CN111855033A - A 1-3 type emulsified asphalt/cement based piezoelectric sensor and its preparation method and use - Google Patents

Abstract

The invention relates to the field of road engineering, in particular to an emulsified asphalt/cement-based piezoelectric sensor. The piezoelectric sensor comprises a packaging part and a piezoelectric sensing element packaged in the packaging part, wherein the piezoelectric sensing element comprises piezoelectric material column arrays and filling phases distributed among the piezoelectric material column arrays, the extension direction of each piezoelectric material column is consistent with the direction of a polarization main shaft of the piezoelectric material column, and the piezoelectric sensing element further comprises two conducting layers which are located on the surfaces of the piezoelectric material column arrays and are respectively connected with two poles of the piezoelectric material columns. According to the piezoelectric sensor provided by the invention, the filling base material, the packaging material and the like are improved, so that the composite material structure between the filling base material and the piezoelectric material is more compact, the stability and compatibility of the cement-based piezoelectric composite material are effectively improved, the sensitivity of the sensor can be improved, the sensor has the advantages of wide frequency band, strong anti-interference capability and the like, and the signal-to-noise ratio is also effectively improved.

Description

A 1-3 type emulsified asphalt/cement based piezoelectric sensor and its preparation method and use

technical field

The invention relates to the field of road engineering, in particular to a 1-3 type emulsified asphalt/cement-based piezoelectric sensor and its preparation method and application.

Background technique

As the lifeline of national economic development, transportation plays an important role in national development. However, the asphalt pavement accounts for more than 95% of the expressway. With the increase of service life, facing the complex and changeable climate environment, coupled with the influence of many vehicles and heavy load, the asphalt pavement appears rutting, crowding, waves, etc. The prevention and maintenance of asphalt pavement has become one of the important problems to be solved urgently in the field of road engineering. The road health monitoring plays an important role in the road management system through real-time, continuous and accurate monitoring of road conditions, and the sensor system is the forefront of road health monitoring. The real-time monitoring of road traffic loads and performance changes is conducive to optimizing roads. material and structure, so as to achieve the purpose of extending the service life of the road.

With the introduction of autonomous driving, in order to make connected cars travel safely and conveniently, the concept of smart roads with automatic sensing capabilities has also emerged, that is, to realize the safe and reliable driving of smart cars on smart roads. Compared with the autonomous driving technology of single perception on the vehicle side, the vehicle-road integration technology of comprehensive perception on the vehicle and road side significantly improves the perception efficiency of autonomous vehicles. Therefore, developing a road dynamic monitoring system with simple preparation, low cost, high sensitivity, wide frequency band, good durability, and good compatibility with the main structure of the road has become one of the key points of the intelligent transportation system.

Cement-based piezoelectric composites are widely used in the health monitoring of civil engineering structures due to their fast response speed, good durability and good compatibility with concrete. However, high-grade highways are mainly asphalt pavements, and the compatibility of traditional cement-based piezoelectric composites with the main structure of asphalt pavements is far worse than that of concrete structures. On the other hand, the interface stability between cement-based materials and piezoelectric ceramics severely limits their service life, which in turn affects their promotion in highways.

SUMMARY OF THE INVENTION

In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an emulsified asphalt/cement-based piezoelectric sensor and its preparation method and use, which are used to solve the problems in the prior art.

In order to achieve the above object and other related objects, one aspect of the present invention provides a piezoelectric sensor, including a package, and a piezoelectric sensing element packaged in the package, the piezoelectric sensing element including a piezoelectric material column array, and The filling phase distributed between the piezoelectric material column arrays, the extension direction of each piezoelectric material column is consistent, and the polarization main axis direction of the piezoelectric material column is consistent with its extension direction, and the piezoelectric induction element further includes two conductive layers , the two conductive layers are located on the surface of the piezoelectric material column array, and are respectively connected with the two poles of the piezoelectric material column.

In some embodiments of the present invention, the material of the piezoelectric material column is selected from inorganic piezoelectric materials, preferably, the inorganic piezoelectric material is selected from piezoelectric ceramics, and the piezoelectric ceramics are selected from lead zirconate titanate A combination of one or more of electric ceramics, niobium lithium lead zirconate titanate piezoelectric ceramics, and niobium magnesium lead zirconate titanate piezoelectric ceramics.

In some embodiments of the present invention, the piezoelectric material has a density of 6.90×10 ³ to 7.75×10 ³ kg/m ³ and a piezoelectric strain constant of 2.25×10 ⁻¹⁰ to 5.95×10 ⁻¹⁰ C/N, relative to The dielectric constant is 1050-3500, and the electromechanical coupling coefficient is 0.31-0.76%.

In some embodiments of the present invention, the height of the piezoelectric material column is 2-4 mm, the cross-sectional area of a single piezoelectric material column is 3.43-14.90 mm ² , and the total cross-sectional area of the piezoelectric material column is 360～720mm ² , the column spacing is 0.5～1.25mm.

In some embodiments of the present invention, in the cross section of a single piezoelectric material column, the extension length in a single direction is generally not more than 3.86 mm, and preferably, the piezoelectric material column is a rectangular parallelepiped.

In some embodiments of the present invention, in the piezoelectric sensing element, the volume percentage of the piezoelectric material pillars is 40-80%.

In some embodiments of the present invention, the material of the filling phase is selected from the mixed substrate of emulsified asphalt and cement, and the raw materials of the mixed substrate of emulsified asphalt and cement, in parts by weight, include the following components:

Cement 60-100 copies;

20-33 parts of emulsified asphalt;

Water 33-60 parts.

In some embodiments of the present invention, the cement is selected from Portland cement.

In some embodiments of the present invention, the emulsified asphalt is selected from cationic emulsified asphalt, the cationic emulsified asphalt is a fast-cracked cationic emulsified asphalt, the sieve balance of the cationic emulsified asphalt is greater than or equal to 0.1%, and the 1d room temperature stability is less than or equal to 1%.

In some embodiments of the present invention, the material of the package is selected from epoxy asphalt, and the raw materials of the epoxy asphalt, in parts by weight, include: 75-93 parts of base asphalt, 1-5 parts of epoxy resin, and 6-20 parts hardener.

In some embodiments of the present invention, a wire is further included, and the wire extends from the package to the conductive layer and is electrically connected to the conductive layer.

Another aspect of the present invention provides a method for preparing the above-mentioned piezoelectric sensor, comprising:

Provide piezoelectric induction unit;

A piezoelectric sensing unit is packaged to provide the piezoelectric sensor.

Another aspect of the present invention provides a road piezoelectric sensing system, comprising a road structure and the above-mentioned piezoelectric sensor, wherein the piezoelectric sensor is distributed in the road structure.

Another aspect of the present invention provides a road dynamic monitoring method, comprising:

The pressure data on the road surface is collected by the above-mentioned piezoelectric sensor or the above-mentioned piezoelectric sensing system.

Description of drawings

FIG. 1 is a schematic diagram of a wireframe of the fabrication process of the piezoelectric sensor in Example 1 of the present invention.

FIG. 2 is a schematic diagram showing the three-dimensional structure of the manufacturing process of the piezoelectric sensor in Example 1 of the present invention.

FIG. 3 is a schematic diagram showing the three-dimensional structure of the manufacturing process of the piezoelectric sensing element in Example 1 of the present invention.

FIG. 4 is a schematic diagram showing the structure of the piezoelectric sensing element in Embodiment 1 of the present invention.

FIG. 5 is a schematic structural diagram of a small and medium-sized rectangular parallelepiped piezoelectric sensor according to Embodiment 1 of the present invention.

FIG. 6 is a schematic diagram showing the linearity of the piezoelectric sensor calculated in Example 2 of the present invention.

FIG. 7( a ) is a schematic diagram showing the monitoring result of the vehicle speed (60 km/h) in Example 3 of the present invention.

Fig. 7(b) is a schematic diagram showing the monitoring result of the vehicle speed (80 km/h) in Example 3 of the present invention.

Component label description

1 Piezoelectric material block

2 Polarized positive and negative electrodes

3 Piezoelectric material after cutting

4 Piezoelectric material after cutting

5 Piezoelectric base

6 Filler phase

7 Conductive layer

8 Packages

9 wires

10 Piezoelectric embedded in road structures

sensor

11 Charge Amplifier

12 Data acquisition equipment

13 Software processing and computer display equipment

Detailed ways

In order to make the purpose, technical solutions and beneficial technical effects of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. Those who are familiar with the technology can easily understand other advantages and other advantages of the present invention from the contents disclosed in this specification. effect.

After a lot of practical research, the inventor of the present invention successfully applied the cement-based piezoelectric composite material to the main structure of the asphalt pavement, which improved the compatibility and stability of the sensor and the main structure of the pavement, and prolonged the service life of the sensor embedded in the asphalt pavement structure. , the modulus matching between the piezoelectric composite material sensor and the asphalt pavement is improved, and the present invention is completed on this basis.

A first aspect of the present invention provides a piezoelectric sensor, including a package, and a piezoelectric sensing element packaged in the package, wherein the piezoelectric sensing element includes a piezoelectric material column array, and a piezoelectric material column array distributed among the piezoelectric material column arrays. The filling phase between the piezoelectric material columns is consistent with the extension direction of each piezoelectric material column, and the polarization main axis direction of the piezoelectric material column is consistent with the extension direction. The piezoelectric sensing element further includes two conductive layers, and the two conductive layers are located in The surface of the piezoelectric material column array is respectively connected with the two poles of the piezoelectric material column. The piezoelectric sensor can usually be arranged in a road structure, and its height direction (which is consistent with the polarization main axis direction of each piezoelectric material column) usually matches the extension direction of the road, that is, the force direction of the road surface is usually the same as its height. The direction is the same, and the mixed substrate of emulsified asphalt and cement can significantly improve the compatibility of the pressure sensor. When the road surface is under pressure, the piezoelectric sensor in the road structure will be correspondingly subjected to a certain pressure, and can convert the pressure into The electrical signal can be transmitted through the conductive layer in contact with the piezoelectric material, and can be received through an external device. The output electrical signal usually has a suitable linearity, which can accurately monitor the actual road conditions pressure.

In the piezoelectric sensor provided by the present invention, the piezoelectric material column can generally be formed of piezoelectric material, and the piezoelectric material generally refers to a type of crystalline material that produces a voltage between two end faces when subjected to pressure. The material of the piezoelectric material column can generally be an inorganic piezoelectric material, preferably a piezoelectric ceramic or the like. The piezoelectric ceramics usually have fast response speed, high measurement accuracy, and relatively stable performance. Those skilled in the art can select suitable piezoelectric ceramics suitable for the piezoelectric sensor, for example, the piezoelectric ceramics can be selected from lead zirconate titanate piezoelectric ceramics (for example, PZT-5A, PZT-5H, PZT- 4, etc.), a combination of one or more of niobium lithium lead zirconate titanate piezoelectric ceramics (eg, PLN, etc.), niobium magnesium lead zirconate titanate piezoelectric ceramics (eg, PMN, etc.), etc.; The density of the piezoelectric material can be 6.90×10 ³ ～7.00×10 ³ kg/m ³ , 7.00×10 ³ ～7.10×10 ³ kg/m ³ , 7.10×10 ³ ～7.20×10 ³ kg/m ³ , 7.20×10 ³ ～7.30×10 ³ kg/m ³ , 7.30×10 ³ ～7.40×10 ³ kg/m ³ , 7.40×10 ³ ～7.50×10 ³ kg/m ³ , 7.50×10 ³ ～7.60× 10 ³ kg/m ³ , 7.60×10 ³ to 7.70×10 ³ kg/m ³ , or 7.70×10 ³ to 7.75×10 ³ kg/m ³ ; for another example, the piezoelectric strain constant of the piezoelectric material can be 2.25×10 ^-10 to 5.95×10 ^-10 C/N, 2.25×10 ^-10 to 2.75×10 ^-10 C/N, 2.75×10 ^-10 to 3.25× 10 ^-10 C/N, 3.25×10 ^{- 10} to 3.75×10 ^-10 C/N, 3.75×10 ^-10 to 4.25×10 ^-10 C/N, 4.25×10 ^-10 to 4.75×10 ^-10 C/N, 4.75×10 ^-10 to 5.25×10 ^-10 C/N, or 5.25×10 ^-10 -5.95×10 ^-10 C/N; for another example, the relative permittivity of the piezoelectric material may be 1050-1200, 1200-1500, 1500-1800, 1800 ~2100, 2100~2400, 2400~2700, 2700~3000, 3000~3200, or 3200~3500; for another example, the electromechanical coupling coefficient of the piezoelectric material may be 0.31~0.76%, 0.31~0.36%, 0.36~ 0.41%, 0.41-0.46%, 0.46-0.51%, 0.51-0.56%, 0.56-0.61%, 0.61-0.66%, 0.66-0.71%, or 0.71-0.76%. In a specific embodiment of the present invention, the piezoelectric material can be PZT-5A, its density can be 7.75×10 ³ kg/m ³ , the piezoelectric strain constant can be 4.781×10 ^-10 C/N, and the relative dielectric The electric constant may be 2000, and the electromechanical coupling coefficient may be 0.711%.

In the piezoelectric sensor provided by the present invention, a plurality of piezoelectric material pillars may generally be provided in the piezoelectric sensing element, and these piezoelectric material pillars may be uniformly distributed in an array in the pressure sensing element to form a piezoelectric material pillar array. The size of the piezoelectric material column usually needs to be matched with the road structure, so that the pressure from the road surface can be fully felt without affecting the stability of the road structure and the stability of the device itself. For example, in the piezoelectric sensing element, the height of the piezoelectric material column (the height direction of the piezoelectric material column is consistent with the height direction of the piezoelectric sensor) may be 2-4 mm, 2-2.5 mm, 2.5-3 mm, 3-3.5mm, or 3.5-4mm; for another example, the cross-sectional area of a single piezoelectric material column can be 3.43-14.90mm ² , 3.43-4.50mm ² , 4.50-5.50mm ² , 5.50-6.50mm ² , 6.50 ～7.50mm ² , 7.50～8.50mm ² , 8.50～9.50mm ² , 9.50～10.50mm ² , 10.50～11.50mm ² , 11.50～12.50mm ² , 12.50～13.50mm ² , or 13.50～14.90mm ² ; , the total cross-sectional area of the piezoelectric material column can be 360～720mm ² , 360～420mm ² , 420～480mm ² , 480～540mm ² , 540～600mm ² , 600～660mm ² , or 660～720mm ² ; , the column spacing can be 0.5-1.25mm, 0.5-0.75mm, 0.75-1mm, or 1-1.25mm; for another example, the shape and size of each piezoelectric material column can be substantially the same. In the cross section of the piezoelectric sensing element, each piezoelectric material column usually does not extend a long distance, so that a more uniformly distributed piezoelectric material column array can be formed, for example, the cross section of a single piezoelectric material column (ie vertical In the cross section of each piezoelectric material column in the extension direction), the extension length in a single direction is generally not more than 3.86 mm. For another example, the piezoelectric material column may be a rectangular parallelepiped, and the cross section of a single piezoelectric ceramic column is The side length can be 1.88-3.86mm, and the cross section can preferably be square. For another example, the formed piezoelectric material column array can be a rectangular matrix of M*N, where M≥2 and M is a positive integer, N≥2 And N is a positive integer, M can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a larger positive integer, and N can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or a larger positive integer.

In the piezoelectric sensor provided by the present invention, the piezoelectric material column usually needs to have a suitable volume ratio in the piezoelectric sensing element, so that a certain gap can be distributed between the column materials, and at the same time, the material can fully sense the road The pressure on the road surface, for example, in the piezoelectric sensing element, the volume percentage of the piezoelectric material column may be 40-80%, 40-50%, 50-60%, 60-70%, or 70-80% %. The overall size of the piezoelectric sensing element usually corresponds to the overall arrangement of the piezoelectric material columns. For example, when the piezoelectric material array is arranged in a rectangular array, the overall shape of the piezoelectric sensing element can be For another example, the size of the piezoelectric sensing element in the height direction may be 2-4mm, 2-2.5mm, 2.5-3mm, 3-3.5mm, or 3.5-4mm (that is, the direction consistent with the height direction of the piezoelectric sensor) ), the size in the length direction (that is, when the piezoelectric sensor is embedded in the road, the direction consistent with the extending direction of the road) can be 30-50mm, 30-35mm, 35-40mm, 40-45mm, or 45-50mm, The dimension in the width direction may be 30-50 mm, 30-35 mm, 35-40 mm, 40-45 mm, or 45-50 mm; for another example, the overall cross-section of the piezoelectric sensor may be a square.

In the piezoelectric sensor provided by the present invention, the existence of the filling phase can usually improve the defects of a single piezoelectric material, such as large brittleness, small limit strain and poor compatibility. The material of the filling phase can be selected from a mixed substrate of emulsified asphalt and cement, and the mixed substrate of emulsified asphalt and cement generally needs to have good adhesion with the piezoelectric phase. The raw materials of the mixed base material of emulsified asphalt and cement, in parts by weight, include the following components: 60-100 parts of cement; 20-33 parts of emulsified asphalt; and 33-60 parts of water.

The mixed base material of emulsified asphalt and cement may include 60-100 parts, 60-70 parts, 70-80 parts, 80-90 parts, or 90-100 parts of cement. The cement is usually used as the cementitious material in the filler phase. The cement may generally be Portland cement, eg, grade 42.5 ordinary Portland cement, or the like.

The mixed base material of the emulsified asphalt and cement may include 20-33 parts, 20-24 parts, 24-28 parts, or 28-33 parts of emulsified asphalt, and the emulsified asphalt is usually asphalt and an emulsifier in a certain process. Under the action, liquid bitumen of oil-in-water or water-in-oil is generated. The existence of emulsified bitumen can improve the connection characteristics between the filling phase and the functional phase (piezoelectric material column), thereby improving the overall flexibility and stability of the material, and prolonging the period of time. The longevity of the piezoelectric sensor, and its ability to provide its sensitivity, durability, and compatibility with the main structure of the pavement when applicable. The emulsified asphalt can be cationic emulsified asphalt, and more preferably can be fast-cracked cationic emulsified asphalt. The state of the material after mixing is qualitatively determined as fast cracking, medium cracking or slow cracking. The test method for qualitative characterization can be tested with reference to T6058. In addition, the sieve balance can be ≥0.1%, and the 1d room temperature stability can be ≤1%. The measurement method of the sieve balance and 1d room temperature stability can refer to JTG F40-2004.

The mixed base material of the emulsified asphalt and cement can also include an appropriate amount of water, and those skilled in the art can adjust the amount of water used in the mixed base material as needed, for example, it can include 33-60 parts, 33-36 parts, 36-40 parts, 40-45 parts, 45-50 parts, 50-55 parts, or 55-60 parts water.

In the piezoelectric sensor provided by the present invention, the material of the filling phase may generally include other additives, for example, a water reducing agent and the like. The water reducing agent can be mainly used to reduce the water-cement ratio on the basis of ensuring the fluidity of the cement emulsified asphalt slurry, so as to obtain a higher strength emulsified asphalt cement-based material as much as possible to adapt to the high strength of piezoelectric ceramics.

In the piezoelectric sensor provided by the present invention, the package needs to have good insulation and mechanical properties (for example, mechanical strength, flexibility, etc.), and needs to have good uniformity and stability, so that it can not only The piezoelectric composite material body inside the package plays a good role in supporting, protecting, and encapsulating, and can significantly improve the compatibility of traditional cement-based piezoelectric sensors with pavement structures. The material of the encapsulation can preferably be selected from epoxy asphalt, which is usually a chemically modified mixture of epoxy resin, curing agent and base asphalt. For example, the raw materials of the epoxy asphalt may include, in parts by weight: 75-93 parts of base asphalt, 1-5 parts of epoxy resin, and 6-20 parts of curing agent.

The epoxy asphalt may include 75-93 parts, 75-78 parts, 78-81 parts, 81-84 parts, 84-87 parts, 87-90 parts, or 90-93 parts. The base asphalt generally needs to use a base asphalt with a penetration degree of No. 70. For example, the penetration degree of the base asphalt can be 60-80, 60-65, 65-70, 70-75, or 75-80.

The epoxy asphalt may include 1-5 parts, 1-2 parts, 2-3 parts, 3-4 parts, or 4-5 parts of epoxy resin. Specifically, the epoxy resin can be E51 epoxy resin, and its epoxy equivalent weight can be 185-192, 185-186, 186-188, 188-190, or 190-192. In a specific embodiment of the present invention, the epoxy equivalent of the epoxy resin is 189.

The epoxy asphalt may include 6-20 parts, 6-8 parts, 8-10 parts, 10-12 parts, 12-14 parts, 14-16 parts, 16-18 parts, or 18-20 parts for curing agent. The curing agent may specifically be an acid complex curing agent, for example, may specifically be methyl hexahydrophthalic anhydride (MTHPA) and the like.

In the piezoelectric sensor provided by the present invention, the package can usually be wrapped around the piezoelectric material to form a piezoelectric sensor of suitable size. 50mm, 50～60mm, 60～70mm, 70～80mm, 80～90mm, or 90～100mm, the size in the width direction can be 40～100mm, 40～50mm, 50～60mm, 60～70mm, 70～80mm, 80-90mm or 90-100mm, the dimension in the height direction can be 8-10mm, 8-8.5mm, 8.5-9mm, 9-9.5mm or 9.5-10mm. The package on the surface of the piezoelectric material usually needs to have a suitable thickness, so as to provide a suitable protection effect to the internal piezoelectric sensing element. ~4mm, or 4~5mm, for example, in the length and width directions of the piezoelectric sensor, the thickness of the package on the surface of the piezoelectric material may be 4.5~5.5mm, 4.5~4.7mm, 4.7~4.9mm, 4.9~5.1mm , 5.1 to 5.3 mm, or 5.3 to 5.5 mm; for another example, in the height direction of the piezoelectric sensor, the thickness of the package on the surface of the piezoelectric material may be 1.8 to 2.2 mm, 1.8 to 1.9 mm, 1.9 to 2.0 mm, 2.0 ~ 2.1mm, or 2.1 ~ 2.2mm.

In the piezoelectric sensor provided by the present invention, the conductive layer is usually located on the surface of the piezoelectric material column array, and is connected to the two poles of each piezoelectric material column. Generally speaking, a piezoelectric sensor may include at least two conductive layers, and the two conductive layers may be located at the two poles of the piezoelectric material column array, so as to be connected to the two poles of each piezoelectric material column. The arrays of piezoelectric material pillars are matched, for example, their extending direction may be perpendicular to the polarization main axis direction of each piezoelectric material pillar in the array. The thickness of the conductive layer is usually very thin, and only needs to achieve a suitable conductive function. Those skilled in the art can select a suitable material for the conductive layer, for example, the raw material of the conductive layer can be conductive silver paste, and after the paste is cured, the conductive layer can be formed.

The piezoelectric sensor provided by the present invention may also include wires, which generally extend from the outside of the package to the conductive layer and are electrically connected to the conductive layer, so that the electrical signals generated by the piezoelectric material can be derived, and the It can be further sent to an external device, and the external device can be, for example, an electrical signal acquisition instrument, etc., specifically an oscilloscope, a dynamic signal acquisition instrument, and the like.

A second aspect of the present invention provides a method for preparing the piezoelectric sensor provided by the first aspect of the present invention, comprising:

Provide piezoelectric induction unit;

A piezoelectric sensing unit is packaged to provide the piezoelectric sensor.

In the preparation method of the piezoelectric sensor provided by the present invention, the method may include: providing a piezoelectric sensing unit. Those skilled in the art can choose a suitable method to provide the piezoelectric sensing unit, for example, it may include: providing a piezoelectric material column array, filling the raw material of the filling phase between the piezoelectric material column arrays, curing, and placing the piezoelectric material in the piezoelectric material column array. The pole array electrodes are coated with a conductive layer to provide the piezoelectric sensing unit. The piezoelectric material column array can usually be obtained by appropriate cutting of the piezoelectric material. During the preparation of the piezoelectric sensing unit, the cutting of the piezoelectric material can be carried out sequentially with the filling of the raw materials of the filling phase, or it can be carried out simultaneously and alternately. Since the filling phase is a mixed base material of emulsified asphalt and cement, and its raw material has good fluidity, during filling, the piezoelectric material column array can be placed in the mold, and the piezoelectric material column array can be filled. . In the filling process, it is usually necessary to fully distribute the raw materials between the piezoelectric material column arrays. For example, the air in the filling material can be removed by vacuuming, vibration, etc., so as to improve the bonding strength between the matrix phase and the functional phase interface. , to enhance the compactness of emulsified asphalt/cement-based composite slurry. After the filling is completed, after the raw material of the filling phase is cured, the raw material of the conductive layer can be coated on the two electrodes to form the conductive layer and provide the piezoelectric induction unit.

In the method for preparing a piezoelectric sensor provided by the present invention, the method may further include: encapsulating a piezoelectric sensing unit to provide the piezoelectric sensor. Those skilled in the art can choose a suitable method to encapsulate the piezoelectric sensing unit. For example, the piezoelectric sensing unit can be placed in a mold, and the wires can be connected to the conductive layer, and the encapsulation material can be poured into the mold for encapsulation, and then cured. The piezoelectric sensor is provided.

A third aspect of the present invention provides a road piezoelectric sensing system, comprising a road structure and the piezoelectric sensor provided in the first aspect of the present invention, wherein the piezoelectric sensor is distributed in the road structure. The extension direction of each piezoelectric material column is usually consistent with the direction in which the road structure is subjected to pressure. For the piezoelectric material column array, the positive electrode side can be located on the side closer to the road surface, or can be located on a side farther away from the road surface. side. The road structure is usually an asphalt pavement structure, which may include an asphalt surface layer, a base layer, a sub-base layer and a road base, and further the asphalt surface layer is composed of an upper layer, a middle surface layer and a lower layer. The piezoelectric sensor can usually be distributed in the surface layer structure of the asphalt pavement structure. For example, the piezoelectric sensor can be arranged at a distance of 1-3 cm, 1-1.5 cm, 1.5-2 cm, 2 to 2.5 cm, or 2.5 to 3 cm; for another example, in the cross section of a single lane, usually at least two piezoelectric sensors can be arranged, and the specific distribution can be combined with the actual road materials, traffic conditions and piezoelectric sensors. The comprehensive response is determined; for another example, in the extension direction of the road, there can usually be a suitable distance between the piezoelectric sensors, for example, 0.16m, 0.32m, 0.64m, etc., until the distance between the axles is increased.

A fourth aspect of the present invention provides a road dynamic monitoring method, comprising: collecting pressure data on a road surface through the piezoelectric sensor provided in the first aspect of the present invention or the piezoelectric sensing system provided in the third aspect of the present invention . As mentioned above, when the road surface is under pressure, the piezoelectric sensor in the road structure will be correspondingly subjected to a certain pressure, and can convert the pressure into an electrical signal, and the electrical signal can be transmitted through the conductive layer in contact with the piezoelectric material. , and can receive electrical signals through external devices to accurately monitor the actual pressure on the road, so as to reflect the conditions that need to be monitored on the road, such as traffic flow monitoring of people and vehicles, and dynamic weighing monitoring of vehicles Wait.

The emulsified asphalt/cement-based piezoelectric sensor provided by the present invention makes the structure of the composite material between the filling substrate and the piezoelectric material more compact by improving the filling substrate, packaging material, etc., and effectively improves the cement-based piezoelectric composite structure. The stability and compatibility of the material can improve the sensitivity of the sensor, and it has the advantages of frequency bandwidth and strong anti-interference ability, and the signal-to-noise ratio is also effectively improved. In addition, the preparation steps of the emulsified asphalt/cement-based piezoelectric sensor are simple and easy, and the cost is low, and it has a good industrialization prospect in the field of road dynamic monitoring.

The invention of the present application is further illustrated by the following examples, but the scope of the present application is not limited thereby.

Example 1

The main body of the emulsified asphalt/cement-based piezoelectric composite material is prepared by cutting and pouring method, which is composed of cement and emulsified asphalt matrix phase and piezoelectric ceramic functional phase. The specific method is as follows:

Using lead zirconate titanate piezoelectric ceramics (PZT-5A), and using a diamond wire cutting machine, cut along the direction parallel to the polarization axis of the piezoelectric ceramic block into a certain volume fraction of piezoelectric ceramic phase functional phases in an array form (see Fig. 2(b)), using the same line width along the other direction of the piezoelectric ceramic block in the same way to cut into a certain volume fraction of the functional phase of the piezoelectric ceramic column in an array (see Figure 2(c)), The size of the piezoelectric ceramic block is 30 × 30 × 10 mm, and the volume fraction of the piezoelectric ceramic phase is 40%. In order to prevent the brittle fracture of the piezoelectric ceramic phase with too small width during the cutting process, the width of the cut piezoelectric ceramic column is controlled as 1.88mm, the column spacing is 1.25mm, the piezoelectric ceramic column is protected by leaving a certain thickness of the piezoelectric ceramic base at the bottom of the piezoelectric ceramic block, and it is cut and removed after the pouring is completed. )).

As shown in Figure 3, the piezoelectric ceramic column can also be obtained by the method of one-time cutting-one-time pouring-secondary cutting-second pouring. After one-time cutting, the piezoelectric ceramic phase can be avoided by pouring the emulsified asphalt/cement matrix phase. Or the fracture of the piezoelectric ceramic column during the cutting process.

After two cuts, the piezoelectric ceramic phase and the piezoelectric ceramic column matrix phase were cleaned with an ultrasonic cleaner to remove the piezoelectric ceramic debris and enhance the bonding strength between the functional phase and the matrix phase interface.

The functional phase of the piezoelectric ceramic column with the base is fixed in the mold, and the emulsified asphalt/cement substrate with uniform mixing and good working performance is poured into the gap of the piezoelectric ceramic column by vibration casting. Emulsify the compactness of asphalt/cement-based materials, place them in a vacuum pump to vibrate and extract air.

Under the condition that the temperature is 20℃±1℃, the relative humidity is more than 90%, and the temperature of the curing water is 20℃±1℃, the mold is released after curing for 2 days, and the curing is continued after the demoulding, and polished after curing for 7 days; further pass the gradient Drying method The polished emulsified asphalt/cement-based piezoelectric composite induction body was dried in a 101-2 electric blast drying oven at 60°C, 80°C and 100°C for 4h, 8h and 1h successively.

The functional phase of the dried emulsified asphalt/cement-based composite material was scrubbed with acetone, and the piezoelectric ceramic base was cut off to obtain a piezoelectric composite material induction body with a height of 2 mm, and a low-temperature conductive silver paste was applied on both sides; the final result was 30×30× 2mm piezoelectric composite sensing body. The emulsified asphalt/cement-based piezoelectric ceramic composite induction body was dried at 100 °C for 1 h to form and solidify. The prepared emulsified asphalt/cement-based piezoelectric ceramic composite material induction body (piezoelectric induction element), the structure is shown in Figure 4, the piezoelectric ceramic cylinders are uniformly arrayed, so the length and width of a piezoelectric ceramic cylinder and a ceramic cylinder are The 1/2 width of the direction is the analysis unit.

As shown in Figure 5, a small cuboid piezoelectric sensor was further prepared, and the surface of the piezoelectric composite material was wiped with a cotton swab smeared with anhydrous alcohol, and left to dry naturally. Paste the thin copper core wires (including lead wires and shielded wires) on the surface of the piezoelectric composite material through polyacrylate and conductive silver paste. After curing, use a low-power electric soldering iron to weld the wires, and pay attention to lightly wipe them with acetone in a short time. Solder paste left on the component surface.

Apply mold release agent in a self-made 40×40×20mm mold, fix the piezoelectric composite material in the mold, use epoxy pitch as the packaging material, prepare the package under the piezoelectric material in the mold, cure for 1d, Paste the emulsified asphalt/cement-based piezoelectric composite material on the package, and then pour the package material above the piezoelectric composite material in the mold, and cure for 28d. During the pouring process, the vibration pouring method is adopted. The small cuboid piezoelectric sensor is placed in a vacuum pump to be evacuated to eliminate the air holes in it to obtain the final small cuboid piezoelectric sensor.

Example 2

The piezoelectric sensor system needs to be grounded to reduce the influence of the external magnetic field, improve the anti-interference ability, and further improve the signal-to-noise ratio. Before practical application, the performance test of the prepared small cuboid piezoelectric sensor should be carried out, including the measurement of linearity (sensitivity) and repeatability, to ensure that it can cope with the working environment of the road, complex stress environment and climatic environment. ability.

A load of 0.1 to 0.7 MPa is sequentially applied to the piezoelectric sensor by a universal testing machine. In order to test the sensitivity of the prepared piezoelectric sensor, simulate the pulse signal, unload it quickly after each load is applied, record the output voltage of the piezoelectric sensor after unloading with an oscilloscope, and use the ratio of the voltage to the load as the linearity of the piezoelectric sensor. Depending on the size and material of the electrical sensor, the specific linearity value is generally different. Therefore, for the piezoelectric sensor that determines the structural size, material composition and material parameters, its linearity remains unchanged, that is, the voltage output and the load are linearly related, but a specific sensor may have a specific linearity value. A defined linearity is a prerequisite for the use of piezoelectric sensors for dynamic vehicle weighing. As shown in Fig. 6, the calculated linearity of the piezoelectric sensor with a piezoelectric phase volume fraction of 40% is 6.62×10 ^-5 V/Pa, indicating that the piezoelectric sensor has suitable sensitivity.

Example 3

The main goal of the piezoelectric sensor is to identify the road traffic conditions by sensing the vibration response of the road under the traffic load, and the vehicle speed is one of the important factors affecting road traffic safety accidents. Safety analysis and road infrastructure design have important reference significance. Therefore, in this embodiment, the piezoelectric sensor is used to identify and analyze the vehicle speed. Specifically, the piezoelectric sensor is buried 1 cm below the pavement surface of the pavement structure with the overall dimensions of length × width × depth = 6 × 3.75 × 4 m; among them, the asphalt pavement The structural parameters are shown in Table 1. The horizontal distance between the two buried sensors is 0.54m, which verifies the recognition ability of the piezoelectric sensor for vehicle speeds of 60km/h and 80km/h. The voltage output results of the two sensors are shown in Figure 7.

Table 1

structural layer Thickness(cm) Density (kg/m³) Elastic Modulus (MPa) Poisson's ratio μ alpha beta (upper layer) SMA-13 4 2400 1800 0.25 0.4 0.003 (middle layer) AC-20 6 2400 1800 0.25 0.4 0.003 (lower floor) AC-25 8 2400 1200 0.25 0.4 0.003 (basic) CTB1 20 2300 1500 0.2 0.4 0.003 (Subbase) CTB2 30 2300 750 0.2 0.4 0.003 (soil layer) SG — 1800 40 0.35 0.25 0.005

Obviously, under different vehicle speeds, there is a time difference between the peaks of the output signals of the two components. The two components that sense the load successively are recorded as component 1 and component 2, respectively, and the time points when the three wave peaks appear are selected according to the difference of the wave peaks. From this, the speed sensed by the components is calculated as shown in Table 2:

Table 2

It can be seen from the data in Table 2 that the piezoelectric sensor provided by the present application can accurately monitor the actual pressure on the road, so as to accurately reflect the situation that needs to be monitored on the road.

To sum up, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

The above-mentioned embodiments merely illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in the present invention should still be covered by the claims of the present invention.

Claims (10)

1. A piezoelectric sensor, characterized in that it comprises a package and a piezoelectric sensing element packaged in the package, wherein the piezoelectric sensing element comprises a piezoelectric material column array and a piezoelectric material column array distributed in the piezoelectric material column array. The filling phase between the piezoelectric material columns is consistent with the extension direction of each piezoelectric material column, and the polarization main axis direction of the piezoelectric material column is consistent with the extension direction. The piezoelectric sensing element further includes two conductive layers, and the two conductive layers are located in The surface of the piezoelectric material column array is respectively connected with the two poles of the piezoelectric material column. 2. The piezoelectric sensor according to claim 1, wherein the material of the piezoelectric material column is selected from inorganic piezoelectric materials, preferably, the inorganic piezoelectric material is selected from piezoelectric ceramics, and the piezoelectric material is selected from piezoelectric ceramics. The electrical ceramic is selected from one or a combination of lead zirconate titanate piezoelectric ceramics, niobium lithium lead zirconate titanate piezoelectric ceramics, and niobium magnesium lead zirconate titanate piezoelectric ceramics. 3 . The piezoelectric sensor according to claim 1 , wherein the piezoelectric material has a density of 6.90×10 ³ to 7.75×10 ³ kg/m ³ and a piezoelectric strain constant of 2.25×10 ⁻¹⁰ to 5.95. 4 . ×10 ^-10 C/N, the relative dielectric constant is 1050-3500, and the electromechanical coupling coefficient is 0.31-0.76%. 4 . The piezoelectric sensor according to claim 1 , wherein the height of the piezoelectric material column is 2-4 mm, and the cross-sectional area of a single piezoelectric material column is 3.43-14.90 mm ² ; And/or, the total cross-sectional area of the piezoelectric material column is 360-720 mm ² , and the column spacing is 0.5-1.25 mm; And/or, in the cross section of a single piezoelectric material column, the extension length in a single direction is generally not more than 3.86 mm, preferably, the piezoelectric material column is a rectangular parallelepiped; And/or, in the piezoelectric sensing element, the volume percentage of the piezoelectric material columns is 40-80%. 5 . The piezoelectric sensor according to claim 1 , wherein the material of the filling phase is selected from a mixed substrate of emulsified asphalt and cement, and the raw materials of the mixed substrate of emulsified asphalt and cement are in parts by weight. 6 . , including the following components: Cement 60-100 copies; 20-33 parts of emulsified asphalt; Water 33-60 parts. 6. The piezoelectric sensor of claim 1, wherein the cement is selected from Portland cement; And/or, the emulsified asphalt is selected from cationic emulsified asphalt, the cationic emulsified asphalt is a fast-cracked cationic emulsified asphalt, the sieve balance of the cationic emulsified asphalt is greater than or equal to 0.1%, and the 1d room temperature stability is less than or equal to 1%. 7 . The piezoelectric sensor according to claim 1 , wherein the material of the package is selected from epoxy asphalt, and the raw materials of the epoxy asphalt, in parts by weight, include: 75-93 parts of matrix asphalt, 1-5 parts epoxy resin, and 6-20 parts curing agent; And/or, it also includes a wire, the wire extends from the package to the conductive layer and is electrically connected to the conductive layer. 8. The method for manufacturing a piezoelectric sensor according to any one of claims 1 to 7, comprising: Provide piezoelectric induction unit; A piezoelectric sensing unit is packaged to provide the piezoelectric sensor. 9. A road piezoelectric sensing system, comprising a road structure and the piezoelectric sensor according to any one of claims 1 to 7, wherein the piezoelectric sensor is distributed in the road structure. 10. A road dynamic monitoring method, comprising: The pressure data on the road surface is collected by the piezoelectric sensor according to any one of claims 1 to 7, or the piezoelectric sensing system according to claim 8.

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