WO2017050452A1 - Procédé et système permettant d'inspecter des structures en forme de plaque par ultrasons - Google Patents

Procédé et système permettant d'inspecter des structures en forme de plaque par ultrasons Download PDF

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Publication number
WO2017050452A1
WO2017050452A1 PCT/EP2016/066138 EP2016066138W WO2017050452A1 WO 2017050452 A1 WO2017050452 A1 WO 2017050452A1 EP 2016066138 W EP2016066138 W EP 2016066138W WO 2017050452 A1 WO2017050452 A1 WO 2017050452A1
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WIPO (PCT)
Prior art keywords
probes
probe
configuration
inspection area
ultrasound
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PCT/EP2016/066138
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English (en)
Inventor
Christophe Mattei
Robert Risberg
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Creo Dynamics Ab
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Publication of WO2017050452A1 publication Critical patent/WO2017050452A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/041—Analysing solids on the surface of the material, e.g. using Lamb, Rayleigh or shear waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
    • G01N29/0654—Imaging
    • G01N29/0672—Imaging by acoustic tomography
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
    • G01N29/265—Arrangements for orientation or scanning by relative movement of the head and the sensor by moving the sensor relative to a stationary material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/4409—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison
    • G01N29/4427—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by comparison with stored values, e.g. threshold values
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0427—Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/10—Number of transducers
    • G01N2291/105—Number of transducers two or more emitters, two or more receivers

Definitions

  • the present disclosure relates to a method of inspecting plate-like structures by means of ultrasound for detecting anomalies in the structure and to a system for inspecting plate-like structures using ultrasound.
  • Such methods rely on scanning of the structure or part of the structure with a probe transmitting an ultrasonic signal into the material and measuring a resulting ultrasonic signal that has travelled through the thickness of the material or has been reflected at an interface or at an imperfection in the material before arriving at the measuring point. Analysis of the resulting ultrasonic signal provides information about the interior of the material.
  • the inspection time is related to the size of the part to be scanned but also to the geometrical complexity of the object as the technique requires a good control of the probe orientation over the object. This requirement leads to complex, expensive and relatively slow inspection systems.
  • the measuring probe comprises a plurality of aligned ultrasonic transducers.
  • the transducers transmit an ultrasonic pulsed wave, one transducer at a time, while the other transducers are used to receive the reflected signals.
  • a first ultrasonic measurement is performed on a flawless reference part and a second ultrasonic measurement is performed on the part to be inspected.
  • a subtraction is performed between the measurements of the inspected part and the reference part, and the topological energy at each position in the part is determined and an indication of defects or modification in the inspected part is obtained.
  • a phased-array technique is thus potentially faster than mechanical scanning. Still, however, it shows limitations for handling complex geometrical variations (such as radii variations, certain joggle configurations, etc). The technique also requires that the probe is positioned close to the inspected part. This particular requirement often results in access limitations especially in the case of integrated structures.
  • a method of inspecting a plate-like structure by means of ultrasound for detecting anomalies in the structure comprising the steps of:
  • acoustic contact is here meant that the probe is in such a contact with the surface that a stable and reproducible acoustic contact between the probe and the surface is obtained.
  • a method of inspecting a plate-like structure by means of ultrasound for detecting anomalies in the structure comprising the steps of:
  • a method of inspecting a plate-like structure by means of ultrasound for detecting anomalies in the structure comprising the steps of: a) positioning a first ultrasonic transmitting/receiving probe in Hertzian contact with a surface of the structure,
  • a plate-like structure is in the above described methods a structure in which the area of a surface of the structure is at least 10-25 times, at least 25- 50 times, at least 50-100 times or at least 100-1000 times larger than a maximum cross-sectional area of the structure.
  • Plate-like structures include plates which are confined by two principle surfaces which may be planar or curved (single curved or double curved).
  • the plate-like structure could form part of a complex object such as I-beams, U-beams etc., and could also be non-homogenous and for example comprise integrated stiffeners.
  • the material of the plate-like structure could be metals, alloys, composites etc.
  • the plate-like structure could for example be a part in aircraft, such as airplanes, or a part in a car or a boat.
  • the plate-like structure could also be a wall or part of a wall of a pressure vessel.
  • the inspection area of the structure defined by the configuration could for example include plane structures, structures with a radius (single- and/or double curved surfaces), structures with one or more holes, structures with rivets, nails etc, or structures with an attached patch.
  • Anomalies may here include any deviation from a thought/intended state which may occur in the plate-like structure during use or which is built-in in the structure.
  • Non-limiting examples of such anomalies are delaminations, cracking, fiber fracture, fiber pullout, matrix cracking, inclusions, voids, impact-damages, hole-defects, corrosion, pits, thickness variations, fatigue cracks, stiffness changes, local stiffness variations, patches coming loose, etc. That the probes are positioned in Hertzian contact with the surface of the structure is here meant that they are positioned in reversible contact with the surface, i.e. the probes are not glued or bonded to the surface of the structure or embedded in the structure.
  • the inspection area may be defined in the centre of the configuration.
  • a larger inspection area of the structure could be covered by moving at least some of the probes or by moving the probe configuration on the structure surface repeating the method at more than one position on the structure surface.
  • the probe configuration could be moved manually, by means of a robot, or the probe configuration could be integrated in a robot.
  • a probe may first be used in transmitting mode and other probes in receiving mode. Thereafter, the probe first used in
  • transmitting mode is used in receiving mode and a probe used in receiving mode is now used in transmitting mode, etc.
  • first probe By using the first probe in another position on the surface such that the configuration is changed while the inspection area is retained is here meant that in these methods this first probe is physically moved on the surface while the other probes are kept in their original positions. The same, now moved, first probe is used in the transmitting mode. By moving the first probe the collected information about the inspection area may be increased. The more probe positions along the line along which the first probe is moveable the more information may be collected from the probes about the inspection area defined by the probe configuration as the scanning density is increased.
  • first movable probe it is possible also when using a first movable probe to use some or all of the second probes in transmitting mode once or several times during an inspection of a certain inspection area and the first probe may be used once or several times in receiving mode during said inspection.
  • polygonal configuration is here meant that the probes are placed in the nodes of a polygonal configuration and imaginary lines between neighboring probes define the polygonal shape and the inspection area.
  • the present method acousto-ultrasonic testing, utilizes plate-like omnidirectional waves (also known as Lamb waves) that propagates in the plane of the structure and interact with the structure ' s geometrical features and potential anomalies present in the structure in the inspection area.
  • the frequency of the plate-like wave should be adapted to the thickness of the plate-like structure in order to control the wavelength of the plate-like wave. For example for an aluminum plate-like structure of thickness 2mm a frequency of 250 kHz can be used for the propagation of the first flexural mode in the plane of the structure with a velocity of 2000 m/s leading to a 8 mm wavelength .
  • Plate-like waves have the ability to propagate in a plate-like structure even when the structure is not planar, why inspection of a structure having a radius is possible.
  • the wave generated by a transmitting probe on one side of the radius propagates through the radius and is detected by receiving probes on other sides of the radius.
  • This configuration eliminates the need for a scanning device in the radius as the wave itself probes the material in the radius and the method, hence makes it possible to inspect all areas of a component even if direct access to the area is limited and enables inspection of complex geometries without having to adapt and change the physical parameters of the equipment (changing probe, re-orienting the probe, repositioning the structure etc).
  • the step of positioning the probes in acoustic contact with the structure in the method according to the first aspect may comprise attaching one or more of the probes to the surface and/or positioning one or more of the probes in Hertzian contact with the surface.
  • the step of positioning the probes in Hertzian contact with the surface of the structure may comprise providing a liquid between the structure surface and the probe.
  • the probes and the structure are in a wet contact with each other.
  • the step of positioning the probes in Hertzian contact with the structure may alternatively comprise positioning the probe in direct dry contact with the structure surface.
  • Attaching the probes to the surface may comprise gluing, bonding or nailing of the probes to the surface.
  • Positioning the probes in Hertzian contact with the surface and in a polygonal configuration may comprise arranging the probes in a probe fixture having a predetermined configuration prior to positioning the probes in contact with the surface of the structure.
  • the fixture may be flexible enough to adapt to structure geometries including flat structures, curved structures or branched structures, such that the probes may be positioned in the same plane or along a non-planar surface.
  • the fixture may be designed to be lockable in certain configurations and included in a dedicated tool.
  • the distance between neighboring probes in a fixture may vary between 10 mm up to 100 mm, and is typically 30 to 80 mm.
  • the second probes may be arranged in a fixture and a distance between neighboring second probes in the fixture may vary between 10 mm to 1000 mm, such as e.g. 250 mm or 500 mm.
  • the first moveable probe may also be arranged in the fixture or may be a stand-alone probe.
  • the first probe may in some of the methods be in Hertzian contact with the surface and movable between at least two positions on the surface, said positions being substantially linearly arranged.
  • the number of positions used for the first probe may be 2-100, 2-50, 20-25, 2-20 or 2-10.
  • the distance between such positions may vary between 1 mm up to 100 mm, and is typically 2.5 to 10 mm.
  • Such a first probe may be arranged in a probe fixture allowing the first probe to be moved in the fixture between at least two positions substantially linearly arranged in the fixture.
  • the positions in the fixture may be predetermined fix positions or adjustable positions.
  • the probes may be positioned in a polygonal or substantially polygonal configuration selected from a group comprising a triangular configuration, a rectangular configuration, a square configuration, a diamond-like
  • a decagonal configuration a polygonal configuration with 1 1 -15 nodes, a polygonal configuration with 15-25 nodes, a polygonal configuration with 25-35 nodes, or a polygonal configuration with 35-50 nodes.
  • the method may comprise causing the probes to generate, when used in a transmitting mode, ultrasound waves at a frequency of less than 1 MHz, preferably 50 kHz-500 kHZ or 100 kHz-250 kHz.
  • the system is, hence, a so called low-frequency ultrasonic system.
  • the frequency range used depends on the thickness of the structure under inspection.
  • the probes may be caused to generate and receive a tone-burst of 1 to 10 cycles.
  • the probes may be caused to generate, when used in transmitting mode, ultrasound waves comprising a flexural mode.
  • the plate-like wave, lambwave generated should preferably be the first antisymmetric mode (or flexural mode) often referred to as AO Lamb mode.
  • AO Lamb mode the first antisymmetric mode
  • other high order modes may also be used. The presence of other modes mixed in the signal does not affect the performance of the method.
  • the reference signals may be obtained by using the method steps a)- e) of the method described above for a separate reference structure or a reference zone of the structure under inspection.
  • the reference structure or reference zone should then have similar geometry and be made of similar material as the inspection area of the structure under inspection and be without anomalies.
  • a similar probe configuration and similar area of inspection should be used as for the structure under inspection.
  • the area of inspection should as closely as possible be the same for the structure under inspection and the reference structure or zone.
  • the location of a feature of interest in the area under inspection should not differ with more than 1 -3 mm, 1 -2 mm or 0.5-1 mm between the structure under inspection and the reference structure or reference zone.
  • the sensitivity of the anomaly detection is dependent on the
  • the reference signals may alternatively be obtained from theoretical analysis of the structure without any anomalies in the inspection area.
  • Such a theoretical analysis may be a Finite Element Method analysis of the structure.
  • the step of comparing the acquired signals with the reference signals may comprise quantifying a difference between the acquired signals and the reference signals by calculating a time shift between the acquired signals and reference signals, calculating a difference in amplitude between the acquired signals and reference signals, and/or calculating a correlation of the signals.
  • the method may further comprise a step of identifying an anomaly in the inspection area based on the comparison in step f) of the method described above.
  • identification of an anomaly is being made using the comparison between acquired signals and reference signals, for example a comparison of height of amplitude, or a function of such a comparison and comparing this with a tabulated or preset value.
  • the method may further comprise a step of visualizing an identified anomaly.
  • the visualization may comprise visualization on a screen indicating the anomaly on the screen as a color difference, or the anomaly being marked on the screen with a box, ring or arrow.
  • Tomographic imaging is one example of such visualization.
  • an anomaly may be marked directly in the inspection area of the structure under inspection by means of for example a beam of light.
  • a system for inspecting plate-like structures using ultrasound comprising:
  • the ultrasonic generator being arranged to drive at least a first probe as an ultrasound transmitting probe generating an ultrasound wave
  • the other probes is arranged to be used as an ultrasound receiver detecting a resulting wave provided by the ultrasound wave propagating through the inspection area
  • system further comprising a signal acquisition unit arranged to acquire detected waves from the probes and to transmit signals
  • the processing device being configured to compare signals from the acquisition unit for a structure under inspection with signals for a
  • a system for inspecting plate-like structures using ultrasound comprising:
  • the ultrasonic generator being arranged to successively drive one probe at the time as an ultrasound transmitting probe generating an
  • ultrasound wave propagating into a plane of the structure in the inspection area while at least one of the other probes is arranged to be used as an ultrasound receiver detecting a resulting wave provided by the ultrasound wave propagating through the inspection area;
  • system further comprising a signal acquisition unit arranged to acquire detected waves from the probes and to transmit signals
  • the processing device being configured to compare signals from the acquisition unit for a structure under inspection with signals for a
  • a system for inspecting plate-like structures using ultrasound comprising:
  • the first probe being moveable between at least two positions on the surface such that the configuration is changed while the inspection area is retained, - the ultrasonic generator being arranged to drive at least the first probe as an ultrasound transmitting probe generating an ultrasound wave propagating into a plane of the structure in the inspection area, while at least one of the second probes is arranged to be used as an ultrasound receiver detecting a resulting wave provided by the ultrasound wave propagating through the inspection area,
  • system further comprising a signal acquisition unit arranged to acquire detected waves from the probes and to transmit signals
  • the processing device being configured to compare signals from the acquisition unit for a structure under inspection with signals for a
  • the system of any of the aspects above may further comprise an anomaly identifying unit arranged to identify any anomaly in the structure under inspection based on the comparison index.
  • the fixture of the system of the fifth aspect may be arranged to hold the probes in a polygonal configuration selected from a group comprising a triangular configuration, a rectangular configuration, a square configuration, a diamond-like configuration, a pentagonal configuration, a hexagonal configuration, a heptagonal configuration, an octagonal configuration, a nonagonal configuration, a decagonal configuration, a polygonal configuration with 1 1 -15 nodes, a polygonal configuration with 15-25 nodes, a polygonal configuration with 25-35 nodes, or a polygonal configuration with 35-50 nodes.
  • the fixture may comprise probe holding elements holding the probes in the fixture.
  • Probe holding elements may hold the probes in such a way that an end surface of the probe ensures full contact with the object to be inspected.
  • the fixture may comprise distance elements holding the probe holding elements together in the fixture.
  • the distance elements may be used for adapting and changing the geometry of the fixture.
  • the probe holding element may comprise a biasing mechanism allowing for perpendicular movement of the probes relative the structure surface.
  • the spring mechanism may allow a movement of the probe between 0.1 mm and 5 mm.
  • the fixture may have a lockable geometry.
  • connection between probe holding elements or probe holding elements and distance elements may be lockable such that a rigid probe configuration is obtained, which is a prerequisite for repeatability when using the system.
  • the locking between the probe holding elements or the probe holding elements and the distance elements may be obtained by means of for example dovetail joints.
  • the distance elements could alternatively provide for at least some mobility around an axis parallel with the surface plane and/or perpendicular to the surface plane. Also for a fixture without distance elements there probe holding elements are directly connected to each other mobility around an axis parallel and/or perpendicular to the surface plane could be provided.
  • the probe may comprise a piezoelectric active element excited in its thickness resonance mode.
  • the ultrasonic generator may be arranged to provide a drive signal to the probes such that the probes generate, when used in a transmitting mode, ultrasound waves at a frequency of less than 1 MHz, preferably 50 kHz-500 kHZ, or 100 kHz-250 kHz.
  • the at least three ultrasonic transmitting/receiving probes may comprise 3-10 probes, 10-15 probes, 15-20 probes, 20-25 probes, 25-30 probes, 30-35 probes, 35-40 probes, 40-45 probes or 45-50 probes.
  • a tip area of the probe for contacting with a surface of the structure may have a conical shape, which conical shape may have contact surface area with a diameter of at most 1/3 of a wavelength of the generated ultrasound wave. This requirement is linked to excitation/detection efficiency
  • the diameter of the contact surface may vary between 1/5 to 1/3 of a wavelength of the generated wave.
  • the piezoelectric element may be arranged in physical contact with the tip area.
  • the ultrasonic generator may be arranged to provide a drive signal to the probes such that the probes generate and receive a tone-burst of 1 to 10 cycles.
  • the ultrasonic generator may be arranged to provide a drive signal to the probes such that the probes, when used in transmitting mode, generate sound waves comprising a flexural mode.
  • the system may further comprise a visualization unit visualizing an identified anomaly of the structure under inspection.
  • the first probe of the system of the fourth or sixth aspect may be arranged in a probe fixture allowing the first probe to be moved in the fixture between at least two positions substantially linearly arranged in the fixture.
  • the position of the moving probe (moveable in a fixture or a stand-alone probe) relative to an origin point or relative to the other probes is recorded using for example a positioning system or an encoder in order to associate all the time signals with the actual probe configuration in which they have been recorded.
  • the system of the fourth aspect may comprise a probe fixture for holding all probes in a polygonal configuration (if all probes are placed in Hertzian contact with the surface).
  • the second probes may be held at fixed positions in the fixture while the first probe may be moveable between different linearly arranged positions in the fixture.
  • Fig. 1 shows a system for inspecting plate-like structures using ultrasound.
  • Fig. 2 shows part of the system in Fig 1 from above.
  • Figs 3a and 3b shows two different probe fixtures from above.
  • Fig. 4a shows an acousto-ultrasonic signal for a reference plate-like structure without any anomaly
  • Fig. 4b an acousto-ultrasonic signal for a plate-like structure with an anomaly in the inspection area
  • Fig. 4c detected signals from the structures in Figs 4a and 4b are shown in the same time domain graph.
  • Fig. 5 illustrates damage index computation and display after tomographic reconstruction.
  • Fig. 6 shows application of the system shown in Fig. 1 on a structure comprising a radius.
  • Fig. 7 shows different probe configurations.
  • Fig. 8 shows an ultrasonic transmitting/receiving probe from different views.
  • Figs 9a-9b show a probe configuration in which a first probe is linearly moveable and the other probes are fixed.
  • Figs 10a-c show another probe configuration in which a first probe is linearly moveable and the other probes are fixed.
  • a system 1 for inspecting plate-like structures 2 using ultrasound for detecting anomalies in the structure is shown in Fig 1 .
  • the structure 2 may be planar, Fig. 1 and Fig. 4, or non-planar, i.e. a structure having a radius, as shown in Fig. 6.
  • the structure may comprise one or more holes, rivets, nails, attached patches etc. (not shown).
  • the plate-like structure could e.g. be of metal, alloy or composite.
  • Anomalies 3 may be delaminations, cracking, fiber fracture, fiber pullout, matrix cracking, inclusions, voids, impact-damages, hole-defects, corrosion, pits, thickness variations, fatigue cracks, stiffness changes, local stiffness variations, patches coming loose etc. e
  • the system 1 comprises at least three ultrasonic transmitting/receiving probes 4 connected to and driven by an ultrasonic generator 5.
  • the number of probes 4 in the system 1 is four but in other embodiments of the system the number of probes may vary between three up to fifty probes.
  • the probes 4 are in Fig. 1 arranged in a squared configuration.
  • the probes may, however, be arranged in a range of different polygonal configurations. In Fig. 7 different possible polygonal configurations with eight probes are shown.
  • an inspection area 6 of the structure 2 is defined by the configuration, indicated by the dotted line in Fig. 1 and Fig. 2.
  • a typical inspection area 6 defined by a squared configuration with eight probes is 250 mm x 250 mm.
  • the probes 4 are positioned in acoustic contact with the surface of the structure 2, and the contact may be a Hertzian contact (non-adhesive, reversible contact), either through direct dry contact or wet contact with a film of liquid between the surface of the structure 2 and the probe 4.
  • the probes are positioned in acoustic contact with the surface by irreversibly attaching the probes to the surface through gluing, bonding or nailing.
  • the probes 4 may be arranged in a probe fixture 30.
  • fixtures 30 with squared configuration are shown, which fixtures hold fourteen and ten probes 4, respectively, giving the probes a predetermined squared configuration.
  • a range of different fixture configurations are possible giving the probes 4 held by the fixture 30 the different configurations discussed above.
  • the fixture in Fig. 3a comprises probe holding elements 31 directly connected to neighboring probe holding elements 31 .
  • the probe holding elements 31 could be lockably connected to each other for example by means of dovetail joints (as shown in Fig. 3a) such that a rigid, lockable, fixture and probe configuration is obtained. Other types of lockable joints are also possible.
  • probe holding elements 31 and distance elements 32 linking the probe holding elements 31 together in the fixture 30.
  • the connection between probe holding elements 31 and distance elements 32 may also be lockable such that a rigid fixture and probe configuration is obtained.
  • the locking between the probe holding elements 31 and the distance elements 32 may also be obtained by means of dovetail joints but other joints are equally possible.
  • the distance elements 32 may also be used for adapting and changing the geometry of the fixture 30.
  • the fixture 30 may alternatively be flexible enough to adapt to different geometries of the structures 2 to be inspected, from flat structures, curved structures or branched structures, such that the probes may be positioned in the same plane or along a non-planar surface.
  • the fixture 30 with probes 4 may be portable, such that it can be moved on the structure surface covering different inspection areas 6 of the structure 2 under inspection, or be moved from one structure to another by hand or by means of a robot.
  • the distance between neighboring probes 4 in a fixture 30 may vary between 10 mm up to 100 mm, and is typically 30 to 80 mm.
  • the probe holding elements 31 hold the probes 4 in such a way that an end surface of the probe 4 ensures full contact with the surface of the structure 2 to be inspected.
  • a good repeatability of the contact quality is a prerequisite for a good sensitivity of the method.
  • the probe holding element 31 may comprise a biasing mechanism, such as a spring-loaded mechanism (not shown), which allows the probe 4 to move perpendicularly to the surface of the structure.
  • a biasing mechanism such as a spring-loaded mechanism (not shown)
  • it may be desirable to bias the probe towards the surface to be tested and preferably with a predetermined force. Thereby, allowing for application of a controlled force on the probe 4 as it is in contact with the structure 2.
  • the spring mechanism may allow a movement of the probe between 0.1 mm and 5 mm.
  • the ultrasonic generator 5 successively drives one probe 4 at the time of the transmitting/receiving probes 4 positioned in contact with the surface of the structure 2 as an ultrasound transmitting probe generating an ultrasound sound wave propagating into a plane of the structure 2 in the inspection area 6, as shown in Figs 4a and 4b and in Fig. 6.
  • the Lamb Waves or plate-like waves the frequency and wave length are selected based on the elastic properties of the material of the inspected structure 2 and on the thickness of the structure.
  • the plate-like structure 2 will then act as a guide for the propagating Lamb waves.
  • the other probes 4, not used as the transmitting probe, are used in a receiving mode, detecting a resulting wave provided by the ultrasound wave propagating through the inspection area 6.
  • the ultrasound wave propagates in the structure and interact with the structure ' s geometrical features and potential anomalies 3 present in the structure. Anomalies 3 in the structure affect the sound wave propagating there through.
  • Fig. 7 it is exemplified how signals are generated and detected by the probes 4 in the configuration.
  • the material of the structure under inspection may be composite.
  • the composite structure be a fiber reinforced polymer. Delaminations in composites do not reflect an incoming volume sound wave used in traditional ultrasonic testing but affect the signal propagating there through, i.e. with the system 1 shown in Fig. 1 such delaminations may be detected.
  • the system 1 comprises a signal acquisition unit 7 which is arranged to acquire detected waves from the probes 4 used in receiving mode, and to transmit signals corresponding to the detected waves to a processing device 8 of the system 1 .
  • the processing device 8 is arranged to compare signals obtained from the acquisition unit 7 for a structure under inspection with signals for a corresponding inspection area of a reference structure without anomalies, providing a comparison index.
  • the reference signals may be obtained by using the system 1 described above on a separate reference structure or in a reference zone of the structure 2 under inspection.
  • the reference structure or reference zone should then have similar geometry and be made of similar material as the inspection area 6 of the structure 2 under inspection and be without anomalies 3.
  • a similar probe configuration and similar inspection area should be used for the reference structure or reference zone as for the structure under inspection.
  • the reference signal can be registered at the time of inspection or be pre-saved from an earlier inspection.
  • the reference signals may be obtained from theoretical analysis of the structure 2 without any anomalies 3 in the inspection area 6. Such a theoretical analysis may be a Finite Element Method analysis of the structure.
  • the processing device 8 quantifies a difference between the acquired signals and the reference signals by calculating a time shift between the acquired signals and reference signals, by calculating a difference in amplitude between the acquired signals and reference signals, and/or by calculating a correlation of the signals.
  • Fig. 4c the time domain reference signal (solid line) for the reference structure shown in Fig. 4a and an acquired signal (dotted line) for a test structure with an anomaly 3 shown in Fig. 4b are plotted in the same graph.
  • the signal shows a time shift ⁇ and an amplitude variation ⁇ due to the fact that that wave velocity and attenuation are locally different over the anomaly in the structure.
  • the difference between the reference and the test signal may be quantified by calculating a so called damage index.
  • the damage index (Dl) can be calculated from time shift ⁇ , amplitude variation ⁇ , difference of the time domain signal and/or through a correlation of the two signals.
  • Dl damage index
  • a visualization unit 1 1 visualizing an identified anomaly 3 in the structure.
  • the visualization may comprise visualization on a screen 1 1 indicating the anomaly 3 on the screen for example as a color difference, or the anomaly 3 being marked on the screen with a box, ring or arrow.
  • an anomaly 3 may be marked directly in the inspection area 6 of the structure under inspection by means of for example a beam of light.
  • Fig. 5 is shown the principle of damage index computation between a reference structure without anomalies a) and b) test structure with an anomaly 3.
  • the differences in acquired signals from the test structure and the reference structure are correlated and a Dl calculated.
  • Xi is an acquired signal matrix for the reference structure and X2 an acquired signal matrix for the test structure.
  • An imaging algorithm is then based on a tomographic reconstruction of the variation of the damage index in the inspection area defined by the probe configuration and illustrated in d), e).
  • a non-planar plate-like structure 2 having a radius is shown. Anomaly inspection of such structures is possible as the transmitting probe 4 is driven by the ultrasonic generator 5 to generate ultrasound waves which have the ability to propagate in a plate-like structure 2 even when the structure is not planar, why inspection of a structure having a radius is possible.
  • the ultrasound wave is generated by a probe 4 used in transmitting mode on one side of the radius, propagates through the radius and is detected on the other side of the radius by other probes 4 used in receiving mode. This configuration eliminates the need for a scanning device in the radius as the wave itself probes the material in the radius.
  • the system 1 may be suitable for detection of anomalies in different kind of features of the plate-like structure under inspection as long as the feature is located in the area of inspection defined by the probe configuration.
  • Such features include, but are not limited to, areas with rivets, nails, holes, attached patches etc (not shown).
  • the performance of the anomaly detection depends on the number of probes 4 and their position in the configuration, which consequently determines the number of paths used for reconstruction of the inspection area 6 defined by the probes 4.
  • a transmitting/receiving probe 4 is shown from various angles.
  • a tip area 12 of the probe 4 has a conical shape, which conical shape has a contact surface area 13 with a diameter d of at most 1/3 and between 1/5 and 1/3 of the wavelength of the generated wave. This requirement is linked to excitation/detection efficiency considerations. Due to the small diameter of the contact surface area 13 of the probe 4, the probe acts as a point source and generates an omnidirectional ultrasound wave in the plate-like structure 2.
  • the probe 4 comprises a piezoelectric active element 14 excited in its thickness resonance mode.
  • the piezoelectric element 14 may be in physical contact with the tip area 12.
  • the probes When used in a transmitting mode, the probes may be driven a by the ultrasonic generator 5 to transmit ultrasound waves at a frequency of less than 1 MHz, preferably 50 kHz-500 kHZ, or 100 kHz-250 kHz. The frequency range used depends on the thickness of the structure under inspection.
  • the ultrasonic generator 5 may drive the probes 4 to generate and receive a tone- burst of 1 to 10 cycles.
  • the ultrasonic generator 5 may be a multi-channel ultrasonic system with as many channels as probes 4 used in the configuration, Fig. 1 .
  • the signal acquisition unit 7 may transmit acquired signals in real time to the processing device 8.
  • the different parts of the system 1 described above and illustrated in Fig. 1 i.e. the probes 4, the ultrasonic generator 5, the signal acquisition unit 7, the processing device 8, the anomaly identifying unit 10 and the visualizing unit 1 1 could be separate parts communicating with each other. Alternatively, some or more of the parts may be integrated as functions in one of the parts.
  • the signal acquisition unit 7 and the ultrasonic generator 5 be functions in the processing device 8 or be integrated in each probe 4.
  • the processing device 8 could comprise the anomaly identifying unit 10 and visualizing unit 1 1 as integrated functions.
  • Figs 9a-9b and 10a-10c different probe configurations are shown in which a first probe 4 is moveable between different substantially linearly arranged positions p1 , p2, p3 on the surface while the other probes 4 are kept in their original positions in the configuration. By moving the first probe 4 in this way the polygonal configuration is changed while the inspection area 6 is retained.
  • the collected information about the inspection area 6 may be increased.
  • the more probe positions p1 , p2, p3 arranged along the line along which the first probe 4 is moveable the more information may be collected from the probes 4 about the inspection area 6 as the scanning density is increased, as illustrated in Figs 10a-c, and the likelihood of identifying an anomaly 3 (indicated in Fig. 9b) is increased.
  • the first probe 4 is in Hertzian contact with the surface.
  • the other, second probes 4 may be in Hertzian contact with the surface or may be attached to the surface.
  • the first probe 4 is used as a transmitter in all positions as shown in Figs 9a-b and 10a-c. However, it is possible to use some or all of the second probes 4 in transmitting mode once or several times during an inspection of a certain inspection area 6 and the first probe 4 may be used once or several times in receiving mode during said inspection.
  • all probes 4 are in Hertzian contact with the surface they may be arranged in the same fixture holding the probes 4 in a polygonal configuration (not shown).
  • the fixture being arranged to hold the second probes 4 at fixed positions and allow the first probe 4 to be moved in the fixture between at least two positions substantially linearly arranged in the fixture.
  • the positions in the fixture may be a number of predetermined fix positions or adjustable positions.
  • the second probes 4 are arranged in one fixture and the first probe in one fixture 40, see Figs 9a-b.
  • the fixture 40 holding the first probe 4 allowing the first probe 4 to be moved in the fixture 40 between at least two positions p1 , p2, p3 substantially linearly arranged in the fixture 40, wherein the positions in the fixture 40 may be a number of predetermined fix positions, as shown in Figs 9a-b, or adjustable positions.
  • the first probe 4 is not arranged in a fixture but moved by hand or by means of a robot between substantially linearly arranged positions.
  • the first probe 4 is arranged to be in Hertzian contact with the surface, while the second probes 4 are irreversibly attached the surface through bonding, nailing or gluing.
  • the first probe 4 may be moved by hand or by means of a robot between substantially linearly arranged positions.
  • the first probe 4 may be arranged in a probe fixture 40 as discussed above.

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  • Physics & Mathematics (AREA)
  • Biochemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Acoustics & Sound (AREA)
  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)

Abstract

L'invention concerne un procédé d'inspection par ultrasons d'une structure en forme de plaque afin de détecter des anomalies (3) dans la structure, ce procédé consistant à positionner au moins trois sondes d'émission/réception d'ultrasons (4) en contact par voie hertzienne avec une surface de la structure (2) et dans une configuration polygonale de sorte qu'une zone d'inspection (6) de la structure est définie par la configuration; commander successivement une sonde (4) au moment où une sonde d'émission d'ultrasons génère une onde ultrasonore se propageant dans un plan de la structure dans la zone d'inspection (6), tandis qu'au moins une des autres sondes (4) est agencée pour être utilisée comme récepteur d'ultrasons détectant une onde résultante générée par l'onde ultrasonore se propageant dans la zone d'inspection (6) ; acquérir des signaux correspondant aux ondes détectées par les deuxièmes sondes (4) et comparer les signaux acquis avec des signaux de référence d'une zone d'inspection correspondante d'une structure de référence sans anomalies.
PCT/EP2016/066138 2015-09-22 2016-07-07 Procédé et système permettant d'inspecter des structures en forme de plaque par ultrasons WO2017050452A1 (fr)

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SE1551214A SE539055C2 (en) 2015-09-22 2015-09-22 Method and system for inspecting plate-like structures using ultrasound

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Cited By (1)

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CN115856076A (zh) * 2022-11-23 2023-03-28 国营芜湖机械厂 基于空耦超声的cfrp板小尺寸缺陷测量方法、装置及系统

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US20070034009A1 (en) * 2005-08-09 2007-02-15 The Boeing Company Method and system for monitoring structural damage
CN101571514A (zh) * 2009-06-16 2009-11-04 北京理工大学 用于复合材料层合板缺陷定位的超声导波检测技术
US7654142B2 (en) 2005-09-28 2010-02-02 Airbus France Method of imaging using topologic energy calculation
US20100319455A1 (en) * 2007-05-16 2010-12-23 Jeong-Beom Ihn Damage volume and depth estimation
CN102353718A (zh) * 2011-07-11 2012-02-15 南京航空航天大学 用于复合材料板结构损伤监测的Lamb波损伤概率成像方法

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Publication number Priority date Publication date Assignee Title
US20070034009A1 (en) * 2005-08-09 2007-02-15 The Boeing Company Method and system for monitoring structural damage
US7654142B2 (en) 2005-09-28 2010-02-02 Airbus France Method of imaging using topologic energy calculation
US20100319455A1 (en) * 2007-05-16 2010-12-23 Jeong-Beom Ihn Damage volume and depth estimation
CN101571514A (zh) * 2009-06-16 2009-11-04 北京理工大学 用于复合材料层合板缺陷定位的超声导波检测技术
CN102353718A (zh) * 2011-07-11 2012-02-15 南京航空航天大学 用于复合材料板结构损伤监测的Lamb波损伤概率成像方法

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115856076A (zh) * 2022-11-23 2023-03-28 国营芜湖机械厂 基于空耦超声的cfrp板小尺寸缺陷测量方法、装置及系统

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