WO2005038449A1

WO2005038449A1 - A probe for non-destructive testing

Info

Publication number: WO2005038449A1
Application number: PCT/AU2004/001431
Authority: WO
Inventors: Laurence Dickinson; Stewart Wagner; Suszanne Thwaites
Original assignee: Commonwealth Scientific And Industrial Research Organisation
Priority date: 2003-10-16
Filing date: 2004-10-18
Publication date: 2005-04-28

Abstract

The present invention provides a probe (10) for non-destructive testing of an item. The probe is movable over a surface of the item and comprises a receiver (12, 14) for receiving a return signal for the non-destructive testing of the item. The probe also comprises a displacement means (16) for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the item. Further, the probe comprises a support structure (20) for holding the displacement means and the receiver over the surface of the item. At least one of the displacement means and the receiver is moveable relative to at least a portion of the support structure whereby testing of an item having a curved surface is facilitated.

Description

A PROBE FOR NON-DESTRUCTIVE TESTING

Field of the Invention The present invention relates to a probe for use in the non-destructive testing of materials and, particularly, but not exclusively, to a probe for use in the non-destructive testing (NDT) of structures such as aircraft panels.

Background of the Invention Non-destructive testing (NDT) is used to test a number of materials, in particular composite materials, utilised to manufacture aircraft and other items. It is not feasible to test items such as an aircraft for damage by disassembling the aircraft first. The testing needs to be non-destructive. Generally, but not exclusively, acoustic and near ultrasonic frequencies are used for NDT. A typical NDT system is the pitch/catch system, employing a pitch/catch probe. The probe assemblies includes contact tips which are spring loaded to contact a test sample. Each probe assemblies is equipped with two transducers such that one can act as a driver and the other as a detector (the operation may be interchangeable) . The available drive frequency range is wide, typically 1 to 70 kHz. The drive signal is generally a short wave train, up to 6 cycles of sinusoid at a user-selected frequency within the above range. The drive signal may alternatively be impulse or step excitation. The detector measures a response of the test sample at its contact point. The propagation of the disturbance from the drive to the detector is influenced by the nature of the intervening structure and in particular, by any damage or anomaly in this region. A return signal detected from a damaged test sample is compared with that from a "good" test sample (to give a reference signal) to determine the extent of any damage to the test sample. In conventional systems, complex electronic hardware is utilised to process the signals and provide a display of the return signal to enable determination of the damage. These systems are often expensive and the equipment is usually bulky. In operation, testing will actually be carried out in situ on the item being tested (for example, an aeroplane) . The pitch/catch probe is passed over the surface of the panels of the item being tested, and readings are taken from a plurality of points across the panel. Typical pitch/catch probes are hand held and move from one place to another over material being tested whilst viewing the result on a graphical readout . International patent application PCT/AU02/00494 discloses a compact probe that combines probe transducers with an optical displacement system that has a function related to that of a so called "optical" computer mouse. For many displacements systems including such optical displacement systems it is important to keep the distance between the displacement system and the surface of the test item as constant as possible. For example, a typical optical displacement system has a distance tolerance of approximately only 0.5mm. However, typical test items, such as aircraft panels, often have different surface curvatures which makes it very difficult to maintain this tolerance when the probe is scanned over the panel. Summary of the Invention The present invention provides in a first aspect a probe for non-destructive testing of an item, the probe is movable over a surface of the item and comprises : a receiver for receiving a return signal for the non-destructive testing of the item, a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the item and a support structure for holding the displacement means and the receiver over the surface of the item, wherein at least one of the displacement means and the receiver is moveable relative to at least a portion of the support structure whereby testing of an item having a curved surface is facilitated.

The receiver may be moveable relative to at least a portion of the support structure, but typically the displacement means is moveable relative to at least a portion of the support structure. Owing to the moveability of the displacement means relative to at least a portion of the support structure, a movement of the probe over the curved surface in a manner such that a substantially constant distance between the displacement means and the surface is largely maintained is facilitated. The probe typically comprises pitch/catch assemblies which include the receiver and an emitter for emitting a signal for the non-destructive testing of the item. In a first embodiment of the present invention the support structure and the displacement means, which may comprise a housing, are coupled in a manner so that the displacement means is moveable relative to the entire support structure . For example, the support structure may have three legs with feet that are arranged in a tripod arrangement . Such an arrangement has the particular advantage that the support structure may follow surface curvatures in a relatively easy and stable manner when the probe is moved over the surface. The displacement means may be positioned over a central portion of the area circumscribed by the feet . The test item may have a curved surface and the curvature may change across the surface. When the probe is moved over the surface and the three feet are in contact with the surface, the displacement means may, if the curvature is suitable, move up or down relative to the support structure to follow the curvature. It is therefore easier to meet the small distance tolerances required by a range of displacement means including optical devices such as those currently used in a so called "optical" computer mouse when curved surfaces are scanned. The displacement means may include a housing and a displacement sensor such as an "optical" sensor positioned in the housing. The housing of the displacement means may have a lower surface and in this case the support structure typically is arranged to hold the lower surface of the housing on the surface of the item. The probe typically has as a flexible coupling between the displacement means and the support structure. The flexible coupling may allow movement of the displacement means in any direction relative to the support structure. The coupling between the displacement means and the support structure may also comprise a guide that guides a movement of the displacement means relative to the support structure for example in a direction perpendicular to the surface under test . The probe typically is arranged so that in use the three feet slide across the surface of a curved item, such as an aircraft panel, and the lower surface of the displacement means maintains contact with the surface even if the curvature of the surface is changing. The probe may also comprise a handle portion that may be connected to the support structure. The connection may be pivotable and typically comprises a universal joint. The handle portion typically is connected to the support structure so that the area circumscribed by support positions at which in use the support structure contacts the surface of the item has a diameter larger than the height of the pivotable connection over the area. This particular geometrical arrangement has the advantage that the likelihood of tipping the probe over when the probe is moved over the surface of the item is reduced.

In a second embodiment of the present invention the support structure comprises at least two portions which are moveable relative to each other and the displacement means is coupled to one of the portions. For example, the displacement means may be coupled to a first portion of the support structure so that the displacement means is stationary relative to the first portion of the support structure and moveable relative to a second portion of the support structure. The receiver may be coupled to the second portion so that the receiver and the displacement means are moveable relative to each other. As in this case the displacement means is moveable relative to the receiver, following of a curvature of a test sample is facilitated even if the curvature is changing. Alternatively, the displacement means and the receiver may both be located in the second portion and the first portion may comprise a handle portion of the probe. For example, the first and the second portions may be coupled by a coupling that includes a hinge or any type of articulated joint or a flexural joint that uses the compliance of material comprising the first and second portions. The first portion and the second portion of the support structure may be coupled in a manner so that the first and the second portions may be separated from each other. For example, the coupling may include a snap-fit connection in which one portion snap-fits into another portion. The second portion may comprise the pitch/catch assemblies and, as the first and the second portions are separable, the pitch/catch assemblies can be replaced in a relatively easy manner. To facilitate replacement of the second portion the pitch/catch assemblies, the second portion typically comprises snap-lock electrical connections for the pitch/catch assemblies. The second portion with the pitch/catch assemblies may also be arranged for operation as a stand-alone non- destructive testing probe. In this case the second portion may or may not comprise the displacement means. The displacement means typically includes a displacement sensor such as an "optical" sensor. The probe typically is arranged so that in use the probe slides across the surface of a curved item, such as an aircraft panel, and a lower surface of the displacement means maintains contact with the surface even if the curvature of the surface is changing. To further facilitate testing of curved items, the lower surface of the support structure may also include a curved surface portion. In both embodiments the probe may comprise visually transparent materials. The probe typically is arranged so that a user can see through the transparent material on the surface of the item. This has the advantage that the user may be able to see the area that is tested or an area close to the area that is tested. For example, the support structure may comprise the transparent material . In one specific example the second portion of the support structure comprises the transparent material. The probe may also comprise pointers or any type of markings that indicates at which position the pitch/catch assemblies are located and therefore in use indicates a test area. For example, the markings may be "datum" markings .

The present invention provides in a second aspect a probe for non-destructive testing of an item, the probe is movable over a surface of the item and comprises: a receiver for receiving a return signal for the no -destructive testing of the item and a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the item and a support structure for holding the displacement means over the surface of the item, such that, when the support structure is moved over the surface of the item, a substantially constant distance is maintained between the displacement means and the surface of the item.

The support structure and the displacement means typically are coupled in a manner so that the displacement means is moveable relative to at least a portion of the support structure . The present invention provides in a third aspect a probe for non-destructive testing of an item, the probe is movable over the surface of the item and comprises: a receiver for receiving a return signal from the non-destructive testing of the item, a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the test item and a support structure for supporting the displacement means over the surface of the item wherein the support structure comprises legs that are arranged in a tripod arrangement .

The present invention provides in a fourth aspect a probe for non-destructive testing of an item, the probe being movable over the surface of the item and comprising a receiver for receiving a return signal from the non-destructive testing of the item, a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the item and a support structure for supporting the displacement means over the surface of the item and wherein the support structure comprises two portions that are moveable relative to each other.

The invention will be more fully understood from the following description of specific embodiments of the invention. The description is provided with reference to the accompanying drawings.

Brief Description of the Drawings Figures 1 shows a schematic representation of a probe for non-destructive testing in accordance with an embodiment of the present invention, Figures 2 - 3 show views of portions of the probe shown in Figure 1, Figure 4 is a schematic block diagram of components of the probe according to an embodiment of the invention, Figure 5 shows a top-view of a probe for nondestructive testing in accordance with another embodiment of the present invention and Figure 6 shows a bottom view of the probe also shown in Figure 5.

Detailed Description of Specific Embodiments Referring initially to Figures 1 to 3 , there is illustrated a probe for non-destructive testing in accordance with an embodiment of the present invention, generally designated by reference numeral 10. The probe 10 is arranged to be passed over a test sample 11, which shows a reflection of the probe, and to provide an acoustic vibration excitation of a drive frequency within the range of 1 to 70 kHz to the sample 11 and receive a return signal to be processed by the computing system (not shown) to provide data on any faults in the test sample. The acoustic vibration excitation may be of single frequency or may be a broad-band excitation such as a band-limited broad-band excitation. In operation, the test sample will usually be a part of equipment being tested, such as an aeroplane, for example. A return signal detected from a damaged test sample is compared with that from a "good" test sample (to give a reference signal) to determine the extent of any damage to the test sample . In one embodiment of the present invention the probe 10 is arranged to store reference signals so that the same reference signal can be used for continued testing of a tests item or for different test items of the same type. The probe 10 comprises pitch/catch assemblies 12 and 14 of the probe 10. The pitch/catch assemblies 12 and 14 assemblies include contact tips which are spring loaded to contact a test sample. One of the assemblies 12 acts as a driver and the other as a detector. The available drive frequency range is wide, typically 1 to 70 kHz. The drive signal is generally a short wave train, up to 6 cycles of sinusoid at a user selected frequency within the above range . In addition to the pitch/catch assemblies 12 and 14, the probe 10 comprises a displacement device 16 that provides information about the displacement of the probe when the probe is moved over the surface of a test item. In this embodiment, the displacement device 16 comprises an optical system in a housing and the optical system is equivalent to those used in the so-called "optical" computer mouse. The housing has a lower surface having an opening 17 through which the optical sensor operates. The displacement device 16 is mounted by a flexible mounting 18 to a support structure 20. In this embodiment, the flexible mounting 18 comprises a resilient material that allows movement of the displacement device 16 in any direction relative to the support structure 20. In this case the resilient material is a rubber type material connecting the support structure 20 with the housing of the displacement device 16. Alternatively, however, the flexible mounting may be a mechanical arrangement comprising parts which function as a whole so that the mounting is flexible. The support structure 20 has three sliding feet 22, 24 and 26 which form part of a tripod arrangement. The sliding feet 22, 24 and 26 which are linked by a bridge portion that is a part of the support structure 20. The displacement device is positioned at a central portion of the area circumscribed by the three feet . The support structure has arc-shaped cut-outs 28. In this embodiment, a handle portion 30 is connected to the support structure 20 by a universal joint 32 that allows pivotable movement about itself in all directions. The universal joint is covered by a flexible rubber sleeve which is not shown. In one embodiment, the handle portion 30 is arranged for connection to an extension pole or is extendable which has advantages when the test item is not easily accessible (eg areas of an aircraft which are difficult to reach) . In an alternative embodiment the handle is fully removable so that the support structure 20 can be used independently in areas having restricted access. In this instance the support structure would be connected to the handle by means of an extension cable . In use the probe 10 may be moved over the surface of the test item, such as an aircraft panel, having a curved surface and, for example, the curvature of the surface may change across the surface. The three feet 22, 24 and 26 are sliding on the surface and because of the tripod arrangement it may be possible to follow the curvature of the surface while at the same time all of the three sliding feet are in contact with the surface of the test item. The displacement device 16 is flexibly mounted on the support structure 20 and in use the lower surface of housing of the displacement device is in contact with the surface. Due to the flexible mounting, contact of the lower surface of the housing with the surface of the test item can be maintained even if the curvature of the surface changes as the displacement means can move (ie. up or down) relative to the support structure 20. It is therefore possible to obtain relaiable displacement information even if the probe is moved over a curved surface having a changing curvature . The probe is arranged so that in use the universal joint 32 is at a relatively low level over the surface of a test item. In this embodiment, the universal joint 32 is positioned so that the distance between the sliding feet 22, 24 and 26 is larger than the height of the universal joint 32 over the surface of the test item. This arrangement has the advantage that it is possible to move the probe over the surface of the test item in a relatively stable manner and the likelihood of tipping is reduced. In the embodiment shown in Figure 3 the probe also comprises a guide which is in this example provided in form of a bracket 29. The bracket 29 guides the displacement device 16 so that it is moveable in a direction towards, or away from, the surface of the test item and a movement in another direction is restricted. Figure 4 shows a schematic block-diagram of electronic components of the probe 10 shown in Figures 1 to 3. The probe 40 comprises NDT data acquisition, processing and analysis electronics in one housing. PC computer 42 functions to store and display data. The probe is operatively connected with the computer 42 using a single USB cable 44. The probe can be connected to any typical PC computer via the USB port which gives the probe a significant commercial advantage. In this case the USB cable may also be used to supply electrical power. Alternatively, the probe may be battery-powered and the data transfer between probe 40 and computer 42 may be wireless in which case the device does not need a USB cable connection. Referring now to Figures 5 and 6, a probe for nondestructive testing according to another embodiment of the present invention is now described. The probe 50 comprises a first portion 52 and a second portion 54. The first portion 52 and the second portion 54 are movable relative to each other. The first portion 52 and the second portion 54 are also connected by an electrical cable 56. In this embodiment the second portion 54 is coupled to the first portion 52 in a manner so that the second portion 54 is pivotable about an axis 55. In this example, the second portion 54 is coupled to the first portion 52 by a snap fit. The second portion 54 and the first portion 52 therefore are separable. The electrical cable 56 also has a snap fit 59 which allows disconnection in a relatively easy manner. In this embodiment the second portion 54 comprises pitch/catch assemblies 60 and 62. The pitch catch assemblies 60 and 62 are analogous to pitch/catch assemblies 12 and 14 discussed above. As the second portion 54 is removable from the first portion 52, it is relatively easy to replace the second portion 54 or the pitch/catch assemblies of the second portion 54. The first portion 52 comprises a displacement device 64 which in this embodiment is analogous to displacement device 16 discussed above. As in this embodiment the second portion 52, which include the pitch/catch assemblies, is movable about axis 55 and relative to the first portion 52, which includes the displacement device 64, it is possible to follow a curved surface of a test item so that a predetermined distance between the displacement device 64 and the surface of the curved test item is largely maintained. Further, the first portion 52 also includes a curved lower surface 66 which further facilitates testing of the curved test item. In this embodiment the second portion 54 is composed of a transparent material such as a transparent polymeric material . This has the advantage that it is possible for a user to see the test area or an area that is close to the test area. In addition, the second portion 54 includes in this embodiment markings, in this case provided in the form of datum markings, which indicate the position of the pitch catch assemblies 60 and 62. The probe 50 includes electronic components analogous to those shown in Figure 4 and operates in the same manner as illustrated by the schematic block diagram of Figure 4. In this embodiment the pitch/catch assemblies 12 and 14, are stationary relative to the second portion 54. It will be appreciated, that alternatively the pitch/catch assemblies may be movable relative to the second portion 54. Further, the second portion 54 may also include the displacement device such as displacement device 64. In a variation of this embodiment the first portion 52 comprises the pitch/catch assemblies and the second portion 54 comprises the displacement device. Further, it will also be appreciated that the first and second portions may be coupled to each other in any manner that allows movability of the first portion 52 relative to the second portion 54. For example, coupling may be effected using a universal joint or any other type of joint. Additionally or alternatively the second portion may also be movable about any axis other than axis 55. Further, the coupling may include a hinge so that the first portion 52 and the second portion 54 are hingedly connected. In the above description, the probe incorporates a pitch/catch arrangement. It will be appreciated that the present invention is not limited to use of a pitch/catch arrangement . Any NDT sensor arrangement which can be incorporated in the probe may be utilised (e.g. ultrasonic pulse echo, eddy current, mechanical impedance) . The particular embodiment of the probe described above utilises optical arrangements for providing positional information. It will be appreciated that the present invention is not limited to optical arrangements, and any sensor arrangement which enables the provision of positional information from motion of the probe may be utilised. For example, an arrangement such as that of a conventional computer ball-mouse may be utilised for this purpose. The probe described above is particularly suitable for use in non-destructive testing. The probe is not limited to the NDT field, however. Any process or system which requires the input of positional information from a probe could utilise the probe of the present invention. Further, the probe may also comprise computer memory for data storage in one housing. In this case a connection to an external computer may only be required for data transfer. The probe may also comprise a display and may form a complete NDT system. It will be appreciated that the reference that is being made to International patent application PCT/AU02/00494 does not constitute an admission that this citation is part of the common general knowledge in Australia or in any other country.

Claims

The Claims :

1. A probe for non-destructive testing of an item, the probe is movable over a surface of the item and comprises: a receiver for receiving a return signal for the non-destructive testing of the item, a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the item and a support structure for holding the displacement means and the receiver over the surface of the item, wherein at least one of the displacement means and the receiver is moveable relative to at least a portion of the support structure whereby testing of an item having a curved surface is facilitated.

2. The probe as claimed in claim 1 wherein the displacement means is moveable relative to at least a portion of the support structure.

3. The probe as claimed in claim 1 or 2 comprising pitch/catch assemblies which include the receiver and an emitter for emitting a signal for the non-destructive testing of the item.

4. The probe as claimed in any one of the preceding claims wherein the support structure and the displacement means are coupled in a manner so that the displacement means is moveable relative to the entire support structure .

5. The probe as claimed in any one of the preceding claims wherein the displacement means includes a housing having a lower surface and the support structure is arranged to hold the lower surface of the housing on the surface of the test item.

6. The probe as claimed in any one of the preceding claims having a flexible coupling that couples the displacement means to the support structure.

7. The probe as claimed in any one of the preceding claims wherein the support structure has three legs with feet that are arranged in a tripod arrangement .

8. The probe as claimed in claim 7 when dependent on claim 5 arranged so that in use the three feet slide across the surface of a curved test item and the lower surface of the displacement means maintains contact with the surface even if the curvature of the surface is changing .

9. The probe as claimed in any one of the preceding claims further comprising a handle portion.

10. The probe as claimed in claim 9 wherein the support structure and the handle portion are connected by a pivotable connection.

11. The probe as claimed in claim 10 wherein the connection comprises a universal joint.

12. The probe as claimed in any one of claims 9 to 11 wherein the handle portion is connected to the support structure so that the area circumscribed by support positions at which in use the support structure contacts the surface of the test item has a diameter larger than the height of the pivotable connection over the area.

13. The probe as claimed in any one of claims 1 to 3 wherein the support structure comprises at least two portions which are moveable relative to each other and the displacement means is coupled to one of the portions.

14. The probe as claimed in claim 13 wherein the displacement means is coupled to a first portion of the support structure so that the displacement means is stationary relative to the first portion of the support structure and moveable relative to a second portion of the support structure.

15. The probe as claimed in claim 13 or 14 wherein the receiver is coupled to the second portion so that the receiver and the displacement means are moveable relative to each other.

16. The probe as claimed in claim 13 or 14 wherein the displacement means and the receiver are both be located in the second portion and the first portion may comprise a handle portion of the probe.

17. The probe as claimed in any one of claims 13 to 16 wherein the first and the second portions are coupled by a coupling that includes a hinge.

18. The probe as claimed in any one of claims 13 to 16 wherein the first and the second portions are coupled by a coupling that includes an articulated joint.

19. The probe as claimed in any one of claims 13 to 16 wherein the first and the second portions are coupled by a coupling that includes a flexural joint that uses the compliance of material comprising the first and second portions .

20. The probe as claimed in any one of claims 13 to 19 wherein the first portion and the second portion of the support structure are coupled in a manner so that the first and the second portions may be separated from each other.

21. The probe as claimed in claim 20 comprising a snap- fit connection for coupling the fist and the second portions .

22. The probe as claimed in any one of claims 13 to 21 when dependent on claim 3 wherein the second portion comprises the pitch/catch assemblies.

23. The probe as claimed in claim 22 being arranged for operation as a stand-alone non-destructive testing probe.

24. The probe as claimed in any one of claims 13 to 23 comprising an optical sensor.

25. The probe as claimed in any one of claims 13 to 24 being arranged so that in use the probe slides across the surface of a curved item and a lower surface of the displacement means maintains contact with the surface even if the curvature of the surface is changing.

26. The probe as claimed in claim 25 wherein the lower surface is curved.

27. The probe as claimed in any one of the preceding claims comprising visually transparent materials.

28. The probe as claimed in claim 27 being arranged so that a user can see through the transparent material onto the surface of the item.

29. The probe as claimed in any one of the preceding claims comprising markings that indicates at which position the pitch/catch assemblies are located.

30. A probe for non-destructive testing of an item, the probe is movable over a surface of the item and comprises: a receiver for receiving a return signal for the nondestructive testing of the item and a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the item and a support structure for holding the displacement means over the surface of the item, such that, when the support structure is moved over the surface of the item, a substantially constant distance is maintained between the displacement means and the surface of the item.

31. The probe as claimed in claim 30 wherein the support structure and the displacement means typically are coupled in a manner so that the displacement means is moveable relative to at least a portion of the support structure.

32. A probe for non-destructive testing of an item, the probe is movable over the surface of the item and comprises : a receiver for receiving a return signal from the non-destructive testing of the item, a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the test item and a support structure for supporting the displacement means over the surface of the item wherein the support structure comprises legs that are arranged in a tripod arrangement .

33. A probe for non-destructive testing of an item, the probe being movable over the surface of the item and comprising a receiver for receiving a return signal from the non-destructive testing of the item, a displacement means for providing a displacement signal indicative of a spatial displacement of the probe over the item as the probe is moved over the item and a support structure for supporting the displacement means over the surface of the item and wherein the support structure comprises two portions that are moveable relative to each other.