An integrated coupled piezoelectric ultrasonic transducer

Abstract

This invention relates to the field of transducer technology, specifically to an integrated coupled piezoelectric ultrasonic transducer, comprising an aluminum alloy cylindrical shell; silver-impregnated electrodes on both the upper and lower surfaces of the sensing unit, which simultaneously excite longitudinal and transverse waves under high-voltage pulse excitation; a backing damping block for absorbing reverse sound waves and improving signal clarity; a stainless steel bottom cover fixed to the open end of the shell and tightly coupled to a piezoelectric ceramic sheet, serving as protection and sound wave transition; an integrated coupling layer consisting of a flexible solid coupling sheet pre-attached to the outside of the stainless steel bottom cover; and a magnetic fixing ring, a ring-shaped neodymium iron boron permanent magnet embedded in the shell, for providing attraction force to the ferromagnetic bolts to stabilize the coupling pressure. Its advantages include: extremely simplified structure, compact size and light weight, low cost, elimination of measurement errors, improved measurement repeatability, and greatly simplified on-site operation procedures.

Description

Technical Field

[0001] This invention relates to the field of transducer technology, and more particularly to an integrated coupled piezoelectric ultrasonic transducer. Background Technology

[0002] To achieve simultaneous transmission and reception of longitudinal and transverse waves, transducers typically employ complex structures such as dual-chip arrays, sound insulation layers, and damping blocks. This results in large probe size, complex structure, and high manufacturing costs. Installation is difficult in space-constrained bolted connection areas (such as densely packed flange bolts), leading to poor portability. Existing technologies heavily rely on liquid or paste-like coupling agents (such as glycerin or special resins) to ensure effective sound wave transmission. The type of coupling agent, the uniformity of application, the thickness, and changes with temperature and time (such as evaporation, drying, and flow) significantly affect the stability and repeatability of the sound wave signal, introducing additional uncertainties, reducing measurement accuracy and reliability, and making on-site operation cumbersome and inefficient. Summary of the Invention

[0003] The purpose of this invention is to provide an integrated coupled piezoelectric ultrasonic transducer that can solve the problems of existing technologies, such as large probe size, complex structure, high manufacturing cost, difficult installation, poor portability, heavy reliance on liquid or paste-like coupling agents (such as glycerin, special resin) to ensure effective sound wave transmission, significant impact on the stability and repeatability of sound wave signals, introduction of additional uncertainties, reduced measurement accuracy and reliability, and cumbersome and inefficient on-site operation.

[0004] The technical solution of the present invention is as follows: an integrated coupled piezoelectric ultrasonic transducer, comprising, Housing, sensing unit, backing damping block, stainless steel bottom cover, integrated coupling layer and magnetic retaining ring; The outer shell has a cylindrical structure, with one end being open and the other end being closed; The upper and lower surfaces of the sensing unit are both infiltrated with silver electrodes. The upper surface silver electrode is connected to the positive signal lead through conductive silver paste, and the lower surface silver electrode is connected to the bottom of the shell and grounded through conductive silver paste to form the negative signal. The positive lead is electrically connected to the cable interface, and longitudinal and transverse waves are synchronously excited under high voltage pulse excitation. The backing damping block is an acoustic damping material made of epoxy resin and tungsten powder, which is filled and cured between the sensing unit and the closed end of the outer shell. The stainless steel bottom cover is fixed to the open end of the outer shell and tightly coupled to the sensing unit; The integrated coupling layer is a flexible solid coupling sheet pre-attached to the outside of the stainless steel bottom cover; The magnetic fixing ring is a ring-shaped neodymium iron boron permanent magnet, embedded in the outer shell, used to provide an attraction force for the ferromagnetic bolt to stabilize the coupling pressure.

[0005] It also includes a cable interface, which is connected to the closed end of the housing for signal transmission with the ultrasonic testing instrument.

[0006] The sensing unit is a single solid circular lead zirconate titanate piezoelectric ceramic sheet.

[0007] Under the excitation of a high-voltage narrow pulse output by an ultrasonic testing instrument, the piezoelectric ceramic sheet can simultaneously generate vibrations in the thickness direction and radial shear vibrations, wherein the vibration in the thickness direction is used to excite longitudinal waves and the radial shear vibration is used to excite transverse waves.

[0008] The filling amount of the backing damping block is based on completely covering the cavity between the lower surface of the piezoelectric ceramic sheet and the closed end of the shell, and the cured backing damping block is tightly attached to the piezoelectric ceramic sheet and the inner wall of the shell.

[0009] The outer diameter of the stainless steel bottom cover is the same as the inner diameter of the open end of the outer shell, and it is fixed to the outer shell by welding or threaded connection.

[0010] The thickness of the integrated coupling layer is selected to match the diameter of the target detection bolt and the temperature range of the detection environment.

[0011] The inner diameter of the magnetic retaining ring is the same as the outer diameter of the outer shell, and the height of the magnetic retaining ring does not exceed the length range of the outer shell.

[0012] The positive electrode lead is made of silver-plated copper wire and is wrapped with a polytetrafluoroethylene insulating layer.

[0013] The core wire of the cable interface is soldered to the positive signal lead and connected to the grounding terminal, which is the bottom of the casing.

[0014] The beneficial effects of this invention are as follows: This invention has an ultrasonic transducer with an extremely simplified structure, small size, light weight, and low cost. It can effectively excite and receive longitudinal and transverse waves using a single solid piezoelectric crystal, completely innovate the coupling method, and provide a pre-set, stable solid-state coupling scheme to eliminate measurement errors caused by state changes in traditional liquid / paste coupling agents, improve measurement repeatability, and greatly simplify the on-site operation process. Attached Figure Description

[0015] Figure 1 A schematic diagram of the overall structure of an integrated coupled piezoelectric ultrasonic transducer provided by the present invention; Figure 2 This is a partial cross-sectional schematic diagram of an integrated coupled piezoelectric ultrasonic transducer provided by the present invention. Figure 3 This is a partial structural end face diagram of an integrated coupled piezoelectric ultrasonic transducer provided by the present invention. Figure 4 This is a schematic cross-sectional view of the overall structure of an integrated coupled piezoelectric ultrasonic transducer provided by the present invention.

[0016] Reference numerals: 1. Housing; 2. Sensing unit; 21. Piezoelectric ceramic sheet; 3. Backing damping block; 4. Stainless steel bottom cover; 5. Integrated coupling layer; 6. Magnetic retaining ring; 7. Cable interface; 8. Ferromagnetic bolt. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0019] like Figure 1-4 As shown, an integrated coupled piezoelectric ultrasonic transducer includes a housing 1, a sensing unit 2, a backing damping block 3, a stainless steel bottom cover 4, an integrated coupling layer 5, and a magnetic fixing ring 6. The housing 1 is an aluminum alloy cylindrical structure with one open end and the other closed end. Both the upper and lower surfaces of the sensing unit 2 are infiltrated with silver electrodes. The upper surface silver electrode is connected to the positive signal lead via conductive silver paste, and the lower surface silver electrode is connected to the bottom of the housing 1 via conductive silver paste and grounded to form the negative signal electrode. The positive lead is electrically connected to a cable interface 7, synchronously exciting longitudinal and transverse waves under high-voltage pulse excitation. The backing damping block 3 is a mixture of epoxy resin and tungsten powder. A damping material is filled and cured between the piezoelectric ceramic sheet 21 and the closed end of the outer shell 1 to absorb reverse sound waves and improve signal clarity. The stainless steel bottom cover 4 is fixed to the open end of the outer shell 1 and tightly coupled with the piezoelectric ceramic sheet 21, serving as protection and sound wave transition. The integrated coupling layer 5 is a flexible solid coupling sheet pre-attached to the outside of the stainless steel bottom cover 4, with silicone rubber or polyurethane as the matrix and doped with micron-sized alumina or tungsten powder. Its acoustic impedance is close to that of a steel bolt and its surface has a slight adhesiveness to achieve stable acoustic coupling. The magnetic fixing ring 6 is a ring-shaped neodymium iron boron permanent magnet embedded in the outside of the outer shell 1 to provide an attraction force for the ferromagnetic bolt 8 to stabilize the coupling pressure.

[0020] The outer casing 1 provides mechanical support and protection for the overall transducer, isolating it from external dust, radiation and other environmental interference; the cable interface 7 serves as the connection hub between the transducer and the ultrasonic detector, realizing the input of high-voltage excitation pulses and the output of echo electrical signals, ensuring the stability and anti-interference of signal transmission.

[0021] The transducer also includes a cable interface 7 that connects to the closed end of the housing 1 for signal transmission with the ultrasonic testing instrument.

[0022] Specifically, the sensing unit 2 is a single solid circular lead zirconate titanate piezoelectric ceramic sheet 21 with a fixed thickness of 0.2 mm. As the core sensing component of the transducer, the thin sheet generates "thickness direction (axial) vibration" and "radial shear vibration" synchronously due to the inverse piezoelectric effect under the high voltage narrow pulse excitation input from the cable interface 7. The axial vibration is used to excite longitudinal waves into the bolt, and the radial shear vibration is used to excite transverse waves, realizing the dual-wave synchronous excitation function that can only be accomplished by traditional dual-chip groups. At the same time, the monolithic structure simplifies the overall design and reduces the size.

[0023] Furthermore, under the excitation of a high-voltage narrow pulse output by an ultrasonic testing instrument, the piezoelectric ceramic sheet 21 can simultaneously generate vibrations in the thickness direction and radial shear vibrations, wherein the vibration in the thickness direction is used to excite longitudinal waves and the radial shear vibration is used to excite transverse waves.

[0024] Furthermore, the filling amount of the backing damping block 3 is based on completely covering the cavity between the lower surface of the piezoelectric ceramic sheet 21 and the closed end of the outer shell 1, and the cured backing damping block 3 is tightly attached to the piezoelectric ceramic sheet 21 and the inner wall of the outer shell 1. The backing damping block 3 absorbs the acoustic energy propagating backward (towards the closed end of the outer shell 1) from the piezoelectric ceramic sheet 21, avoiding the superposition and interference of reverse and forward acoustic waves. At the same time, it shortens the acoustic pulse width, improves the axial resolution of the transducer, ensures the clarity of longitudinal and transverse echo signals, and provides high-quality raw signals for subsequent signal extraction.

[0025] Furthermore, the outer diameter of the stainless steel bottom cover 4 is consistent with the inner diameter of the open end of the outer shell 1, and it is fixed to the outer shell 1 by welding or threaded connection. The stainless steel bottom cover 4 protects the internal piezoelectric ceramic sheet 21 from external mechanical impact and wear, extending the service life of the component. On the other hand, it serves as a transition medium for sound wave transmission, transmitting the longitudinal and transverse waves excited by the piezoelectric ceramic sheet 21 to the subsequent coupling layer without loss, thus avoiding wear or signal attenuation caused by direct contact between the sheet and the coupling layer.

[0026] The thickness of the integrated coupling layer 5 is selected to be adapted to the diameter of the target detection bolt and the temperature range of the detection environment. The integrated coupling layer 5 replaces the traditional liquid / paste-like coupling agent. Through its acoustic impedance characteristics, which are close to those of steel bolts, it constructs a stable and repeatable acoustic coupling channel, ensuring efficient transmission of longitudinal and transverse waves between the transducer and the bolt. At the same time, it is not affected by temperature, humidity, or time, avoiding measurement errors caused by changes in the state of the coupling agent. Furthermore, it eliminates the need for on-site application and cleaning, simplifying the operation process.

[0027] Furthermore, the inner diameter of the magnetic retaining ring 6 is the same as the outer diameter of the outer shell 1, and the height of the magnetic retaining ring 6 does not exceed the length range of the outer shell 1. For the ferromagnetic bolt 8, the adsorption force of the permanent magnet makes the transducer fit tightly against the bolt end face, maintaining stable pressure between the integrated coupling layer 5 and the bolt, without the need for continuous manual pressing; in scenarios such as nuclear power where remote operation is required, it can assist robotic arms and long-handled tools to quickly fix and disassemble the transducer, reducing personnel's radiation exposure time.

[0028] Furthermore, the positive electrode lead is made of silver-plated copper wire and is wrapped with a polytetrafluoroethylene insulating layer.

[0029] Furthermore, the core wire of cable interface 7 is soldered to the positive signal lead and connected to the grounding terminal, which is the bottom of the outer casing 1.

[0030] The working principle is as follows: (1) Electro-acoustic conversion and dual-wave excitation: When the high-voltage narrow pulse generated by the ultrasonic detector is applied to the two poles of the solid circular piezoelectric ceramic sheet 21 through the coaxial cable, the sheet vibrates due to the inverse piezoelectric effect. Due to its extreme thinness (0.2 mm), its vibration mode is complex under high-voltage pulse excitation. It can not only generate strong thickness-direction (axial) vibration (mainly exciting longitudinal waves), but also generate radial shear vibration components, thereby coupling and exciting transverse waves (S-waves) in the bolt. A single solid circular sheet can effectively generate dual waves.

[0031] (2) Sound-to-electric conversion and signal reception: The ultrasonic waves propagating in the bolt are reflected back to the transducer end face after encountering the bottom surface, causing the piezoelectric ceramic sheet 21 to vibrate. Due to the positive piezoelectric effect, the sheet generates a corresponding electrical signal. This signal contains longitudinal and transverse wave echo information, which is transmitted back to the detection instrument through the cable.

[0032] (3) Signal processing and preload calculation: The signal acquired by the instrument is amplified and digitally processed, and the longitudinal wave transit time (t) is accurately extracted using algorithms such as cross-correlation. L ) and transverse wave transit time (tS). The transit time ratio (tS) was determined beforehand through calibration experiments. S / t L The current preload of the bolt can be calculated using the relationship model of "σ - axial stress".

[0033] This transducer provides a stable, reliable, and repeatable acoustic coupling channel, completely avoiding various errors and inconveniences caused by manual application of coupling agent during field operation.

[0034] The specific operation process is as follows: (1) Select a large-sized transducer whose outer diameter matches the bolt head. Due to its solid circular plate design, even if the size is increased, the structure remains simple, and the manufacturing difficulty and cost are controllable.

[0035] (2) The operator uses a long-handled tool or a robotic arm to hold the transducer. First, use a rotating wire brush head mounted on the handle to clean the light oxide layer and dirt from the bolt end face.

[0036] (3) Align the end of the pre-attached high-performance solid-state coupling layer transducer with the center of the cleaned bolt end face. Thanks to the strong adsorption force of the magnetic retaining ring, the transducer can still be firmly fixed to the bolt under remote operation without the need for continuous manual pressing, which greatly reduces the difficulty of operation and the time personnel are exposed to irradiation.

[0037] (3) Connect the transducer to a remote ultrasonic testing instrument via an extension line.

[0038] (4) The instrument automatically excites and acquires signals. Due to the optimization of the backing damping block, clear echo signals can be obtained even for large-sized components. The system algorithm accurately extracts the P-wave transit time (t). L ) and transverse wave transit time (t S ).

[0039] (5) The instrument calls up the "t" pre-calibrated in the laboratory for this batch of bolts. S / t L The database of "preload" curves automatically calculates and displays the current preload value and determines whether it is within the allowable range.

[0040] (6) After recording the data, the transducer is removed by overcoming the magnetic force using a robotic arm or operating lever and moved to the next detection point. The entire process requires no application of coupling agent, and the single-point detection time is extremely short, effectively meeting the extremely high requirements for efficiency and safety during nuclear power plant shutdown inspections.

[0041] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An integrated coupled piezoelectric ultrasonic transducer, characterized in that: include, Housing, sensing unit, backing damping block, stainless steel bottom cover, integrated coupling layer and magnetic retaining ring; The outer shell has a cylindrical structure, with one end being open and the other end being closed; The upper and lower surfaces of the sensing unit are both infiltrated with silver electrodes. The upper surface silver electrode is connected to the positive signal lead through conductive silver paste, and the lower surface silver electrode is connected to the bottom of the shell and grounded through conductive silver paste to form the negative signal. The positive lead is electrically connected to the cable interface, and longitudinal and transverse waves are synchronously excited under high voltage pulse excitation. The backing damping block is an acoustic damping material made of epoxy resin and tungsten powder, which is filled and cured between the sensing unit and the closed end of the outer shell. The stainless steel bottom cover is fixed to the open end of the outer shell and tightly coupled to the sensing unit; The integrated coupling layer is a flexible solid coupling sheet pre-attached to the outside of the stainless steel bottom cover; The magnetic fixing ring is a ring-shaped neodymium iron boron permanent magnet, embedded in the outer shell, used to provide an attraction force for the ferromagnetic bolt to stabilize the coupling pressure.

2. The integrated coupled piezoelectric ultrasonic transducer as described in claim 1, characterized in that: It also includes a cable interface, which is connected to the closed end of the housing for signal transmission with the ultrasonic testing instrument.

3. The integrated coupled piezoelectric ultrasonic transducer as described in claim 1, characterized in that: The sensing unit is a single solid circular lead zirconate titanate piezoelectric ceramic sheet.

4. The integrated coupled piezoelectric ultrasonic transducer as described in claim 3, characterized in that: Under the excitation of a high-voltage narrow pulse output by an ultrasonic testing instrument, the piezoelectric ceramic sheet can simultaneously generate vibrations in the thickness direction and radial shear vibrations, wherein the vibration in the thickness direction is used to excite longitudinal waves and the radial shear vibration is used to excite transverse waves.

5. An integrated coupled piezoelectric ultrasonic transducer as described in claim 1, characterized in that: The filling amount of the backing damping block is based on completely covering the cavity between the lower surface of the piezoelectric ceramic sheet and the closed end of the shell, and the cured backing damping block is tightly attached to the piezoelectric ceramic sheet and the inner wall of the shell.

6. The integrated coupled piezoelectric ultrasonic transducer as described in claim 1, characterized in that: The outer diameter of the stainless steel bottom cover is the same as the inner diameter of the open end of the outer shell, and it is fixed to the outer shell by welding or threaded connection.

7. An integrated coupled piezoelectric ultrasonic transducer as described in claim 1, characterized in that: The thickness of the integrated coupling layer is selected to match the diameter of the target detection bolt and the temperature range of the detection environment.

8. An integrated coupled piezoelectric ultrasonic transducer as described in claim 1, characterized in that: The inner diameter of the magnetic retaining ring is the same as the outer diameter of the outer shell, and the height of the magnetic retaining ring does not exceed the length range of the outer shell.

9. An integrated coupled piezoelectric ultrasonic transducer as described in claim 1, characterized in that: The positive electrode lead is made of silver-plated copper wire and is wrapped with a polytetrafluoroethylene insulating layer.

10. An integrated coupled piezoelectric ultrasonic transducer as described in claim 2, characterized in that: The core wire of the cable interface is soldered to the positive signal lead and connected to the grounding terminal, which is the bottom of the casing.

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