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WO2008151369A1 - Procédé et appareil permettant une surveillance de l'état des structures - Google Patents

Procédé et appareil permettant une surveillance de l'état des structures Download PDF

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Publication number
WO2008151369A1
WO2008151369A1 PCT/AU2008/000840 AU2008000840W WO2008151369A1 WO 2008151369 A1 WO2008151369 A1 WO 2008151369A1 AU 2008000840 W AU2008000840 W AU 2008000840W WO 2008151369 A1 WO2008151369 A1 WO 2008151369A1
Authority
WO
WIPO (PCT)
Prior art keywords
pressure
vessel
impedance
circuit
port
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/AU2008/000840
Other languages
English (en)
Inventor
Kenneth Davey
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Structural Monitoring Systems Ltd
Original Assignee
Structural Monitoring Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2007903155A external-priority patent/AU2007903155A0/en
Application filed by Structural Monitoring Systems Ltd filed Critical Structural Monitoring Systems Ltd
Publication of WO2008151369A1 publication Critical patent/WO2008151369A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
    • G01M5/0033—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining damage, crack or wear

Definitions

  • the present invention is based on a method and system for condition monitoring of structures and, in particular but not exclusively, to the condition monitoring of structures subjected to varying ambient pressures such as aircraft or submarines .
  • the systems and methods described in the above referenced US Patents are largely single -ended having a sensor cavity that has one end connected via a high fluid flow impedance to a pressure source which is different to (i.e. greater or lower than) ambient pressure, with an opposite end of the cavity terminating on or in the component or monitoring device or otherwise sealed to ambient pressure.
  • a monitoring device is connected in parallel across the high fluid flow impedance.
  • a miniscule flow of air through the impedance which may arise from a crack penetrating the cavity, produces a pressure change across the impedance that can be monitored by the monitoring device to provide an indication of the condition of the component.
  • the present invention arises from further research and development in the area of condition monitoring.
  • a condition monitoring system comprising:
  • a sensor cavity formed on or in a component or structure to be monitored; a pressure storage vessel containing fluid at a pressure different to ambient pressure; and, a monitoring device which provides an indication when a difference in fluid pressure between the cavity and the pressure vessel exceeds a threshold level;
  • the system may further comprise a pressure adjustment port provided in the series circuit, the port located between the sensor cavity and the pressure vessel at a point where a ratio of volume to fluid flow impedance of a first portion of the circuit from the port to one side of the monitoring device, is substantially equal to a ratio of volume to fluid flow impedance of a second portion of the circuit from the port to an opposite side of the monitoring device.
  • the system may further comprise an adjustable flow device connected in series between the port and either the first portion of the circuit or the second portion of the circuit, the adjustable flow device configured to vary volume or impedance or both volume and impedance of the portion of the circuit in which the device is series connected to facilitate a matching of volume to impedance ratio with the other portion of the circuit.
  • the adjustable flow device may comprise an adjustable flow impedance such as a needle valve.
  • the adjustment flow advice may comprise a conduit or container of adjustable volume.
  • the adjustable flow device is in series connection between the port and the pressure vessel .
  • condition monitoring system may further comprise a high fluid flow impedance connected in series between the sensor cavity and the pressure vessel.
  • the system may further comprise a pressure adjustment source coupled to the port, the pressure adjustment source operable to vary fluid pressure within the circuit.
  • the pressure adjustment source may comprise a vacuum pump or a vacuum vessel.
  • the pressure adjustment source may comprise a positive pressure pump or a positive pressure vessel.
  • the pressure adjustment source may be operated continuously; or, periodically on the basis of a sensed change in pressure in the pressure vessel in comparison to ambient pressure.
  • a method of condition monitoring comprising:
  • a sensor cavity on or in a component or structure to be condition monitored; connecting opposite ends of the sensor cavity to be in fluid pressure communication with a pressure vessel and a monitoring device to form a closed series circuit; and, operating the monitoring device to provide an indication when a difference in fluid pressure between the sensor cavity and the pressure vessel exceeds a threshold level.
  • the method may further comprise adjusting fluid pressure within the circuit by connection of a pressure adjustment device at a port in the circuit, the port being at a location where a ratio of volume to impedance of a first portion of the circuit from the port to one side of the monitoring device is substantially equal to a ratio of volume to impedance of a second portion of the circuit from the port to an opposite side of the monitoring device.
  • the method may comprise balancing a volume to impedance ratio of a first portion of the circuit containing the sensor cavity with a volume to impedance ratio of a second portion of the circuit containing the pressure vessel and coupling a pressure adjustment device to a port in the circuit located at a junction of the first and second portions of the circuit.
  • the method comprises operating the pressure adjustment device continuously.
  • the pressure adjustment device is operable periodically to maintain a pressure differential between fluid pressure in the vessel and ambient pressure.
  • Fig 1. is a schematic representation of a condition monitoring system in accordance with the present invention in a steady pressure state
  • Fig 2. is a schematic representation of the system depicted in Figure 1 in a changing pressure state.
  • Fig 3. is a schematic representation of the system shown in Figures 1 and 2 depicting the fluid flow in the system in the event of a crack or flaw developing in a component or structure being monitored by the system;
  • Fig 4 is a schematic representation showing fluid flow in an embodiment of the system depicted in Figures 1 and 2 in the event of condensate being drawn into a sensor cavity of the system via a crack or flaw formed in a component or structure being monitored;
  • Fig 5. is a schematic representation of second embodiment of the system
  • Fig 6 is a schematic representation of a third embodiment of the system.
  • Fig 7 is a schematic representation of a fourth embodiment of the system comprising a combination of the second and third embodiments depicted in Figures 5 and 6 respectively .
  • an embodiment of a condition monitoring system 10 comprises a sensor cavity 12, a pressure storage vessel 14, and a monitoring device 16.
  • the sensor cavity 12, vessel 14 , and monitoring device 16 are connected in series with each other to form a closed circuit.
  • This circuit is closed to the extent that opposite ends 18 and 20 of the sensor cavity 12 are in fluidic pressure communication with the vessel 14. That is end 18 is in fluid pressure communication with the vessel 14 via a high fluid flow impedance 22, while end 20 is in fluid pressure communication with the vessel 14 via the monitoring device 16.
  • the sensor cavity 12 is formed on or in a component or structure being the subject of condition monitoring.
  • the monitoring device 16 is in fluid communication between end 20 of the sensor 12 and the vessel 14, and provides a signal when the difference in fluid pressure between the sensor cavity 12 and the storage vessel 14 exceeds the threshold level. As explained in greater detail, this may occur in the event of a crack or flaw being formed in the component or structure which penetrates the sensor cavity 12; or, a blockage in the sensor cavity 12.
  • the system 10 further comprises an adjustable flow device 24 connected in series between the high fluid flow impedance 22 and the vessel 14.
  • a pressure adjustment port 26 is provided in the fluidic circuit between the impedance 22 and the pressure adjustment device 24.
  • a pressure adjustment source 28 is coupled to the port 26 via a conduit 30.
  • the vessel 14 contains air at say -20KPa relative to ambient pressure (i.e. a relative vacuum)
  • the sensor cavity 12 is in the form of a manifold adhered to the surface a component or structure being monitored.
  • the monitoring device 16 which may be in the form of a differential pressure switch is set to close when a pressure difference between the sensor cavity 12 and the vessel 14 is greater than the pressure difference caused by the permeable air flow into the sensor cavity 12.
  • the pressure differential caused by the permeable air flow represented by the small black arrows, does not exceed a threshold level of the monitoring device 16 and thus is the monitoring device 16 does not provide any signal indicative of this threshold level being exceeded.
  • the monitoring device 16 being represented as a differential pressure switch comprises a body 34 divided into two cavities 36 and 38 by a diaphragm 40.
  • the cavity 36 is a fluid communication with end 20 of the sensor 12 via a duct or tube 42.
  • the cavity 38 of the monitoring device 16 is in fluid communication with the source 14 via a duct or tube 44.
  • An inflow of air into the sensor cavity 12 via the crack 32 provides an increase in fluid pressure in the duct 42 which is transmitted to the cavity 36 resulting in a bowing or deformation of the diaphragm 40 causing a subsequent increase in fluid pressure in the duct 44 which is transmitted to the vessel 14.
  • the extent of defamation of the diaphragm 40 is dependent on the pressure differential between the cavity 12 and the vessel 14 caused by the inflow of air to the crack 22. This in turn is dependent on the size and period of opening of the crack 32.
  • the monitoring device 16 may be adjusted to set the predetermined threshold pressure differential which, when exceeded, causes the monitoring device 16 to provide a signal indicative the presence of the crack 32.
  • Embodiments of the present invention avoid this by adjusting the pressure state of the vessel 14 and the sensor cavity 12 proportionately. This is achieved by balancing the volume to impedance ratio of two portions of the circuit on opposite sides of the port 26. Thus, there is a proportional flow of air to the device 28 from the vessel 14 and the sensor cavity 12 thereby maintaining any existing pressure differential between the sensor cavity 12 and vessel 14. Accordingly, the state of the monitoring device 16 is unaffected by the fluidic connection between the device 28 and the vessel 14 and sensor cavity 12.
  • the adjustor flow device 24 can be configured to enable either an adjustment in: impedance between the vessel 14 and the port 26; the volume between the vessel 14 and the port 26; or, both the impedance and the volume for the portion of the circuit between the vessel 14 and the port 26.
  • the adjustable flow device 24 is illustrated in the Figures as comprising a duct 46 in which is provided an adjustable needle valve 48.
  • the impedance in the duct 46 can be adjusted so that the ratio of volume to impedance from opposites sides of the port 26 can be matched.
  • the duct 46 may initially be provided as a relatively long length of large bore tubing and the length subsequently being adjusted, for example by cutting, to provide the required balance in ratio of volume to impedance on both sides of the port 26.
  • the port 26 may be considered as the junction between a first portion of the circuit having the sensor and a second portion of the circuit containing the vessel 14, with the adjustable flow device 24 being considered as a volume to impedance ratio matching or tuning system which enables matching the volume to impedance radio for the first and second portions to be matched,
  • the balancing of the volume to impedance ratios is most conveniently performed on initial installation and setup of the system 10. This balancing may be performed in two stages. Firstly, assuming the high fluid flow impedance 22 has a fixed impedance, the flow impedance of the duct 46 is determined by the minimum volume of the sensor cavity 12 that can be expected to be monitored in service.
  • the needle valve 48 is used to further restrict the rate of flow of fluid from the vessel 14 to favour the larger volume of air that needs to be extracted from the larger sensor cavity 12 to restore the relative rates of flow required for balance.
  • the system 10 may be evacuated at a rapid rate by providing the pressure adjustment source 28 as a vacuum storage device and allowing fluid communication with the port 26 through the duct 30.
  • the needle valve 48 is then adjusted until a minimal differential pressure excursion of the monitoring device 16 is achieved.
  • the needle valve 48 is now fixed at the setting.
  • the constant vacuum source for the test was derived from a small side channel blower type vacuum pump with an electronic controller.
  • the device 28 is operated when necessary to either evacuate the vessel 14 (when altitude increases) or relieve vacuum from the vessel 14 (when altituide decreases) .
  • This may be achieved by the provision of a controller which upon detecting a variation between the pressure level in the vessel 14 and ambient pressure being greater than a threshold difference operates the device 28 to readjust the pressure differential between the vessel 14 and the ambient pressure to the required range .
  • the device 28 may run continuously. This provides an unregulated vacuum in the vessel 14 as the pressure differential between the vessel 14 ambient pressure will change with altitude of the aircraft. Nevertheless, the stable relationship between the sensor cavity 12 and the vessel 14 is maintained due to the balancing of the volume to impedance ratios on opposite sides of the port 26. In this regard, a test using a small peristaltic vacuum pump running continuously at its ultimate performance of about -98 KPa was found to detect sub millimetre cracks at the same rate of altitude change as described above .
  • the monitoring device 16 may comprise or be coupled to a signal integration means, for example an electronic counter which runs when the threshold level is exceeded, but stops when the pressure differential is below threshold level. This provides an effective automatic device for continuous unattended operation where a crack is detected by the integration of time rather than as single alarm signals on each occurrence of a crack opening to the extent that it causes a pressure differential greater than the threshold level.
  • the signal produced by the device 16 will have different characteristics (e.g. different frequency response) than when there is a crack 32 with no ingestion of moisture or contaminant 50. This allows a blockage induced signal to be distinguished from a crack induced signal. Inducing additional perturbation of the pressure in vessel 14 by means of operation of the pump 28 according to a predetermined regime will induce an imbalance in the device 16 with characteristics sufficient to confirm the identity of the cause as a blockage or crack .
  • a typical sensor cavity 12 may comprise an elongate gallery of typically 250 micron width or less and have a height of perhaps 100 micron.
  • the blocking effect of the moisture 50 is enhanced by surface tension.
  • the device 16 can be a differential pressure transducer connected by electrical conductors to an amplifier in the same manner as the cited patents, however, a differential pressure switch, set at a predetermined trigger level above expected permeable flow levels to give warning that a crack has been detected, provides simplicity as bulk and electrical interference is a consideration especially with high performance aircraft.
  • the device 16 could be subjected to temperatures at the tropopause typically to - 60 degrees Celsius. Accordingly, if a device 16 such as miniature switch rated for low temperature service having, for example, a Mylar diaphragm 40 is not available, or cannot be placed in a suitably warmed location on the structure, then a temperature controlled electrical heating jacket 60 surrounding the device 16 may be provided as shown in Figure 5.
  • FIG. 5 schematically shows a practical layout of the system 10 where the device 16 comprises a differential pressure switch.
  • the impedance 22, port 26, duct 46 and monitoring device 16 are housed inside a vessel 14a.
  • the vessel 14a acting also as the vacuum source as per the vessel 14 in Figures 1-4.
  • the vessel 14a may for example have a volume of 0.075 litre.
  • the cavity 12 is coupled by conduit 42 to the device 16 via a port 54 on the vessel 14a, and a conduit 56 connects end 18 of conduit 12 to the impedance 22 via a port 58 on the vessel 14a.
  • the differential pressure switch 16 is surrounded by a heater 60.
  • a wire S provides signal communication from the device 16, while wires V+ and V- provide power to the device 16 and the heater 60 from a power supply 62 (shown in Figure 7) .
  • a temperature controlling means such as a thermistor and simple amplifier 64 is provided to maintain the device 16 above its minimum operating temperature (for example say -4 degrees Celsius) .
  • a removable plug or sealing means 64 is shown to allow access for adjustment of device 16 to set the desired trigger level above the maximum expected permeability effect.
  • the needle valve 48 is sealed in the vessel 14a to allow convenient adjustment and is configured to restrict one end the duct 48.
  • the other end of the duct 48 is connected to the port 26 which further connects both high impedance to fluid flow duct 22 and the duct 30, with the duct 30 connecting to pump 28.
  • Pump 28 could be situated in a distant location on the aircraft or be replaced by some other pressure/ vacuum source .
  • the duct 30 may be isolated during this step. This facility could be provided by a miniature change-over type solenoid activated valve (not shown) and controlled automatically at intervals for total system integrity checking.
  • Figure 6 shows a configuration of the system 10 where the sensor cavity 12 is remote from a vessel 14b.
  • This configuration may be appropriate for example to avoid the vessel 14b from exposure to low temperature or when there is insufficient space for the vessel 14b.
  • the heater 60 may not be required. Also depending on the electrical connection system it may be possible to dispense with wire V- .
  • the high impedance 22 is not contained within the vessel 14b, but is used to form at least part of the connecting duct 56 which connects with a simple connection duct 66 located inside vessel 14b.
  • This arrangement helps improve frequency response as previously mentioned.
  • Duct 42 can also be of minimal size as it only needs to carry minuscule flow sufficient to deflect the diaphragm of the device 16.
  • Figure 7 shows a schematic drawing of a system 10 comprising a combination of the systems 10 shown in
  • FIG. 5 and 6 in a notional installation on an aircraft.
  • a common pump 28 is connected via: a duct 30a to a vessel 14a, corresponding to vessel 14a of Figure 5; and, duct 30b to vessel 14b corresponding to vessel 14b of Figure 6.
  • the power supply 62 is connected by conductor V+ to both vessels 14a and 14b.
  • Signal wires Sa and Sb connect to vessels 14a and 14b respectively and to corresponding warning indicators 45 and 47.
  • a signal return wire SR provides connection of the warning indicators 45 and 47 to the power supply 62 via conductor V- which is also connected to capsule 14a to allow internal warming of its enclosed differential pressure switch (not shown) .
  • the sensor cavity 12a is defined within a manifold 70 and its attachment to component 72 being condition monitored is representative of the situation where the vessel 14a is located proximate to a sensor cavity 12a similarly to the arrangement of Figure 5.
  • the sensor cavity 12b is defined within a manifold 74 attached to a component 76 being condition monitored and is representative of the situation where the capsule 14b is located remotely from a sensor cavity 12b similarly to the arrangement of Figure 6.
  • the dotted outline 78 defines a warm zone protected from the low ambient temperatures experienced within an aircraft flying at high altitude.
  • Figure 7 is representative of a system 10 where the vessels 14a/14b provide a vacuum and the pump 28 is a vacuum pump.
  • a relative positive pressure may be used rather than a vacuum if the sensor cavities 12a and 12b are in the form of cavities for in or between components of structure rather than formed on components of structure.
  • the cavities may be in the form of cavities or galleries formed internally in a stringer or frame.
  • a plurality of further cavities 12, 12a, 12b could be monitored and arranged in series for assurance of continuity .
  • a simple electronic counter (not shown) may be employed and used as a recording means in conjunction with the indicators 45 and 47. Signals produced by the devices 16 produced by a crack opening up under transient loads in turbulence, which activate the indicators 45 and 47 can then be recorded.
  • This arrangement together with a miniature vacuum pump, activated for a predetermined time by an inertia type of switch (such as advantageously mounted mercury switches or the like) during periods of turbulence or high "G" manoeuvres, allows a simple automatic periodic monitoring method that records the presence of a crack when the crack is first expected to be advantageously detectible and then gives follow up confirmation that the crack exists.
  • the device 16 could be used to activate a solenoid actuated miniature indexing device for the monitoring of the propagation rate of a crack.
  • the indexing device may be of the form described in Australian Patent No 2001254524, "SYSTEM AND METHOD FOR THE DETECTION AND PROPAGATION MEASUREMENTS OF FLAWS IN A COMPONENT OR STRUCTURE" , and in particular shown in Figure 8 of that specification.
  • the first detected differential pressure pulse (above a predetermined level of differential pressure) from the momentary opening of a crack under a transient load, would activate a solenoid and index a device to isolate the effected sensor cavity typically corresponding to the "channels" referred to in Figures 8, 9, and 10 of the Australian Patent No 2001254524 above.
  • the indexing device would then remain dormant until the next said sensor cavity or "channel" was influenced by the advancing crack.
  • Various additional signalling means and or direct observation of the indexing device could be used of course to indicate that the said indexing device is responding to an intercepted crack.
  • the impedance 22 utilised in embodiments for the system 10 may comprise a micro bore duct, for example a PE tube having a bore diameter of about 0.28 mm and a length in the order of 3 metres.
  • the impedance 22 may also take other forms such as a permeable membrane, sintered glass, or any other means sufficient to produce a detectable pressure drop in response to permeable flow of fluid through the material defining or forming the sensor cavity 12, including a surface of a component on which the sensor cavity 12 is formed when the cavity is formed on a surface rather than inside a component or structure.
  • the duct 30 may have an internal diameter of about 0.8 mm.

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  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

L'invention concerne un appareil (10) permettant une surveillance de l'état des structures. Ledit appareil comprend une cavité de capteur (12) formée sur la structure, ou dans la structure, qui doit être surveillée, un appareil de stockage sous pression (14) et un dispositif de surveillance (16). La cavité de capteur (12), l'appareil (14) et le dispositif de surveillance (16) sont raccordés en série les uns avec les autres pour former un circuit fermé. Une impédance d'écoulement de fluide élevée (22) est raccordée en série entre une extrémité de la cavité (12) et l'appareil (14) avec un dispositif d'écoulement réglable (24) couplé en série entre l'impédance (22) et l'appareil (14). Le dispositif (24) permet la mise en correspondance du volume avec des rapports d'impédance entre une partie du circuit comprenant la cavité (12) et une partie comprenant l'appareil (14). Un dispositif de réglage de pression (28) est couplé entre l'impédance (22) et le dispositif d'écoulement réglable (24), ce qui permet une recharge ou une décharge de la cavité (12) et de l'appareil (14) de manière proportionnelle ou équilibrée de telle sorte que le dispositif de surveillance (16) ne transmet pas de faux signaux de surveillance d'état.
PCT/AU2008/000840 2007-06-12 2008-06-12 Procédé et appareil permettant une surveillance de l'état des structures Ceased WO2008151369A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2007903155A AU2007903155A0 (en) 2007-06-12 Method and apparatus for the condition monitoring of aircraft structures
AU2007903155 2007-06-12

Publications (1)

Publication Number Publication Date
WO2008151369A1 true WO2008151369A1 (fr) 2008-12-18

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PCT/AU2008/000840 Ceased WO2008151369A1 (fr) 2007-06-12 2008-06-12 Procédé et appareil permettant une surveillance de l'état des structures

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112539895A (zh) * 2019-09-20 2021-03-23 沈阳美茵联合检测有限公司 一种航天贮箱专用气密试验台
CN116295208A (zh) * 2023-05-17 2023-06-23 中国土木工程集团有限公司 一种适于无缝桥梁伸缩缝监测装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0886709A (ja) * 1994-09-14 1996-04-02 Fukuda:Kk エアリークテスト方法および装置
US5770794A (en) * 1993-05-06 1998-06-23 Tulip Bay Pty Ltd Monitoring apparatus for monitoring impending faults in the integrity of a component or structure
US6539776B2 (en) * 2000-06-19 2003-04-01 Structural Monitoring Systems, Ltd. Apparatus for condition monitoring of the integrity of fasteners and fastened joints

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5770794A (en) * 1993-05-06 1998-06-23 Tulip Bay Pty Ltd Monitoring apparatus for monitoring impending faults in the integrity of a component or structure
JPH0886709A (ja) * 1994-09-14 1996-04-02 Fukuda:Kk エアリークテスト方法および装置
US6539776B2 (en) * 2000-06-19 2003-04-01 Structural Monitoring Systems, Ltd. Apparatus for condition monitoring of the integrity of fasteners and fastened joints

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112539895A (zh) * 2019-09-20 2021-03-23 沈阳美茵联合检测有限公司 一种航天贮箱专用气密试验台
CN116295208A (zh) * 2023-05-17 2023-06-23 中国土木工程集团有限公司 一种适于无缝桥梁伸缩缝监测装置
CN116295208B (zh) * 2023-05-17 2023-09-29 中国土木工程集团有限公司 一种适于无缝桥梁伸缩缝监测装置

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