Thermally compensating compound wedge for acoustic inspection

Abstract

Approaches such as volumetric acoustic shear wave inspection can include use of an acoustic coupling wedge structure, such as to orient acoustic energy and couple such acoustic energy into an object. For example, a wedge structure can orient a direction of propagation of acoustic energy at a specified oblique angle of incidence that is not normal (e.g., perpendicular) to the surface of the object under test. At temperatures other than a nominal temperature, acoustic velocities of propagation within the wedge and material under inspection change, resulting in refraction angle variation. The present subject matter can be used to help compensate for such temperature-dependent angle variation. A configuration can be used that includes two or more solid prisms to propagate acoustic energy using a near-constant specified nominal acoustic refraction angle within the object under test, such as largely independent of temperature at a nominal temperature or within a specified range of temperatures.

Description

THERMALLY COMPENSATING COMPOUND WEDGE FOR ACOUSTIC INSPECTIONCLAIM OF PRIORITY

[0001] This patent application claims the benefit of priority of Stanton et al., U.S. Provisional Patent Application Number 63 / 594,810, titled “THERMALLY COMPENSATING COMPOUND WEDGE,” filed on October 31, 2023 (Attorney Docket No. 6409.270PRV), which is hereby incorporated by reference herein in its entirety.FIELD OF THE DISCLOSURE

[0002] This document pertains generally, but not by way of limitation, to nondestructive evaluation, and more particularly, to apparatus and techniques for providing compensation for deviation in acoustic refractive properties of a coupling wedge structure versus temperature.BACKGROUND

[0003] Non-destructive testing (NDT) can refer to use of one or more different techniques to inspect regions on or within an object, such as to ascertain whether flaws or defects exist, or to otherwise characterize the object being inspected. Examples of non-destructive test approaches can include use of an eddy-current testing approach where electromagnetic energy is applied to the object and resulting induced currents on or within the object are detected, with the values of a detected current (or a related impedance) providing an indication of the structure of the object under test, such as to indicate a presence of a crack, void, porosity, or other inhomogeneity.

[0004] Another approach for NDT can include use of an acoustic inspection technique, such as where one or more electroacoustic transducers are used to insonify a region on or within the object under test, and acoustic energy that is scattered or reflected can be detected and processed. Such scattered or reflected energy can be referred to as an acoustic echo signal. Generally, such an acoustic inspection scheme involves use of acoustic frequencies in an ultrasonic range of frequencies, such as including pulses having energy in a specified range that can include value from, forexample, a few hundred kilohertz, to tens of megahertz, as an illustrative example.SUMMARY OF THE DISCLOSURE

[0005] Acoustic testing, such as ultrasound-based inspection, can include use of individual transducers, or arrays of such transducers including providing focusing or beam-forming techniques to aid in construction of data plots or images representing a region of interest on or within a test specimen. Use of an array of ultrasound transducer elements can include use of a phased-array beamforming approach and can be referred to as Phased Array Ultrasound Test (PAUT). For example, a delay-and- sum beamforming technique can be used, such as including coherently summing timedomain representations of received acoustic signals from respective transducer elements or apertures. Approaches such as angle beam inspection approach can be used to excite shear waves in an object under test (e.g., volumetric shear waves). In such an approach, an ultrasonic transducer assembly (such as including a single transducer or an array of such transducers) can be mounted to an acoustic coupling wedge structure. The wedge establishes a specified angle for mounting of the transducer assembly, resulting in a specified incident angle within the wedge. The acoustic energy is refracted at the surface of an object under test, resulting in a specified beam angle within the object under test that is not normal (e.g., perpendicular) to the surface.

[0006] The present inventors have recognized, among other things that at temperatures other than a nominal temperature, acoustic velocities of propagation within the wedge structure and object under test may change, resulting in refraction angle variation deviating from a nominal angle. The present inventors have also recognized, among other things, that the present subject matter can be used to help compensate for such temperature-dependent variation. As an illustration, a wedge configuration can be used that stacks two or more solid acoustic prisms comprising different materials. Such a configuration can be used to launch or receive acoustic energy at a near-constant specified angle incident to or from an object under test. A temperature-dependent acoustic refraction in one of the prisms can vary differently with respect to temperature than a corresponding temperature-dependent acoustic refraction of the other of the two prisms, resulting in a refracted beam angle in the object under test that varies less with respect to temperature as compared to a single-material acoustic coupling wedge structure.

[0007] In an example, an acoustic coupling wedge structure, comprising a first acoustic prism comprising a first material having a first acoustic propagation velocity that varies according to a first temperature dependence, and a second acoustic prism acoustically coupled to the first acoustic prism, the second acoustic prism comprising a different second material having a different second acoustic propagation velocity that varies according to a second temperature dependence. Generally, the second temperature dependence compensates for at least a portion of the first temperature dependence across a specified temperature range. In an example, a method for performing acoustic inspection can include generating acoustic energy using an acoustic transducer acoustically coupled to the acoustic coupling wedge structure of the example above, including coupling the generated acoustic energy through the acoustic coupling wedge structure and using the acoustic coupling wedge, establishing propagation of the generated acoustic energy at a specified nominal acoustic refraction angle within an object under test. Reciprocally, in an example, the acoustic coupling wedge structure can receive acoustic energy scattered or reflected from within the object under test.

[0008] In an example the acoustic transducer comprises a phased array ultrasound transducer, and a method for performing acoustic inspection can include varying an acoustic refraction angle about a specified nominal acoustic refraction angle by steering the generated acoustic energy established by the phased array ultrasound transducer. In an example, the acoustic coupling wedge structure or an associated method can include or provide a specified nominal acoustic refraction angle that varies less with respect to temperature due the compensation by the second temperature dependence of at least a portion of the first temperature dependence within a specified temperature range encompassing a specified temperature, as compared to a wedge structure comprising only the first material or only the second material. In an example, in the acoustic coupling wedge structure or an associated method, at least one of the first material or the second comprises a polymer material, such as polybenzimidazole. In an example, in the acoustic coupling wedge structure or an associated method, at least one of the first material or the second material comprises a carbon allotrope, such as graphite.

[0009] This summary is intended to provide an overview of subject matter of thepresent patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.

[0011] FIG. 1 illustrates generally an example comprising an acoustic inspection system, such as can be used to perform at least a portion of one or more techniques as shown and described herein.

[0012] FIG. 2A shows an illustrative example of an acoustic wedge coupling structure comprising a first acoustic prism and a second acoustic prism.

[0013] FIG. 2B shows respective angles of incidence and refraction that can be established by the acoustic wedge coupling structure of FIG. 2A.

[0014] FIG. 3 shows as a table comprising different material characteristics for an illustrative example of an acoustic couple wedge structure.

[0015] FIG. 4A shows as a table comprising respective angles of incidence and refraction corresponding to the geometry shown in FIG. 2B, evaluated versus temperature.

[0016] FIG. 4B shows a plot of values of an acoustic refraction angle within an object under test evaluated versus temperature.

[0017] FIG. 5 illustrates generally a technique for performing acoustic inspection, such as can include use of an acoustic coupling wedge as shown and described elsewhere herein.DETAILED DESCRIPTION

[0018] Non-destructive testing of structures can be performed using an acoustic technique, such as involving ultrasonic inspection using a single transducer or phased- array transducer architecture. As mentioned above, approaches such as volumetric acoustic shear wave inspection can include use of an acoustic coupling wedgestructure, such as to orient acoustic energy and couple such acoustic energy into an object. For example, a wedge structure can orient a direction of propagation of acoustic energy at a specified oblique angle of incidence that is not normal (e.g., perpendicular) to the surface of the object under test. At temperatures other than a nominal temperature, acoustic velocities of propagation within the wedge and material under inspection change, resulting in refraction angle variation. The present subject matter can be used to help compensate for such temperature-dependent angle variation. A configuration can be used that includes two or more solid prisms to propagate acoustic energy using a near-constant specified nominal acoustic refraction angle within the object under test, such as largely independent of temperature at a nominal temperature or within a specified range of temperatures.

[0019] FIG. 1 illustrates generally an example comprising an acoustic inspection system 100, such as can include or use the acoustic couple wedge structure shown and described herein. The system 100 of FIG. 1 can be used to perform at least a portion of one or more techniques as shown and described herein. The inspection system 100 can include a test instrument 140, such as a hand-held or portable assembly. The test instrument 140 can be electrically coupled to a probe assembly 150, such as using a multi-conductor interconnect 130. The probe assembly 150 can include one or more electroacoustic transducers, such as a transducer assembly 152 such as including a single transducer or respective transducers 154A through 154N. An active surface of the transducer assembly 152 can follow a linear or curved contour or can include an array of elements. Element size and pitch can be varied according to the inspection application.

[0020] A modular probe assembly 150 configuration can be used, such as to allow a test instrument 140 to be used with various different probe assemblies. Generally, the transducer assembly 152 includes one or more piezoelectric transducers, such as can be acoustically coupled to a target 158 (e.g., a test specimen or “object-under-test”) through a coupling medium 156. The coupling medium can include a fluid or gel or a solid membrane (e.g., an elastomer or other polymer material), or a combination of fluid, gel, or solid structures. For example, an acoustic transducer assembly can include a transducer array coupled to a wedge structure 155 comprising a rigid material, such as a thermoset polymer having known acoustic propagation characteristics (for example, a cross-linked polystyrene such as Rexolite® availablefrom C-Lec Plastics Inc. or another material or combination of materials as shown and described elsewhere herein). Water can be injected between the wedge and the structure under test as a coupling medium 156 during testing, or testing can be conducted with an interface between the probe assembly 150 and the target 158 otherwise immersed in a coupling medium. As shown in the examples described below, the wedge structure 155 can include multiple regions or portions, such as comprising materials having different temperature-dependent acoustic propagation velocities and associated acoustic refraction characteristics. An arrangement of such different materials can be used to compensate for temperature-dependent variation in acoustic propagation (e.g., beam) angle within the wedge structure 155, such as in a shear-wave propagation mode.

[0021] The test instrument 140 can include digital and analog circuitry, such as a front-end circuit 122 including one or more transmitter signal chains, receiver signal chains, or switching circuitry (e.g., transmit / receive switching circuitry). The transmitter signal chain can include amplifier and filter circuitry, such as to provide transmit pulses for delivery through an interconnect 130 to a probe assembly 150 for insonifying the target 158, such as to image or otherwise detect a flaw 160 on or within the target 158 structure by receiving scattered or reflected acoustic energy elicited in response to the insonification.

[0022] While FIG. 1 shows a single probe assembly 150 and a single transducer assembly 152, other configurations can be used, such as multiple probe assemblies connected to a single test instrument 140, or multiple transducer assemblies 152 used with a single probe assembly 150 or multiple probe assemblies for pitch / catch inspection modes. Similarly, a test protocol can be performed using coordination between multiple test instruments 140, such as in response to an overall test scheme established from a master test instrument 140 or established by another remote system such as a compute facility 108 or general -purpose computing device such as a laptop 132, tablet, smart-phone, desktop computer, or the like. The test scheme may be established according to a published standard or regulatory requirement and may be performed upon initial fabrication or on a recurring basis for ongoing surveillance, as illustrative examples.

[0023] The receiver signal chain of the front-end circuit 122 can include one or more filters or amplifier circuits, along with an analog-to-digital conversion facility, such asto digitize echo signals received using the probe assembly 150. Digitization can be performed coherently, such as to provide multiple channels of digitized data aligned or referenced to each other in time or phase. The front-end circuit can be coupled to and controlled by one or more processor circuits, such as a processor circuit 102 included as a portion of the test instrument 140. The processor circuit can be coupled to a memory circuit 104, such as to execute instructions that cause the test instrument 140 to perform one or more of acoustic transmission, acoustic acquisition, processing, or storage of data relating to an acoustic inspection, or to otherwise perform techniques as shown and described herein. The test instrument 140 can be communicatively coupled to other portions of the system 100, such as using a wired or wireless communication interface 120.

[0024] For example, performance of one or more techniques as shown and described herein can be accomplished on-board the test instrument 140 or using other processing or storage facilities such as using a compute facility 108 or a general- purpose computing device such as a laptop 132, tablet, smart-phone, desktop computer, or the like. For example, processing tasks that would be undesirably slow if performed on-board the test instrument 140 or beyond the capabilities of the test instrument 140 can be performed remotely (e.g., on a separate system), such as in response to a request from the test instrument 140. Similarly, storage of imaging data or intermediate data such as A-scan matrices of time-series data or other representations of such data, for example, can be accomplished using remote facilities communicatively coupled to the test instrument 140. The test instrument can include a display 110, such as for presentation of configuration information or results, and an input device 112 such as including one or more of a keyboard, trackball, function keys or soft keys, mouse-interface, touch-screen, stylus, or the like, for receiving operator commands, configuration information, or responses to queries.

[0025] As discussed elsewhere herein, different acoustic propagation modes can be used to perform non-destructive inspection of objects. For example, volumetric shear wave inspection can be used to inspect metallic structures such as pipes or vessels. Such inspection can be used to detect cracks or other flaws, or for inspection of weld structures, as illustrative (but non-restrictive) examples. Volumetric shear wave inspection can include use of an acoustic coupling wedge structure to refract acoustic energy (either for transmitting acoustic pulses or receiving acoustic echoes) using aspecified nominal angle (or range of such angles) to provide desired inspection coverage. Use of the acoustic coupling wedges provides a controlled angle of acoustic energy transmission or reception from within the object under test, through a surface to which the wedge is acoustically coupled. As temperature varies, acoustic propagation velocities associated with the coupling wedge and material under inspection change, resulting in acoustic refraction angle variation. Such variation can be significant where testing is performed at elevated temperatures (e.g., above 100 degrees C, such as in the range of about 200 degrees C to about 300 degrees C, or otherwise above ambient temperature). The refraction angle variation can cause inaccuracy in resulting feature size estimation or location indications. Such inaccuracies can be present when using either non-phased array or phased-array inspection approaches.

[0026] An effect of such inaccuracies may be ignored (e.g., the error is tolerated), or accounted for by calibration using, for example, a test block or other article that is exposed to the same elevated temperature as is used for inspection. In another approach, temperature sensing or related modeling (or both) can be used to perform compensation. As in illustration, such as in phased array ultrasound testing (PAUT), beamforming or associated steering can be adjusted based on temperature, such as by altering a beam angle in response to sensed temperature.

[0027] The present inventors have recognized that ignoring inaccuracy may not be desirable or even acceptable depending on the nature of the inspection being performed, and using the other approaches mentioned above can present various challenges. The present inventors have also recognized, among other things, that a composite wedge structure (e.g., comprising at least two different materials) can be used to compensate for temperature-induced refraction angle variation, such as to reduce or suppress errors associated with such refraction angle variation. In this manner, sizing or dimensional inspection accuracy can be enhanced as compared to a monolithic wedge structure. Such reduction in refraction angle variation can be established across or within a specified temperature range encompassing a specified temperature (e.g., a target temperature), without requiring the other techniques mentioned above (e.g., without requiring calibration at elevated temperature, temperature-based monitoring for compensation, or modification of beamforming or beamsteering based on sensed temperature).

[0028] As an illustrative example, FIG. 2A shows an acoustic wedge coupling structure 255 comprising a first acoustic prism 257A comprising a first propagation medium and a second acoustic prism 257B comprising a different second propagation medium, in a stacked configuration. The view in FIG. 2A can represent a side view, where the first acoustic prism 257A comprises a first surface 265 to which an acoustic transducer 254 (or an array of such transducers) is coupled. The acoustic wedge coupling structure 255 can be modular, such as allowing different combinations of first acoustic prism 257A and second acoustic prism 257B to be used, such as in combination with different acoustic transducer assembly 252 configurations.

[0029] A ray, RMI, forming a portion of an acoustic energy propagation path in a first medium can be refracted at an interface of a second surface 263 of the first acoustic prism 257A and a first surface of the second acoustic prism 257B. The angle of refraction is generally governed by Snell’s law, where the refraction at the interface between materials depends on the acoustic refractive indices of the first acoustic prism 257A and the second acoustic prism 257B, which depend on corresponding acoustic propagation velocities. A refracted second ray, RM2 can be conveyed by the second acoustic prism 257B to a second surface 267 on or near a surface of an object under test, representing the acoustic energy propagation path in the second medium. A resulting ray RM3 can be established within the object under test. Generally, the object under test comprises yet another different propagation medium (such as a metallic structure). Reciprocity applies to the ray directions mentioned above, so the discussion herein is equally applicable to acoustic pulse transmission and scattered energy reception contexts.

[0030] Generally, the first acoustic prism 257A and second acoustic prism 257B comprise different materials, having different temperature dependence of their respective acoustic propagation velocities. Most materials expand with increasing temperature, but the rates and degrees of such expansion vary significantly from one material to another. Accordingly, the present inventors have recognized, among other things that it is possible to pair materials having different temperature-dependent propagation velocity profiles that, in sum, provide a refracted ray RM3 in the object under test that varies less across a specified temperature range than would occur with use of a single wedge material. This does not require that the temperature dependence of acoustic propagation velocities in each of the materials are complementary (e.g.,opposite in sign), but merely that when one varies a great deal with temperature, the other may not, and vice versa, so that the combined effect of the respective velocities is far less variable than either of the materials used alone. To quantify such improvement, illustrative examples are discussed further below.

[0031] The first acoustic prism 257 A and the second acoustic prism 257B can be mechanically anchored together using screws (e.g., through the materials but otherwise outside the propagation path of an acoustic beam), or other fasteners. In an example, the prism materials can be mechanically anchored together or otherwise coupled together using other approaches such as an external clamp, bracket, housing, or the like. In an example, the first acoustic prism 257A and second acoustic prism 257B can be fused together (such as by molding or pressing one material into another or heating one or both materials) or adhered together using a pressure sensitive adhesive or contact adhesive, as illustrative examples.

[0032] The approach for securing the first acoustic prism 257A to the second acoustic prism 257B can be selected in part by considering a temperature range of operation. For example, higher temperature applications may benefit from some degree of compliance at the interface between the prisms. In an example, such as when the first acoustic prism 257A and second acoustic prism 257B are mechanically fastened together either internally or externally, a region 271 at an interface between the first acoustic prism 257A and the second acoustic prism 257B can include a couplant such as a liquid or gel or other material. Use of a liquid, gel, or flexible material at the interface between the first acoustic prism 257A and the second acoustic prism 257B can provide a compliant medium to help to accommodate differences in the coefficients of thermal expansion associated with the different materials comprising the first acoustic prism 257A and the second acoustic prism 257B. Similarly, a region 256 at an interface between the second acoustic prism 257B and the object under test can include a couplant such as a liquid or gel. In another approach, the entire acoustic wedge coupling structure 255 and surface of the object under test can be immersed so that the region 256 (and optionally, the region 271) are filled with liquid such as water or another couplant.

[0033] The acoustic wedge coupling structure 255 can include other portions, such as an absorbing material 261 that is different from the materials used for the first acoustic prism 257A and second acoustic prism 257B, such as to suppress scattered orreflected acoustic energy that is off-axis from the beam direction or nominal angle of refraction. Unlike other approaches, the present subject matter generally includes a primary acoustic energy or beam propagation path that traverses the two dissimilar materials of the first acoustic prism 257 A and the second acoustic prism 257B.

[0034] As an illustration, FIG. 2B shows respective angles of incidence and refraction that can be established by the acoustic wedge coupling structure 255 of FIG. 2A. An acoustic transmission can be generated using the acoustic transducer 254. A propagation angle of ray RMI in the first acoustic prism 257A can be defined as a wedge angle, 0mi, relative to a normal vector from the second surface 263 of the first acoustic prism 257A. In this example, 0miis nominally 31.6 degrees. This angle can be defined by the angle of the first surface 265 to which the acoustic transducer 254 is mounted. A wedge angle, 0m2, in the second acoustic prism 257B can be defined relative to a normal vector from a first surface of the second acoustic prism 257B (e.g., aligned in the same direction as the normal vector from the second surface 263 of the first acoustic prism 257A, because the two prisms are stacked). In this example 0m2 is nominally 14.4 degrees. A refracted ray in the object under test 258, RM3, can have an angle represented by 0r2-3. In this example, for angle beam inspection, the nominal value of 0r2-3 is 55 degrees. This is merely illustrative, and different wedge configurations may be used based on the desired nominal beam angle in the object under test 258.

[0035] Variation in the refracted angle of the ray RM2 angle, 0ri-2, from the interface between the first acoustic prism 257A and the second acoustic prism 257B can be used to compensate for corresponding variation in the incident angle, 0i2-3, at the interface between the second acoustic prism 257B and the object under test 258 (e.g., these two angles vary at different rates with respect to temperature, in a manner that results in a more stable 0r2-3 value across temperature as compared to a monolithic wedge structure comprising only a single material in the beam path).

[0036] FIG. 3 shows as a table comprising different material characteristics for an illustrative example of an acoustic couple wedge structure. The table shows acoustic propagation velocity values for Celazole® u60 (e.g., a tradename for a thermoset polybenzimidazole polymer) as material 1 (corresponding to the first acoustic prism 257A), first row; hot isostatically-pressed (HIP) graphite as material 2 (correspondingto the second acoustic prism 257B), second row; and steel as the object under test, as material 3, third row. The table shown in FIG. 3 also shows temperature coefficients of change in acoustic propagation velocity per degree C. FIG. 4 A shows as a table comprising respective angles of incidence and refraction corresponding to the geometry shown in FIG. 2B, evaluated versus temperature (from zero to 600 degrees C) using simulation. For the values shown in FIG. 4A, uniform temperature is assumed across the acoustic prism structures and object under test (e.g., no thermal gradient). FIG. 4B shows a plot of values of an acoustic refraction angle within an object under test evaluated versus temperature, corresponding to the results shown in FIG. 4A.

[0037] The simulation results of FIG. 4 A and FIG. 4B illustrate that the composite wedge structure of FIG. 2 A can be used to mimic a polystyrene monolithic wedge for 55-degree refraction in a shear mode for volumetric inspection of steel structures. For example, the 55-degree nominal angle can support PAUT testing using beam-steering across a range from 40 degrees to 70 degrees (e.g., refraction angle internally within the object under test). The use of a 55-degree nominal value is merely illustrative, and other configurations can be used to target other nominal refraction angles such as 45 degrees, 60 degrees, or 70 degrees, as illustrative examples. In the example simulated in FIG. 4A and FIG. 4B, using the materials of the table of FIG. 3, a nominal target incident angle of 42.4 degrees is established at the interface between the second material and the object under test, to achieve a 55-degree refraction angle within the object under test.

[0038] As shown in FIG. 4A, across the entire simulated temperature range, the refracted angle within the object under test, 0r2-3, only varies by 0.06 degrees. If a monolithic wedge structure were used, such as comprising Celazole® alone, the variation across a similar temperature range is over three degrees (corresponding to the difference, A0, in 0i2-3, across all simulated temperatures).

[0039] The example of placing the graphite material at the surface of the object under test is merely illustrative, and the materials could be swapped. However, use of graphite in contact with an object under test at elevated temperature and use of a polymer closer to the acoustic transducer may help to isolate the acoustic transducer thermally from the object under test. Generally, graphite and other carbon allotropes have higher thermal conductivity than polymer materials generally used for acousticcoupling wedge structures. Also, use of a thinner path length through polymer such as Celazole® may help suppress excess acoustic attenuation. For example, hot isostatically pressed (HIP) graphite exhibits a lower acoustic attenuation than Celazole®, and use of graphite for the material in contact with the object under test results in the longer acoustic path being through the graphite prism.

[0040] Depending on temperature range and application, other material combinations can be used. Generally, the material in contact with the object under test should have a melting point for thermoplastic compounds or glass transition temperature for thermosetting compounds that is well above an expected temperature of the object under test. For applications involving testing below 60 to 80 degrees C, materials such as polystyrene, polyetherimide, or an acrylic, can be used. For higher-temperature applications, polyetheretherketone (PEEK) could be used.

[0041] FIG. 5 illustrates generally a technique 500, such as an automated or semiautomated method, for performing acoustic inspection, such as can include use of an acoustic coupling wedge as shown and described elsewhere herein. At 505, acoustic energy can be generated using an acoustic transducer. For example, an acoustic transducer or assembly of such transducer can be electrically excited to generate one or more pulses defining envelopes corresponding to a specified acoustic frequency. Such generation can be performed such as using a portion of a system 100 as shown in FIG. 1. Referring to FIG. 5, at 510, the acoustic energy generated at 505 can be coupled to an object under test, such as using a composite acoustic wedge coupling structure as shown illustratively in FIG. 2A and discussed in relation to other examples herein.

[0042] For example, acoustic energy can be refracted through a first acoustic prism comprising a first material at 515, and then acoustic energy can be coupled into and refracted through a second acoustic prism at 520, where the second prism comprises a different second material. The combination of first and second materials can compensate for a temperature dependence of acoustic propagation velocity, such as where a temperature dependence of the second material helps to compensate for a temperature dependence of the first material. Reciprocity applies to such compensation, and accordingly, for example, scattered or reflected acoustic energy from within the object under test can be coupled from the object under test back to the second acoustic prism, and through the first acoustic prism back to the acoustictransducer used for transmission (or to another acoustic transducer). In this manner, non-destructive acoustic inspection can be performed. Alternatively, or in addition, another transducer could be used to receive acoustic energy that is scattered or reflected, from within the object under test, in response to acoustic excitation by a first transducer (or array of such transducers). In an example, such inspection can be performed on an object under test that has a surface above ambient temperature.Various Notes and Examples

[0043] Example 1 comprises an acoustic coupling wedge structure, comprising: a first acoustic prism comprising a first material having a first acoustic propagation velocity that varies according to a first temperature dependence; and a second acoustic prism acoustically coupled to the first acoustic prism, the second acoustic prism comprising a different second material having a different second acoustic propagation velocity that varies according to a second temperature dependence; wherein the second temperature dependence compensates for at least a portion of the first temperature dependence across a specified temperature range.

[0044] Example 2 comprises the acoustic coupling wedge structure of Example 1, wherein the first acoustic prism comprises a first surface to which an acoustic transducer can be coupled and a second surface to which the second acoustic prism is acoustically coupled; and wherein the second acoustic prism comprises a first surface to transmit or receive acoustic energy to or from the first acoustic prism through the second surface of the first acoustic prism; and wherein the second acoustic prism comprises a second surface that can be acoustically coupled to an object under test to transmit or receive the acoustic energy using a specified nominal acoustic refraction angle within the object under test.

[0045] Example 3 comprises the acoustic coupling wedge structure of Example 2, wherein the specified nominal acoustic refraction angle varies less with respect to temperature due the compensation by the second temperature dependence of at least a portion of the first temperature dependence within a specified temperature range encompassing a specified temperature, as compared to a wedge structure comprising only the first material or only the second material.

[0046] Example 4 comprises the acoustic coupling wedge structure of any of Examples 2 or 3, wherein the specified nominal acoustic refraction angle is 55degrees with respect to a normal direction from a surface of the object under test, for a volumetric shear wave acoustic mode.

[0047] Example 5 comprises the acoustic coupling wedge structure of any of Examples 2 through 4, wherein the specified nominal acoustic refraction angle is within a range of acoustic beam steering angles established by a phased array ultrasound transducer assembly acoustically coupled to the first surface of the first acoustic prism.

[0048] Example 6 comprises the acoustic coupling wedge structure of Example 1, wherein at least one of the first material or the second comprises a polymer material.

[0049] Example 7 comprises the acoustic coupling wedge structure of Example 6, wherein the polymer material comprises at least one of polystyrene, polyetherimide, an acrylic, or polyetheretherketone.

[0050] Example 8 comprises the acoustic coupling wedge structure of Example 6, wherein the first material or the second material comprises polybenzimidazole.

[0051] Example 9 comprises the acoustic coupling wedge structure of any of Examples 1 through 7, wherein the first material or the second material comprises a carbon allotrope.

[0052] Example 10 comprises the acoustic coupling wedge structure of Example 8, wherein the first material or the second material comprises pressed graphite.

[0053] Example 11 comprises the acoustic coupling wedge structure of any of Examples 1 through 10, wherein the first acoustic prism and the second acoustic prism are mechanically anchored to each other.

[0054] Example 12 comprises the acoustic coupling wedge structure of Example 11, wherein a mechanical anchor comprises one or more fasteners.

[0055] Example 13 comprises the acoustic coupling wedge structure of Example 10, wherein mechanical anchoring is established by fusing or adhering the first material and second material together.

[0056] Example 14 comprises the acoustic coupling wedge structure of any of Examples 1 through 13, wherein an interface between the first acoustic prism and the second acoustic prism comprises a liquid.

[0057] Example 15 comprises the acoustic coupling wedge structure of any of Examples 1 through 14, wherein an interface between the first acoustic prism and the second acoustic prism is compliant to accommodate a difference between coefficientsof thermal expansion of the first material versus the second material.

[0058] Example 16 comprises the acoustic coupling wedge structure of any of Examples 1 through 15, comprising a third material acoustically coupled to at least one of the first acoustic prism or the second acoustic prism, the third material comprising a scattering or absorbing material to suppress acoustic propagation and reflection of acoustic energy off a desired axis.

[0059] Example 17 comprises an acoustic inspection probe assembly, comprising: the acoustic coupling wedge structure of any of Examples 1 through 16; and an acoustic transducer acoustically coupled to the acoustic coupling wedge structure and configured to transmit or receive acoustic energy using a propagation path through a first acoustic prism and a second acoustic prism of the acoustic coupling wedge structure of any of Examples 1 through 16.

[0060] Example 18 comprises the acoustic inspection probe assembly of Example 17, wherein the acoustic transducer comprises an array of acoustic elements.

[0061] Example 19 comprises a method for performing acoustic inspection, the method comprising: generating acoustic energy using an acoustic transducer acoustically coupled to the acoustic coupling wedge structure of any of Examples 1 through 16; coupling the generated acoustic energy through the acoustic coupling wedge structure; and using the acoustic coupling wedge, establishing propagation of the generated acoustic energy at a specified nominal acoustic refraction angle within an object under test.

[0062] Example 20 comprises the method of Example 19, wherein the acoustic transducer comprises a phased array ultrasound transducer; and wherein the method comprises varying an acoustic refraction angle about the specified nominal acoustic refraction angle by steering the generated acoustic energy established by the phased array ultrasound transducer.

[0063] Each of the non-limiting Examples above can stand on its own or can be combined in various permutations or combinations with one or more of the other Examples or other subject matter described in this document.

[0064] The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to generally as “examples.” Such examples can includeelements in addition to those shown or described. However, the present inventor also contemplates examples in which only those elements shown or described are provided. Moreover, the present inventor also contemplates examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein.

[0065] In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls.

[0066] In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc., are used merely as labels, and are not intended to impose numerical requirements on their objects.

[0067] The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on itsown as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

Claims

WHAT IS CLAIMED IS:

1. An acoustic coupling wedge structure, comprising: a first acoustic prism comprising a first material having a first acoustic propagation velocity that varies according to a first temperature dependence; and a second acoustic prism acoustically coupled to the first acoustic prism, the second acoustic prism comprising a different second material having a different second acoustic propagation velocity that varies according to a second temperature dependence; wherein the second temperature dependence compensates for at least a portion of the first temperature dependence across a specified temperature range.

2. The acoustic coupling wedge structure of claim 1, wherein the first acoustic prism comprises a first surface to which an acoustic transducer can be coupled and a second surface to which the second acoustic prism is acoustically coupled; and wherein the second acoustic prism comprises a first surface to transmit or receive acoustic energy to or from the first acoustic prism through the second surface of the first acoustic prism; and wherein the second acoustic prism comprises a second surface that can be acoustically coupled to an object under test to transmit or receive the acoustic energy using a specified nominal acoustic refraction angle within the object under test.

3. The acoustic coupling wedge structure of claim 2, wherein the specified nominal acoustic refraction angle varies less with respect to temperature due the compensation by the second temperature dependence of at least a portion of the first temperature dependence within a specified temperature range encompassing a specified temperature, as compared to a wedge structure comprising only the first material or only the second material.

4. The acoustic coupling wedge structure of claim 2, wherein the specified nominal acoustic refraction angle is 55 degrees with respect to a normal direction from a surface of the object under test, for a volumetric shear wave acoustic mode.

5. The acoustic coupling wedge structure of claim 2, wherein the specified nominal acoustic refraction angle is within a range of acoustic beam steering angles established by a phased array ultrasound transducer assembly acoustically coupled to the first surface of the first acoustic prism.

6. The acoustic coupling wedge structure of claim 1, wherein at least one of the first material or the second comprises a polymer material.

7. The acoustic coupling wedge structure of claim 6, wherein the polymer material comprises at least one of polystyrene, polyetherimide, an acrylic, or polyetheretherketone.

8. The acoustic coupling wedge structure of claim 6, wherein the first material or the second material comprises polybenzimidazole.

9. The acoustic coupling wedge structure of claim 1, wherein the first material or the second material comprises a carbon allotrope.

10. The acoustic coupling wedge structure of claim 8, wherein the first material or the second material comprises pressed graphite.

11. The acoustic coupling wedge structure of claim 1, wherein the first acoustic prism and the second acoustic prism are mechanically anchored to each other.

12. The acoustic coupling wedge structure of claim 11, wherein a mechanical anchor comprises one or more fasteners.

13. The acoustic coupling wedge structure of claim 10, wherein mechanical anchoring is established by fusing or adhering the first material and second material together.

14. The acoustic coupling wedge structure of claim 1, wherein an interface between the first acoustic prism and the second acoustic prism comprises a liquid.

15. The acoustic coupling wedge structure of claim 1, wherein an interface between the first acoustic prism and the second acoustic prism is compliant to accommodate a difference between coefficients of thermal expansion of the first material versus the second material.

16. The acoustic coupling wedge structure of claim 1, comprising a third material acoustically coupled to at least one of the first acoustic prism or the second acoustic prism, the third material comprising a scattering or absorbing material to suppress acoustic propagation and reflection of acoustic energy off a desired axis.

17. An acoustic inspection probe assembly, comprising: an acoustic coupling wedge structure comprising: a first acoustic prism comprising a first material having a first acoustic propagation velocity that varies according to a first temperature dependence; and a second acoustic prism acoustically coupled to the first acoustic prism, the second acoustic prism comprising a different second material having a different second acoustic propagation velocity that varies according to a second temperature dependence; an acoustic transducer acoustically coupled to the acoustic coupling wedge structure and configured to transmit or receive acoustic energy using a propagation path through a first acoustic prism and a second acoustic prism of the acoustic coupling wedge structure; wherein the second temperature dependence compensates for at least a portion of the first temperature dependence across a specified temperature range.

18. The acoustic inspection probe assembly of claim 17, wherein the acoustic transducer comprises an array of acoustic elements.

19. A method for performing acoustic inspection, the method comprising: generating acoustic energy using an acoustic transducer acoustically coupled to an acoustic coupling wedge structure comprising:a first acoustic prism comprising a first material having a first acoustic propagation velocity that varies according to a first temperature dependence; and a second acoustic prism acoustically coupled to the first acoustic prism, the second acoustic prism comprising a different second material having a different second acoustic propagation velocity that varies according to a second temperature dependence; coupling the generated acoustic energy through the acoustic coupling wedge structure; and using the acoustic coupling wedge, establishing propagation of the generated acoustic energy at a specified nominal acoustic refraction angle within an object under test; wherein the second temperature dependence compensates for at least a portion of the first temperature dependence across a specified temperature range.

20. The method of claim 19, wherein the acoustic transducer comprises a phased array ultrasound transducer; and wherein the method comprises varying an acoustic refraction angle about the specified nominal acoustic refraction angle by steering the generated acoustic energy established by the phased array ultrasound transducer.

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