Apparatus, apparatus, and method for exciting guided waves

Abstract

This disclosure relates to an ultrasonic excitation device (100) comprising a high-power ultrasonic transducer (10) and a housing (20) that defines the volume of a space (21) for housing an ultrasonic transmission medium (22). The housing (20) is adapted so that, during use, the ultrasonic transmission medium (22) receives ultrasonic waves (1) emitted by the high-power ultrasonic transducer (10), and the test structure (30) receives ultrasonic waves (1) from the ultrasonic transmission medium (22). As a result, high-amplitude guided waves can be uniformly excited on the test structure (30), thereby expanding the guided wave inspection range.

Description

Technical Field

[0001] The present invention relates to an apparatus for exciting guided waves, and more particularly, to an apparatus for exciting guided waves that uses a high-power ultrasonic transducer to generate guided waves within a test structure. The present invention further relates to related guided wave test equipment and methods. More particularly, the present invention relates to non-destructive test applications, such as detecting defects, including but not limited to corrosion, in various structures such as long metal structures (such as tendons, bars, pipes, rods, or rails) or metal plates, especially when these test structures are embedded in highly attenuating materials such as concrete, soil, gravel, sand, or rock. The present invention further relates to an infrastructure (such as columns, bridges, etc.) equipped with the above apparatus or the above equipment, for example, for continuous structural integrity monitoring.

Background Art

[0002] Mechanical guided waves are typically excited on a test structure using one of the following three types of transducers. (a) A piezoelectric transducer that can be used in "dry contact" with the test structure or can be closely coupled to the test structure through a contact medium, which is usually an ultrasonic transmission gel. (b) A magnetostrictive transducer that uses the magnetostrictive properties of the material to generate vibrations. (c) An electromagnetic transducer (or EMAT) that uses the principle of Lorentz force.

[0003] However, these transducers can only generate very limited guided wave amplitudes on the test structure (typically in the order of nanometers, or even picometers), meaning that the amount of energy associated with the guided wave traveling along the test structure is very small. A standard technique using guided wave testing is to inspect using a "pulsed echo" system. The pulsed echo system uses guided wave reflections generated by the presence of defects in the test structure to detect the potential presence of defects. In this way, defects such as corrosion, fatigue cracks, or different types of defects can be detected in the member under inspection. Existing guided wave transducers use very low excitation power so that the type of guided wave excited on the test structure can be precisely controlled, resulting in guided waves with sufficiently submicron amplitudes (typically in the order of nanometers, or even picometers, as mentioned above).

[0004] Furthermore, the electronics typically associated with pulsed echo guided wave test systems serve both the excitation and reception sides of the test, meaning they inevitably limit the measurement dynamic range for received guided waves, which usually have amplitudes more than an order of magnitude smaller than the excitation guided wave amplitude.

[0005] Due to the low power output of the guided wave excitation methods described above, a known limitation of guided wave inspection methods is their "range," i.e., the space (more specifically, length in the case of long test structures) that the guided wave can cover for the test purpose. This occurs, for example, when metal members such as tendons, bars, pipes, or other long structural shapes such as rails are embedded in an attenuating medium such as concrete, buried underground, or covered with an attenuating coating. The excited guided wave (which, as mentioned above, can be said to have a relatively small amplitude) "leaks" into the outer attenuating material, which exacerbates the problem of limited inspection range.

[0006] Furthermore, all of the above transducers have difficulty achieving uniform excitation when the transducer is coupled to the test structure via an irregular surface (for example, a non-planar surface such as that found in steel tendons).

[0007] Therefore, it is necessary to improve the guided wave inspection method compared to conventional technology.

[0008] At least one solution of the present invention addresses at least some of the above-mentioned limitations or drawbacks of the prior art.

[0009] In addition, at least one of the solutions of the present invention enables the use of improved damping-based nondestructive testing methods that use amplitude or energy (or a combination thereof) loss to determine the likelihood of the presence of damage or defects, particularly dispersed forms of damage, such as general corrosion (rather than extremely localized corrosion) within the structure under test. [Overview of the project]

[0010] Embodiments described in this disclosure provide an ultrasonic excitation device comprising a high-power ultrasonic transducer and a housing. The housing defines a volume of space for housing an ultrasonic transmission medium, such as a gel or other liquid or semi-liquid medium (however, in principle, any medium capable of effectively transmitting ultrasonic waves can be housed within the housing and can be used on an inspection structure, around a test structure, or in close proximity to a test structure). The housing is adapted in use so that the ultrasonic transmission medium can receive ultrasonic waves emitted by the high-power ultrasonic transducer. The housing is further adapted in use so that the test structure can receive ultrasonic waves from the ultrasonic transmission medium.

[0011] Advantageously, the housing helps concentrate high-power ultrasonic levels within the volume of the space occupied by the ultrasonic transmission medium. The ultrasonic transmission medium is exposed to ultrasonic waves received directly from the high-power ultrasonic transducer, as well as ultrasonic waves reflected from the housing.

[0012] Advantageously, the ultrasonic transmission medium, due to the uniformity of its distribution throughout the periphery of the test structure and / or near the test structure, uniformly excites the test structure.

[0013] The above effects, combined, favorably determine the uniform excitation of high-amplitude guided waves in the test structure. The excited guided waves have been measured to have an amplitude 40 decibels (dB) greater than the corresponding amplitude obtained using a conventional guided ultrasonic transducer, and these values ​​were measured at the end face of a bar under identical conditions using a standard ultrasonic receiver. Thus, the guided waves can travel over the test structure over an expanded range, improving testing and inspection.

[0014] High-power ultrasonic transducers can be adapted to excite ultrasound having one or more frequency components in a spectrum from approximately 20 kHz to approximately 100 kHz. This range is selected for the low-frequency ultrasonic spectrum. The low-frequency ultrasonic spectrum can be selected to generate a high vibration amplitude in a desired guided wave vibration mode in the test structure.

[0015] To enhance the high-power nature of the embodiment described, the high-power ultrasonic transducer may be equipped with a mechanical resonator. The mechanical resonator may have at least one nominal resonant frequency in the spectrum from about 20 kHz to about 100 kHz so as to "match" to the excitation frequencies that can be excited by the high-power ultrasonic transducer.

[0016] The housing may be provided as a substantially rigid enclosure. Alternatively, the housing may comprise at least a substantially rigid enclosure portion. Optionally, the substantially rigid enclosure or enclosure portion may be made of a metal such as steel (but not limited to steel).

[0017] Similarly, the housing may be provided as a substantially flexible enclosure or comprise a substantially flexible enclosure portion. Optionally, the substantially flexible enclosure or enclosure portion may be made of a thin plastic material such as a film or foil. Optionally, the substantially flexible enclosure or enclosure portion may be provided as a pouch made of a thin film or foil of plastic material.

[0018] In one preferred configuration, the housing comprises a substantially rigid enclosure portion to which a substantially flexible housing portion can be attached, and the ultrasonic transmission medium can fill the volume of the space shared between the substantially rigid and flexible enclosure portions of the housing (i.e., the volume of the space filled with the ultrasonic transmission medium is defined by both the substantially rigid and flexible enclosure portions). In one preferred configuration, a pouch or pocket made of a thin film or foil of plastic material is added to the substantially rigid enclosure portion, such as a metal box, metal cylinder, or metal cone, to give some examples of shapes, so as to protrude outward from the rigid enclosure portion. The advantage of this configuration is that the outwardly protruding pouch or pocket filled with the ultrasonic transmission medium can be fitted to a suitable metal test member, such as a long metal test member (e.g., wrapped around it). The inventors recognize that the test structure does not need to occupy the volume of the space filled with the ultrasonic transmission medium within the substantially rigid enclosure. Alternatively, a substantially flexible enclosure or enclosure portion may be adapted to conform to the test structure, for example, by wrapping around (but not limited to) the test structure, which is particularly suitable for long test structures, but not limited to them. In this preferred configuration, the test structure remains outside the volume of the space filled with the ultrasonic transmission medium.

[0019] The substantially rigid enclosure or enclosure portion of the housing may be provided in a generally parallelepiped, conical, or cylindrical shape or form. Optionally, the substantially rigid enclosure or enclosure portion may comprise two or more assembleable parts, which may be useful for filling or refilling the spatial volume with an ultrasonic transmission medium. Optionally, the two or more assembleable parts may comprise a receiving part and a cover part for practicality and ease of use. Optionally, the two or more assembleable parts may be disassembled, i.e., these parts may be taken apart for removal or replenishment with respect to the ultrasonic transmission medium.

[0020] Advantageously, the housing may be provided with an aperture for receiving a high-power ultrasonic transducer, so that at least a portion of the ultrasonic transducer or, if present, the tip (i.e., distal end) of the mechanical resonator may directly occupy the spatial volume for housing the ultrasonic transmission medium. In other words, during use, the tip or resonator of the high-power ultrasonic transducer may come into direct contact with the ultrasonic transmission medium. However, different methods of transmitting the ultrasound generated by the high-power ultrasonic transducer may be employed. For example, the housing may be integrally provided as part of the mechanical resonator. Alternatively, the mechanical resonator may be in direct contact with the housing, either outside or inside the housing.

[0021] However, it is preferable that the aperture is in direct communication with the above-mentioned spatial volume for accommodating the ultrasonic transmission medium.

[0022] The apparatus may further include a seal for sealing the space between the housing and the high-power ultrasonic transducer, thereby enclosing the ultrasonic transmission medium within the volume of a space provided inside the housing. The seal may be fitted to fit snugly within or around the aperture for the high-power ultrasonic transducer. However, the ultrasonic transmission medium does not necessarily have to be confined within the housing. For example, depending on the embodiment, a flow of the ultrasonic transmission medium through the housing may be implemented.

[0023] The test structure itself may be part of the apparatus. However, it is assumed that the apparatus described herein may be sold separately from the test structure, for example, as a kit of components including a high-power ultrasonic transducer and housing. The housing may be fitted to a specific test structure at the time of sale, or it may be fitted in the field or at any event prior to or during preparation for an inspection or monitoring campaign.

[0024] The device described in this specification is particularly suitable for test structures in the form of long metal members. However, as shown below, other test structures can be tested using the device described in this specification.

[0025] In certain embodiments (some of which are described herein), the metal member can be one of a bar, rod, tendon, rail, or pipe.

[0026] Thus, the housing can include at least one opening for receiving a portion of the long metal member within the above-mentioned spatial volume for accommodating the ultrasonic transmission medium.

[0027] In some implementations described herein, the housing can include a single opening for receiving the end of the long metal part.

[0028] The aperture and the opening can be relatively positioned on the housing such that, in use, the high-power ultrasonic transducer and the end of the long metal member can be arranged generally opposite to each other. Optionally, the high-power ultrasonic transducer and the end of the long metal member can be arranged generally facing each other. Optionally, the high-power ultrasonic transducer and the end of the long metal member can be arranged generally along a common straight line. However, other geometric configurations can also be possible.

[0029] For example, the housing can include at least two openings for receiving the length of the long metal member. Thus, the aperture and the opening can be relatively positioned on the housing such that, in use, the high-power ultrasonic transducer and the end of the long metal member are arranged along an intersecting or non-intersecting direction. For example, the length of the high-power ultrasonic transducer and the long metal member can be arranged substantially parallel to each other. Alternatively, the high-power ultrasonic transducer and the end of the long metal member can be arranged substantially perpendicular to each other or at another angle.

[0030] Alternatively, the test structure may be a metal plate, such as a flat plate, like the base (or floor) of a storage tank, or a curved wall, such as the cylindrical wall of the storage tank. Optionally, the plate or wall may define a perfect circle, for example, in the case of an entire cylindrical tank for storing fuel.

[0031] The housing may be configured in particular to test non-long metal structures such as the plates or walls described above. For example, the housing may have at least one outlet for outputting ultrasonic waves received by the structure under test from an ultrasonic transmission medium. The outlet may be located on a flat or curved wall or side of the housing to conform to the shape of the plate or wall described above.

[0032] Advantageously, the outlet may be equipped with a barrier to prevent the ultrasonic transmission medium from flowing out of the housing onto the test structure. Optionally, the barrier may be a film or in the form of a film. Alternatively, the barrier may be in the form of a sleeve, such as an inwardly projecting sleeve that protrudes into the housing to accommodate a portion of the test structure.

[0033] In the alternative apparatus, a substantially flexible enclosure or enclosure portion is fitted to at least partially match a long metal member, for example, by wrapping around the long metal member. Optionally, the long metal member is one of a bar, rod, tendon, rail, or pipe. Optionally, the substantially flexible enclosure or enclosure portion is provided as a pouch made of a thin film or foil of plastic material. This configuration may be particularly advantageous when there is little available space around the test structure to access the test structure together with the excitation device. Thus, rather than fitting a rigid housing around the test structure so that the test structure is positioned within the housing, a flexible, shape-fitting pouch or pocket filled with an ultrasonic transmission medium may be provided, which can optionally hang from the rigid housing, to provide better access to the test structure while the test structure remains outside the housing and outside the medium-filled volume of the space defined by the housing.

[0034] It will be understood that the device described may further include an ultrasonic transmission medium. For example, a suitable ultrasonic transmission gel may be sold as part of the aforementioned component kit.

[0035] In some implementations described herein, the high-power ultrasonic transducer may be piezoelectric. This is often advantageous for the use of simple housings (i.e., housings with simple geometric shapes), as also described herein. However, at least in principle, there is no need to specify the use of a piezoelectric transducer as long as the excited guided wave has an amplitude large enough to improve the defect detection and / or inspection range compared to prior art methods, as described herein.

[0036] Advantageously, the apparatus may further comprise one or more ultrasonic receivers, which may optionally be piezoelectric transducers, such as standard acoustic emission transducers, adapted to receive guided waves at excited frequency and amplitude and to measure the received guided waves.

[0037] Furthermore, the apparatus may include electronic equipment for operating a high-power ultrasonic transducer and one or more ultrasonic receivers in transmit mode. The transmit mode may involve continuous ultrasonic transmission, or the ultrasonic waves may be generated in bursts by the high-power ultrasonic transducer in a transient transmit mode. In this mode, as will be recognized by those skilled in the art, it is also possible to measure the "time of flight" between the time the emitted ultrasonic burst is generated by the high-power ultrasonic excitation device and the time the ultrasonic burst is received by the receiving ultrasonic transducer in the form of guided wave packets.

[0038] Accordingly, this disclosure further describes a non-destructive testing method that includes exciting ultrasonic guided waves into a test structure using an ultrasonic excitation device described herein.

[0039] The ultrasonic receiver may be placed on the test structure itself or on the material in which the test structure is embedded. In a typical example, the test structure may be a tendon embedded in concrete.

[0040] The method described herein may further include calculating parameters representing the peak amplitude and / or frequency spectrum and / or attenuation parameters and / or energy of the received guided wave, which is received and measured by the ultrasonic receiver.

[0041] A particular advantage of the method described herein is that the presence or absence of distributed defects (such as generalized corrosion rather than localized corrosion) in the test structure can be assessed solely by calculating the attenuation parameter of the measured guided wave. This is particularly useful in “monitoring” applications where the potential deterioration of the test structure is assessed over time, either continuously or periodically, by observing changes in the attenuation parameter. However, in other test applications, the attenuation level between ultrasonic excitation and reception at two arbitrary select points at a certain distance from each other can also be examined using the attenuation parameter. By changing the location of the arbitrary select points across the test structure, a baseline value of attenuation that is likely to correspond to a low probability of defect presence can be assessed. In this way, the measurement of additional attenuation above the baseline attenuation can be interpreted as indicating the possibility of, for example, generalized corrosion between two specific points used for excitation and reception of the guided wave, respectively.

[0042] In some embodiments described herein, the test structure is a metal tendon, and the method may further include estimating the tension of the metal tendon, since the properties of the excited guided wave depend on the tension of the metal tendon. For example, one application may be the detection of the presence or absence of tension in the tendon.

[0043] When the method described herein is applied to non-destructive guided wave testing of a metal plate or the like, the method may further include arranging a plurality of ultrasonic receivers on the metal plate, exciting an ultrasonic guided wave onto the metal plate from a first selected position on the metal plate, exciting an ultrasonic guided wave onto the metal plate from at least one further selected position on the metal plate, and measuring the excited guided waves in the plurality of ultrasonic receivers. Thus, not only the presence or absence of defects on the plate, but also the location of the defects can be estimated.

[0044] The method may further include exciting ultrasonic guided waves onto a metal plate from multiple positions adjacent to multiple ultrasonic receivers arranged on the metal plate. In this way, a complete defect "map" of the region of the plate surrounded by the multiple ultrasonic receivers can be calculated and represented graphically.

[0045] The apparatus described herein can be permanently or semi-permanently installed in infrastructure such as reinforced concrete columns, highways, bridges, railways, and fuel storage tanks. To achieve this, it may be necessary to prepare the infrastructure for ultrasonic non-destructive testing (which may comprise one or more test structures in the form of long metal members covered with a damping material such as concrete) by removing a portion of a damping material such as concrete to expose one or more portions of a long metal member, and then placing one or more ultrasonic excitation devices described herein on each of the one or more exposed portions of the metal member.

[0046] Next, one or more ultrasonic receivers may be placed on one or more exposed portions of each of the metal members. Alternatively, the ultrasonic receivers may be placed on the outer surface of the attenuating material itself, for example, on the concrete surface of the infrastructure.

[0047] Here, with reference to the attached drawings, a specific embodiment of the present invention will be described as merely an example. [Brief explanation of the drawing]

[0048] [Figure 1] This is a schematic diagram of the first ultrasonic excitation device disclosed herein. [Figure 2] Furthermore, this is a schematic diagram of a second ultrasonic excitation device disclosed herein. [Figure 3] Furthermore, this is a schematic diagram of a third ultrasonic excitation device disclosed herein. [Figure 4] Furthermore, this is a schematic diagram of a fourth ultrasonic excitation device disclosed herein. [Figure 5]Furthermore, this is a schematic diagram of a fifth ultrasonic excitation device disclosed herein. [Figure 6] This is a top view immediately before use of a sixth ultrasonic excitation device, similar to the ultrasonic excitation device of Figure 1, as further disclosed herein. [Figure 7] This is a slightly oblique top view of a seventh ultrasonic excitation device, further disclosed herein, just before use, similar to the ultrasonic excitation device in Figure 2. [Figure 8] This is a perspective view of an ultrasonic excitation device similar to the ultrasonic excitation device shown in Figure 5, as well as an eighth ultrasonic excitation device further disclosed herein, in use on a metal tendon. [Figure 9] This is a schematic diagram of a ninth ultrasonic excitation device, further disclosed herein, attached to the floor of a storage tank. [Figure 10] Figure 9 is an enlarged schematic diagram of the ultrasonic excitation device. [Figure 11] Figures 9 and 10 schematically illustrate the ultrasonic testing method for testing the storage tank floor. [Figure 12] Figures 9, 10, and 11 schematically illustrate the ultrasonic testing method for testing the walls of the storage tanks. [Figure 13] This is a perspective view of a test rod with simulated distributed defects. [Figure 14] The results of a test performed on the rod shown in Figure 13 using the ultrasonic testing apparatus disclosed herein are shown. [Figure 15] This shows an ultrasonic receiver placed on the reinforced concrete surface of a sample reinforced concrete infrastructure. [Figure 16] Figure 15 shows the results of tests conducted on the infrastructure shown. [Figure 17] This is a wider perspective view of the apparatus shown in Figure 8, where tests are conducted to detect the tension of the tendon. [Figure 18] The results of the tests conducted on the tendons shown in Figures 8 and 17 are presented. [Figure 19]Two frequency spectra obtained from guided waves excited using the high-power ultrasonic excitation apparatus described herein, and measured in a defect-free structure and a defect-affected structure, are shown for comparison. [Figure 20] An alternative excitation device is shown, comprising a metal cone and a plastic pouch filled with an ultrasonic transmission medium and adapted to wrap around a long test structure. [Modes for carrying out the invention]

[0049] This disclosure is based on the need to generate guided waves that produce relatively high wave displacements within a test structure, well beyond the orders of magnitude of typical nanometers in the prior art. Using this type of guided wave, it is possible to achieve the desired inspection range even for test structures embedded in highly damped materials. It is a known problem that the guided wave inspection range for test structures embedded in highly damped materials is very limited, depending on the damping characteristics of the highly damped material. If only short segments or areas of the test structure can be tested at a time (i.e., the possible inspection range is very narrow), testing long (and / or large) structures such as tendons embedded in concrete becomes difficult, or at least costly, and therefore may be commercially unfeasible.

[0050] While high-power ultrasonic transducers exist, they are typically not applied to guided wave generation due to the difficulty in controlling excitation (i.e., the difficulty in reproducibly generating excitation modes). Careful selection of excitation modes and modeling the interaction between these guided waves and defects have traditionally been the focus of research and development in the field of guided waves. On the other hand, high-power ultrasound has traditionally been used in a variety of applications such as ultrasonic cleaning, cavitation, welding, cutting, and infrared imaging.

[0051] The present invention proposes the use of a high-power ultrasonic transducer for guided wave excitation, enabling reliable and uniform excitation of guided waves within a test structure with relatively high vibration amplitude, and consequently enabling defect detection within an improved inspection range using the guided waves.

[0052] Figure 1 is a schematic diagram of a first high-power ultrasonic excitation device 100 disclosed herein. The ultrasonic excitation device 100 essentially comprises a high-power ultrasonic transducer 10 and a housing 20. The housing 20 defines the volume of a space 21 for housing an ultrasonic transmission medium 22. In Figure 1, the volume of the space 21 is filled with the ultrasonic transmission medium 22, or the ultrasonic transmission medium 22 may be introduced into the housing 20 at a later time.

[0053] Importantly, the housing 20 is adapted so that, during use, the ultrasonic transmission medium 22 can receive the ultrasonic waves 1 emitted by the high-power ultrasonic transducer 10 (in this case, the high-power ultrasonic transducer directly imparts the ultrasonic waves 1 to the ultrasonic transmission medium 22, which is a gel in the embodiment described). The housing 20 is further adapted to interact with the test structure 30 so that the test structure 30 can receive the ultrasonic waves 1 imparted to the gel 22 by the high-power ultrasonic transducer 10 from the gel 22. As a result, high-amplitude guided waves 2 can be uniformly excited on the test structure 30.

[0054] Figures 2 to 5 show modified forms of the high-power excitation device 100 of Figure 1. In the configurations shown in Figures 1 to 5, the same or similar test structure 30 is used. Furthermore, the high-power ultrasonic transducer 10 is powered by the same electronic equipment 13, some of which is shown, for example, in Figure 1. However, in Figures 1, 2, 4, and 5, the high-power ultrasonic transducer 10 includes a mechanical resonator 11 (or "horn" 11) that is not present in the configuration of Figure 3 (and therefore not shown). In Figure 3, the device 100 includes only a commercially available high-power ultrasonic transducer 10 (in this case, a conventional 50-watt ultrasonic cleaner (other similar transducers may also be used)).

[0055] The configuration in Figure 1 and the configuration in Figure 2 differ in the length of insertion of the end 32 of the test structure 30 into the volume of the space 21 filled with gel 22 inside the housing 20. In Figure 1, the test structure 30 (in this case, a metal rod with a diameter of approximately 15 mm (as an example)) protrudes several centimeters into the volume of the space 21 filled with gel 22, while in Figure 2, the end face of the test structure 30 protrudes only slightly into the space 21. Also, as shown in the figures, the protrusion of the resonator 11 into the volume of the space 21 differs slightly between Figure 1 and Figure 2. However, this did not change the result of uniformly inducing high-amplitude guided waves into the test structure 30.

[0056] In Figure 5, the entire length 33 of the test structure 30 is housed inside the housing 20 and in contact with the gel 22. The mechanical resonator 11 is almost completely inserted within the volume of the space 21 that houses the gel 22. The respective longitudinal axes defined by the transducer 10 and the test structure 30 itself are substantially perpendicular to each other, but can also have different angles, including a "zero" angle (corresponding to the parallel relationship between the longitudinal axis of the long test structure 30 and the longitudinal axis of the horn 11). In this case as well, this did not change the result of uniformly inducing high-amplitude guided waves in the test structure 30.

[0057] In Figure 4, the mechanical resonator 11 is further extended outward from the housing 20 compared to the configurations shown in Figures 1 and 2. In Figure 4, as illustrated, the distal end face of the mechanical resonator 11 is nearly flush with the inner surface of the housing 20, i.e., coplanar. In this case as well, this did not change the result of uniformly inducing high-amplitude guided waves into the test structure 30.

[0058] Despite the differences described above, in all configurations shown in Figures 1 to 5, the high-power ultrasonic transducer 10 (with or without the mechanical resonator 11) was able to excite a guided wave 2 with the desired amplitude into the test structure 30, as schematically shown in each of Figures 1 to 5, regardless of the configuration of the test structure 30 within the housing 20.

[0059] Figures 6, 7, and 8 show embodiments of actual prototypes of the high-power ultrasonic excitation device 100, which are in principle similar to those shown in Figures 1, 2, and 5, respectively. All of the high-power ultrasonic devices 100 shown in these figures are designed using a parallelepiped box to accommodate the housing 20 described above. However, commercially available versions of the high-power ultrasonic excitation device 100 are intended to have a cylindrical enclosure 20 to better fit the shape of the elongated metal structure 30, which is the particular subject of this specification. However, other shapes may be considered and implemented depending on the application. Figure 20 described below shows, for example, one alternative excitation configuration comprising a relatively rigid housing portion and a relatively flexible housing portion cooperating to define the volume of the space occupied by the gel.

[0060] The high-power ultrasonic excitation device 100 in Figure 6 strictly follows the schematic ultrasonic excitation device 100 shown in Figure 1. However, in Figure 6, an O-ring shaped seal 25 is also provided, which serves to prevent the ultrasonic transmission gel 22 from flowing out of the excitation opening 23 to the outside of the housing 20 between the resonator 11 and the wall of the housing in which the resonator 11 is housed.

[0061] The high-power ultrasonic excitation apparatus 100 in Figure 7 is a practical embodiment of the schematic ultrasonic excitation apparatus 100 shown in Figure 2. Conversely, the high-power ultrasonic excitation apparatus 100 in Figure 8 is essentially identical to the schematic ultrasonic excitation apparatus 100 schematically shown in Figure 5. In particular, it should be noted that in both apparatuses 100, the longitudinal axes defined by the high-power ultrasonic transducer 10 and the test structure 30, respectively, do not intersect each other and are substantially 90 degrees to each other. After filling the volume of the space 21 defined inside the housing 20 with the ultrasonic transmission medium 22, the housing 20 (in the apparatus 100 described here, in the form of a square walled receiver or container) can be closed using a lid 27 (shown in Figure 8). The lid 27 may, if applicable, be removed or replaced, for example, if the ultrasonic transmission medium 22 requires replacement or replenishment.

[0062] Figures 7 and 8 further show further parts of the electronic equipment 13 used to drive the high-power ultrasonic transducer 10. A detailed description of such electronic equipment 13 is not within the scope of this disclosure, as these components are in complete agreement with components readily available from the prior art.

[0063] Before describing Figures 9 to 12, which show the use of the high-power ultrasonic apparatus 100 described herein adapted to excite high-amplitude guided waves 2 within a test structure 30 different from the elongated metal members shown in Figures 1 to 8 (i.e., on an essentially two-dimensional structure of floors, plates, or walls, such as the floors and walls of a fuel storage tank), some additional points of interest here shall be noted regarding the features of the housing 20 that enable the high-power ultrasonic transducer 10 to effectively inject the ultrasound 1 into one side of the ultrasonic transmission medium 22, and for any elongated metal test structure 30 that receives most of the ultrasound 1 from the ultrasonic transmission medium 22 (with some of its energy inevitably dissipating within the housing 20, for example, by friction or dispersion).

[0064] More specifically, the ultrasonic excitation apparatus 100 shown in Figures 1 to 8 comprises one aperture 23 formed in the wall of the housing 20 to receive a high-power ultrasonic transducer 10 and / or (if present) its resonator 11, and one or more openings 24 similarly formed in the wall of the housing 20 (which may be the same or different wall compared to the wall of the housing 20 on which the aperture 23 is provided) to allow either the end 32 of the elongated metal structure 30 or its entire length 33 to be housed in the housing 20 so as to be immersed in and surrounded by the ultrasonic transmission medium 22 when the ultrasonic transmission medium 22 is present inside the housing 20.

[0065] Those skilled in the art will likely conceive of adaptations of the housing 20 different from those described herein. This disclosure teaches that the housing 20 needs to be adapted so that the ultrasound 1 can first travel from the high-power ultrasonic transducer 10 to the ultrasonic transmission medium 22 present within the housing 20, and then travel from the ultrasonic transmission medium 22 to the test structure 30 so that a high-amplitude guided wave 2 can be uniformly generated on the test structure 30. When the high-power ultrasonic transducer 10 (having its horn 11, if provided) and the test structure 30 are in direct contact with the ultrasonic transmission medium 22, this configuration is convenient because it requires a minimal and inexpensive adaptation of the housing 20. However, other adaptations that do not require such direct contact may be devised, as shown in Figures 9 and 10. In the case of Figure 20, only the transducer / horn is in direct contact with the ultrasonic transmission medium, but not with the test member, as will be further described below.

[0066] Figure 9 is a schematic diagram of a further ultrasonic excitation apparatus 100 disclosed herein for inspection of the floor 30 (i.e., plate) of a fuel storage tank. Apparatus 100 in Figures 9 and 10 (showing an enlarged view of apparatus 100 in Figure 9) is similar in many respects to the apparatus in Figures 1 to 8. However, the housing 20 defines an ultrasonic outlet 28 rather than an opening 24 for receiving a portion of the test structure 30, and the ultrasonic outlet 28 is in the form of an opening similar to those shown in Figures 1 to 8, but is used to transmit ultrasound 1 from the gel 22 to the plate 30 (located here outside the housing 20). In the apparatus 100 described herein, the ultrasonic outlet 28 further comprises a barrier 26 (provided in the form of a film in the apparatus 100 described herein, but other materials may be used). This barrier 26 not only prevents the ultrasonic transmission medium 22 from spilling out of the housing 20, but also allows the ultrasound 1 to be transmitted through the barrier 26 to the floor 30 of the fuel storage tank, resulting in the generation of a guided wave 2 as shown in Figure 10.

[0067] In the modified configurations of the apparatus described herein, the film 26 may be provided in the form of an inwardly extending sleeve for use with any one of the configurations shown in Figures 1, 3, 4, and 5. By using such a sleeve, contact between the test structure 30 and the ultrasonic transmission gel 22 can be advantageously prevented, which may be desirable in some implementation configurations. In the excitation apparatus of Figure 20 (further described below), a sleeve made of plastic material protrudes outward from a metal cone, performing a function similar to that of the boxes in Figures 1 to 10.

[0068] Here, we will describe some test results obtained on the sample test structure 30 using the guided wave excitation configuration 100 described herein. Returning to Figures 11 and 12, Figures 11 and 12 conceptually represent extending the scope of testing from essentially one-dimensional (i.e., mainly linear) test structures (such as rods, bars, tendons, rails, or pipes) to essentially two-dimensional test structures such as plates or walls.

[0069] Therefore, for the time being, we will mainly describe the area of ​​testing linear test structures 30. Figure 13 is a perspective view of a test rod 30 with a simulated defect 31. The test rod 30 was specially made to verify the use of the high-power ultrasonic excitation device 100 described herein. The test was first performed with a test rod 30 without the defect 31. The defect 31 was artificially introduced on only one side of the test rod 30 by removing a portion (several millimeters) of the rod material from its periphery over a length of approximately 10 to 15 centimeters. Next, experiments were performed using the configurations shown in Figures 1 to 5. All configurations were able to excite similar guided waves 2 onto the test rod 30. However, the results shown below were obtained from experiments using the configuration shown in Figure 1. Thus, the high-power ultrasonic excitation device 100 was used at one end of the test rod 30, and a standard acoustic emission receiver 12 (an example of which is shown in Figure 15) was used at the other end to receive the guided waves 2 in direct contact with the end face of the test rod 30.

[0070] With respect to Figure 14, three tests were initially performed using a metal test rod 30 free of defects 31. Both the peak amplitude 51 and energy value 53 of the measured ultrasonic signal 50 received by the receiver 12 were reproducible, as shown below. Figure 14(b) shows the response signal 50 measured by the ultrasonic receiver 12. Figure 14(a) shows the peak amplitude values ​​of 51 for the three initial tests on the left. Figure 14(d) further shows, on the left, the values ​​of the energy parameter 53, which is also relevant to the three initial tests.

[0071] Continuing to refer to Figure 14, the aforementioned defect 31 was introduced to simulate general corrosion. Three more tests were performed under equivalent conditions. The simulated corrosion 31 caused attenuation in both the measured peak amplitude value 52 and the energy parameter value 54 in these three subsequent tests. Figure 14(c) shows the spectrum related to the signal measured in one of the tests of the test rod 30 with defect 31.

[0072] Moving to Figure 15, Figure 15 shows an ultrasonic receiver 12 placed directly on the reinforced concrete surface 35. Tests were conducted to confirm whether the excited guided wave 2 could be detected by the ultrasonic receiver 12. The results of these tests are summarized in Figure 16. Figures 16(a) and 16(b) show, on the left, the peak amplitude value and the values ​​related to the energy parameter as a function of time in the first test, respectively. Figures 16(b) and 16(d) show, on the right, the same peak amplitude value and the same energy parameter value as a function of time in the second test, respectively. The tests show that the excited guided wave 2 has sufficient energy for the ultrasonic receiver 12 to sense from the reinforced concrete surface 35. This is not possible with conventional guided waves according to prior art, where the ultrasonic receiver 12 would only display noise or, in any case, only display boundary signal levels (e.g., with a peak amplitude of only 40 dB) that would make it difficult or even impossible to detect defects. If a defect exists within the test structure 30 in Figure 15, such as the artificial defect 31 in Figure 13, the peak amplitude and energy parameter values ​​shown in Figure 16 are expected to decrease in accordance with the decrease observed in Figures 14(a) and 14(d), i.e., a decrease of several decibels (dB). These decreases clearly represent achievable defect sensitivity.

[0073] Figure 17 shows the high-power ultrasonic excitation device 100, already shown in Figure 8, from a wider angle. Here, tests were performed with and without tension on the tendon 30, and the results are plotted in Figure 18. In the first three tests, the tension was set to 1000N to 1500N on a 14mm diameter tendon, resulting in higher peak amplitude values ​​55. In the next three tests, the tension was completely released (which actually happens to a damaged tendon, for example, inside a concrete coating), resulting in lower peak amplitude values ​​56. Considering the relationship between tension and signal amplitude, it is also possible to use this technique to measure the tension of a tendon.

[0074] Figure 19 shows a comparison of two frequency spectra 57, 58 obtained from guided waves excited using the apparatus described herein and measured in a defect-free structure and a defective structure, respectively. The difference in the frequency components of the two spectra indicates the presence of a defect.

[0075] Finally, moving on to the explanation of Figures 11 and 12, Figure 11 shows 16 positions, XD1 to XD16, where an ultrasonic receiver 12 similar to that shown in Figure 15 can be positioned. The test structure is a metal plate 30 as shown in Figures 9 and 10, and a corresponding high-power ultrasonic excitation device 100, also seen in Figures 9 and 10, is used. The guided wave 2 is first generated on the metal plate 30 from a first selected position on the metal plate surface 34 (e.g., near position XD1). Next, this process is repeated with excitation from a second selected position on the metal plate surface 34 (e.g., near XD2). Then, parameters such as "time of flight" or "attenuation" are calculated for each ultrasonic receiver 12. By comparing these values ​​and plotting them as a function of space, a map can be displayed showing not only the possibility of the presence of potential defects on the plate, but also their locations. To improve the accuracy of the map thus obtained, the process of excitation can be repeated sequentially, starting from the position closest to each ultrasonic receiver 12 shown in Figure 11. Furthermore, instead of using 16 positions around the circular plate 30 as shown in Figure 11, more positions can be added (or fewer positions can be used).

[0076] Figure 12 schematically illustrates a method for inspecting the outer cylindrical wall 30 of a fuel storage tank, as mentioned in relation to Figures 9 and 10. As shown in Figure 12, two robots R1 and R2 have been devised, adapted to move around the base and top of the cylindrical wall 30 to be inspected, respectively. This method includes equipping one of the two robots, for example R1, with a high-power ultrasonic excitation device of the type shown in Figures 9 and 10. This method further includes equipping the second robot D2 with at least one ultrasonic receiver 12 (similar in principle to the one shown in Figure 15). By moving robots R1 and R2 simultaneously along the aforementioned perimeter, it is possible to inspect the entire area of ​​the cylindrical wall for defects, preferably using detection parameters such as "time of flight" or decay. Moving robots R1 and R2 simultaneously is not the only applicable approach. Alternatively, one robot, e.g., R1, holding the high-power ultrasonic excitation device 100 described herein may be held in a fixed position, and robot R2, holding the ultrasonic receiver, may be moved to measure the guided wave 2 at various positions around each other, or vice versa. In either case, a map similar in principle to that obtained using the apparatus of Figure 11 can be obtained.

[0077] Inspectors intending to use the high-power ultrasonic excitation device 100 of the present invention must wear hearing protection, as is the case with other high-power ultrasonic applications such as ultrasonic cleaning, welding, cutting, or ultrasonic infrared imaging. While imperceptible to the human ear (as it arises from frequencies well above 20 kHz), noise with high intensity levels (e.g., 80 dB or higher) can damage ear tissue. However, this is not a necessary requirement for guided wave applications.

[0078] In this disclosure, several applications have been discussed for the purpose of illustrating one or more advantages associated with the introduction of the high-power ultrasonic excitation device 100 of the present invention; however, this list of applications should not be considered exhaustive. Those skilled in the art will be able to use the teachings of the present invention in a wide range of applications, for example, in non-destructive testing.

[0079] One such application will be described, for example, with reference to Figure 20. Figure 20(a) shows a hollow conical metal enclosure 20R coupled to a substantially flexible housing portion 20F (in this case realized as a plastic pouch 29 made of a thin plastic material). Together, the conical enclosure 20R and the plastic pouch 29 define the volume of a space 21 that will be occupied by an ultrasonic transmission medium (not shown in Figure 20) when in use. The cone 20R is substantially rigid or, in any case, relatively rigid than the pouch 29, and the cone 20R may be made from a rigid plastic material as an alternative. In Figure 20(b), the ultrasonic horn 10 is inserted into the space 21 defined by the hollow cone. This helps to generate ultrasound in, for example, a gel pre-supplied to fill the conical cavity 21. The gel also occupies the volume of the space 21 defined by the plastic pouch 29, so the ultrasound propagates into the internal volume of the pouch 29. In Figure 20(c), the pouch 29 is at least partially wrapped around the test structure 30 (in this case, a metal pipe), and the ultrasonic transducer / horn 10 is powered by an electrical connection before it can generate excitation in the test structure 30 as needed, allowing the test to be performed. In this configuration, the test structure 30 is not placed inside the housing 20, but the flexible portion 20F of the housing 20 conforms to (more specifically, completely wraps around in this case) the test structure 30, and similar excitation results can be obtained. This is possible because the ultrasonic waves 1 can still resonate inside the ultrasonic transmission medium, and the thin walls of the plastic pouch 29 significantly transmit the ultrasonic waves 1 to the outside, directly into the test structure 30, thereby generating the desired guided wave 2.

[0080] The excitation device in Figure 20 is more suitable for test structures 30 that are more difficult to access, given the flexibility of the pouch 29 which can be easily conformed to the shape of the test structure 30. In Figure 20, the plastic pouch 29 defines only a portion of the volume of the space 21 of the entire housing 20 filled with an ultrasonic transmission medium (not shown), but in principle the housing 20 may be made entirely from a substantially flexible and / or shape-conforming material, and similarly the housing may be made entirely from a relatively rigid material such as metal (as described herein) or a relatively rigid plastic material such as thermosetting plastic. Thus the test structure may be located inside or outside the housing, depending on the intended application and the appropriate configuration therefor, as long as it can ultimately receive the ultrasound generated within the ultrasonic transmission medium-filled volume of the space defined by the housing.

[0081] This disclosure focuses on mechanical aspects related to the excitation of high-amplitude guided waves on a test structure and, therefore, does not disclose details relating to any electronic equipment that may be used to drive a transducer on the excitation side or to measure the excitation guided wave on the receiving side. Those skilled in the art will find electronic equipment suitable for the purposes of the present invention in the prior art.

[0082] Furthermore, while calculations of specific parameters related to excitation guide waves are mentioned herein, this list of mentioned parameters should not be interpreted exhaustively. Depending on the specific application, certain other parameters may be more suitable for detecting the defect being investigated, and those skilled in the art will be able to select appropriate parameters based on the teachings of the prior art. [Explanation of Symbols]

[0083] 1. Ultrasound 2 Guided wave 10 High-power ultrasonic transducers 11 Mechanical resonator 12 Ultrasonic receiver 13 Electronic equipment 20 Housing Substantial and / or relatively rigid parts of the 20R housing 20F Substantial and / or relatively flexible portion of the housing 21 Volume of space within the housing 22 Ultrasonic transmission medium 23 Aperture 24 openings 25 stickers 26 Barriers 27 Lid 28. Ultrasonic outlet (from housing) 29 Plastic pouches or pockets 30 Test Structures 31. Defects to be detected 32 End of the test structure 33. Length of the test structure 34 Surface of the test structure 35 Damping materials 40 Infrastructure 50 Measurement of ultrasonic signals in an ultrasonic receiver 51 Peak amplitude (no defects) 52 Peak Amplitude (Defect) 53 Energy parameters (defect-free) 54. Energy Parameters (Defects) 55 Peak Amplitude (Tension) 56. Peak amplitude (without tension) 57 Frequency spectrum (defect-free) 58. Frequency spectrum (defect) 100 Ultrasonic Excitation Devices XD1, XD2, XD3, ..., XD16 Position of ultrasonic receiver on the test structure R1 First Robot R2, the second robot

Claims

1. An ultrasonic excitation device, High-power ultrasonic transducer and, A housing that defines the volume of the space for containing the ultrasonic transmission medium, An ultrasonic excitation device equipped with, An ultrasonic excitation device wherein, during use, the housing is adapted so that the ultrasonic transmission medium receives ultrasonic waves emitted by the high-power ultrasonic transducer, and the test structure receives the ultrasonic waves from the ultrasonic transmission medium.

2. The apparatus according to claim 1, wherein the high-power ultrasonic transducer is adapted to excite ultrasound having one or more frequency components of a spectrum in the range of about 20 kHz to about 100 kHz.

3. The aforementioned high-power ultrasonic transducer is equipped with a mechanical resonator, The apparatus according to claim 1 or 2, wherein the mechanical resonator optionally has at least one nominal resonant frequency in a spectrum of about 20 kHz to about 100 kHz.

4. The apparatus according to claim 1, 2, or 3, wherein the high-power ultrasonic transducer is selected to generate a displacement of 1 micrometer or more, more preferably 2 micrometers or more, more preferably 5 micrometers or more, and more preferably 10 micrometers or more on the active transducer surface.

5. The apparatus according to any one of the preceding claims, wherein the housing is provided as a substantially rigid enclosure, or the housing comprises a substantially rigid enclosure portion, and optionally the substantially rigid enclosure or enclosure portion is made of metal.

6. The apparatus according to any one of the preceding claims, wherein the housing is provided as a substantially flexible enclosure, or the housing comprises a substantially flexible enclosure portion, optionally the substantially flexible enclosure or enclosure portion is made of a thin plastic material such as a film or foil, and optionally the substantially flexible enclosure or enclosure portion is provided as a pouch made of a thin film or foil of the plastic material.

7. The apparatus according to claims 5 and 6, wherein the housing comprises a substantially rigid enclosure portion and a substantially flexible enclosure portion, and optionally the substantially flexible enclosure portion is provided as a pocket or pouch of thin plastic material attached to the substantially rigid enclosure portion of the housing and protruding outward from the substantially rigid enclosure portion.

8. The substantially rigid enclosure and / or enclosure portion is generally in the shape of a parallelepiped, cone, or cylinder. Optionally, the substantially rigid enclosure and / or enclosure portion comprises two or more assembleable parts, Optionally, the two or more assembled parts include a receiving part and a cover part. The apparatus according to claim 5, 6, or 7, wherein optionally, the two or more assemblyable parts are also disassemblable.

9. The apparatus according to any prior claim, wherein the housing comprises an aperture for receiving the high-power ultrasonic transducer.

10. The apparatus according to claim 9, wherein the aperture is in communication with the spatial volume.

11. The apparatus according to claim 9 or 10, further comprising a seal for sealing the space between the housing and the high-power ultrasonic transducer.

12. The apparatus according to any prior claim, further comprising the aforementioned test structure.

13. The apparatus according to claim 12, wherein the test structure is a long metal member.

14. The apparatus according to claim 13, wherein the metal member is one of a bar, rod, tendon, rail, or pipe.

15. The apparatus according to claim 13 or 14, wherein the housing comprises at least one opening for receiving a portion of the elongated metal member within the spatial volume for housing the ultrasonic transmission medium.

16. The housing comprises only one opening for receiving the end of the elongated metal member, and the aperture and the opening are positioned relative to each other such that, in use, the high-power ultrasonic transducer and the end of the elongated metal member are positioned approximately opposite each other. Optionally, the high-power ultrasonic transducer and the ends of the long metal member are arranged to be generally opposite each other. The apparatus according to claims 9 and 15, wherein optionally, the ends of the high-power ultrasonic transducer and the long metal member are arranged along a generally common straight line.

17. The housing comprises at least two openings for receiving the length of the elongated metal member, and the aperture and the openings are positioned such that, in use, the high-power ultrasonic transducer and the ends of the elongated metal member are aligned in a non-crossing direction. Optionally, the lengths of the high-power ultrasonic transducer and the long metal member are arranged substantially parallel to each other. The apparatus according to claims 9 and 15, wherein optionally, the ends of the high-power ultrasonic transducer and the elongated metal member are arranged substantially perpendicular to each other.

18. The aforementioned test structure is a metal plate such as a flat plate or a curved wall such as a cylindrical wall. The apparatus according to claim 12, wherein optionally the plate and / or wall define a circle.

19. The apparatus according to claim 18, wherein the housing comprises at least one outlet for outputting ultrasonic waves received by the test structure from the ultrasonic transmission medium.

20. The apparatus according to claim 19, wherein the outlet is provided with a barrier to prevent the ultrasonic transmission medium from flowing out of the housing onto the test structure.

21. The apparatus according to claim 20, wherein the barrier comprises a film such as a thin film or thin foil made from a plastic material, or is in the form of a film.

22. The apparatus according to claims 7 and 13, wherein the substantially flexible enclosure or enclosure portion is adapted to wrap at least partially around the elongated metal member, optionally the elongated metal member being one of a bar, rod, tendon, rail, or pipe, and optionally the substantially flexible enclosure or enclosure portion is provided as a pouch made of a thin film or foil of a plastic material.

23. The ultrasonic transmission medium further comprises, The apparatus according to any prior claim, wherein the ultrasonic transmission medium is optionally a gel.

24. The apparatus according to any prior claim, wherein the high-power ultrasonic transducer is of the piezoelectric type.

25. A non-destructive testing apparatus comprising an ultrasonic excitation device according to any of the preceding claims, and one or more ultrasonic receivers, which are optionally piezoelectric.

26. The high-power ultrasonic transducer and the one or more ultrasonic receivers are further equipped with electronic equipment for operating them in transmission mode. Optionally, the transmission mode operates using continuous ultrasonic transmission, or The nondestructive testing apparatus according to claim 25, wherein the transmission mode operates using burst or transient ultrasonic transmission.

27. Non-destructive testing method, Exciting ultrasonic guided waves into a test structure using an ultrasonic excitation device according to any one of claims 1 to 23, or the device according to claim 24 or claim 25. Non-destructive testing methods, including those mentioned above.

28. The aforementioned method, The excitation guide wave is measured using one or more ultrasonic receivers. The method of claim 27, as dependent on claim 25 or 26, further comprising:

29. The aforementioned method, Placing at least one of the one or more ultrasonic receivers mentioned above on the test structure. The method according to claim 28, further comprising:

30. The method involves placing at least one of the one or more ultrasonic receivers on the material in which the test structure is embedded. The method according to claim 28 or 29, further comprising:

31. The aforementioned method, Calculating the peak amplitude and / or energy parameter and / or frequency spectrum and / or attenuation parameter and / or time of flight of the measured guide wave. The method according to claim 28, 9, or 30, further comprising:

32. The method according to claim 31, further comprising calculating only the attenuation parameter of the measured guide wave.

33. The aforementioned test structure is a metal tendon, and the method is as follows: Estimating the tension of the metal tendon and / or detecting the presence or absence of tension in the metal tendon. The method according to any one of claims 28 to 32, further comprising:

34. The method according to claim 27, as dependent on claim 22, further comprising wrapping at least partially the substantially flexible enclosure or enclosure portion around the elongated metal member, optionally the elongated metal member being one of a bar, rod, tendon, rail, or pipe, and optionally the substantially flexible enclosure or enclosure portion being provided as a pouch made of a thin film or foil of a plastic material.

35. The aforementioned test structure is a metal plate, and the method is as follows: The arrangement of multiple ultrasonic receivers on the aforementioned metal plate, Exciting an ultrasonic guided wave onto the metal plate from a first selected position on the metal plate, Exciting ultrasonic guided waves onto the metal plate from at least one further selected position on the metal plate, The excitation guide wave is measured in the plurality of ultrasonic receivers, The method according to any one of claims 28 to 32, further comprising:

36. The aforementioned method, Ultrasonic guided waves are excited onto the metal plate from multiple positions adjacent to each of the multiple ultrasonic receivers arranged on the metal plate. The method according to claim 35, further comprising:

37. The aforementioned method, The ultrasonic excitation device is installed on the first robot, The second robot is provided with at least one of the one or more ultrasonic receivers, Moving at least one of the first robot and the second robot The method according to any one of claims 28 to 33, further comprising:

38. An infrastructure comprising an ultrasonic excitation device according to any one of claims 1 to 24.

39. The infrastructure according to claim 38, wherein the ultrasonic excitation device is permanently or semi-permanently installed in the infrastructure.

40. The infrastructure according to claim 38 or 39, further comprising one or more ultrasonic receivers.

41. The infrastructure according to claim 40, wherein one or more ultrasonic receivers are permanently or semi-permanently installed in the infrastructure.

42. A method for preparing a test structure comprising a metal member covered with an attenuating material for ultrasonic nondestructive testing, wherein the method is: Removing a portion of the damping material to expose one or more portions of the metal member, The ultrasonic excitation device according to any one of claims 1 to 24 is placed on at least one of the exposed portions of the metal member, Methods that include...

43. The aforementioned method, One or more ultrasonic receivers are placed on one or more exposed portions of each of the aforementioned metal members, or One or more ultrasonic receivers are placed on the attenuating material. The method according to claim 42, further comprising:

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