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CN108831990B - Preparation method of full-stress sensor based on cement-based piezoelectric composite material element - Google Patents

Preparation method of full-stress sensor based on cement-based piezoelectric composite material element Download PDF

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CN108831990B
CN108831990B CN201810637464.1A CN201810637464A CN108831990B CN 108831990 B CN108831990 B CN 108831990B CN 201810637464 A CN201810637464 A CN 201810637464A CN 108831990 B CN108831990 B CN 108831990B
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cement
mode
mode element
mould
piezoelectric ceramic
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CN108831990A (en
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李应卫
姜清辉
马永力
丁绍华
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Wuhan University WHU
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/04—Treatments to modify a piezoelectric or electrostrictive property, e.g. polarisation characteristics, vibration characteristics or mode tuning
    • H10N30/045—Treatments to modify a piezoelectric or electrostrictive property, e.g. polarisation characteristics, vibration characteristics or mode tuning by polarising
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/02—Forming enclosures or casings
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/06—Forming electrodes or interconnections, e.g. leads or terminals
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/08—Shaping or machining of piezoelectric or electrostrictive bodies
    • H10N30/085—Shaping or machining of piezoelectric or electrostrictive bodies by machining
    • H10N30/086—Shaping or machining of piezoelectric or electrostrictive bodies by machining by polishing or grinding
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/08—Shaping or machining of piezoelectric or electrostrictive bodies
    • H10N30/085—Shaping or machining of piezoelectric or electrostrictive bodies by machining
    • H10N30/088—Shaping or machining of piezoelectric or electrostrictive bodies by machining by cutting or dicing

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Abstract

本发明公开了一种基于水泥基压电复合材料元件的全应力传感器的制备方法，包括：第一步，制备d15模式的1‑3型水泥基压电复合材料元件，即d15模式元件；第二步，制备d33模式的1‑3型水泥基压电复合材料元件，即d33模式元件；第三步，利用d15模式元件和d33模式元件制备全应力传感器，主要包括：在水泥基体两两相邻的三个表面的每一面上，均布置一d33模式元件和一d15模式元件；三个d15模式元件的极化方向两两垂直，三个d33模式元件的极化方向也两两垂直。本发明所制备的全应力传感器灵敏度高、频带响应宽、抗干扰效果好，且与混凝土结构相容性好。将其埋入混凝土结构内部或粘贴于混凝土结构表面，可同时测量混凝土结构的全应力。

Figure 201810637464

The invention discloses a preparation method of a full stress sensor based on a cement -based piezoelectric composite material element. The second step is to prepare the d 33 mode 1-3 type cement-based piezoelectric composite element, namely the d 33 mode element; the third step is to use the d 15 mode element and the d 33 mode element to prepare a full stress sensor, which mainly includes: A d 33 mode element and a d 15 mode element are arranged on each of the three adjacent surfaces of the cement matrix; the polarization directions of the three d 15 mode elements are perpendicular to each other, and the three d 33 mode elements The polarization directions are also perpendicular to each other. The full stress sensor prepared by the invention has high sensitivity, wide frequency band response, good anti-interference effect and good compatibility with concrete structures. It can be embedded in the concrete structure or pasted on the surface of the concrete structure, and the total stress of the concrete structure can be measured at the same time.

Figure 201810637464

Description

Preparation method of full-stress sensor based on cement-based piezoelectric composite material element
Technical Field
The invention belongs to the technical field of cement-based piezoelectric composite materials, and particularly relates to a preparation method of a full-stress sensor based on a cement-based piezoelectric composite material element.
Background
In the field of civil engineering, concrete structures are the most widely used civil structures. The safety and stability of the structure is a very important point in the overall life of the concrete structure. Therefore, in recent years, health monitoring of concrete structures has been increasingly emphasized. The sensing elements currently used in the civil engineering field are generally relatively mature materials used in other fields, such as optical fibers, piezoelectric ceramics, memory alloys, etc. These materials often have very significant compatibility problems with concrete, the most prominent structural material in the field of civil engineering. The stress-strain condition of the concrete structure cannot be reflected in situ and really. Therefore, it is necessary to develop a sensor which can be directly embedded in the concrete and can be directly used for measuring the three-dimensional stress in the concrete.
The cement-based piezoelectric composite material is a novel functional material developed in recent years, has the characteristics of good piezoelectric property, outstanding electromechanical coupling property, good mechanical and acoustic property matching property with concrete materials and the like, and has potential application prospect in health monitoring of civil engineering structures. The cement-based piezoelectric composite material sensor made of the cement-based piezoelectric composite material overcomes the problem that the traditional sensor is incompatible with a concrete structure, has high sensitivity and good durability, and can be used for monitoring the conditions of stress strain and the like in the concrete structure. However, at present, there is no effective means for directly measuring the total stress state in the concrete structure, and if a total stress sensor which can be directly embedded in the concrete and directly used for simultaneously measuring the normal stress and the shear stress in the concrete can be developed, the method has important significance for measuring the stress in the concrete in a working state.
Disclosure of Invention
The invention aims to provide a preparation method of a full-stress sensor based on a cement-based piezoelectric composite material element, and the prepared full-stress sensor is suitable for full-stress measurement in a concrete structure.
The invention provides a preparation method of a full-stress sensor based on a cement-based piezoelectric composite material element, which comprises the following steps:
first step, preparation d15The model 1-3 type cement-based piezoelectric composite material element specifically includes:
(101) polarizing the piezoelectric ceramic block;
(102) removing the polarizing electrode of the piezoelectric ceramic block;
(103) cutting the piezoelectric ceramic block into a plurality of ceramic columns which are uniformly arranged by using a cutting machine to obtain a piezoelectric ceramic column array, wherein the cutting direction is vertical to the polarization direction;
(104) placing the piezoelectric ceramic column array base into a mould, pouring the cement base material into the mould, and after pouring, placing the mould into a curing box for curing;
(105) after the maintenance is finished, taking out the green body, cutting off the base, and polishing and grinding the green body;
(106) working electrodes are manufactured on two opposite surfaces in the blank body perpendicular to the cutting direction, and the d of the ceramic column accounting for 20-80% of the volume is obtained15Mode 1-3 Cement-based piezoelectric composite element, abbreviated as d15A mode element;
second step, preparation d33The model 1-3 type cement-based piezoelectric composite material element specifically includes:
(201) polarizing the piezoelectric ceramic block;
(202) removing the polarizing electrode of the piezoelectric ceramic block;
(203) cutting the piezoelectric ceramic block into a plurality of ceramic columns which are uniformly arranged by using a cutting machine to obtain a piezoelectric ceramic column array, wherein the cutting direction is parallel to the polarization direction;
(204) placing the piezoelectric ceramic column array base into a mould, pouring the cement base material into the mould, and after pouring, placing the mould into a curing box for curing;
(205) after the maintenance is finished, taking out the green body, cutting off the base, and polishing and grinding the green body;
(206) working electrodes are manufactured on two opposite surfaces in the blank body perpendicular to the cutting direction, and the d of the ceramic column accounting for 20-80% of the volume is obtained33Mode 1-3 Cement-based piezoelectric composite element, abbreviated as d33A mode element;
third step, using d15Mode element and d33The mode element preparation full stress sensor specifically includes:
(301) will d15Mode element and d33The working electrodes of the mode elements are all led out through wires;
(302) three d15Mode element and three d33The pattern elements are arranged on three adjacent surfaces of a cubic cement matrix, and a d is arranged on each surface33Mode element and d15A mode element; three d15The polarization directions of the mode elements are two by two perpendicular, three d33Polarization method of mode elementThe directions are also vertical two by two;
(303) using encapsulating material to arrange d on cement base15Mode element and d33Integrally packaging the mode element, and curing;
(304) preparing a shielding layer outside the packaging layer by adopting a shielding material;
(305) will be reacted with d15Mode element and d33The wire connected to the working electrode of the mode element is connected to the shield wire, and the shield wire is connected to the shield layer via another wire.
Further, in the first step and the second step, before the cement base material is poured into the mould, the cement base material is vacuumized in vacuum equipment; the method is characterized in that the cement base material is poured into the mould, and the mould is vacuumized and vibrated.
Further, the cement base material used in the first step and the second step is formed by mixing cement, fly ash and water, wherein the mass ratio of the fly ash to the cement is (0.05-0.5): 1, the water-cement ratio is (0.2-0.7): 1.
further, the formula of the packaging material comprises epoxy resin, fly ash, cement, a curing agent and water, wherein the epoxy resin, the fly ash and the cement are used as main packaging materials, and the mass ratio of the epoxy resin to the fly ash to the cement is (0.5-1): (0.05-0.5): 1, the mass ratio of the epoxy resin to the curing agent is (1-4): 1, the mass ratio of water to the main packaging material is (0.2-0.7): 1.
further, the formula of the shielding material comprises graphite powder, cement and water, wherein the graphite powder and the cement are used as main shielding materials, and the mass ratio of the graphite powder to the cement is (0.05-0.3): 1, the mass ratio of water to the main shielding material is (0.2-0.7): 1.
compared with the prior art, the invention has the following advantages and beneficial effects:
(1) the method firstly prepares the self-designed 1-3 type cement-based piezoelectric composite material element, and then prepares the full-stress sensor by utilizing the prepared 1-3 type cement-based piezoelectric composite material element, and the prepared full-stress sensor has high sensitivity, wide frequency band response, good anti-interference effect and good compatibility with the concrete structure. The full-stress sensor prepared by the invention is buried in a concrete structure or is adhered to the surface of the concrete structure, can simultaneously measure the normal stress and the shear stress of the concrete structure, and has important significance for the application of the cement-based piezoelectric composite material in the health monitoring of the concrete structure.
(2) The 1-3 type cement-based piezoelectric composite material element with two modes prepared by the full-stress sensor improves the cement base material, so that the structure of the cement-based piezoelectric composite material is more compact, and the stability of the cement-based piezoelectric composite material is improved.
(3) The full-stress sensor adopts the mixture of the epoxy resin, the cement and the fly ash to prepare the packaging layer, so that the sensitivity and the frequency bandwidth of the full-stress sensor can be improved, and the packaging bonding strength is high; meanwhile, the composite material has good heat resistance, alkali resistance and insulativity, and plays a role in protecting and packaging the 1-3 type cement-based piezoelectric composite material elements in two modes.
(4) The full-stress sensor provided by the invention adopts the mixture of cement and graphite powder to prepare the shielding layer, and the shielding layer enables the full-stress sensor to have a good coupling effect with a concrete structure and a good noise shielding effect, and can improve the signal-to-noise ratio of the full-stress sensor.
(5) The full-stress sensor adopts the copper core wire and the shielding copper core cable, so that the noise influence can be better reduced.
(6) The preparation process is simple and easy to operate, and is suitable for large-scale production.
Drawings
FIG. 1 shows example d15A preparation process flow of the mode element;
FIG. 2 shows example d33A preparation process flow of the mode element;
FIG. 3 is a schematic structural diagram of an embodiment of a full-stress sensor;
figure 4 is a schematic three-dimensional stress diagram of any point in space within a concrete structure;
FIG. 5 shows a diagram of d in the present invention33Mode element and d15Piezoelectric effect principle of mode elementWherein d is shown in the drawing (a)33Schematic diagram of piezoelectric effect of mode element, diagram (b) being d15A schematic diagram of the piezoelectric effect of the mode element;
FIG. 6 is a flow chart of the manufacturing process of the all-stress sensor in the embodiment.
In the figure, 1-piezoelectric ceramic block, 2-polarizing electrode, 3-ceramic column, 4-base, 5-cement substrate, 6-blank, 7-working electrode, 8-first d15Mode element, 9-second d15Mode element, 10-third d15Mode element, 11-first d33Mode element, 12-second d33Mode element, 13-third d33Mode element, 14-cement matrix, 15-encapsulation layer, 16-shielding layer, 17-wire, 18-shielding wire, 19-charge;
a and f represent the step of removing the polarized electrode, b and g represent the step of cutting the ceramic post, c and h represent the step of pouring the cement base material, d and i represent the steps of cutting the base and polishing, and e and j represent the step of making the working electrode.
Detailed Description
In order to more clearly illustrate the present invention and/or the technical solutions in the prior art, the following will describe embodiments of the present invention with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
For convenience of description, d is defined herein15Mode and d33Model 1-3 Cement-based piezoelectric composite elements, each abbreviated as d15Mode element and d33A mode element.
In this embodiment, the cutting-casting method is used to prepare d15The preparation process of the mode element is shown in figure 1, and the specific steps are as follows:
(101) the piezoelectric ceramic block 1 with the size of 8mm multiplied by 8mm is polarized, and the piezoelectric ceramic block 1 can be a lead zirconate titanate piezoelectric ceramic block, a lead magnesium niobate zirconate titanate piezoelectric ceramic block, a lead lithium niobate zirconate titanate piezoelectric ceramic block, and the like.
(102) The polarizing electrodes 2 of the piezoelectric ceramic block 1 are removed.
(103) And cutting the piezoelectric ceramic block 1 into a plurality of ceramic columns 3 which are uniformly arranged by using a cutting machine to obtain a piezoelectric ceramic column array, wherein the cutting direction is vertical to the polarization direction. The ceramic posts 3 are 2mm by 7mm in size.
(104) And (3) placing the piezoelectric ceramic column array and the base 4 into a mould, pouring the cement base material 5 into the mould, and after pouring, placing the mould into a curing box for curing.
Preferably, before the step is performed, an ultrasonic cleaning machine can be used for performing ultrasonic cleaning on the piezoelectric ceramic column array to remove residual ceramic residues so as to avoid affecting the performance of the element. And then, placing the dried piezoelectric ceramic column array into a mold.
In order to eliminate air bubbles in the cement base material and improve the compactness of the cement base material, the prepared cement base material is fully stirred and then is placed into vacuum equipment for vacuum pumping treatment; meanwhile, a vacuumizing vibration casting method is adopted for casting, namely, the mould is vacuumized and vibrated while casting.
In order to reduce holes in a cement base material, enhance the compactness of the cement base material and further improve the overall performance of the cement-based piezoelectric composite material, the invention also provides the cement base material formed by mixing cement, fly ash and water, wherein the mass ratio of the fly ash to the cement is (0.05-0.5): 1, the water-cement ratio is (0.2-0.7): 1. the water-cement ratio is mWater (W)：(mFly ash+mCement) Wherein m isWater (W)、mFly ash、mCementRespectively representing the mass of water, fly ash and cement. The cement can be sulphoaluminate cement, calcium barium sulphoaluminate cement, silicate cement, chlorate cement, fluorine chlorate cement and the like; the fly ash can be I-grade fly ash, II-grade fly ash, III-grade fly ash and the like. By adopting the cement base material for pouring, the compactness of the cement-based piezoelectric composite material can be obviously improved, so that better stability is obtained.
(105) And after the maintenance is finished, taking out the blank body 6, cutting off the base 4, and polishing the blank body 6 until all the surfaces of the blank body 6 are completely exposed out of the end of the ceramic column 3. In the present embodiment, the size of the ceramic posts 3 in the finally obtained green body 6 is 2mm × 2mm × 6 mm.
(106) Working electrodes 7 are formed on the surfaces of the green body 6 where the two ends of the ceramic posts 3 are exposed, i.e., the two opposite surfaces perpendicular to the cutting direction, to obtain d15A mode element. The working electrode 7 includes a positive electrode and a negative electrode. D produced in this example15In the mode element, the volume of the ceramic column 3 accounts for 20-80%, and the working electrode 7 adopts low-temperature conductive silver paste.
In this embodiment, the cutting-casting method is also used to prepare d33The preparation process of the mode element is shown in figure 2, and the specific steps are as follows:
(201) the piezoelectric ceramic block 1 with the size of 8mm multiplied by 8mm is polarized, and the piezoelectric ceramic block 1 can be a lead zirconate titanate piezoelectric ceramic block, a lead magnesium niobate zirconate titanate piezoelectric ceramic block, a lead lithium niobate zirconate titanate piezoelectric ceramic block, and the like.
(202) The polarizing electrodes 2 of the piezoelectric ceramic block 1 are removed.
(203) Cutting the piezoelectric ceramic block 1 into a plurality of ceramic columns 3 which are uniformly arranged by using a cutting machine to obtain a piezoelectric ceramic column array; the cutting direction is parallel to the polarization direction of the piezoelectric ceramic block 1. The ceramic posts 3 are 2mm by 7mm in size.
(204) And (3) placing the piezoelectric ceramic column array and the base 4 into a mould, pouring the cement base material 5 into the mould, and after pouring, placing the mould into a curing box for curing.
Preferably, before the step is performed, an ultrasonic cleaning machine can be used for performing ultrasonic cleaning on the piezoelectric ceramic column array to remove residual ceramic residues so as to avoid affecting the performance of the element. And then, placing the dried piezoelectric ceramic column array into a mold.
In order to eliminate air bubbles in the cement base material and improve the compactness of the cement base material, the cement base material is fully stirred and then is placed into vacuum equipment for vacuum pumping treatment; meanwhile, a vacuumizing vibration casting method is adopted for casting, namely, the mould is vacuumized and vibrated while casting.
Reinforcing cement to reduce voids in cement substratesThe invention further provides a cement base material formed by mixing cement, fly ash and water, wherein the mass ratio of the fly ash to the cement is (0.05-0.5): 1, the water-cement ratio is (0.2-0.7): 1. the water-cement ratio is mWater (W)：(mFly ash+mCement) Wherein m isWater (W)、mFly ash、mCementRespectively representing the mass of water, fly ash and cement. The cement can be sulphoaluminate cement, calcium barium sulphoaluminate cement, silicate cement, chlorate cement, fluorine chlorate cement and the like; the fly ash can be I-grade fly ash, II-grade fly ash, III-grade fly ash and the like. By adopting the cement base material for pouring, the compactness of the cement-based piezoelectric composite material can be obviously improved, so that better stability is obtained.
(205) And after the maintenance is finished, taking out the blank body 6, cutting off the base 4, and polishing the blank body 6 until all the surfaces of the blank body 6 are completely exposed out of the ceramic posts 3. In this example, the size of the ceramic posts 3 in the finally obtained green body 6 is 2mm × 2mm × 6 mm.
(206) Working electrodes 7 are made on the surfaces of the blank 6 exposed at the two ends of the ceramic column 3, namely two opposite surfaces vertical to the cutting direction, so as to obtain d33A mode element. D thus produced33In the mode element, the volume ratio of the ceramic posts 3 is 20-80%. In this embodiment, the working electrode 7 is made of low-temperature conductive silver paste.
Referring to FIG. 3, a diagram based on d is shown15Mode element and d33A full stress sensor made of mode elements. The full stress sensor mainly comprises three d15Mode element and three d33Mode element, three d15The mode elements are respectively marked as the first d15Mode element 8, second d15Mode element 9, third d15Mode element 10, three d33The mode elements are respectively marked as the first d33Mode element 11, second d33Mode element 12, third d33 A mode element 13. Three d15Mode element and three d33The pattern elements being arranged in a cubic cementThree adjacent surfaces of the substrate 14 are arranged pairwise, and one surface d is arranged on each surface33Mode element and d15A mode element. In the present embodiment, the first d15Mode element 8 and first d33The pattern elements 11 being arranged on the same plane, the second d15Mode element 9 and second d33The pattern elements 12 being arranged on the same plane, the third d15Mode element 10 and third d33The pattern elements 13 are arranged on the same plane. In this embodiment, d on each side15Mode element and d33The working electrode of the mode element is parallel to the plane.
Arranging d on the cement matrix 1415Mode element and d33When the elements are in a pattern, d is arranged15Mode element and d33Mode elements, the polarization directions being perpendicular to one another in space two by two, i.e. three d15The polarization directions of the mode elements should be perpendicular two by two, three d33The polarization directions of the mode elements should also be perpendicular two by two. For example, see FIG. 3, first d15The polarization direction of the mode element 8 is in the x-y plane and parallel to the y direction, second d15The polarization of the mode element 9 is reversed in the x-z plane and parallel to the x-direction, third d15The polarization direction of the mode element 10 is in the y-z plane and parallel to the z direction.
Three d15Mode element and three d33The mode element is externally encapsulated with an encapsulation layer 15, the encapsulation layer 15 is externally encapsulated with a shielding layer 16, wherein three d15Mode element and three d33The working electrodes of the mode elements are all led out of the shielding layer 16 through a lead 17 and connected with a shielding wire 18, and the shielding wire 18 is also connected with the shielding layer 16 through another lead. In this embodiment, the conductor 17 is a copper core conductor, and the shield wire 18 is a shield copper core.
Referring to fig. 4, a three-dimensional stress diagram of any point in space within a concrete structure is shown. According to the theory of mechanics of materials, the spatial stress state of a spatial point can be studied by analyzing the tiny regular hexahedron unit bodies surrounding the spatial point around the spatial point. In FIG. 4, σx、σy、σzRespectively represent three of x, y and zA directional positive stress; tau isxy、τyx、τyz、τzy、τxz、τzxRespectively, is shear stress of the space cube, in numerical valuexy＝τyx，τyz＝τzy，τxz＝τzx. Therefore, the normal stress and the shear stress on three adjacent surfaces of the space cube are measured, and the whole stress state of the space point can be known. In the full-stress sensor of the invention, d33The mode element being used to measure the normal stress, d15The mode element is used to measure shear stress. On three adjacent surfaces of the cement matrix, each surface being provided with d15Mode element and d33The mode element can measure the stress state of the space point.
FIG. 5 shows d33Mode element and d15The piezoelectric effect of the mode element is schematically shown in FIG. 5(a), where d is shown33Schematic diagram of piezoelectric effect of mode element, when positive stress σ is applied to the element body, which generates electric displacement in the polarization direction and then accumulates equal but opposite charges 19 on the surfaces of the two working electrodes 7, the applied positive stress σ can be represented by σ ═ q/(d)33A) calculation, q represents the amount of charge, d33Denotes d33Piezoelectric constant of mode element, a represents d33The area of the working electrode surface of the mode element. Thus, d33The mode element may monitor for positive stress.
See FIG. 5(b), denoted as d15The principle diagram of the piezoelectric effect of the mode element is that when a shear stress tau is applied to the element body, equal but opposite charges 19 are accumulated on the surfaces of two working electrodes 7 parallel to the polarization direction, and the applied shear stress tau can be increased by tau-q/(d)15A) calculation, q represents the amount of charge, d15Denotes d15Piezoelectric constant of mode element, a represents d15The area of the working electrode surface of the mode element.
Thus, d is prepared33The mode element can be used to measure normal stress, prepared d15The mode element measures shear stress. On three adjacent surfaces of the cement matrix, each surface being provided with d33Mode element and d15The mode element can measure the stress state of the space point.
In the present embodiment, based on d15Mode element and d33The preparation process of the full-stress sensor of the mode element is shown in FIG. 6, and the specific steps are as follows:
(301) will d15Mode element and d33The working electrodes of the mode elements are all led out through leads.
(302) Will d15Mode element and d33The pattern elements are arranged on three faces of the cubic cement matrix adjacent to each other in pairs.
(303) Using encapsulating material to arrange d on cement base15Mode element and d33The pattern elements are integrally encapsulated and cured. The packaging material is epoxy resin-based packaging material.
In this embodiment, the encapsulation layer is used to protect and encapsulate d15Mode element and d33The formula of the mode element comprises epoxy resin, fly ash, cement, a curing agent and water, wherein the epoxy resin, the fly ash and the cement are used as main packaging materials, and the mass ratio of the epoxy resin to the fly ash to the cement is (0.5-1): (0.05-0.5): 1, the mass ratio of the epoxy resin to the curing agent is (1-4): 1, the mass ratio of water to the main packaging material is (0.2-0.7): 1. preferably, the epoxy resin is AB-grouting resin, E-55 epoxy resin or W95 epoxy resin; the cement is sulphoaluminate cement, calcium barium sulphoaluminate cement, silicate cement, chlorate cement or fluorine chlorate cement; the fly ash is I-grade fly ash, II-grade fly ash or III-grade fly ash. The packaging layer can improve the sensitivity and the frequency bandwidth of the full-stress sensor, has high bonding strength with the 1-3 type cement-based piezoelectric composite material element, and has good heat resistance, alkali resistance, insulativity and the like.
(304) And preparing a shielding layer outside the packaging layer by adopting a shielding material, wherein the adopted shielding material is a cement-based shielding material.
In the specific embodiment, the formula of the shielding layer comprises graphite powder, cement and water, wherein the graphite powder and the cement are main shielding materials, and the mass ratio of the graphite powder to the cement is (0.05-0.3): 1, the mass ratio of water to the main shielding material is (0.2-0.7): 1. preferably, the cement is sulphoaluminate cement; the graphite powder is superfine graphite powder. The shielding layer can enable the full-stress sensor to have a better coupling effect with a concrete structure, and enable the full-stress sensor to better shield noise, thereby improving the signal-to-noise ratio of the full-stress sensor.
(305) Will be reacted with d15Mode element and d33The wire connected to the working electrode of the mode element is connected to the shield wire, and the shield wire is connected to the shield layer via another wire.
The full-stress sensor can be used for monitoring the full stress on the surface or inside of a concrete structure, and specifically comprises the following steps: the normal stress and the shear stress on the surface or inside of the concrete structure can be monitored by sticking the full-stress sensor on the surface of the concrete structure or placing the full-stress sensor inside the concrete structure, so that the health monitoring of the concrete structure is realized.
Although the present invention has been described in detail with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (2)

1. A preparation method of a full-stress sensor based on a cement-based piezoelectric composite material element is characterized by comprising the following steps:
first step, preparation d15The model 1-3 type cement-based piezoelectric composite material element specifically includes:
(101) polarizing the piezoelectric ceramic block;
(102) removing the polarizing electrode of the piezoelectric ceramic block;
(103) cutting the piezoelectric ceramic block into a plurality of ceramic columns which are uniformly arranged by using a cutting machine to obtain a piezoelectric ceramic column array, wherein the cutting direction is vertical to the polarization direction;
(104) placing the piezoelectric ceramic column array base into a mould, pouring the cement base material into the mould, and after pouring, placing the mould into a curing box for curing;
(105) after the maintenance is finished, taking out the green body, cutting off the base, and polishing and grinding the green body;
(106) working electrodes are manufactured on two opposite surfaces in the blank body perpendicular to the cutting direction, and the d of the ceramic column accounting for 20-80% of the volume is obtained15Mode 1-3 Cement-based piezoelectric composite element, abbreviated as d15A mode element;
second step, preparation d33The model 1-3 type cement-based piezoelectric composite material element specifically includes:
(201) polarizing the piezoelectric ceramic block;
(202) removing the polarizing electrode of the piezoelectric ceramic block;
(203) cutting the piezoelectric ceramic block into a plurality of ceramic columns which are uniformly arranged by using a cutting machine to obtain a piezoelectric ceramic column array, wherein the cutting direction is parallel to the polarization direction;
(204) placing the piezoelectric ceramic column array base into a mould, pouring the cement base material into the mould, and after pouring, placing the mould into a curing box for curing;
(205) after the maintenance is finished, taking out the green body, cutting off the base, and polishing and grinding the green body;
(206) working electrodes are manufactured on two opposite surfaces in the blank body perpendicular to the cutting direction, and the d of the ceramic column accounting for 20-80% of the volume is obtained33Mode 1-3 Cement-based piezoelectric composite element, abbreviated as d33A mode element;
third step, using d15Mode element and d33The mode element preparation full stress sensor specifically includes:
(301) will d15Mode element and d33The working electrodes of the mode elements are all led out through wires;
(302) three d15Mode element and three d33The pattern elements are arranged on three adjacent surfaces of a cubic cement matrix, and a d is arranged on each surface33Mode element and d15Mode element(ii) a Three d15The polarization directions of the mode elements are two by two perpendicular, three d33The polarization directions of the mode elements are also vertical two by two;
(303) using encapsulating material to arrange d on cement base15Mode element and d33Integrally packaging the mode element, and curing;
(304) preparing a shielding layer outside the packaging layer by adopting a shielding material;
(305) will be reacted with d15Mode element and d33The conducting wire connected with the working electrode of the mode element is connected with the shielding wire, and in addition, the shielding wire is also connected with the shielding layer through another conducting wire;
the cement base material used in the first step and the second step is formed by mixing cement, fly ash and water, wherein the mass ratio of the fly ash to the cement is (0.05-0.5): 1, the water-cement ratio is (0.2-0.7): 1;
the formula of the packaging material comprises epoxy resin, fly ash, cement, a curing agent and water, wherein the epoxy resin, the fly ash and the cement are used as main packaging materials, and the mass ratio of the epoxy resin to the fly ash to the cement is (0.5-1): (0.05-0.5): 1, the mass ratio of the epoxy resin to the curing agent is (1-4): 1, the mass ratio of water to the main packaging material is (0.2-0.7): 1;
the formula of the shielding material comprises graphite powder, cement and water, wherein the graphite powder and the cement are used as main shielding materials, and the mass ratio of the graphite powder to the cement is (0.05-0.3): 1, the mass ratio of water to the main shielding material is (0.2-0.7): 1.
2. the method for preparing a full-stress sensor based on a cement-based piezoelectric composite material element according to claim 1, wherein the method comprises the following steps:
in the first step and the second step, before the cement base material is poured into a mould, the cement base material is vacuumized in vacuum equipment; and (3) vacuumizing and vibrating the mould while pouring the cement base material into the mould.
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