Stress detection method of graphene composite piezoelectric material integrated optical fiber sensing

Abstract

The invention discloses a stress detection method for graphene composite piezoelectric material integrated optical fiber sensing, and relates to the field of multi-mode sensor integration, and the method comprises the steps: generating a signal through a signal generator, and transmitting the signal to a composite flexible piezoelectric material through a power amplifier; the composite flexible piezoelectric material is used for generating ultrasonic waves, and the ultrasonic waves are conducted in the tested material; the fiber grating sensing and demodulation module is used for demodulating ultrasonic waves conducted in the tested material and transmitting the demodulated ultrasonic waves to the upper computer; the upper computer is used for displaying, storing and processing the demodulated ultrasonic signals, the stress borne by the detected material is obtained, and stress detection of the graphene composite piezoelectric material integrated optical fiber sensor is completed. According to the invention, the problems that the micro stress change in a complex structure cannot be detected in real time and the application environment is limited in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the field of multi-mode sensor integration, and in particular to a stress detection method of graphene composite piezoelectric material integrated optical fiber sensing. Background Art

[0002] Flexible transducers and fiber optic sensors each have a series of unique advantages in pressure measurement, making them widely used in different application scenarios. First, the flexible transducer has high sensitivity and can respond quickly and accurately to small pressure changes, which makes it particularly suitable for occasions where low pressure needs to be measured and maintains high stability and reliability. In addition, the flexible transducer uses corrosion-resistant materials and sealing technology, which can resist erosion by various corrosive media. In addition, the flexible transducer has a simple structure, small size, and light weight. It can be easily installed in various small and limited spaces, and is suitable for some applications with restrictions on weight and volume.

[0003] Fiber optic sensors have shown several advantages in pressure measurement, making them a popular measurement technology. First, fiber optic sensors are based on optical principles and are highly sensitive to small pressure changes and subtle strains. This enables fiber optic sensors to provide high-precision pressure measurements, especially for applications that require high measurement accuracy. The flexibility and sophisticated design of fiber optic sensors are another advantage. They can adapt to measurement objects of various sizes and shapes, minimize interference with the measurement target, and simultaneously monitor pressure changes at different locations, thereby improving the comprehensiveness and flexibility of the system. This is very beneficial for application scenarios that require simultaneous monitoring at multiple locations.

[0004] However, existing stress detection methods are unable to detect tiny stress changes in complex structures in real time and their application environments are limited. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a stress detection method of graphene composite piezoelectric material integrated optical fiber sensing, which solves the problem that the existing method cannot detect tiny stress changes in complex structures in real time and has limited application environment.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a stress detection method of graphene composite piezoelectric material integrated optical fiber sensing, comprising the following steps:

[0007] S1: Generate a signal using a signal generator and transmit it to the composite flexible piezoelectric material through a power amplifier;

[0008] S2: Use composite flexible piezoelectric materials to generate ultrasonic waves and conduct them in the material being tested;

[0009] S3: Use the fiber grating sensing and demodulation module to demodulate the ultrasonic wave transmitted in the material under test and transmit it to the host computer;

[0010] S4: Use the host computer to display, store and process the demodulated ultrasonic signal to obtain the stress of the material under test and complete the stress detection of graphene composite piezoelectric material integrated optical fiber sensing.

[0011] Furthermore, the preparation of the composite flexible piezoelectric material in S1 comprises the following steps:

[0012] S11: Preparation of graphene on single-crystal silicon substrate using metal-free and atmospheric pressure chemical vapor deposition technology;

[0013] S12: Preparation of titanium zirconium oxide by sol-gel method;

[0014] S13: Compounding the prepared graphene and zirconium oxide titanium to obtain a composite flexible piezoelectric material.

[0015] Furthermore, the S13 includes the following sub-steps:

[0016] S131: grinding zirconium titanium oxide, adding an ethanol solution as a dispersant to the graphene and the ground zirconium titanium oxide, and uniformly mixing them;

[0017] S132: The uniformly mixed graphene and zirconium oxide titanium are heat treated and characterized using a scanning electron microscope to obtain a composite flexible piezoelectric material.

[0018] Furthermore, the fiber Bragg grating sensing and demodulation module in S3 includes a free-enhanced laser bandwidth light source, an optical circulator, a reference grating, a sensing grating, a photodetector and a data acquisition card.

[0019] Furthermore, S3 includes the following sub-steps:

[0020] S31: transmitting the ultrasonic wave conducted in the material to be tested to a sensing grating located on the material to be tested through a single-mode optical fiber, and using the sensing grating to identify the ultrasonic signal;

[0021] S32: guiding the broadband light emitted by the free-enhanced laser broadband light source to the sensing grating located on the material to be tested through a circulator, and based on the ultrasonic signal recognition result, if the broadband light meets the wavelength condition, the broadband light is reflected back to the circulator and enters the reference grating;

[0022] S33: using a photodetector to capture a light signal transmitted by the reference grating, and converting the light signal into a voltage signal;

[0023] S34: using a data acquisition card to acquire the voltage signal, and transmitting the acquired voltage signal to a host computer.

[0024] Furthermore, the reference grating is pasted on the surface of the composite flexible piezoelectric material.

[0025] Furthermore, in the S31, under the action of the ultrasonic wave, the strain field model along the axial direction of the sensing grating is:

[0026]

[0027] Among them, ε AE (·) is the strain field model, A AE is the ultrasonic amplitude, λ AE is the wavelength of the ultrasonic wave in the material being measured, z is the coordinate point along the axial direction of the sensing grating, ω AE is the angular frequency of the ultrasonic wave, and t is the time.

[0028] Furthermore, the central wavelength λ of the sensing grating B (t) is:

[0029] λ B (t) = λ B0 +Δλ0cos(ω s t)

[0030]

[0031] Among them, λ B0 is the reference wavelength of the sensing grating, Δλ0 is the change in the central wavelength of the sensing grating after the action of ultrasound, ω s is the period of the sensing grating, ε AE (·) is the strain field model, n eff0 is the effective refractive index of the core axial of the sensing grating when it is not affected by external forces, p 11 is the first Poisson's ratio of the material being tested, p 12 is the second Poisson’s ratio of the material being tested, and v is the propagation speed of ultrasound in the material.

[0032] The beneficial effects of the present invention are:

[0033] (1) In the present invention, graphene has extremely high strength and toughness due to its two-dimensional carbon atom planar structure. Introducing it into zirconium oxide titanium can significantly improve the mechanical strength of the composite material. At the same time, the flexibility of graphene makes the composite material have better bending and deformation capabilities, which is an important property for piezoelectric materials used in monitoring equipment for stress deformation.

[0034] (2) In the present invention, graphene has extremely high chemical stability and can maintain its structure and performance in a variety of environments. This stability, when combined with zirconium oxide titanium, can help the composite material maintain its piezoelectric properties in harsh environments (such as high temperature, corrosive gas or liquid).

[0035] (3) In the present invention, zirconium oxide titanium itself has good piezoelectric properties, and the composite with graphene not only maintains this property, but also provides a good electron transmission channel for the composite material due to the high conductivity of graphene. The high specific surface area and conductivity of graphene may also enhance its piezoelectric effect to a certain extent.

[0036] (4) In the present invention, the comprehensive properties of this composite material provide a new approach for designing new flexible piezoelectric materials, which has certain reference significance for further research and development of flexible electronic devices, sensors, actuators, etc., and is also expected to have broad application prospects in the fields of energy conversion, sensor technology and smart materials.

[0037] (5) In the present invention, the flexible transducer and the optical fiber sensor are integrated into a structure design to achieve multimodal sensing, that is, to obtain different types of sensing information at the same time. The flexible transducer generates sound waves and transmits them to the FBG through the material being tested. The change in the central wavelength of the FBG reflects the degree of pressure.

[0038] (6) In the present invention, the optical fiber sensor generally has high sensitivity and accuracy, and can provide real-time monitoring and feedback. The flexible transducer also responds quickly to mechanical changes. When combined with the flexible transducer, real-time perception and feedback can be achieved, thereby realizing high-sensitivity perception in the application scenario of structural health monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flow chart of a stress detection method of graphene composite piezoelectric material integrated with optical fiber sensing.

[0040] Figure 2 Schematic diagram of metal-free APCVD equipment

[0041] Figure 3 It is the composition of the integrated detection system of fiber grating and flexible transducer.

[0042] Figure 4 The reference grating structure diagram.

[0043] Figure 5 Schematic diagram of FBG detecting the acoustic wave signal of the material being tested. DETAILED DESCRIPTION

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

[0045] like Figure 1 As shown, a stress detection method of graphene composite piezoelectric material integrated optical fiber sensing includes the following steps:

[0046] S1: Generate a signal using a signal generator and transmit it to the composite flexible piezoelectric material through a power amplifier;

[0047] In the present invention, the power amplifier is also connected to a digital oscilloscope, which can monitor the output signal from the power amplifier in real time and display the waveform of the signal including information such as amplitude, frequency, phase, etc. In addition, the digital oscilloscope has data recording and storage functions, and can save the monitored signal data for subsequent comparison and analysis of the center frequency offset with the demodulated ultrasonic waveform.

[0048] S2: Use composite flexible piezoelectric materials to generate ultrasonic waves and conduct them in the material being tested;

[0049] S3: Use the fiber grating sensing and demodulation module to demodulate the ultrasonic wave transmitted in the material under test and transmit it to the host computer;

[0050] S4: Use the host computer to display, store and process the demodulated ultrasonic signal to obtain the stress of the material under test and complete the stress detection of graphene composite piezoelectric material integrated optical fiber sensing.

[0051] The preparation of the composite flexible piezoelectric material in S1 comprises the following steps:

[0052] S11: Preparation of graphene on single-crystal silicon substrate using metal-free and atmospheric pressure chemical vapor deposition technology;

[0053] In this embodiment, when preparing graphene, chemical vapor deposition (CVD), chemical oxidation-reduction method and mechanical stripping method are compared, among which the chemical reduction method has a lower cost, but the quality and structure of the prepared graphene are difficult to control, and large-scale, continuous production cannot be achieved; although the mechanical stripping method can prepare high-quality graphene from natural graphite or other materials with high graphite content, it is a manual or semi-automatic process with low production efficiency, and can only prepare small-scale graphene;

[0054] Chemical vapor deposition (CVD) is highly controllable and scalable, and can achieve precise control of parameters such as temperature, gas composition, and pressure during graphene growth, making it suitable for large-scale production. Therefore, chemical vapor deposition was selected for preparation.

[0055] Low-temperature CVD can effectively catalyze the growth of graphene at a relatively low temperature by using metal catalysts (such as copper or nickel). However, considering that metal impurities may remain in the graphene, affecting the performance of the finished product, the present invention uses metal-free, atmospheric pressure chemical vapor deposition technology to grow graphene on a single crystal silicon substrate, thereby avoiding the introduction of metal impurities and making the graphene quality purer.

[0056] We selected single crystal silicon (500 μm thick, (100), (111), (110) surface, N-type, P-type, intrinsic silicon, R a <0.5nm) as an example of substrate;

[0057] Graphene is grown using a custom portable chamber with a ceramic wafer as a heating platform. Temperature control is precisely calibrated with an error of less than ±0.1°C.

[0058] The single crystal silicon substrate (upside down) was placed on the heating platform, pre-treated by immersion in 15% HF for 15 min, then cleaned with deionized water, and dried with N2 flow. Figure 2 Schematic diagram of metal-free APCVD equipment.

[0059] The vapor deposition chamber was evacuated and backfilled with argon (Ar) three times to create an inert environment;

[0060] The single crystal silicon surface is heated to the desired temperature (900-930°C) and stabilized under 100 sccm H2 (1 sccm = 1 ml / min at standard atmospheric pressure) and 200 sccm Ar for 10 minutes to remove any organic residues and activate the growth sites;

[0061] Graphene growth was carried out in a gas mixture of 180 sccm CH4 and 10 sccm H2 for 1 h, followed by cooling to room temperature with 180 sccm CH4 and 10 sccm H2 within 1 h.

[0062] S12: Preparation of titanium zirconium oxide by sol-gel method;

[0063] The precursors of zirconium and titanium are zirconium chloride (ZrCl4) and tetrabutyl titanate (Ti(OC4H9)4), which are dissolved in ethanol respectively.

[0064] The pH range suitable for generating zirconium titanium oxide (ZrTiO3) is between acidic and neutral. Acidic substances such as acetic acid are used to adjust the pH value of the solution to between 1 and 5, and then the two solutions are fully stirred and evenly mixed to form a sol.

[0065] The sol is gelled by stirring or heating (gradually increasing the temperature) to form a gel, and then the gel is calcined at a high temperature (1000° C.) to form a precursor of zirconium oxide titanium.

[0066] The formed zirconium oxide titanium particles are separated by centrifugation, washed with ethanol to remove unreacted precursors and solvent residues, and then dried to remove water and ethanol.

[0067] Scanning electron microscopy (SEM) was used to verify that the obtained material had a special structure with piezoelectric properties, such as the arrangement of particles in the polarization direction, to eliminate interfering factors for the subsequent characterization of the composite material.

[0068] S13: Compounding the prepared graphene and zirconium oxide titanium to obtain a composite flexible piezoelectric material.

[0069] The S13 includes the following sub-steps:

[0070] S131: grinding zirconium titanium oxide, adding an ethanol solution as a dispersant to the graphene and the ground zirconium titanium oxide, and uniformly mixing them;

[0071] S132: heat treating the uniformly mixed graphene and zirconium oxide titanium in the range of 500-800° C. and characterizing them using a scanning electron microscope to obtain a composite flexible piezoelectric material.

[0072] Through heat treatment, the structure of the material can be deeply changed, promoting chemical and physical interactions between the two, which helps to improve its stability. After compounding, the material is characterized by scanning electron microscopy (SEM) to determine the distribution of graphene in the zirconium oxide titanium matrix.

[0073] The present invention combines the prepared graphene with zirconium oxide titanium with excellent piezoelectric properties to form a new type of flexible piezoelectric material, which can replace traditional materials for use in transducers. This material not only has high flexibility and conductivity, but is also suitable for monitoring stress deformation and can fit well with the material being tested.

[0074] The fiber Bragg grating sensing and demodulation module in S3 includes a free enhanced laser bandwidth light source, an optical circulator, a reference grating, a sensing grating, a photodetector and a data acquisition card. Figure 3 shown.

[0075] The S3 includes the following sub-steps:

[0076] S31: transmitting the ultrasonic wave conducted in the material to be tested to a sensing grating located on the material to be tested through a single-mode optical fiber, and using the sensing grating to identify the ultrasonic signal;

[0077] S32: guiding the broadband light emitted by the free-enhanced laser broadband light source to the sensing grating located on the material to be tested through a circulator, and based on the ultrasonic signal recognition result, if the broadband light meets the wavelength condition, the broadband light is reflected back to the circulator and enters the reference grating;

[0078] S33: using a photodetector to capture a light signal transmitted by the reference grating, and converting the light signal into a voltage signal;

[0079] S34: using a data acquisition card to acquire the voltage signal, and transmitting the acquired voltage signal to a host computer.

[0080] The reference grating is pasted on the surface of the composite flexible piezoelectric material.

[0081] The present invention uses dual Bragg gratings and piezoelectric materials for detection, and combines flexible transducers with optical fiber sensors. Bragg gratings (FBGs) are used to replace traditional piezoelectric sensors to detect ultrasonic signals. When the system is working, the sound wave signal is transmitted to the FBG through a single-mode optical fiber, and the FBG is used as a sensing element to identify the ultrasonic signal.

[0082] FBG is an optical sensor, usually made of optical fiber, in which the refractive index is periodically modulated to form a grating structure. This structure can reflect light of a specific wavelength while passing other wavelengths. By introducing such a structure in the optical fiber, the optical fiber can be made sensitive to light of a specific wavelength, and this sensitivity can be changed according to factors such as environmental conditions or strain.

[0083] When the sensing grating is embedded in the material being tested and is affected by ultrasound, the central wavelength in the grating reflection spectrum will change. This is because the presence of ultrasound causes a slight deformation of the grating, which in turn changes the optical properties of the grating. Through the fiber demodulation system, the grating reflection spectrum can be demodulated and the offset of the central wavelength can be measured. By analyzing this offset, the defect location can be obtained, and the characteristics of the acoustic wave signal propagating in the material being tested, such as frequency, amplitude, etc., can be determined. This technology can be used to non-contactly detect and monitor acoustic wave signals in the material being tested, providing an efficient and accurate method for acoustic detection and material evaluation.

[0084] The system structure of the present invention includes two FBGs: one is a reference FBG, which is pasted on the surface of the piezoelectric material and serves as a reference grating. Figure 4 The spectral characteristics of this FBG are used as a reference under normal conditions. The second is an elastic wave sensor FBG: Another FBG is designed as an elastic wave sensor, and changes in its position or shape will cause changes in the spectral characteristics of the FBG.

[0085] With this design, when elastic waves act on the grating, stress is generated on the Bragg grating (FBG), and its parameters such as the effective refractive index will change, which causes the grating spacing to change, thereby shifting its reflection wavelength, realizing the sensing of sound waves, and intuitively reflecting the stress as a change in the central wavelength of the FBG. The ultrasonic signal is demodulated by the grating demodulation system, and the time domain signal and frequency domain signal of the ultrasonic wave are analyzed by the host computer to obtain information such as the size and location of the internal defects of the material being tested.

[0086] like Figure 5 As shown in the figure, the ultrasonic signal passes through the material under test and is transmitted to the FBG through the single-mode optical fiber. During this process, the peak wavelength λ of the FBG reflection spectrum is B satisfy:

[0087]

[0088] in, is the initial refractive index of the FBG without stress wave, Λ is the period of the FBG;

[0089] When there is no external force, the effective refractive index of the FBG core axial direction is:

[0090]

[0091] Where Λ0 is the initial period of the FBG and n is the maximum change in the refractive index.

[0092] In S31, under the action of ultrasound, the strain field model along the axial direction of the sensing grating is:

[0093]

[0094] Among them, ε AE (·) is the strain field model, A AE is the ultrasonic amplitude, λ AE is the wavelength of the ultrasonic wave in the material being measured, z is the coordinate point along the axial direction of the sensing grating, ω AE is the angular frequency of the ultrasonic wave, and t is the time.

[0095] By deriving the change of refractive index under elastic wave energy, the central wavelength λ of the sensing grating is obtained. B (t) is:

[0096] λ B (t) = λ B0 +Δλ0cos(ω s t)

[0097]

[0098] Among them, λ B0is the reference wavelength of the sensing grating, which is the central wavelength of reflection or transmission corresponding to the grating without any stress or environmental changes. Δλ0 is the change in the central wavelength of the sensing grating after the action of ultrasonic wave. s is the period of the sensing grating, which defines the distance between adjacent reflection areas in the grating, represents the repetitive distance of the microstructure of reflection or transmission in the grating, and affects the selective reflection or transmission of the grating to light of different wavelengths. AE (·) is the strain field model, n eff0 is the effective refractive index of the core axial of the sensing grating when it is not affected by external forces, p 11 The first Poisson's ratio of the material under test reflects the ratio of the strain in the perpendicular direction to the strain in the direction when the material is subjected to force in one direction. For fiber Bragg gratings, this parameter is related to the mechanical properties of the material and directly affects the response of the grating under external stress. 12 is the second Poisson's ratio of the material being tested, which describes the strain caused in other directions when stress is applied in one direction. This parameter is also related to the elastic properties of the grating, affecting the sensitivity of the grating to external pressure or stress. v is the propagation speed of ultrasound in the material. The change of sound speed can affect the reflection wavelength of the grating, because the propagation of ultrasound will cause dynamic strain of the material, thus affecting the structure and optical properties of the grating.

[0099] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the invention.

Claims

1. A stress detection method of graphene composite piezoelectric material integrated optical fiber sensing, characterized in that: The following steps are involved: S1: Generate a signal using a signal generator and transmit it to the composite flexible piezoelectric material through a power amplifier; S2: Use composite flexible piezoelectric materials to generate ultrasonic waves and conduct them in the material being tested; S3: Use the fiber grating sensing and demodulation module to demodulate the ultrasonic wave transmitted in the material under test and transmit it to the host computer; S4: Use the host computer to display, store and process the demodulated ultrasonic signal to obtain the stress of the material under test and complete the stress detection of graphene composite piezoelectric material integrated optical fiber sensing.

2. The stress detection method of graphene composite piezoelectric material integrated optical fiber sensing according to claim 1, characterized in that: The preparation of the composite flexible piezoelectric material in S1 comprises the following steps: S11: Preparation of graphene on single-crystal silicon substrate using metal-free and atmospheric pressure chemical vapor deposition technology; S12: Preparation of titanium zirconium oxide by sol-gel method; S13: Compounding the prepared graphene and zirconium oxide titanium to obtain a composite flexible piezoelectric material.

3. The stress detection method of graphene composite piezoelectric material integrated optical fiber sensing according to claim 2, characterized in that: The S13 includes the following sub-steps: S131: grinding zirconium titanium oxide, adding an ethanol solution as a dispersant to the graphene and the ground zirconium titanium oxide, and uniformly mixing them; S132: The uniformly mixed graphene and zirconium oxide titanium are heat treated and characterized using a scanning electron microscope to obtain a composite flexible piezoelectric material.

4. The stress detection method of graphene composite piezoelectric material integrated optical fiber sensing according to claim 1, characterized in that: The fiber grating sensing and demodulation module in S3 includes a free-enhanced laser bandwidth light source, an optical circulator, a reference grating, a sensing grating, a photoelectric detector and a data acquisition card.

5. The stress detection method of graphene composite piezoelectric material integrated optical fiber sensing according to claim 4, characterized in that: The S3 includes the following sub-steps: S31: transmitting the ultrasonic wave conducted in the material to be tested to a sensing grating located on the material to be tested through a single-mode optical fiber, and using the sensing grating to identify the ultrasonic signal; S32: guiding the broadband light emitted by the free-enhanced laser broadband light source to the sensing grating located on the material to be tested through a circulator, and based on the ultrasonic signal recognition result, if the broadband light meets the wavelength condition, the broadband light is reflected back to the circulator and enters the reference grating; S33: using a photodetector to capture a light signal transmitted by the reference grating, and converting the light signal into a voltage signal; S34: using a data acquisition card to acquire the voltage signal, and transmitting the acquired voltage signal to a host computer.

6. The stress detection method of graphene composite piezoelectric material integrated optical fiber sensing according to claim 5, characterized in that: The reference grating is pasted on the surface of the composite flexible piezoelectric material.

7. The stress detection method of graphene composite piezoelectric material integrated optical fiber sensing according to claim 5, characterized in that: In S31, under the action of ultrasound, the strain field model along the axial direction of the sensing grating is: Among them, ε AE (·) is the strain field model, A AE is the ultrasonic amplitude, λ AE is the wavelength of the ultrasonic wave in the material being measured, z is the coordinate point along the axial direction of the sensing grating, ω AE is the angular frequency of the ultrasonic wave, and t is the time.

8. The stress detection method of graphene composite piezoelectric material integrated optical fiber sensing according to claim 7, characterized in that: The central wavelength λ of the sensing grating B (t) is: l B (t)=λ B0 +Δλ0cos(ω s t) Among them, λ B0 is the reference wavelength of the sensing grating, Δλ0 is the change in the central wavelength of the sensing grating after the action of ultrasound, ω s is the period of the sensing grating, ε AE (·) is the strain field model, n eff0 is the effective refractive index of the core axial of the sensing grating when it is not affected by external force, p 11 is the first Poisson's ratio of the material being tested, p 12 is the second Poisson’s ratio of the material being tested, and v is the propagation speed of ultrasound in the material.

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