CN115078531A - High-frequency piezoelectric transduction vibration element, high-frequency ultrasonic probe and preparation method - Google Patents

Abstract

The invention relates to a high-frequency piezoelectric transduction vibration element, a high-frequency ultrasonic probe and a preparation method, which are used for monitoring defects of a steel rail and belong to the technical field of measurement. The high-frequency piezoelectric transduction vibration element comprises a first electrode layer, a flexible piezoelectric transduction layer, a second electrode layer and a conductive epoxy solder mixture layer; the first electrode layer is connected with the front surface of the flexible piezoelectric energy conversion layer and is connected with a positive lead; the upper surface of the second electrode layer is connected with the back surface of the flexible piezoelectric energy conversion layer and is connected with a negative lead; the lower surface of the second electrode layer is connected with the conductive epoxy solder mixture layer. The high-frequency piezoelectric transduction vibration element is used for a high-frequency ultrasonic probe, and the high-frequency ultrasonic probe can automatically and accurately detect the rail head defect of the steel rail in real time on line.

Description

High-frequency piezoelectric transduction vibration element, high-frequency ultrasonic probe and preparation method

Technical Field

The invention belongs to the technical field of measurement, and particularly relates to a high-frequency piezoelectric transduction vibration element, a high-frequency ultrasonic probe and a preparation method.

Background

In the prior art, a rail used for train/train running has damage defects such as cracks, cracks or breaks and the like during long-term running of the train/train, so the damage of the rail needs to be detected. Because the defect of nuclear injury with great harmfulness of the rail head of the steel rail cannot be found in time, the serious threat of rail break accident possibly caused after the defect expansion to the traffic safety is inevitable.

Disclosure of Invention

The invention aims to provide a high-frequency piezoelectric transduction vibration element, a high-frequency ultrasonic probe and a preparation method, which are used for solving the problems in the prior art.

A high-frequency piezoelectric transduction vibration element for steel rail defect monitoring comprises a first electrode layer, a flexible piezoelectric transduction layer, a second electrode layer and a conductive epoxy solder mixture layer;

the first electrode layer is connected with the front surface of the flexible piezoelectric energy conversion layer and is connected with a positive lead;

the upper surface of the second electrode layer is connected with the back surface of the flexible piezoelectric energy conversion layer and is connected with a negative lead;

the lower surface of the second electrode layer is connected with the conductive epoxy solder mixture layer.

Further, the flexible piezoelectric energy conversion layer is a copolymer PVDF layer with a certain thickness.

Further, the PVDF layer of the copolymer is a polyvinylidene fluoride-trifluoroethylene film or a vinylidene fluoride-tetrafluoroethylene film with the thickness of 20 mu m.

Further, the first electrode layer and the second electrode layer are both two-layer evaporation structure bodies.

Furthermore, the two layers of evaporation structure bodies are a titanium (Ti) evaporation electrode layer with the thickness of 10nm and a gold (Au) evaporation electrode layer with the thickness of 200nm, which are covered on the titanium (Ti) evaporation electrode layer from inside to outside in sequence.

Furthermore, the high-frequency piezoelectric transduction oscillator is a square block with the side length of 3mm multiplied by 3 mm.

The invention also provides a method for manufacturing the high-frequency piezoelectric transduction vibration element, which comprises the following steps:

s1, preparing the flexible piezoelectric energy conversion layer;

s2, connecting a first electrode layer and a second electrode layer to two sides of the flexible piezoelectric energy conversion layer respectively;

s3, connecting the conductive epoxy solder mixture layer with the lower surface of the second electrode layer, wherein the first electrode layer, the flexible piezoelectric energy conversion layer, the second electrode layer and the conductive epoxy solder mixture layer form a multilayer structure;

s4, placing the multilayer structure body into an oven with the temperature of 30-60 ℃, curing for 3-6 hours, and polarizing for 20-40 minutes in room-temperature silicone oil by using a 2000V direct-current electric field;

and S5, cutting the polarized multilayer structure body to obtain the high-frequency piezoelectric transduction vibration element.

Further, in step S5, after the high-frequency piezoelectric transduction element is obtained by cutting, the positive electrode lead and the negative electrode lead are respectively welded to the first electrode layer and the second electrode layer.

The invention also provides a high-frequency ultrasonic probe which comprises a high-frequency piezoelectric transduction vibration element, a flexible bonding connecting layer, a positive connecting wire, a negative connecting wire, a multi-core high-frequency cable and a waterproof joint, wherein the high-frequency piezoelectric transduction vibration element is bonded on the flexible bonding connecting layer.

Furthermore, the flexible bonding connection layer is a Polydimethylsiloxane (PDMS) layer, the high-frequency piezoelectric transduction vibration elements are arranged in a plurality of layers, and the distance between the high-frequency piezoelectric transduction vibration elements is 1 mm.

The invention has the advantages of

Compared with the prior art, the invention has the following beneficial effects:

(1) the flexible piezoelectric energy conversion layer adopts the copolymer PVDF to manufacture the high-frequency piezoelectric energy conversion vibration element, and the copolymer PVDF is a flexible piezoelectric material and has the characteristics of fluororesin and general resin, so that the high-frequency piezoelectric energy conversion vibration element has good chemical corrosion resistance, high temperature resistance, oxidation resistance, good mechanical property, softness, brittleness resistance, light weight, impact resistance, good piezoelectric property and good acoustic sound transmission property. Because all the on-line monitoring positions are outdoor, the performance of the copolymer PVDF under high and low temperatures is not changed, the service life is longer, the temperature resistance of the copolymer PVDF is between 40 ℃ below zero and 140 ℃, and the aging resistance is strong.

(2) Utilize flexible piezoelectricity energy conversion layer preparation high frequency piezoelectricity energy conversion vibration element, adopt flexible bonding tie layer bonding fixed, preparation high frequency ultrasonic probe, flexible bonding tie layer adopts polydimethylsiloxane PDMS, polydimethylsiloxane PDMS has stronger pliability, better elasticity, low young modulus, excellent gas permeability, performance such as chemical stability and thermal stability, thereby make high frequency ultrasonic probe have good pliability and bending property, can place the optional position at the rail, especially when monitoring railhead nuclear injury defect, can laminate high frequency ultrasonic probe and rail chin completely, form good supersound incident plane, can carry out real-time online automated inspection to the railhead nuclear injury defect of rail.

Drawings

FIG. 1 is a schematic structural diagram of a high-frequency piezoelectric transduction transducer;

FIG. 2 is a schematic structural diagram of a high-frequency ultrasonic probe;

fig. 3 is a schematic view of the high-frequency ultrasonic probe mounted on a steel rail.

In the figure: 1. a high-frequency piezoelectric transduction vibration element; 2. a first electrode layer; 3. a flexible piezoelectric transducer layer; 4. a second electrode layer; 5. a conductive epoxy solder compound layer; 6. a positive electrode lead; 7. a negative electrode lead; 8. a high-frequency ultrasonic probe; 9. a flexible adhesive connecting layer; 10. a positive electrode connecting wire; 11. a negative electrode connecting wire; 12. a multi-core high-frequency cable; 13. an epoxy resin; 14. rivet holes; 15. a waterproof joint; 16. a multi-core shielded cable.

Detailed Description

In order to better understand the technical solution of the present invention, the present disclosure includes but is not limited to the following detailed description, and similar techniques and methods should be considered as within the scope of the present invention. In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.

It should be understood that the described embodiments of the invention are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

In order to achieve the above object, the present invention provides a high-frequency piezoelectric transducing element, as shown in fig. 1, the high-frequency piezoelectric transducing element 1 including a first electrode layer 2, a flexible piezoelectric transducing layer 3, asecond electrode layer 4, and a conductive epoxysolder mixture layer 5;

wherein: the first electrode layer 2 is connected with the front surface of the flexible piezoelectric energy conversion layer 3 and is connected with apositive electrode lead 6;

the upper surface of thesecond electrode layer 4 is connected with the back surface of the flexible piezoelectric energy conversion layer 3 and is connected with anegative lead 7;

the lower surface of thesecond electrode layer 4 is connected with the conductive epoxysolder mixture layer 5.

Preferably, the copolymer PVDF has the characteristics of both fluororesin and general resin, and the resin has good chemical corrosion resistance, high temperature resistance, oxidation resistance and mechanical property, is soft and not brittle, is light in weight and resists impact, so that the high-frequency ultrasonic probe made of the material has good bending property. The flexible piezoelectric transducer layer 3 of the present invention is realized by using a copolymer PVDF, and as shown in fig. 1, in order to manufacture the high-frequency piezoelectric transducer element 1, the copolymer PVDF layer is selected as a polyvinylidene fluoride-trifluoroethylene (P (VDF-TrFE)) film or a vinylidene fluoride-tetrafluoroethylene film, a polyvinylidene fluoride-trifluoroethylene (P (VDF-TrFE)) film or a vinylidene fluoride-tetrafluoroethylene copolymer having a thickness of 20 μm in the examples of the present invention, and since the crystallinity thereof is high, the piezoelectric performance determined by the crystallinity is also excellent, and the higher the crystallinity is, the larger the piezoelectric response is, the higher the piezoelectric constant is, and the excellent acoustic performance is obtained.

When the high-frequency piezoelectric transduction vibration element is prepared, the preparation steps are as follows:

(1) preparing a 12mm x 12mm polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE) or vinylidene fluoride-tetrafluoroethylene thin film layer having a thickness of 20 μm;

(2) connecting a first electrode layer and a second electrode layer on two sides of a polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE) or vinylidene fluoride-tetrafluoroethylene film layer, wherein in the embodiment, an adhesion mode is adopted, namely a first electrode layer 2 is adhered to the front surface of the polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE) or vinylidene fluoride-tetrafluoroethylene film layer, the upper surface of asecond electrode layer 4 is adhered to the back surface of the polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE) or vinylidene fluoride-tetrafluoroethylene film layer, the first electrode layer 2 and thesecond electrode layer 4 are evaporation electrode structure bodies, and an evaporation process is adopted, namely, a conductive material is deposited on the corresponding electrode layers in a mode that the electrode material is heated to form steam and then is adsorbed on a target object;

in a preferred embodiment, the first electrode layer 2 and thesecond electrode layer 4 are both a two-layer deposited electrode structure, that is, a titanium (Ti) deposited electrode layer having a thickness of 10nm and a gold (Au) deposited electrode layer having a thickness of 200nm and covering the titanium (Ti) deposited electrode layer, which is bonded to a polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE) or a vinylidene fluoride-tetrafluoroethylene thin film layer, in this order from the inside to the outside.

(3) Mixing the conductive epoxy Solder (E-Solder)3022 with a hardening agent in a certain mass ratio, placing the mixture into a centrifuge to centrifuge at 10000rpm for 10 minutes to obtain a centrifuged conductive epoxy Solder mixture, and then connecting the centrifuged conductive epoxy Solder mixture layer to the lower surface of thesecond electrode layer 4, which is performed in a casting manner in this embodiment;

(4) placing a multilayer structure formed by the first electrode layer 2, the polyvinylidene fluoride-trifluoroethylene P (VDF-TrFE) or the vinylidene fluoride-tetrafluoroethylene film layer, thesecond electrode layer 4 and the conductive epoxysolder mixture layer 5 into an oven, and carrying out heat treatment at the temperature of 30-60 ℃, preferably 45 ℃; curing is carried out for 3 to 6 hours, preferably for 5 hours. And (3) polarizing in the silicone oil at room temperature by using a 2000V direct current electric field for 20-40 minutes, preferably 30 minutes, and forming a multilayer structure with high-frequency piezoelectric performance.

(5) Cutting the polarized multilayer structure into 16 square blocks with the side length of 3mm multiplied by 3mm by using a cutting tool such as a cutting saw, wherein each square block is a manufactured high-frequency piezoelectric transduction oscillator, apositive lead 6 of the first electrode layer 2 and anegative lead 7 of thesecond electrode layer 4 are respectively welded, and the positive/negative leads are externally connected with a power supply and used for carrying out electric pulse excitation on the high-frequency piezoelectric transduction oscillator to generate ultrasonic waves with high-frequency narrow pulse characteristics.

In the invention, the high-frequency piezoelectric transduction vibration element is bonded by the flexible bonding connection layer to manufacture the high-frequency ultrasonic probe. The flexible bonding connecting layer is realized by adopting polydimethylsiloxane PDMS, the polydimethylsiloxane PDMS material belongs to a high-molecular elastic polymer, and the polydimethylsiloxane PDMS material is prepared by a special process, has good elasticity, low Young modulus, excellent gas permeability, chemical stability, thermal stability and low-temperature flexibility, and can still maintain excellent performance at minus 60-200 ℃. Because the polydimethylsiloxane PDMS material has the special mechanical properties, the high-frequency ultrasonic probe manufactured by adopting the polydimethylsiloxane PDMS material as the bonding connection layer has good bending property.

High frequency ultrasonic probe includes a plurality of high frequency piezoelectricity transduction vibration element and polydimethyl siloxane PDMS connecting layer, wherein each high frequency piezoelectricity transduction vibration element gomphosis is glued to polydimethyl siloxane (PDMS) connecting layer, and the vibration element interval of each high frequency piezoelectricity transduction vibration element sets up to 1mm, all high frequency piezoelectricity transduction vibration element distribution structure is shown in figure 2, in this embodiment, high frequency ultrasonic probe adopts a plurality of high frequency piezoelectricity transduction vibration elements, adopt 16 high frequency piezoelectricity transduction vibration elements in this embodiment, and every four are arranged into a line,form 4X 4's square, make things convenient for high frequency ultrasonic probe can laminate in rail chin cambered surface all-roundly when using, be used for monitoring the damage position of rail railhead, make the signal that detects more accurate reliable.

The rear part of the high-frequency ultrasonic probe is designed into a combined planar structure, and the rear part of the whole high-frequency ultrasonic probe also comprises a positive connectingwire 10, a negative connectingwire 11, a multi-core high-frequency cable 12,epoxy resin 13, arivet hole 14 and a waterproof joint 15. Thepositive lead 6 of each high-frequency piezoelectric transduction vibration element 1 is coated with a film, but needs to be led out from each high-frequency piezoelectric transduction vibration element 1 independently to ensure that the positive poles of each high-frequency piezoelectric transduction vibration element 1 are not mutually conducted, and the separately led-outpositive leads 6 are connected in parallel to form a positive connectingwire 10 of the high-frequencyultrasonic probe 8; the negativeelectrode connection line 11 of the high-frequencyultrasonic probe 8 is formed as follows: the cathode leads 7 of the high-frequency piezoelectric transduction vibration elements 1 are combined and connected in a film coating mode according to the figure 2, and a common cathode is led out to be used as acathode connecting wire 11 of the high-frequencyultrasonic probe 8. Uniformly arranging all the positive connectingwires 10 and the negative connectingwires 11, leading out all the positive connectingwires 10 and the negative connectingwires 11 in a film coating mode, punching rivet holes 14 on each positive connectingwire 10 and each negative connectingwire 11 for fixing all the positive connectingwires 10 and the negative connectingwires 11, connecting a multi-core high-frequency cable 12 to a waterproof joint 15, welding and fixing all the positive connectingwires 10 and the negative connectingwires 11 by one end of the multi-core high-frequency cable 12 to form a cable for signal transmission, welding the other end of the multi-core high-frequency cable to the waterproof joint 15, wherein the waterproof joint is of a multi-core structure, and finally integrally pouring and sealing the high-frequency cable 12 and the waterproof joint 15 byepoxy resin 13. Thewatertight connector 15 is used for connecting a measuring instrument. The sealingepoxy resin 13 is used to achieve waterproofing of the high-frequency ultrasonic probe. In order to ensure the water resistance and the driving safety, the waterproof joint 15 is arranged at the bottom of the steel rail in the field and is connected with amulti-core shielding cable 16 of an ultrasonic instrument in actual use.

The high-frequency ultrasonic probe in the embodiment is used for detecting rail damage of a steel rail, and rail head transverse fatigue cracks of the steel rail are commonly called rail head nuclear damage and are called nuclear damage for short, and the rail head transverse fatigue cracks refer to that extremely complex stress distribution and stress states occur in the rail head under the repeated action of train load, so that fine cracks are transversely expanded into the nuclear damage until the strength of steel around the nuclear damage is not enough to resist the stress under the action of wheel load, and the steel rail is suddenly brittle failure. The rail head nuclear damage defect is a steel damage which has the greatest threat to driving and is the most dangerous rail damage, and the rail head nuclear damage is easy to develop and expand due to continuous impact of vehicles, so that rail breakage is caused. Railhead nuclear damage generally occurs on the inside surface of the railhead where the rail is most stressed in compression, and forms a certain included angle with the vertical section of the rail, which is about 14 degrees. When the conventional ultrasonic detection railhead nuclear damage is carried out, sound waves are generally incident from the rail surface of the steel rail for flaw detection, but under the condition of online monitoring application, the probe cannot be arranged on the rail surface of the steel rail due to the limitation of vehicle operation, and the monitoring probe cannot be arranged on the inner side surface of the rail head of the steel rail due to the existence of the wheel rim. The high-frequency ultrasonic probe of the embodiment has good bending property and flexibility, so that the high-frequencyultrasonic probe 8 can be placed on the mandible part of the outer side surface of the rail head of the steel rail, as shown in fig. 3, is not influenced by the running of a train on the steel rail, can automatically monitor the rail head of the steel rail on line in real time without manual intervention, detects the rail head nuclear injury of the inner side surface of the rail head by the ultrasonic longitudinal wave generated by the high-frequency ultrasonic probe, sends the detected measurement signal to a multi-channel ultrasonic instrument connected with the high-frequency ultrasonic probe, and can be a 16-channel ultrasonic transmitting and receiving instrument, and the multi-channel ultrasonic instrument analyzes the measurement signal acquired by the high-frequency ultrasonic probe to construct a defect outline image of the steel rail, and determines the edge and the shape of the nuclear injury defect of the rail head of the steel rail according to the outline image. Meanwhile, if the nuclear damage defect in the steel rail is expanded or deformed under the action of the impact stress of the train/train, the change of the defect shape before and after the nuclear damage defect is expanded can be monitored through the signal measured by the high-frequency ultrasonic probe provided by the embodiment, so that a decision can be made in time.

The foregoing description shows and describes several preferred embodiments of the invention, but as aforementioned, it is to be understood that the invention is not limited to the forms disclosed herein, but is not to be construed as excluding other embodiments and is capable of use in various other combinations, modifications, and environments and is capable of changes within the scope of the inventive concept as expressed herein, commensurate with the above teachings, or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A high-frequency piezoelectric transduction vibration element is used for monitoring defects of a steel rail and is characterized by comprising a first electrode layer, a flexible piezoelectric transduction layer, a second electrode layer and a conductive epoxy solder mixture layer;

the first electrode layer is connected with the front surface of the flexible piezoelectric energy conversion layer and is connected with a positive lead;

the upper surface of the second electrode layer is connected with the back surface of the flexible piezoelectric energy conversion layer and is connected with a negative lead;

the lower surface of the second electrode layer is connected with the conductive epoxy solder mixture layer.

2. The high frequency piezoelectric transducing element of claim 1, wherein the flexible piezoelectric transducing layer is a copolymer PVDF layer having a certain thickness.

3. The high-frequency piezoelectric transduction element according to claim 2, wherein the copolymer PVDF layer is a polyvinylidene fluoride-trifluoroethylene film or a vinylidene fluoride-tetrafluoroethylene film having a thickness of 20 μm.

4. The oscillator element of the high-frequency ultrasonic probe for steel rail defect monitoring according to claim 1, wherein the first electrode layer and the second electrode layer are both two layers of evaporation structure bodies.

5. The high-frequency piezoelectric transducer according to claim 4, wherein the two evaporation structure layers are a titanium (Ti) evaporation electrode layer with a thickness of 10nm and a gold (Au) evaporation electrode layer with a thickness of 200nm covering the titanium (Ti) evaporation electrode layer from inside to outside in sequence.

6. The high-frequency piezoelectric transducing vibrator according to any one of claims 1 to 4, wherein the high-frequency piezoelectric transducing vibrator is a square block having a side of 3mm x 3 mm.

7. A method of manufacturing a high-frequency piezoelectric transducing element according to any one of claims 1 to 6, characterized in that the manufacturing method comprises the steps of:

s1, preparing the flexible piezoelectric energy conversion layer;

s2, connecting a first electrode layer and a second electrode layer to two sides of the flexible piezoelectric energy conversion layer respectively;

s3, connecting the conductive epoxy solder mixture layer with the lower surface of the second electrode layer, wherein the first electrode layer, the flexible piezoelectric energy conversion layer, the second electrode layer and the conductive epoxy solder mixture layer form a multilayer structure;

s4, placing the multilayer structure body into an oven with the temperature of 30-60 ℃, curing for 3-6 hours, and polarizing for 20-40 minutes in room-temperature silicone oil by using a 2000V direct-current electric field;

and S5, cutting the polarized multilayer structure body to obtain the high-frequency piezoelectric transduction vibration element.

8. The method for manufacturing a high-frequency piezoelectric transducing element according to claim 7, wherein said positive electrode lead and said negative electrode lead are welded to said first electrode layer and said second electrode layer, respectively, after said high-frequency piezoelectric transducing element is obtained by dicing in said step S5.

9. A high-frequency ultrasonic probe comprising the high-frequency piezoelectric transducing element defined in any one of claims 1 to 6, a flexible adhesive bonding layer, a positive electrode connecting wire, a negative electrode connecting wire, a multi-core high-frequency cable and a waterproof joint, wherein the high-frequency piezoelectric transducing element is adhered to the flexible adhesive bonding layer.

10. The high-frequency ultrasonic probe according to claim 9, wherein the flexible adhesive layer is a Polydimethylsiloxane (PDMS) layer, the high-frequency piezoelectric transduction elements are arranged in a plurality of layers, and the distance between every two adjacent high-frequency piezoelectric transduction elements is 1 mm.

Images