating the inducing, detecting and processing steps until each position can be uniquely identified.

8. The method of claim 6, further comprising determining optimised positions for said sensors.

9. The method of claim 8, further comprising repeating the inducing detecting and processing steps when said sensors are in said determined optimised positions and only storing said determined model data if the acoustic emissions enable each position to be uniquely identified.

10. The method of claim 8, wherein the determined optimised positions enable said sensors to still uniquely identify said positions even if up to a predetermined number of sensors fail.

11. The method of claim 1, including adding to said model data by inducing acoustic emissions at one or more additional positions interspersed said positions, detecting said acoustic emissions using said sensors, processing the detections to determine additional model data and storing said additional model data in said model data.

12. A method of building a model of the effect of acoustic paths in a structure, the method comprising:

inducing a plurality of types of acoustic emissions at a plurality of positions on said structure;

detecting said acoustic emissions using at least three sensors arranged on said structure; and

determining whether the acoustic emissions from each position enable each position to be uniquely identified, and if so processing the detections to determine model data characterising effects of paths between said positions and said sensors and storing said determined model data.

13. The method of claim 12, wherein said acoustic emissions are induced at each position sequentially.

14. The method of claim 12, further comprising adding sensors to said structure and/or moving at least one of said sensors from a first position on said structure to a second position on said structure if each position cannot be uniquely identified, and repeating the inducing, detecting and determining steps until each position can be uniquely identified.

15. The method of claim 12, further comprising determining optimised positions for said sensors.

16. The method of claim 15, further comprising repeating the inducing detecting and determining steps when said sensors are in said determined optimised positions.

17. The method of claim 15, wherein the step of determining optimised positions comprises processing the detections to determine the reciprocity of acoustic paths.

18. The method of claim 12, wherein said induced acoustic emissions comprise bursts of acoustic emissions at each position.

19. The method of claim 12, wherein said model is for use in identifying structural damage in a structure, and said acoustic emissions are induced in one or more regions where structural damage is likely.

20. The method of claim 12, wherein the determined model data comprises at least one of differences in times of arrival of said acoustic emissions between said sensors, emission duration, wave-shape information, amplitudes of said acoustic emissions and rise times of said acoustic emissions.

21. The method of claim 12, wherein said inducing step comprises inducing a plurality of types of acoustic emissions at each position, said processing step comprises processing said detections for each type of acoustic emission for each position, and said storing step comprises storing data characterising each type of acoustic emission from each of said plurality of positions in said model data.

22. The method of claim 12, including adding to said model data by inducing acoustic emissions at one or more additional positions interspersed said positions, detecting said acoustic emissions using said sensors, processing the detections to determine additional model data and storing said additional model data in said model data.

23. A method of building a model of the effect of acoustic paths in a structure, the method comprising:

inducing a plurality of types of acoustic emissions at a plurality of positions on said structure;

detecting said acoustic emissions using at least three sensors arranged on said structure;

processing the detections to determine model data characterising effects of acoustic paths between said positions and said sensors;

storing said determined model data; and

adding to said model data by inducing acoustic emissions at one or more additional positions interspersed said positions, detecting said acoustic emissions using said sensors, processing the detections to determine additional model data and storing said additional model data in said model data.

24. The method of claim 23, wherein said acoustic emissions are induced at each position sequentially.

25. The method of claim 23, wherein said induced acoustic emissions comprise bursts of acoustic emissions at each position.

26. The method of claim 23, wherein said model is for use in identifying structural damage in a structure, and said acoustic emissions are induced in one or more regions where structural damage is likely.

27. The method of claim 23, wherein the determined model data comprises at least one of differences in times of arrival of said acoustic emissions between said sensors, emission duration, wave-shape information, amplitudes of said acoustic emissions and rise times of said acoustic emissions.

28. A system for building a model of the effect of acoustic paths in a structure for use in the detection of a plurality of types of structural damage at each of a plurality of locations in said structure, the system comprising:

an inducing arrangement for inducing a plurality of types of acoustic emissions at each of a plurality of positions on said structure, said plurality of types of acoustic emissions corresponding to a respective plurality of types of structural damage;

at least three sensors for detecting said acoustic emissions;

a data processing system for processing detections by said at least three sensors for each type of acoustic emission for each position to determine model data characterising effects on each type of acoustic emission from each position of acoustic paths between said positions and said sensors; and

a data store for storing said determined model data.

29. The system according to claim 28, wherein said inducing arrangement is adapted to induce said acoustic emissions at each position sequentially.

30. The system of claim 28, wherein said inducing arrangement is adapted to induce said acoustic emissions as bursts of acoustic emissions at each position.

31. The system of claim 28, wherein said model data is for use in identifying structural damage in a structure, and said inducing arrangement is adapted to induce acoustic emissions on one or more regions where structural damage is likely.

32. The system of claim 28, wherein said data processing system is configured to determine said model data comprising at least one of differences in times of arrival of said acoustic emissions at said sensors, emission duration, wave-shape information, amplitude of said acoustic emissions and rise time of said acoustic emissions.

33. The system of claim 28, wherein said data processing system is configured to determine whether the acoustic emissions enable each of said plurality of positions to be uniquely identified and to only store said determined model data in said data store if the acoustic emissions enable each position to be uniquely identified.

34. The system of claim 33, wherein at least one said sensors is adapted to be individually moveable from a first position to a second position if it is determined by said data processing system that each of said plurality of positions cannot be uniquely identified.

35. The system of claim 33, wherein said data processing system is adapted to determine a minimum number of said sensors that can uniquely identify each of said plurality of positions, and to determine sensor optimum positions for said minimum number of sensors.

36. The system of claim 35, wherein said data processing system is adapted to determine the optimised positions and number of sensors to enable said sensors to still uniquely identify said positions even if up to a predetermined number of sensors fail.

37. The system of claim 28, wherein said inducing arrangement is adapted to induce acoustic emissions at one or more additional positions interspersed said positions, said sensors are adapted to detect acoustic emissions from said additional positions, and said data processing system is adapted to process the detections to determine additional model data and add said additional model data to said model data in said data store.

38. A system for building a model of the effect of acoustic paths in a structure, the system comprising:

an inducing arrangement for inducing a plurality of types of acoustic emissions at a plurality of positions on said structure;

at least three sensors for detecting said acoustic emissions;

a processing system for determining whether the acoustic emissions from each position enable each position to be uniquely identified, and if so processing the detections to determine model data characterising effects of paths between said positions and said sensors and storing said determined model data.

39. The system of claim 38, wherein said inducing arrangement is adapted to induce said acoustic emissions at each position sequentially.

40. The system of claim 38, wherein at least one said sensors is adapted to be individually moveable from a first position to a second position if it is determined by said data processing system that each of said plurality of positions cannot be uniquely identified.

41. The system of claim 38, wherein said data processing system is adapted to determine optimised positions for said sensors.

42. The system of claim 41, wherein the processing system is further adapted to process the detections to determine the reciprocity of acoustic paths.

43. The system of claim 38, wherein said inducing arrangement is adapted to induce said acoustic emissions as bursts of acoustic emissions at each position.

44. The system of claim 38, wherein said model data is for use in identifying structural damage in a structure, and said inducing arrangement is adapted to induce acoustic emissions on one or more regions where structural damage is likely.

45. The system of claim 38, wherein said data processing system is configured to determine data comprising at least one of differences in times of arrival of said acoustic emissions at said sensors, emission duration, wave-shape information, amplitude of said acoustic emissions and rise time of said acoustic emissions.

46. The system of claim 38, wherein said inducing means is adapted to induce a plurality of types of acoustic emissions at each position, said data processing system is adapted to process said detections for each type of acoustic emission for each position, and to store data characterising each type of acoustic emission from each of said plurality of positions in said model data.

47. The system of claim 38, wherein said inducing arrangement is adapted to induce acoustic emissions at one or more additional positions interspersed said positions, said sensors are adapted to detect acoustic emissions from said additional positions, and said data processing system is adapted to process the detections to determine additional model data and add said additional model data to said model data.

48. A system for building a model of the effect of acoustic paths in a structure, the system comprising:

an inducing arrangement for inducing a plurality of types of acoustic emissions at a plurality of positions on said structure;

at least three sensors for detecting said acoustic emissions;

a data processing system for processing the detections to determine model data characterising effects of acoustic paths between said positions and said sensors; and

a data store for storing said determined model data;

wherein said inducing arrangement is adapted to induce acoustic emissions at one or more additional positions interspersed said positions, said sensors are adapted to detect said acoustic emissions from said additional positions, and said data processing system is adapted to process the detections to determine additional model data and storing said additional model data in said model data.

49. The system of claim 48, wherein said inducing arrangement is adapted to induce said acoustic emissions at each position sequentially.

50. The system of claim 48, wherein said inducing arrangement is adapted to induce said acoustic emissions as bursts of acoustic emissions at each position.

51. The system of claim 48, wherein said model data is for use in identifying structural damage in a structure, and said inducing arrangement is adapted to induce acoustic emissions on one or more regions where structural damage is likely.

52. The system of claim 48, wherein said data processing system is configured to determine said model data comprising at least one of differences in times of arrival of said acoustic emissions at said sensors, emission duration, wave-shape information, amplitude of said acoustic emissions and rise time of said acoustic emissions.

53. A method of locating a site of structural damage in a structure, the method comprising:

detecting acoustic emissions from said site of structural damage at a plurality of acoustic sensors arranged on said structure; and

processing the detected acoustic emissions using a model characterising effects of acoustic paths between a plurality of positions on said structure and said acoustic sensors to locate said structural damage;

wherein the model includes data identifying different types of acoustic emissions and corresponding types of structural damage, and said processing includes locating and identifying structural damage using the model data.

54. The method of claim 53, wherein the processing comprises comparing processed parameters determined from the detected acoustic emissions with the model.

55. The method of claim 53, wherein said acoustic emissions are processed to determine at least one of differences in times of arrival of said acoustic emissions at said sensors, wave-shape information, emission duration, amplitudes of said acoustic emissions and rise times of said acoustic emissions;

and said model comprises at least one of differences of times of arrival of said acoustic emissions at said sensors, wave-shape information, emission duration, amplitudes of said acoustic emissions and rise times of said acoustic emissions for each position.

56. The method of claim 53, further comprising storing acoustic emission data obtained by said processing of the detected acoustic emissions.

57. The method of claim 53, wherein said model includes wave-shape information for different types of structural damage, and said processing includes determining wave-shape information for the detected acoustic emissions and comparing the determined wave-shape information with the model to identify the structural damage.

58. The method of claim 53, wherein said acoustic emissions comprise bursts of acoustic emissions.

59. The method of claim 58, wherein said processing includes accumulating bursts having similar time of arrival properties, and when a threshold is reached for a group of bursts having similar time of arrival properties, determining a location of origin of the bursts and the structural damage using the model and generating an indication of structural damage.

60. The method of claim 58, wherein said processing includes determining a location of origin of each burst using the model, accumulating bursts having similar locations of origin, and when a threshold is reached for a group of bursts having similar locations of origin, generating an indication of structural damage.

61. The method of claim 53, further comprising determining and storing physical data on the structure when acoustic emissions are detected.

62. A system for locating a site of structural damage in a structure, the system comprising:

a plurality of sensors for detecting acoustic emissions from said site of structural damage; and

a data processing system for processing acoustic emissions detected by said sensors using data defining a model characterising effects of acoustic paths between a plurality of positions in said structure and said acoustic sensors;

wherein said model data includes data identifying different types of acoustic emissions and corresponding types of structural damage, and said data processing system is adapted to locate and identify structural damage using the model data.

63. The system of claim 62, wherein the data processing system is adapted to compare processed parameters determined from detected acoustic emissions with the data defining the model.

64. The system of claim 62, wherein said data processing system is adapted to process said acoustic emissions detected by said sensors to determine at least one of differences in times of arrival of said acoustic emissions at said sensors, wave-shape information, emission duration, amplitudes of said acoustic emissions and rise times of said acoustic emissions;

and said model comprises at least one of times of arrival of said acoustic emissions at said sensors, wave-shape information, amplitudes of said acoustic emissions and rise times of said acoustic emissions for each position.

65. The system of claim 62, further comprising a store for storing acoustic emission data obtained by said processing of the detected acoustic emissions.

66. The system of claim 65, wherein said model data includes wave-shape information for different types of structural damage, and said data processing system is adapted to determine wave-shape information for the detected acoustic emissions and compare the determined wave-shape information with the model data to identify the structural damage.

67. The system of claim 62, wherein said acoustic emissions comprise bursts of acoustic emissions, said data processing system is adapted to accumulate bursts having similar time of arrival properties, and when a threshold is reached for a group of bursts having similar time of arrival properties, to determine a location of origin of the bursts and the structural damage using the model data, and to generate an indication of structural damage.

68. The system of claim 62, wherein said acoustic emissions comprise a burst of acoustic emissions, said data processing system is adapted to determine a location of origin of each burst using the model data, to accumulate bursts having similar locations of origin, and when a threshold is reached for a group of bursts having similar locations of origin, to generate an indication of structural damage.

69. The system of claim 62, further comprising an arrangement for determining and storing physical data on the structure when acoustic emissions are detected.

70. A method of correlating structural damage to a structure with causal modes of structure use, the method comprising:

detecting acoustic emissions from a site of structural damage at a plurality of acoustic sensors arranged on said structure;

processing said acoustic emissions to determine structural damage;

acquiring operating parameters from the structure;

processing said operating parameters to determine a mode of use of the structure;

correlating the structural damage with the determined mode of use of the structure to determine a causal mode of structure use; and

outputting information on the correlated structural damage and determined causal mode of structure use.

71. The method of claim 70, including storing the information during use of the structure, wherein the information is output after operation of the structure.

72. The method of claim 70, wherein the information is output to a user of a structure during use of the structure.

73. The method of claim 72, further comprising preventing the user from performing a further said causal mode of structure use.

74. The method of claim 72, further comprising storing said information and generating a maintenance output at the end of a period of use of the structure to indicate to a maintenance crew that a particular maintenance operation is required as a result of structural damage resulting from the causal mode of structure use.

75. The method of claim 70, wherein the detected acoustic emissions are processed using a model characterising effects of acoustic paths between a plurality of positions in the vehicle structure and said acoustic sensors.

76. The method of claim 75, wherein the processing comprises comparing processed parameters determined from the detected acoustic emissions with the model.

77. The method of claim 75, wherein said acoustic emissions are processed to determine at least one of differences in times of arrival of said acoustic emissions at said sensors, wave-shape information, emission duration, amplitudes of said acoustic emissions and rise times of said acoustic emissions;

and said model comprises at least one of differences in times of arrival of said acoustic emissions at said sensors, wave-shape information, emission duration, amplitudes of said acoustic emissions and rise times of said acoustic emissions for each position.

78. The method of claim 75, further comprising storing acoustic emission data obtained by said processing of the detected acoustic emissions.

79. The method of claim 75, wherein said model includes data identifying different types of acoustic emissions and corresponding types of structural damage, and said processing includes locating and identifying structural damage using the model data.

80. The method of claim 79, wherein said model includes wave-shape information for different types of structural damage, and said processing includes determining wave-shape information for the detected acoustic emissions and comparing the determined wave-shape information with the model to identify the structural damage.

81. The method of claim 75, wherein said acoustic emissions comprise a burst of acoustic emissions.

82. The method of claim 81, wherein said processing includes accumulating bursts having similar time of arrival properties, and when a threshold is reached for a group of bursts having similar time of arrival properties, determining a location of origin of the bursts and the structural damage using the model and generating an indication of structural damage.

83. The method of claim 82, wherein said processing includes determining a location of origin of each burst using the model, accumulating bursts having similar locations of origin, and when a threshold is reached for a group of bursts having similar locations of origin, generating an indication of structural damage.

84. The method of claim 70, including defining a region of interest on said structure, wherein the output information on the correlated structural damage and determined causal mode of structure use relate only to said region of interest.

85. The method of claim 84, wherein said processing and correlation steps are only performed for structural damage in said region of interest.

86. The method of claim 84, wherein said region is defined by inducing emissions in the region of interest in the structure using an acoustic emission source, detecting said acoustic emissions induced in said region of interest, and identifying the location of the region using the detected acoustic emissions.

87. A system for correlating structural damage to a structure with causal modes of structure use, the system comprising:

a plurality of sensors for detecting acoustic emissions from a site of structural damage;

at least one structure operation data source for acquiring structure use parameters from the structure;

a data processing system for processing said acoustic emissions to determine structural damage and said structure use parameters to determine a structure use mode and for correlating the structural damage with the determined structure use mode to determine a causal mode of structure use; and

an output device for outputting information on the correlated structural damage and determined causal mode of structure use.

88. The system of claim 87, including a data store for storing the information during use of the structure, wherein said output device is adapted to output the information after operation of the structure.

89. The system of claim 87, wherein said output device is arranged to output the information to a user of the structure during structure use.

90. The system of claim 89, including an arrangement for preventing the user from performing a further said causal mode of structure use.

91. The system of claim 89, including a data store for storing said information, wherein said output device is adapted to generate a maintenance output at the end of a period of use of the structure based on said stored information to indicate to a maintenance crew that a particular maintenance operation is required as a result of structural damage resulting from the causal mode of structure use.

92. The system of claim 87, wherein the data processing system is adapted to compare processed parameters determined from detected acoustic emissions with model data characterising effects of acoustic paths between a plurality of positions and said acoustic sensors.

93. The system of claim 92, wherein said data processing system is adapted to process said acoustic emissions detected by said sensors to determine at least one of differences in times of arrival of said acoustic emissions at said sensors, wave-shape information, emissions duration, amplitudes of said acoustic emissions and rise times of said acoustic emissions;

and said model data comprises at least one of differences in times of arrival of said acoustic emissions at said sensors, wave-shape information, emission duration, amplitudes of said acoustic emissions and rise times of said acoustic emissions for each position.

94. The system of claim 92, further comprising a store for storing acoustic emission data obtained by said processing of the detected acoustic emissions.

95. The system of claim 92, wherein said model data includes data identifying different types of acoustic emissions and corresponding types of structural damage, and said data processing system is adapted to locate and identify structural damage using the model data.

96. The system of claim 95, wherein said model data includes wave-shape information for different types of structural damage, and said data processing system is adapted to determine wave-shape information for the detected acoustic emissions and compare the determined wave-shape information with the model data to identify the structural damage.

97. The system of claim 92, wherein said acoustic emissions comprise bursts of acoustic emissions, said data processing system is adapted to accumulate bursts having similar time of arrival properties, and when a threshold is reached for a group of bursts having similar time of arrival properties, to determine a location of origin of the bursts and the structural damage using the model data, and to generate an indication of structural damage.

98. The system of claim 92, wherein said acoustic emissions comprise bursts of acoustic emissions, said data processing system is adapted to determine a location of origin of each burst using the model data, to accumulate bursts having similar locations of origin, and when a threshold is reached for a group of bursts having similar locations of origin, to generate an indication of structural damage.

99. The system of claim 87, including means for defining a region of interest on said structure, wherein said output device is adapted to output the information on the correlated structural damage and determined causal mode of structure use to relate only to said region of interest.

100. The system of claim 99, wherein said data processing system is adapted to only process said acoustic emissions to determine structural damage in said region of interest.

101. The system of claim 99, wherein said means for defining said region of interest comprises an acoustic emission source for inducing emissions in the region of interest in the structure, said sensors are adapted to detecting said acoustic emissions induced in said region of interest, and said data processing system is adapted to identify the location of the region using the detected acoustic emissions.

102. A method of confirming a source of structural damage in a structure where said structural damage has been detected by receiving acoustic emissions at a plurality of sensors and recording a first position in the structure from which the acoustic emissions are received, the method comprising:

inducing acoustic emissions at a second position in a region of said first position in the structure using an acoustic emission source;

detecting said acoustic emissions induced at said second position;

determining said second position using the received acoustic emissions; and

moving said acoustic emission source until said determined second position is substantially concurrent with said first position in the structure.

103. The method of claim 102, wherein said first position is determined using a method comprising:

detecting acoustic emissions from a site of said structural damage at said plurality of acoustic sensors arranged on said structure; and

processing the detected acoustic emissions using a model characterising effects of acoustic paths between a plurality of positions on said structure and said acoustic sensors to locate said structural damage;

wherein the model includes data identifying different types of acoustic emissions and corresponding types of structural damage, and said processing includes locating and identifying structural damage using the model data.

104. The method of claim 102, wherein said second position is determined using a method comprising:

detecting acoustic emissions from a site of said structural damage at said plurality of acoustic sensors arranged on said structure; and

processing the detected acoustic emissions using a model characterising effects of acoustic paths between a plurality of positions on said structure and said acoustic sensors to locate said structural damage;

wherein the model includes data identifying different types of acoustic emissions and corresponding types of structural damage, and said processing includes locating and identifying structural damage using the model data.

105. The method of claim 102, wherein said induced acoustic emissions are of a first type to simulate a first type of damage, further comprising comparing said recorded acoustic emission data with said detected acoustic emissions when said first and second positions are substantially concurrent to determine if the recorded acoustic emissions correspond to damage of a first type, inducing acoustic emissions of a second type to simulate damage of a second type and repeating the comparison if it is determined that the damage is not of the first type.

106. The method of claim 102, including generating an audible or visible output indicating the proximity of the first and second positions.

107. A system for confirming a source of structural damage in a structure, where said damage has been detected by receiving acoustic emissions and recording a first position on the structure from which the acoustic emissions are received, the system comprising:

an acoustic emission source for inducing acoustic emissions at a second position in a region of said first position;

a plurality of sensors for receiving said acoustic emissions induced at said second position;

a data analysis system for determining said second position using the received acoustic emissions;

means for moving said acoustic emission source until said determined second position is substantially concurrent with said first position in the structure; and

an output device for generating an output indicating the proximity of the first and second positions.

108. The system of claim 107, wherein said plurality of sensors and said data analysis system further comprises:

a data processing system for processing acoustic emissions detected by said sensors using data defining a model characterising effects of acoustic paths between a plurality of positions in said structure and said acoustic sensors;

wherein said model data includes data identifying different types of acoustic emissions and corresponding types of structural damage, and said data processing system is adapted to locate and identify structural damage using the model data.

109. The system of claim 107, wherein said acoustic emission source is adapted to induce acoustic emissions of a first type to simulate a first type of damage, said data analysis system is adapted to compare said recorded acoustic emission data with said detected acoustic emissions when said first and second positions are substantially concurrent to determine if the recorded acoustic emissions correspond to damage of a first type, said acoustic emission source is adapted to induce acoustic emissions of a second type to simulate damage of a second type if it is determined that the damage is not of the first type, and said data analysis system is adapted to repeat the comparison.

110. The system of claim 107, wherein the output device is adapted to generate an audible or visible output.

111. A method of simulating acoustic emissions generated from structural damage in a structure, the method comprising:

acquiring acoustic emission data from a plurality of regions of different types of structural damage to obtain at least one acoustic emission signature associated with each of said types of structural damage; and

adapting an acoustic emission source to generate appropriate acoustic emissions at each said region to generate each respective acoustic emission signature.

112. The method of claim 111, wherein said acquisition step is performed sequentially for different types of structural damage.

113. A system for simulating acoustic emissions generated from structural damage in a structure, the system comprising:

an acquisition system for acquiring acoustic emission data from a plurality of regions of different types of structural damage to obtain at least one acoustic emission signature associated with each of said types of structural damage; and

an acoustic emission source adaptable to generate appropriate acoustic emissions at each said region to generate each respective acoustic emission signature.

114. The system of claim 113, wherein said acquisition system is adapted to acquire the acoustic emission data sequentially for different types of structural damage.

115. A method of verifying structural damage in a region of interest in a structure, said damage having been recorded in a database for a plurality of locations, the method comprising:

inducing acoustic emissions in the region of interest in the structure using an acoustic emission source;

detecting said acoustic emissions induced at said region of interest;

identifying the location of the region using the detected acoustic emissions; and

determining all recorded locations of damage recorded in said database using the identified location of the region.

116. A method according to claim 115, wherein the step of inducing acoustic emissions further comprises inducing acoustic emissions at a boundary of the region of interest, and the step of identifying the location of the region further comprises determining the location of the acoustic emissions and determining the boundary of the region of interest in accordance with the determined locations.

117. A method of correlating a site of structural damage in a structure with causal modes of structure use, the method comprising:

detecting acoustic emissions from said site of structural damage at a plurality of acoustic sensors arranged on said structure;

processing the detected acoustic emissions to locate said structural damage;

acquiring structure use parameters from the structure;

processing said structure use parameters to determine a structure use mode;

correlating the structural damage with the determined structure use mode to determine a causal mode of structure use;

recording said site of structural damage as a first position and said determined causal mode of structure use;

inducing acoustic emissions at a second position in a region of said first position in the structure using an acoustic emission source;

receiving said acoustic emissions induced at said second position;

determining said second position using the received acoustic emissions;

moving said acoustic emission source until said determined second position is substantially concurrent with said first position in the structure to confirm the location of the structural damage; and

outputting information on the confirmed location of the structural damage and determined causal mode of structure use.

118. A method of determining a site of structural damage in a structure, the method comprising:

detecting acoustic emissions from said site of structural damage at a plurality of acoustic sensors arranged on said structure;

processing the detected acoustic emissions using a model characterising effects of acoustic paths between a plurality of predetermined positions on said structure and said acoustic sensors to determine a first approximate position of said structural damage, said first predetermined position lying on one of said predetermined positions;

inducing acoustic emissions at a second position in a region of said first position in the structure using an acoustic emission source;

detecting said acoustic emissions induced at said second position at said sensors;

processing the detected acoustic emissions using the model to determine said second position using the received acoustic emissions; and

comparing the processed acoustic emissions from the structural damage with the processed acoustic emissions from the acoustic emission source to determine if said second position is said site of structural damage.

119. The method of claim 118, including, if the comparison does not determine that said second position is said site of structural damage, repeatedly moving said acoustic emission source and repeating the inducing detecting and processing steps to determine said second position until said second position is determined to be said site of structural damage.

120. The method of claim 119, wherein a direction to move the acoustic emission source is determined using said model.

121. The method of claim 120, wherein a direction indicator is output to an operator.

122. The method of claim 118, including updating the model using the processed acoustic emissions from the acoustic emission source and information on said second position.

123. A system for determining a site of structural damage in a structure, the system comprising:

a plurality of acoustic sensors for detecting acoustic emissions from said site of structural damage on said structure;

a data processing system for processing the detected acoustic emissions using a model characterising effects of acoustic paths between a plurality of predetermined positions on said structure and said acoustic sensors to determine a first approximate position of said structural damage, said first predetermined position lying on one of said predetermined positions; and

an acoustic emission source for inducing acoustic emissions at a second position in a region of said first position in the structure;

wherein said sensors are adapted to detect said acoustic emissions induced at said second position;

said data processing means is adapted to processing the detected acoustic emissions using the model to determine said second position using the received acoustic emissions, and to compare the processed acoustic emissions from the structural damage with the processed acoustic emissions from the acoustic emission source to determine if said second position is said site of structural damage.

124. The system of claim 123, wherein said data processing system is adapted to determine a direction to move the acoustic emission source using said model.

125. The system of claim 124, including an output device for outputting a direction indicator to an operator to indicate the direction to move the acoustic emission source.

126. Apparatus for simulating acoustic emissions, comprising:

input means for inputting a selection of one of a plurality of types of structural damage; and

an inducing arrangement for inducing acoustic emissions corresponding to the selected type of structural damage.

127. Apparatus according to claim 126, further comprising storage means for storing acoustic emission data corresponding to the plurality of types of structural damage;

and processing means for selecting stored data corresponding to the selected type of structural damage and operating the inducing arrangement in accordance with the selected data.

128. Apparatus according to claim 126, adapted for use in a system for building a model of the effect of acoustic paths in a structure for use in the detection of a plurality of types of structural damage at each of a plurality of locations in said structure, the system comprising:

an inducing arrangement for inducing a plurality of types of acoustic emissions at each of a plurality of positions on said structure, said plurality of types of acoustic emissions corresponding to a respective plurality of types of structural damage;

at least three sensors for detecting said acoustic emissions;

a data processing system for processing detections by said at least three sensors for each type of acoustic emission for each position to determine model data characterising effects on each type of acoustic emission from each position of acoustic paths between said positions and said sensors; and

a data store for storing said determined model data.

129. A hand-held device, comprising apparatus for simulating acoustic emissions, said apparatus comprising:

input means for inputting a selection of one of a plurality of types of structural damage; and

an inducing arrangement for inducing acoustic emissions corresponding to the selected type of structural damage.