A fine-beam ultrasonic probe and a design method

Abstract

The application discloses a fine sound beam ultrasonic probe and a design method, and relates to the technical field of nondestructive testing. The probe comprises a probe connector, a probe shell, a cable, a piezoelectric element and a combined acoustic lens. The cable is connected between the probe connector and the piezoelectric element capable of emitting and receiving ultrasonic waves, and is used for conducting high-frequency alternating electric pulses to the piezoelectric element. The combined acoustic lens is installed at the bottom of the piezoelectric element, is used for receiving the ultrasonic beam generated by the piezoelectric element, converging the ultrasonic beam and controlling the ultrasonic propagation direction, so that the ultrasonic beam forms an ultrasonic beam which is focused first and then propagates in parallel. Through implementation of the technical scheme, the technical problems of low detection precision of a conventional ultrasonic probe and low detection efficiency of an existing focused probe can be solved, the defect area or the indication length can be accurately measured, the probe is suitable for detecting internal defects of a thin-walled part and near-surface defects of a medium-thickness part, and the probe has the advantages of high-precision detection and high detection efficiency.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology, and in particular to a thin-beam ultrasonic probe and its design method. Background Technology

[0002] Ultrasonic testing is a common non-destructive testing method that uses ultrasonic waves to inspect internal defects in components. It can quickly, conveniently, non-destructively, and accurately detect, locate, evaluate, and diagnose various internal defects (such as cracks, inclusions, folds, pores, and sand holes) in workpieces. It has a wide range of applications, among which piezoelectric ultrasonic probes are the most commonly used.

[0003] Conventional piezoelectric ultrasonic probes come in a wide variety of types and have diverse applications, but their basic structures are similar. They generally consist of a wafer, a damping block, a protective film, a high-frequency cable connector, and a housing. However, with the development of science and technology, the requirements for the location and quantification of product defects in industrial production are increasing, especially for critical equipment and components with extremely high safety requirements (such as aero-engine parts, nuclear reactor construction, and aerospace equipment). High-sensitivity, high-resolution non-destructive testing is required to ensure that these workpieces operate in a defect-free state (i.e., no macroscopic or microscopic defects exceeding the specified limits are allowed) to ensure the safety of equipment use and prevent catastrophic accidents. However, the detection accuracy of existing conventional ultrasonic probes is insufficient to meet the requirements for the location and quantification of defects in critical components.

[0004] Currently, the most accurate and relatively mature ultrasonic testing method is the (immersion) focused flaw detection method. This method has the function of focusing the sound beam, which not only has the advantage of high-precision defect measurement, but also overcomes the influence of conventional ultrasonic probe detection and the near-field region on the detection results, enabling it to detect internal defects in thin-walled parts and near-surface defects in medium-thickness parts. However, according to the inventors' experience in practice, the above-mentioned focused flaw detection method has a major drawback of very low detection efficiency. It often requires changing the focusing probe with different focuses in stages during the detection process to complete the detection. After each change of focusing probe, it is necessary to readjust the water distance and the scanning starting point, which is cumbersome and results in very low detection efficiency. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a fine-beam ultrasonic probe that effectively solves both the technical problem of low detection accuracy of conventional ultrasonic probes and the technical problem of low detection efficiency of existing focused probes. It can accurately measure the defect area or indication length and is suitable for detecting internal defects in thin-walled parts and near-surface defects in medium-thickness parts, offering the advantages of high-precision detection and high detection efficiency.

[0006] The technical solution adopted in this invention is as follows:

[0007] A thin-beam ultrasonic probe includes a probe connector, a probe housing connected to the probe connector, a cable located inside the probe housing, a piezoelectric element capable of emitting and receiving ultrasonic waves, and a combined acoustic lens; wherein the cable is connected between the probe connector and the piezoelectric element capable of emitting and receiving ultrasonic waves, and is used to transmit high-frequency alternating electrical pulses to the piezoelectric element.

[0008] The combined acoustic lens is installed at the bottom of the piezoelectric element to receive and converge the ultrasonic beam generated by the piezoelectric element and control the direction of ultrasonic propagation so that the ultrasonic beam is focused and then propagates in parallel.

[0009] This technical solution improves upon the limitation of focusing probes, which are only suitable for detecting defects within a specific depth range (focal column region). For medium-thickness parts with high inspection requirements, the ultrasonic waves generated by the combination of acoustic lenses and piezoelectric elements in this invention enter the workpiece as a thin, straight sound beam, rather than a focused sound beam concentrated at a specific depth point or line. Therefore, when inspecting workpieces, it is not necessary to change probes with different focal lengths for different thickness ranges of the workpiece. Compared with conventional ultrasonic probes, it has higher detection accuracy, and compared with focusing probes, it has higher working efficiency. This contact ultrasonic probe for flaw detection can accurately measure the defect area or indication length, and is suitable for detecting internal defects in thin-walled parts and near-surface defects in medium-thickness parts, which can significantly improve inspection efficiency.

[0010] In a preferred embodiment of the present invention, the piezoelectric element is a piezoelectric crystal with a piezoelectric effect. The piezoelectric element in this technical solution is both a receiving and sensing element for ultrasonic waves and an emitting element for ultrasonic waves. The structural design of the combined acoustic lens preferably uses a larger piezoelectric crystal to obtain stronger ultrasonic radiation energy and a smaller half-diffusion angle, better beam directivity, and stronger long-distance detection capability, thereby obtaining a concentrated and straight ultrasonic beam.

[0011] In a preferred embodiment of the present invention, the ultrasonic probe further includes an absorption block, which fills the inner side of the probe housing and is located on the back and side of the piezoelectric element and the combined acoustic lens. In this technical solution, the absorption block is also called a damping block. One function of the absorption block is to make the piezoelectric element stop vibrating as soon as possible after it starts to vibrate, thereby reducing the pulse width and improving the resolution. Another function of the absorption block is to absorb the noise on the back of the piezoelectric crystal or the combined acoustic lens, thereby improving the signal-to-noise ratio. As a preferred embodiment of the present technical solution, the material selected for the absorption block is preferably epoxy resin with good sound absorption performance and tungsten powder. The ratio of the epoxy resin and tungsten powder should be made as close as possible to the acoustic impedance of the piezoelectric crystal. After heating, the liquid is poured into the probe housing and solidified.

[0012] In a preferred embodiment of the present invention, the piezoelectric element is a circular block structure or a non-planar structure with one side being a plane and the other side being a concave spherical surface.

[0013] In a preferred embodiment of the present invention, when the piezoelectric element is a circular block structure, the combined acoustic lens includes an upper acoustic lens, a central acoustic lens, and a lower acoustic lens bonded together in sequence. The side of the upper acoustic lens connected to the piezoelectric element is a plane, and the side of the upper acoustic lens connected to the central acoustic lens is a concave spherical surface. The side of the lower acoustic lens connected to the central acoustic lens is a concave spherical surface, and the other side of the lower acoustic lens is a plane. The side of the central acoustic lens connected to the upper acoustic lens has a first convex spherical surface adapted to the concave spherical surface of the upper acoustic lens, and the side of the central acoustic lens connected to the lower acoustic lens has a second convex spherical surface adapted to the concave spherical surface of the lower acoustic lens. The materials selected for each adjacent acoustic lens in this scheme should meet the impedance matching requirements, and materials with similar acoustic impedances should be selected as much as possible to reduce energy transmission loss. At the same time, as a preferred option for this technical solution, the piezoelectric element and the combined acoustic lens, as well as the upper acoustic lens, the central acoustic lens and the lower acoustic lens, are tightly bonded together, and each bonding surface must be thin, tight and seamless to ensure that the sound beam propagates in heterogeneous interfaces in accordance with Snell's law. Therefore, the piezoelectric element in this technical solution has a circular block structure, which emits an approximately plane wave when excited by high-frequency alternating electrical pulses. The ultrasonic sound beam first passes through the upper acoustic lens with a spherical surface used for focusing, then enters the central acoustic lens for focusing, and then passes through the lower acoustic lens to form a parallel, thin, straight sound beam.

[0014] In another preferred embodiment of the present invention, when the piezoelectric element is an anisoplanar structure with one side being a plane and the other side being a concave spherical surface, the combined acoustic lens includes a central acoustic lens and a lower acoustic lens bonded together, wherein the side of the lower acoustic lens connected to the central acoustic lens is a concave spherical surface and the other side of the lower acoustic lens is a plane; the side of the central acoustic lens connected to the piezoelectric element has a first convex spherical surface adapted to the concave spherical surface of the piezoelectric element and is connected to the piezoelectric element through the first convex spherical surface, and the side of the central acoustic lens connected to the lower acoustic lens has A second convex spherical surface, adapted to the concave spherical surface of the lower acoustic lens, is connected to the lower acoustic lens through the second convex spherical surface. This technical solution, combined with the structural change of the piezoelectric element, eliminates the upper acoustic lens in the combined acoustic lens. The side of the piezoelectric element bonded to the central acoustic lens is designed as a concave spherical surface, so that the high-frequency electrical pulse excites an approximately spherical wave. The spherical wave directly enters the central acoustic lens, is focused, and then passes through the lower acoustic lens to form a parallel, thin, straight sound beam. This technical solution works on the same principle as the above embodiment, except that the upper part of the central acoustic lens is replaced with a part that is bonded and matched to the piezoelectric chip.

[0015] In a preferred embodiment of the present invention, the concave spherical radius R1 of the upper acoustic lens is greater than the concave spherical radius R2 of the lower acoustic lens, and R1 < f1 and R2 < f2, L1 is approximately 1 / 3L. 总 Where L1 is the distance between the center of the spherical surface of the central acoustic lens and the corresponding chord of the arc of the cross-section of the spherical surface of the central acoustic lens, L 总 The height designed for the probe, and the overall height L of the ultrasonic probe. 总 The focal length is 50-100mm; f1 is the focal length of the upper spherical focusing surface of the central acoustic lens, and f2 is the focal length of the lower spherical focusing surface of the central acoustic lens. To reduce acoustic energy loss, the materials of each adjacent acoustic lens should meet the impedance matching requirements, and materials with similar acoustic impedance should be selected. The size of L1 is determined to facilitate the installation of the piezoelectric crystal of the designed size, thereby obtaining stronger ultrasonic radiation energy and a smaller half-diffusion angle.

[0016] In a preferred embodiment of the present invention, the overall height of the thin-beam ultrasonic probe is between 50-100mm, and a support frame structure is provided inside the probe housing to fix the piezoelectric element and the combined acoustic lens connection position in the middle of the inner side of the entire probe housing. The probe housing wraps or partially wraps the other components. Preferably, the probe housing is made of metal, which can effectively shield the external wireless signal interference of the probe.

[0017] In a preferred embodiment of the present invention, the probe connector includes a connector jacket, an insulating sleeve, and a conductive contact seat. The connector jacket is used to connect with the probe wire connector. The insulating sleeve is disposed between the connector jacket and the conductive contact seat and is separated by the insulating sleeve. The connector jacket and the insulating sleeve, as well as the insulating sleeve and the conductive contact seat, are bonded together. The lower part of the conductive contact seat is welded to the upper part of the cable, and the lower part of the cable is welded to the piezoelectric element. The lower part of the piezoelectric element is in close contact with the combined acoustic lens. The probe connector with this structural design can effectively prevent the alternating electrical signal transmitted by the instrument to the piezoelectric crystal from being affected by external interference.

[0018] On the other hand, the present invention also provides a design method for a thin-beam ultrasonic probe, which includes a design method for a combined acoustic lens, wherein the combined acoustic lens includes an upper acoustic lens, a central acoustic lens, and a lower acoustic lens bonded together in sequence, and the design method for the central acoustic lens in the combined acoustic lens includes the following steps:

[0019] Predetermine the desired narrow acoustic beam diameter D2 and the diameter D1 of the piezoelectric element to be used, as well as the probe design height dimension L. 总 Obtain the distance L1 between the center of the spherical surface of the central acoustic lens and the corresponding chord of the arc of the cross-section of the spherical surface of the central acoustic lens, where L1 is approximately 1 / 3L. 总 ;

[0020] Based on the trigonometric relationship and the values ​​of L1 and D1, the radius R1 of the upper spherical surface of the central acoustic lens is calculated, and the incident angle α1 of the ultrasonic wave at the edge of the upper spherical surface is determined.

[0021] Under the premise that the materials of the combined acoustic lenses meet the impedance matching requirements, the materials of the upper acoustic lens and the center acoustic lens are determined and the longitudinal wave velocity c1 and c2 in the upper acoustic lens and the center acoustic lens are obtained, where c1 > c2. The refraction angle β1 of the ultrasonic wave passing through the edge of the spherical surface of the center acoustic lens is calculated according to Snell's law.

[0022] Calculate the focal length f1 when the spherical surface of the central acoustic lens is focused;

[0023] The material of the lower acoustic lens is selected based on the conditions of impedance matching and parallel sound velocity, and the longitudinal wave velocity c3 in the lower acoustic lens is obtained, where c3 > c2.

[0024] Based on existing geometric relationships and Snell's law, the incident angle α2 and refraction angle β2 of the ultrasonic wave at the spherical interface under the central acoustic lens are calculated.

[0025] Calculate the lower spherical radius R2 based on D2 and β2;

[0026] Calculate the focal length f2 of the spherical surface under the central acoustic lens;

[0027] The height L of the central acoustic lens is calculated based on f1 and f2, thus completing the design of the central acoustic lens.

[0028] The present invention has at least the following beneficial effects:

[0029] 1. The thin-beam ultrasonic probe of the present invention has a simple structural design and can obtain a thin, straight ultrasonic beam that is close to non-divergent and energy-concentrated. Compared with existing focusing probes that generally focus the ultrasonic beam on a point or line at a certain flaw detection depth, the thin-beam ultrasonic probe of the present invention has higher working efficiency for ultrasonic flaw detection, especially for full-thickness ultrasonic testing of thick and large parts with high detection accuracy requirements.

[0030] 2. Compared with conventional ultrasonic straight probes, the fine-beam ultrasonic probe of this invention has higher accuracy in defect localization and quantification. It can accurately measure the defect area or indicate the length, and is also suitable for detecting internal defects in thin-walled parts and near-surface defects in medium-thickness parts. Therefore, it has the advantages of high-precision detection and high detection efficiency, and has good application prospects and promotion value.

[0031] 3. The structural design of the thin-beam ultrasonic probe combined with the combined acoustic lens of this invention allows for the use of a larger piezoelectric crystal compared to existing focusing probes. The size of the piezoelectric crystal in existing focusing probes should not be too large, otherwise the focal column will become shorter, further reducing the detection efficiency. This invention overcomes the above defects and ultimately obtains a thin, straight ultrasonic beam that is focused first and then emitted in parallel. This results in stronger ultrasonic radiation energy and a smaller half-diffusion angle, better beam directivity, and stronger long-distance detection capability, thereby achieving high-precision and high-efficiency workpiece defect detection.

[0032] 4. In the thin-beam ultrasonic probe of this invention, the ultrasonic waves emitted by the piezoelectric element first pass through the combined acoustic lens in the probe before entering the workpiece being inspected. By rationally selecting the size and material of the piezoelectric element and the combined acoustic lens, the blind zone and near-field zone of the ultrasonic probe can be retained inside the probe as much as possible, thereby eliminating the ultrasonic flaw detection blind zone and near-field zone inside the workpiece. This enables the detection of internal defects in thin-walled parts and near-surface defects in medium and thick parts. Compared with existing high-precision ultrasonic testing, it can achieve low-cost, high-precision, and high-efficiency ultrasonic testing, and has a higher cost-performance ratio. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram of the structure of the thin-beam ultrasonic probe in Embodiment 1 of the present invention is shown;

[0035] Figure 2 A schematic diagram of the appearance of the thin-beam ultrasonic probe in an embodiment of the present invention is shown;

[0036] Figure 3 An embodiment of the present invention is shown. Figure 1 Sectional view of AA;

[0037] Figure 4 This shows a schematic diagram of the appearance of the thin-beam ultrasonic probe from another perspective in an embodiment of the present invention;

[0038] Figure 5 A schematic diagram of the propagation path of the internal ultrasonic beam in Embodiment 1 of the present invention is shown;

[0039] Figure 6 An embodiment of the present invention is shown. Figure 5 Working principle diagram of the application;

[0040] Figure 7A schematic diagram illustrating the design principle of the combined acoustic lens according to an embodiment of the present invention is shown;

[0041] Figure 8 A schematic diagram of the structure of the thin-beam ultrasonic probe in Embodiment 2 of the present invention is shown;

[0042] Figure 9 A schematic diagram of the propagation path of the internal ultrasonic beam in Embodiment 2 of the present invention is shown.

[0043] In the figure: 10-Probe connector; 101-Connector jacket; 102-Insulating sleeve; 103-Conductive contact seat; 2-Cable; 3-Piezoelectric crystal; 401-Upper acoustic lens; 402-Center acoustic lens; 403-Lower acoustic lens; 50-Probe housing; 501-Probe top cover; 502-Probe outer shell; 503-Probe bottom cover; 6-Absorbing block; 7-Ultrasonic beam propagation path in Example 1; 8-Ultrasonic beam propagation path in Example 2. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0046] Example 1

[0047] Please refer to Figures 1 to 7 As shown, this embodiment provides a thin-beam ultrasonic probe, which includes a probe connector 10, a probe housing 50 connected to the probe connector 10, a cable 2 located inside the probe housing 50, a piezoelectric element capable of emitting and receiving ultrasonic waves, and a combined acoustic lens; wherein the cable 2 is connected between the probe connector 10 and the piezoelectric element capable of emitting and receiving ultrasonic waves, and is used to transmit high-frequency alternating electrical pulses to the piezoelectric element; the combined acoustic lens is installed at the bottom of the piezoelectric element, and is used to receive the ultrasonic beam generated by the piezoelectric element, converge it, and control the direction of ultrasonic wave propagation, so that the ultrasonic beam forms an ultrasonic beam that is first focused and then propagates in parallel.

[0048] Specifically, to facilitate the connection between the probe and the probe cable connector, the probe connector 10 provided in this embodiment includes a connector sleeve 101, an insulating sleeve 102, and a conductive contact seat 103. The connector sleeve 101 is used to connect with the probe cable connector. The insulating sleeve 102 is located between the connector sleeve 101 and the conductive contact seat 103 and isolates the connector sleeve 101 from the conductive contact seat 103. The connector sleeve 101 and the insulating sleeve 102, as well as the insulating sleeve 102 and the conductive contact seat 103, are bonded together. The lower part of the conductive contact seat 103 is welded to the upper part of the cable 2, and the lower part of the cable 2 is welded to the piezoelectric element. The lower part of the piezoelectric element is in close contact with the combined acoustic lens. The probe connector 10 with this structure design can effectively prevent the alternating electrical signal transmitted by the instrument to the piezoelectric crystal 3 from being affected by external interference.

[0049] In this embodiment, the overall height of the thin-beam ultrasonic probe is between 50-100mm. The probe housing 50 includes a probe top cover 501, a probe outer shell 502, and a probe bottom cover 503, which are fixedly connected. A support frame structure is provided inside the probe housing 50 to fix the piezoelectric element and the combined acoustic lens connection position in the middle of the inner side of the entire probe housing 50. The probe housing 50 encloses or partially encloses other components. As a preferred embodiment, the probe top cover 501, probe outer shell 502, and probe bottom cover 503 are all made of metal, which can effectively shield the probe from external wireless signal interference. Of course, the specific materials are not limited to this, and other materials that can effectively shield the probe from external wireless signal interference in the prior art can also be used, all of which should be included within the protection scope of this invention.

[0050] In the illustrated embodiment, the piezoelectric element can be a piezoelectric crystal 3 with a piezoelectric effect. The piezoelectric element provided in this embodiment takes the piezoelectric crystal 3 as an example. The piezoelectric crystal 3 is both a receiving and sensing element for ultrasonic waves and an element for emitting ultrasonic waves. The structural design of the combined acoustic lens preferably uses a larger size piezoelectric crystal 3, thereby obtaining stronger ultrasonic radiation energy and a smaller half-diffusion angle, better beam directivity, stronger long-distance detection capability, and thus obtaining a concentrated, thin, and straight ultrasonic beam.

[0051] Specifically, the piezoelectric wafer 3 is a circular block structure or a non-planar structure with one side being a plane and the other side being a concave spherical surface. In this embodiment, the piezoelectric wafer 3 is a circular block structure, which has a mutually parallel upper plane and a lower plane. Combined with the circular block structure design of the piezoelectric wafer 3, in the illustrated embodiment, the combined acoustic lens includes an upper acoustic lens 401, a central acoustic lens 402, and a lower acoustic lens 403 that are bonded together in sequence. The side of the upper acoustic lens 401 that is connected to the piezoelectric wafer 3 is a plane, and the side of the upper acoustic lens 401 that is connected to the central acoustic lens 402 is a concave spherical surface. The side of the lower acoustic lens 403 that is connected to the central acoustic lens 402 is a concave spherical surface, and the other side of the lower acoustic lens 403 is a plane. The side of the central acoustic lens 402 that is connected to the upper acoustic lens 401 has a first convex sphere that is adapted to the concave spherical surface of the upper acoustic lens 401. The piezoelectric crystal 3 has a second convex spherical surface that matches the concave spherical surface of the lower acoustic lens 403 on the side where the central acoustic lens 402 is connected to the lower acoustic lens 403. In this embodiment, the material selection of each adjacent acoustic lens should meet the impedance matching requirements, and materials with similar acoustic impedance should be selected as much as possible to reduce energy transmission loss. In this embodiment, the piezoelectric crystal 3 and the combined acoustic lens, as well as the upper acoustic lens 401, the central acoustic lens 402 and the lower acoustic lens 403 are bonded together tightly, and each bonding surface must be thin, tight and seamless to ensure that the sound beam propagates in the heterogeneous interface in accordance with Snell's law. At the same time, in this embodiment, the piezoelectric crystal 3 has a circular block structure, which emits an approximately plane wave after being excited by high-frequency alternating electric pulses. The ultrasonic sound beam first passes through the upper acoustic lens with a spherical surface used for focusing, then enters the central acoustic lens for focusing, and then passes through the lower acoustic lens to form a parallel thin and straight sound beam.

[0052] When a piezoelectric crystal is excited by a high-frequency electrical pulse, it will exhibit reverse piezoelectric efficiency, resulting in alternating contraction and expansion, which in turn causes vibration. As a result, the emitted ultrasonic waves are similar to plane waves, and plane waves approximate spherical waves at a sufficiently far distance from the sound source.

[0053] In the illustrated embodiment, the ultrasonic probe further includes an absorption block 6. The absorption block 6 fills the inside of the probe housing 50 and is located on the back and side of the piezoelectric element and the combined acoustic lens. In this embodiment, the absorption block 6 is also called a damping block. One function of the absorption block 6 is to stop the piezoelectric element as soon as possible after it starts to vibrate, thereby reducing the pulse width and improving the resolution. Another function of the absorption block 6 is to absorb the noise from the back of the piezoelectric crystal 3 or the combined acoustic lens, thereby improving the signal-to-noise ratio. The material selected for the absorption block 6 is preferably epoxy resin with good sound absorption performance and tungsten powder. The ratio of the epoxy resin to tungsten powder should be made as close as possible to the acoustic impedance of the piezoelectric crystal 3. After heating, the liquid is poured into the probe housing 50 and solidified. It is then fixed to the inside of the probe by the frame structure inside the probe housing 50.

[0054] Combined Figure 5 and Figure 6As shown, according to the structural design of the thin-beam ultrasonic probe in this embodiment, the thin, straight ultrasonic beam obtained in this embodiment is based on the principle of plane wave refraction at curved interfaces:

[0055] like Figure 6 As shown in (a), when the parallel sound beam emitted by the piezoelectric crystal 3 enters the medium 2# from the concave spherical surface of medium 1#, if the ultrasonic speed c1 (the speed of ultrasonic wave propagation in medium 1#) is greater than c2 (the speed of ultrasonic wave propagation in medium 2#), the sound beam will converge; while if... Figure 6 As shown in (b), when the spherical wave emanating from the focal point enters medium 3# through the convex spherical surface of medium 2#, if the ultrasonic speed c2 (the propagation speed of ultrasonic waves in medium 2#) is less than c3 (the propagation speed of ultrasonic waves entering medium 3#) and an appropriate surface radius R, focal length f, and incident angle θ are selected, the ultrasonic beam can be transformed into a parallel beam again. If the selected sound-transmitting medium changes, other parameters will also change accordingly. In this embodiment, the propagation of the sound beam at the heterogeneous interface follows Snell's law. Therefore, in this embodiment, the piezoelectric crystal 3 is a circular block structure. In embodiment one, the ultrasonic beam propagation path 7 is an approximately plane wave excited by a high-frequency alternating electric pulse. The ultrasonic beam first passes through the upper acoustic lens 401 with a spherical surface for focusing, then enters the central acoustic lens 402 for focusing, and then passes through the lower acoustic lens 403 to form a parallel, thin, straight beam.

[0056] On the other hand, according to the thin-beam ultrasonic probe provided in the embodiment of the present invention, this embodiment also provides a design method for the above-mentioned thin-beam ultrasonic probe, combined with Figures 1 to 7 As shown, the design method includes a method for designing a combined acoustic lens, wherein the combined acoustic lens includes an upper acoustic lens, a central acoustic lens, and a lower acoustic lens that are bonded together in sequence. The design method for the central acoustic lens in the combined acoustic lens includes the following steps:

[0057] Predetermine the desired narrow acoustic beam diameter D2 and the diameter D1 of the piezoelectric element to be used, as well as the probe design height dimension L. 总 Obtain the distance L1 between the center of the spherical surface of the central acoustic lens and the corresponding chord of the arc of the cross-section of the spherical surface of the central acoustic lens, where L1 is approximately 1 / 3L. 总 ;

[0058] Based on the trigonometric relationship and the values ​​of L1 and D1, the radius R1 of the spherical surface on the central acoustic lens is calculated. And determine the incident angle α1 of the ultrasound at the edge of the upper spherical surface;

[0059] Assuming the materials of the combined acoustic lenses meet the impedance matching requirements, the materials of the upper and central acoustic lenses are determined, and the sound velocities c1 and c2 in the upper and central acoustic lenses are obtained, where c1 > c2. Based on Snell's law, the refraction angle β1 of the ultrasonic wave passing through the edge of the spherical surface of the central acoustic lens is calculated. It is worth noting that, based on the principle of plane wave refraction on curved surfaces, to satisfy the point focusing condition, α1 > β1 is required. In addition, to reduce the attenuation of acoustic energy when ultrasonic waves propagate at the interface, the two adjacent acoustic lenses should have similar acoustic impedances. Based on this, the materials of the two adjacent acoustic lenses that meet the conditions are selected.

[0060] Calculate the focal length f1 when the spherical surface of the central acoustic lens is focused, which is the length of line segment AF in the figure:

[0061] Based on the conditions of impedance matching and parallel sound velocity, the material of the lower acoustic lens is selected, and the sound velocity c3 in the lower acoustic lens is obtained. Based on the principle of plane wave refraction on curved surfaces, to satisfy the condition of parallel ultrasonic wave emission, β2 > α2, therefore c3 > c2. In other words, the sound velocity in the lower acoustic lens should be greater than the sound velocity in the central acoustic lens. In addition, to reduce the attenuation of sound energy when ultrasonic waves propagate at the interface, the two adjacent acoustic lenses should have similar acoustic impedances, and the material of the lower acoustic lens that meets this condition should be selected accordingly.

[0062] Based on existing geometric relationships and Snell's law, the incident angle α2 and refraction angle β2 of the ultrasonic wave at the spherical interface under the central acoustic lens are calculated, i.e., ∠GO1B=α1=β1+∠GFB, ∠GFB=∠NFD, β2=∠NO2D in the figure. The system of equations can then be derived. Then the values ​​of α2 and β2 are obtained;

[0063] Calculate the lower spherical radius R2 based on D2 and β2.

[0064] Calculate the focal length f2 of the spherical surface under the central acoustic lens, which is the length of line segment FE in the diagram:

[0065] The height L of the central acoustic lens is calculated based on f1 and f2, which is shown in the diagram:

[0066]

[0067] Thus, the design of the central acoustic lens is completed. The combined acoustic lens formed by the central acoustic lens, the upper acoustic lens, and the lower acoustic lens can obtain a thin, straight ultrasonic beam that is first focused and then emitted in parallel, thereby achieving high-precision and high-efficiency workpiece defect detection.

[0068] The concave spherical radius R1 of the upper acoustic lens is larger than the concave spherical radius R2 of the lower acoustic lens, and R1 < f1 and R2 < f2, with L1 approximately 1 / 3L. 总 Where L1 is the distance between the center of the spherical surface of the central acoustic lens and the corresponding chord of the arc of the cross-section of the spherical surface of the central acoustic lens, L 总 The height of the probe is defined as follows: f1 is the focal length of the upper spherical focusing surface of the central acoustic lens, and f2 is the focal length of the lower spherical focusing surface of the central acoustic lens. To reduce acoustic energy loss, the materials of adjacent acoustic lenses should meet the impedance matching requirements, and materials with similar acoustic impedances should be selected. Among them, the materials of adjacent acoustic lenses can be plexiglass and epoxy resin, but are not limited to these. Other materials that meet the impedance matching requirements in the prior art can also be selected, all of which are within the protection scope of this invention.

[0069] Example 2

[0070] Example 2 is basically the same as Example 1, except that: [The following is a separate, unrelated sentence:] ...combination Figure 8 and Figure 9 As shown, this embodiment provides a thin-beam ultrasonic probe. In this embodiment, the piezoelectric wafer 3 has an anisoplanar structure with one side being a plane and the other side being a concave spherical surface. Based on the piezoelectric wafer 3 structure design, the combined acoustic lens in this embodiment includes a central acoustic lens 402 and a lower acoustic lens 403 bonded together. The side of the lower acoustic lens 403 connected to the central acoustic lens 402 is a concave spherical surface, and the other side of the lower acoustic lens 403 is a plane. The side of the central acoustic lens 402 connected to the piezoelectric wafer 3 has a first convex spherical surface adapted to the concave spherical surface of the piezoelectric wafer 3, and is connected to the piezoelectric wafer 3 through this first convex spherical surface. The side of the central acoustic lens 402 connected to the lower acoustic lens 403 has a surface that matches the concave spherical surface of the lower acoustic lens 403. A second convex spherical surface that matches the concave spherical surface is connected to the lower acoustic lens 403 through the second convex spherical surface. In the illustrated embodiment, the upper acoustic lens 401 in the combined acoustic lens is eliminated by combining the structural changes of the piezoelectric chip 3. The side of the piezoelectric chip 3 that is bonded to the central acoustic lens 402 is designed as a concave spherical surface, which can obtain the ultrasonic beam propagation path 8 in embodiment 2. This allows the high-frequency electrical pulse to excite an approximately spherical wave. The spherical wave directly enters the central acoustic lens 402 and is focused before passing through the lower acoustic lens 403 to form a parallel, thin, straight sound beam. This embodiment has the same working principle as the one described in embodiment 1. The difference is that the upper part of the central acoustic lens 402 is replaced with a part that is bonded and matched to the piezoelectric chip 3 by combining the structural changes of the piezoelectric chip 3.

[0071] The design method of the combined acoustic lens in this embodiment is basically the same as that in Embodiment 1. The difference is that the combined acoustic lens provided in this embodiment includes a central acoustic lens 402 and a lower acoustic lens 403 bonded together. The piezoelectric wafer 3 is a non-planar structure with one side being a plane and the other side being a concave spherical surface. The piezoelectric wafer 3 with the non-planar structure replaces the upper acoustic lens design in Embodiment 1. Then, under the premise that the material of the combined acoustic lens meets the impedance matching requirements, the longitudinal wave velocity in the piezoelectric wafer 3 is determined to be c1. That is to say, the sound velocity in the piezoelectric wafer should be greater than the sound velocity in the central acoustic lens and meet the point focusing condition. This embodiment simplifies the structural design of the combined acoustic lens, but the design principle of this embodiment is the same as that of Embodiment 1, so it will not be described in detail here.

[0072] As described above, both the thin-beam ultrasonic probes in Embodiments 1 and 2 can obtain a thin, straight ultrasonic beam with concentrated energy that is close to non-divergent. Furthermore, the combined acoustic lens design of this probe allows for the use of a larger piezoelectric crystal 3 compared to existing focusing probes, resulting in stronger ultrasonic radiation energy and a smaller half-diffusion angle, better beam directivity, and enhanced long-distance detection capability. It is worth noting that if the diameter of the piezoelectric crystal 3 used in the focusing probe is too large, the result is a smaller focal length or shorter focal column, further reducing detection efficiency and hindering flaw detection. Ordinary straight probes cannot obtain a thin, straight beam by reducing the size of the piezoelectric crystal 3, because a smaller crystal size leads to an increased half-diffusion angle, energy disconcentration, and decreased defect measurement accuracy. Therefore, the combined acoustic lens design of this invention, combined with the piezoelectric crystal 3, can obtain stronger acoustic radiation energy, enhance long-distance detection capability, and achieve higher defect location accuracy.

[0073] In summary, the thin-beam ultrasonic probe of this invention has a simple structural design and can obtain a nearly non-divergent and energy-concentrated thin straight ultrasonic beam. Compared with existing focusing probes that generally focus the ultrasonic beam on a point or line at a certain inspection depth, the thin-beam ultrasonic probe of this invention has higher work efficiency for ultrasonic flaw detection, especially for full-thickness ultrasonic inspection of thick and large parts with high inspection accuracy requirements. At the same time, compared with conventional straight ultrasonic probes, it has higher defect localization and quantitative accuracy, which can accurately measure the defect area or indication length, and is suitable for detecting internal defects in thin-walled parts and near-surface defects in medium-thickness parts, thus achieving high-precision detection and detection... Advantages of high efficiency: In this invention, the ultrasonic waves emitted by the piezoelectric element in the fine-beam ultrasonic probe first pass through the combined acoustic lens in the probe before entering the workpiece under inspection. By rationally selecting the size and material of the piezoelectric element and the combined acoustic lens, the blind zone and near-field zone of the ultrasonic probe can be retained inside the probe as much as possible, thereby eliminating the ultrasonic flaw detection blind zone and near-field zone in the workpiece. This enables the detection of internal defects in thin-walled parts and near-surface defects in medium and thick parts. Compared with existing high-precision ultrasonic testing, it can achieve low-cost, high-precision, and high-efficiency ultrasonic testing, with a higher cost-performance ratio. It has good application prospects and promotional value in the field of non-destructive testing technology and is suitable for widespread application.

[0074] The specification and drawings of this invention are intended to be illustrative rather than restrictive. Based on this invention, those skilled in the art can make substitutions and modifications to some of the technical features without creative effort, and all such modifications are within the scope of protection of this invention.

Claims

1. A method of designing a fine-beam ultrasonic probe, characterized by: The design method comprises a design method of a combined acoustic lens, wherein the combined acoustic lens comprises an upper acoustic lens, a central acoustic lens and a lower acoustic lens which are sequentially bonded, and the combined acoustic lens is installed at the bottom of the piezoelectric element; the design method of the central acoustic lens in the combined acoustic lens comprises the following steps: predetermined to be obtained D 2 and the piezoelectric element diameter used D 1 and the design height dimension of the probe obtaining the distance between the corresponding chord of the arc of the cross section circle of the spherical surface on the center acoustic lens and the spherical center of the spherical surface on the center acoustic lens L 1 wherein L 1 is about 1 / 3 ; According to the trigonometric relations and L 1 , D 1 the values of the spherical radius R 1 on the central acoustic lens and the angle of incidence of the ultrasound at the edge of the upper spherical surface are calculated. Under the premise that the material of the combined acoustic lens meets the impedance matching requirement, the materials of the upper acoustic lens and the central acoustic lens are determined, and the longitudinal wave speeds in the upper acoustic lens and the central acoustic lens are obtained c 1 and c 2 wherein and the refraction angle of the ultrasonic wave passing through the upper spherical edge of the central acoustic lens is calculated according to Snell's law ; Focal length when focusing on a spherical surface of a computational acoustic lens ; The material of the lower acoustic lens is selected according to the conditions of impedance matching and parallel emission of the sound beam, and the longitudinal wave speed in the lower acoustic lens is obtained c 3 wherein ; According to the existing geometric relationship and Snell's law, the incidence angle of the ultrasonic wave on the spherical surface interface under the central acoustic lens is calculated and the refraction angle ; According to D 2 and Calculate the lower spherical radius R 2 ; Computing the focal length of a spherical lens under a sound-transmitting lens ; According to and calculating the center acoustic lens height L i.e. completing the center acoustic lens design.

2. The method of designing a fine acoustic beam ultrasonic probe according to claim 1, characterized in that: The ultrasonic probe comprises a probe connector, a probe shell connected with the probe connector, and a cable, a piezoelectric element capable of emitting and receiving ultrasonic waves and a combined acoustic lens located in the probe shell; wherein the cable is connected between the probe connector and the piezoelectric element capable of emitting and receiving ultrasonic waves, and is used for conducting high-frequency alternating electric pulses to the piezoelectric element; The combined acoustic lens is installed at the bottom of the piezoelectric element, and is used for receiving and converging the ultrasonic beam generated by the piezoelectric element and controlling the ultrasonic propagation direction, so as to form an ultrasonic beam which firstly focuses and then propagates in parallel.

3. The method of designing a fine acoustic beam ultrasonic probe according to claim 2, characterized in that: The piezoelectric element is a piezoelectric wafer with a piezoelectric effect.

4. The method of designing a fine acoustic beam ultrasonic probe according to claim 2, characterized in that: The ultrasonic probe further comprises an absorbing block which is filled in the inside of the probe shell and located at the back and side of the piezoelectric element and the combined acoustic lens.

5. The method of designing a fine acoustic beam ultrasonic probe according to claim 2, characterized in that: The piezoelectric element is a circular block structure or an uneven structure with a flat side and a concave spherical side.

6. The method of designing a fine acoustic beam ultrasonic probe according to claim 5, characterized in that: When the piezoelectric element is a circular block structure, the combined acoustic lens comprises an upper acoustic lens, a central acoustic lens and a lower acoustic lens which are sequentially bonded, wherein the side of the upper acoustic lens connected with the piezoelectric element is flat, the side of the upper acoustic lens connected with the central acoustic lens is a concave spherical surface; the side of the lower acoustic lens connected with the central acoustic lens is a concave spherical surface and the other side of the lower acoustic lens is flat; the side of the central acoustic lens connected with the upper acoustic lens has a first convex spherical surface matched with the concave spherical surface of the upper acoustic lens, and the side of the central acoustic lens connected with the lower acoustic lens has a second convex spherical surface matched with the concave spherical surface of the lower acoustic lens.

7. The method of designing a fine acoustic beam ultrasonic probe according to claim 5, characterized in that: When the piezoelectric element is an uneven structure with a flat side and a concave spherical side, the combined acoustic lens comprises a central acoustic lens and a lower acoustic lens which are bonded together, wherein the side of the lower acoustic lens connected with the central acoustic lens is a concave spherical surface and the other side of the lower acoustic lens is flat; the side of the central acoustic lens connected with the piezoelectric element has a first convex spherical surface matched with the concave spherical surface of the piezoelectric element and is connected with the piezoelectric element through the first convex spherical surface, and the side of the central acoustic lens connected with the lower acoustic lens has a second convex spherical surface matched with the concave spherical surface of the lower acoustic lens and is connected with the lower acoustic lens through the second convex spherical surface.

8. The method of designing a fine acoustic beam ultrasonic probe according to claim 5 or 6, characterized in that: The concave spherical radius of the upper acoustic lens R 1 The concave spherical radius of the lower acoustic lens R 2 , and and , L 1 about 1 / 3 ; wherein L 1 is the distance between the center of the upper spherical surface of the central acoustic lens and the corresponding chord of the circular arc of the cross section of the upper spherical surface of the central acoustic lens, is the design height of the probe; is the focusing focal length of the upper spherical surface of the central acoustic lens, is the focusing focal length of the lower spherical surface of the central acoustic lens.

9. The method of designing a fine acoustic beam ultrasonic probe according to claim 4, characterized in that: A support frame structure is arranged inside the probe shell, so as to fix the connection position of the piezoelectric element and the combined acoustic lens in the middle of the inside of the whole probe shell.

10. The method of designing a fine acoustic beam ultrasonic probe according to claim 2, characterized in that: The probe connector comprises a connector sleeve, an insulating sleeve and a conductive contact seat, the connector sleeve is used for connecting with the probe wire connector, the insulating sleeve is arranged between the connector sleeve and the conductive contact seat and is isolated by the insulating sleeve, and the connector sleeve and the insulating sleeve and the insulating sleeve and the conductive contact seat are connected by cementing.

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