CN112985316B - High-temperature-resistant wide-range surface acoustic wave strain sensor - Google Patents
High-temperature-resistant wide-range surface acoustic wave strain sensor Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
- G01B17/04—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring the deformation in a solid, e.g. by vibrating string
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Abstract
The invention discloses a high-temperature-resistant wide-range surface acoustic wave strain sensor, which comprises an elastomer support and a surface acoustic wave device arranged on the arch elastomer support, wherein the elastomer support and the surface acoustic wave device are bonded through high-temperature ceramic glue; the surface acoustic wave device comprises a piezoelectric substrate layer, interdigital electrodes and a reflecting grid; the strain sensor is attached to the surface of the object to be measured through the elastomer support; the elastic body support transmits the strain of the object to be measured to the surface acoustic wave device, so that the strain sensor is subjected to uniform strain, and the linear transmission proportion of the frequency change of the surface acoustic wave device and the measured strain is kept. The strain range of the invention can reach 9-10 times of that of a surface acoustic wave sensor made of the same material and the same thickness, and an additional complex process is not needed; the invention can be applied to more tiny, complex, closed and high-temperature environments.
Description
Technical Field
The invention relates to the application field of acoustic wave sensors, in particular to a high-temperature-resistant wide-range acoustic surface wave strain sensor.
Background
In the high-precision production and manufacturing process of machinery, parts moving at high speed are often core parts, such as rollers, bearings, blades, rotating shafts and the like, and the strain of the moving parts needs to be subjected to in-situ online sensing, so that the sensors are widely applied to important fields of mechanical system structure design, health monitoring, field real-time regulation and control of manufacturing precision, intelligent fault diagnosis and the like. A good strain sensor may provide better control over the precision manufacturing process and thus may help break the manufacturing accuracy bottleneck. A wireless passive Surface Acoustic Wave (SAW) sensor is the most ideal sensing technology and meets the sensing requirements of complex environments such as inconvenient wiring, high temperature and high pressure, incapability of taking electricity and the like.
Surface Acoustic Wave (SAW) devices are widely used in mass sensing, temperature sensing, gas sensing, biochemical sensing, humidity sensing, air pressure sensing, and the like due to the characteristics of high operating frequency, high frequency quality factor, high sensitivity, high stability, and the like. Meanwhile, the strain SAW sensor can be used for wirelessly and passively monitoring strain in real time, is small in size and easy to use, and can well control the whole production process.
However, the strain generated in the actual workpiece is often very large, and the strain that the material of the surface acoustic wave device can bear is limited, for example, the turbine blade can be plastically deformed under the micro strain of more than 3500 mu epsilon, but the piezoelectric crystal ceramics used by the current SAW can only reach 1000 mu epsilon at most, so the SAW is only elastic deformation which can be recovered by measurement, and the more important plastic deformation cannot be measured. Meanwhile, when the surface acoustic wave is used for testing strain, the surface acoustic wave device is often bonded with a tested object by using glue. The application of excessive strain easily causes the surface acoustic wave device and the workpiece to be bonded and fall off, and even causes the sensor to be broken, so that the sensor cannot be reused.
In addition, in practical production, the sensor is also applied in a high temperature environment. However, in a high temperature environment, the high temperature may degrade the performance of the saw device, further limiting the strain that the saw device can withstand. Meanwhile, the high-temperature adhesive for bonding the surface acoustic wave device and the object to be measured, the surface acoustic wave device and the object to be measured can generate thermal expansion at high temperature, so that the surface acoustic wave device is easy to crack. Therefore, the upper limit of the strain that can be measured by the SAW device is also greatly limited in high temperature applications.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the high-temperature-resistant wide-range surface acoustic wave strain sensor, when the sensor is attached to the surface of a measured object to measure strain, an arch bridge strain transfer structure of the sensor can convert and transfer the larger strain of the measured surface into the smaller strain of the upper surface of an arch bridge, and a surface acoustic wave resonator realizes the measurement of the larger strain of the measured surface by measuring the smaller strain of the upper surface of the arch bridge, so that the strain range which can be measured by a surface acoustic wave device is enlarged.
The purpose of the invention is realized by the following technical scheme:
a high-temperature-resistant wide-range surface acoustic wave strain sensor comprises an elastomer support and a surface acoustic wave device arranged on the elastomer support;
the surface acoustic wave device comprises a piezoelectric substrate layer, interdigital electrodes and reflection gratings, wherein the upper surface of the piezoelectric substrate layer is a polished surface, the interdigital electrodes and the reflection gratings are arranged on the polished surface, and the reflection gratings are symmetrically arranged on two sides of the interdigital electrodes; a layer of ceramic film is sputtered on the lower surface of the piezoelectric substrate layer; the elastomer bracket and the lower surface of the surface acoustic wave device are bonded together through high-temperature ceramic glue;
the strain sensor is attached to the surface of an object to be measured through the elastomer support; the elastic body support transmits the strain of the object to be measured to the surface acoustic wave device, so that the strain sensor is subjected to uniform strain, and the linear transmission proportion of the frequency change of the surface acoustic wave device and the measured strain is kept.
Furthermore, the elastomer support is an arch bridge-shaped elastomer support, is of an inverted U shape, and comprises an upper flat plate and side plates which are positioned on two sides of the upper flat plate and used for supporting the upper flat plate, the surface acoustic wave device is bonded on the upper flat plate, the thickness of the upper flat plate of the arch bridge-shaped elastomer support is equal to that of the surface acoustic wave device, and the area of the upper surface of the upper flat plate of the arch bridge-shaped elastomer support is not less than that of the surface acoustic wave device; the thickness of the side plate of the arch bridge-shaped elastomer support is not less than that of the upper flat plate, and is positively correlated with the thickness of the upper flat plate.
Furthermore, the arch bridge-shaped elastomer support is in a shape of a Chinese character ji, and the arch bridge-shaped elastomer support is attached to the surface of the measured object through bending of two sides of the bottom of the arch bridge-shaped elastomer support.
Furthermore, the material of the arch bridge-shaped elastomer support meets the tensile strength sigma within 0-800 DEG C b Not less than 400MPa, conditional yield strength sigma 0.2 ≥180Mpa。
Furthermore, the elastomer bracket is made of high-temperature elastic alloy and mainly comprises nickel and chromium.
Further, the elastomer support is two parallel support bars, the width of the parallel support bar is L1, the height of the parallel support bar is H1, the length of the parallel support bar is a1, the distance between the two parallel support bars is L2, the length of the surface acoustic wave device is B1, and the width of the surface acoustic wave device is L3, and the following conditions are satisfied:
(1)L2+2L1<L3，A1>B1；
(2) the Poisson ratio of the parallel supporting rods is more than 0.25, and the Young modulus is less than 300 Gpa.
Furthermore, L2 ═ (0.1 to 0.8) × L3, and a1 ═ 1 to 3) × B1.
Further, the SAW device electrode is made of platinum or a platinum alloy.
Furthermore, the piezoelectric substrate layer of the surface acoustic wave device is selected from high-temperature-resistant piezoelectric crystals, including langasite and doped crystals thereof, aluminum nitride and doped crystals thereof, and the thickness is 1um-1 mm.
The invention has the following beneficial effects:
compared with the common surface acoustic wave sensor, the surface acoustic wave strain sensor with high temperature resistance and wide measuring range has larger measuring range which can reach 10 times that of the surface acoustic wave sensor made of the same material and with the same thickness. And the method does not need additional complex processes such as etching, thinning and the like, does not need rare materials, is simple to manufacture, has low cost and can be produced in batches.
Compared with a general wide-range resistance type strain sensor, the strain sensor can work wirelessly and passively, has small size and can be made into several millimeters. High-temperature piezoelectric materials such as lanthanum gallium silicate and the like are adopted, and the high-temperature piezoelectric materials can bear the high temperature of more than 1000 ℃. Therefore, the invention can be applied to more tiny, complex, closed and high-temperature environments.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment 1 of a high-temperature wide-range SAW strain sensor of the present invention;
FIG. 2 is a schematic structural diagram of embodiment 2 of the high-temperature wide-range SAW strain sensor of the present invention;
FIG. 3 is a sectional view of a SAW strain sensor of embodiment 1;
FIG. 4 is a schematic view of a SAW strain sensor of the present invention bonded to a deformed steel sheet;
FIG. 5 is a strain curve obtained by a strain test using the SAW strain sensor in an embodiment;
FIG. 6 is a schematic structural view of embodiment 3;
FIG. 7 is a sectional view of a SAW strain sensor of embodiment 3;
FIG. 8 is a schematic view of a SAW strain sensor of example 3 bonded to a deformed steel sheet;
FIG. 9 is a strain plot obtained from a strain test using the SAW strain sensor of example 3;
the device comprises an elastomer support 1, high-temperature ceramic glue 2, a surface acoustic wave device 3, a piezoelectric substrate layer 31, an interdigital electrode 32, a reflecting grid 33, a ceramic film 34, an upper flat plate 11, a side plate 12 and a base 13.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the present invention will become more apparent, it being understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
The high-temperature-resistant wide-range surface acoustic wave strain sensor comprises an elastomer support 1 and a surface acoustic wave device 3 arranged on the elastomer support, wherein the elastomer support and the surface acoustic wave device are bonded together through high-temperature ceramic glue 2. The high temperature resistance of the invention means resistance to temperatures above 600 ℃.
The surface acoustic wave device 3 comprises a piezoelectric substrate layer 31, an interdigital electrode 32 and a reflection grid 33, wherein the upper surface of the piezoelectric substrate layer 31 is a polished surface, the interdigital electrode 32 and the reflection grid 33 are arranged on the polished surface, and the reflection grid 33 is symmetrically arranged on two sides of the interdigital electrode 32; a ceramic film 34 is sputtered on the lower surface of the piezoelectric substrate layer 31.
In order to enable the whole strain sensor to resist high temperature, an interdigital electrode 32 and a reflection gate 33 in the surface acoustic wave device 3 are made of platinum alloy, and a piezoelectric substrate layer 31 is made of lanthanum gallium silicate or aluminum nitride and is 1-1 mm thick. In order to make surface acoustic wave device 3 and arched bridge shape elastomer support still can laminate firmly under high temperature environment, be difficult to drop or destroyed, one deck ceramic film of lower surface reactive sputtering at piezoelectric substrate layer 31, and the adhesive chooses for use high temperature ceramic glue, thereby piezoelectric substrate layer 31's lower surface is crude, and ceramic film is close with the nature of high temperature ceramic glue, and the affinity is strong, interface department lattice constant matches, interface department chemical bond easily becomes the key, thereby guarantee that surface acoustic wave device and arched bridge shape elastomer support combine firmly. Meanwhile, during bonding, the sensor is required to be arranged in the vacuum cavity, bubbles in high-temperature ceramic adhesive are reduced as much as possible (the bubbles expand to crack the surface acoustic wave device at high temperature), the high-temperature adhesive is required to be as thin and uniform as possible, the surface acoustic wave sensor is not easy to fall off in a high-temperature strain test environment, and stable transmission of high-temperature strain is ensured. The ceramic film is preferably alumina and has a thickness of 1nm-1 um.
The ceramics specifically refer to silicates and aluminosilicates, refractory metal oxides and metal nitrides, borides.
The strain sensor is attached to the surface of an object to be measured through the elastomer support; the elastic body support transmits the strain of an object to be measured to the surface acoustic wave device, so that the strain sensor generates uniform strain, and the frequency change of the surface acoustic wave device and the measured strain are kept in a linear transmission proportion.
Several examples of elastomeric stents are given below.
Example 1
As shown in fig. 1, the elastomer mount is in an arch bridge shape, i.e., a zigzag shape, and includes an upper plate 11, side plates 12 located on both sides of the upper plate 11 and supporting the upper plate, and bases 13 located on both sides of the side plates, and the surface acoustic wave device 3 is bonded to the upper plate 11.
Example 2
As shown in fig. 2, the arch bridge-shaped elastomer bracket is in an inverted U shape, i.e. the bases 13 on both sides of the bottom are reduced on the basis of a Chinese character 'ji'. When the length of the susceptor is 0, it is changed from embodiment 1 to embodiment 2.
The elastomer stents of examples 1 and 2 are both arch bridge-shaped elastomer stents, and the conditions to be satisfied by such arch bridge-shaped elastomer stents of examples 1 and 2 will be described below by taking the zigzag-shaped elastomer stent of fig. 1 as an example.
As shown in FIG. 3, the height of the whole arch bridge-shaped elastomer bracket is h1, the thickness of the upper flat plate is h3, the thickness of the bottom base is h2, the length is l1, the thickness of the side plate is l3, and the distance between the two side plates is l 2. The specific conditions to be met are as follows:
(1) the thickness h3 of the upper plate 11 is close to, preferably equal to, the thickness of the surface acoustic wave device 3; or the thickness of the upper flat plate 11 is 0.1-1.1 times of that of the piezoelectric substrate layer of the surface acoustic wave device.
(2) The area of the upper surface of the upper plate 11 is not smaller than the area of the surface acoustic wave device 3;
(3) the thickness of the side plate 12 is not less than the thickness of the upper flat plate 11, and is positively correlated with the thickness of the upper flat plate 11, i.e. l3 is not less than h3, and l3 is not more than h 3.
In the aspect of materials, the material of the arch bridge-shaped elastomer bracket meets the requirement of tensile strength sigma within the range of 0-800 DEG C b Not less than 400MPa, conditional yield strength sigma 0.2 Not less than 180MPa, high temperature elastic alloy is preferred, and the main components comprise nickel and chromium.
As shown in fig. 4, when the surface acoustic wave strain sensors of embodiments 1 and 2 are used to test strain, the arch bridge-shaped elastomer support is welded or bonded to the surface of an object to be tested, when the object to be tested deforms, the arch bridge-shaped elastomer support of the sensor can convert the larger strain of the measured surface into the smaller strain of the upper surface of the arch bridge, and the surface acoustic wave device measures the smaller strain of the upper surface of the arch bridge to realize the measurement of the larger strain of the measured surface, thereby increasing the strain range that the surface acoustic wave device can test.
In addition, increasing the arch bridge height h1 changes the strain transfer ratio. The strain transmission ratio can be increased by increasing the thickness h2 of the lower base of the arch bridge. The thickness h3 of the upper surface of the arch bridge is close to the thickness of the surface acoustic wave device, so that strain can be better transferred from the structure to the surface acoustic wave device, and the linearity is improved. Increasing the arch bridge sub-base width l1 increases the strain transfer ratio. Increasing the arch bridge upper surface width l2 reduces the strain transfer ratio. Increasing the arch bridge elastomer leg width l3 increases the strain transfer ratio. Arch bridge elastomer shelf width l3 should be wide enough to prevent plastic deformation.
A specific test example of the elastomer bracket in the shape of the Chinese character 'ji' is given below to prove the technical effect of the strain sensor of the invention.
The material of the zigzag-shaped elastomer bracket is nickel-chromium-iron heat-resistant alloy, the height h1 is 1.5mm, the height h3 is 0.5mm, the width l3 is 2mm, the width l1 is 2mm, the width l2 is 14mm, and the width h2 is 0.5 mm. The material of surface acoustic wave device 3 is Lanthanum Gallium Silicate (LGS), and surface acoustic wave device 3's thickness is 200um, and the wavelength is 6.6um, is single-ended resonance type sensor. Aluminum oxide is sputtered on the bottom of the surface acoustic wave device 3, and the adhesiveness of the surface acoustic wave device and high-temperature ceramic adhesive is improved. The high-temperature glue is high-temperature ceramic glue, and the main component of the high-temperature glue is aluminum oxide. The object to be measured is a 301 stainless steel sheet with the width of 3cm, the length of 20cm and the thickness of 500 mu m. The sensor passes through the electric welding and welds in the middle of the steel sheet, utilizes and adds the holder with steel sheet one end fixed, and appointed displacement is applyed to the appointed direction to another section, test steel sheet strain.
Lanthanum Gallium Silicate (LGS) can withstand high temperatures of 1450 ℃. The acoustic surface wave sensor can generate fixed resonant frequency under normal work, the resonant frequency can be changed by the aid of applied strain and temperature, frequency changes can be counted, the relation between the frequency changes and the strain size and temperature can be fitted, and the acoustic surface wave sensor can be used for measuring the strain and the temperature. The single-ended resonator made of lanthanum gallium silicate can still normally generate resonance under the non-strain environment of 1000 ℃ in an experiment. The high temperature strain test reaches above 650 ℃, and stable output can still be obtained. After the aluminum oxide is sputtered on the bottom surface of the surface acoustic wave device, the main component of the high-temperature ceramic adhesive is aluminum oxide, so that the surface acoustic wave device can be well adhered to the high-temperature ceramic adhesive, the bonding force is large, and the device is not easy to fall off. And the ceramic adhesive can make the strain on the surface acoustic wave device uniform, and can obtain stable strain output at high temperature. After the high-temperature ceramic adhesive is subjected to vacuum treatment, bubbles in the high-temperature ceramic adhesive are greatly reduced, the high-temperature ceramic adhesive is not easy to expand at high temperature, and the surface acoustic wave device is large in thickness, is not easy to break at high temperature and can work at high temperature for a long time.
In the actual strain test, the sub-mount 3 is bonded to the object to be tested, as shown in fig. 4. When the measured object generates transverse deformation, the strain caused by the deformation can be transmitted to the surface acoustic wave device from the measured object along the arch bridge structure. Huge deformation that the testee produced can be alleviated to arch bridge shape elastomer support 3's both sides, and the deformation that finally transmits the upper surface will be restricted in a less scope to the strain that makes the surface acoustic wave device receive reduces by a wide margin. Meanwhile, the upper flat plate can transfer uniform strain to the surface acoustic wave device, so that the frequency change of the surface acoustic wave device and the size of the measured strain have good linearity. In addition, the size of the structure of the invention is adjusted, the strain transmission proportion can be adjusted, and the invention has flexible range adjustment range.
When the surface acoustic wave device is strained, the frequency shifts. The frequency deviation and the strain magnitude are generally linear, and the relationship between the frequency variation and the strain of the device can be obtained by counting the relationship between the frequency variation and the strain. A surface acoustic wave device with the same material and size, the same tangential direction and the same electrode design is selected as a comparison sensor, and the strain magnitude tested by the sensor under the same frequency deviation is observed, so that the specific range of the embodiment can be obtained.
As shown in fig. 5, for the strain transfer ratio test of the embodiment of the present invention, it can be obtained that the strain experienced by the saw device on the sensor is only 1800 μ ∈ when the true strain of the steel sheet has reached 5000 μ ∈. That is, the strain reading of the sensor is 5000 mu epsilon when the sensor is subjected to 1800 mu epsilon, only a plurality of groups of data need to be tested in a certain range, the relationship between the strain and the reading of the sensor can be obtained by fitting a curve, and meanwhile, the maximum strain range of the sensor can be obtained by testing the maximum strain of a conventional device.
In addition, the size of the structure is changed, the expanded range can be changed, the maximum range can be adjusted to the required range, the range can be reduced, the maximum range can be ensured to be suitable for the actual test environment, and meanwhile, the test precision is good. If the height of the invention is increased, under other conditions, the strain on the surface acoustic wave device on the sensor is only 1800 mu epsilon when the strain reading of the sensor is 6200 mu epsilon, and the measuring range is further expanded. The strain transfer ratio can reach an ideal range by adjusting other parameters.
Example 3
As shown in fig. 6, the elastomer frame is two parallel supporting rods, and if the width of the parallel supporting rod is L1, the height is H1, the length is a1, the distance between the two parallel supporting rods is L2, the length of the surface acoustic wave device is B1, and the width is L3, the following conditions (as shown in fig. 7) need to be satisfied:
(1)L2+2L1<L3，A1>B1；
(2) the Poisson ratio of the parallel supporting rods is more than 0.25, and the Young modulus is less than 300 Gpa.
Preferably, L2 ═ (0.1 to 0.8) × L3, and a1 ═ (1 to 3) × B1. The elastomer bracket is made of high-temperature soft alloy and mainly comprises silver.
Similarly, the high-temperature ceramic adhesive bonds the surface acoustic wave device above the elastomer support through the aluminum oxide layer on the back of the piezoelectric substrate, and the sensor needs to be placed in the vacuum cavity to reduce air bubbles in the high-temperature ceramic adhesive and ensure stable transmission of high-temperature strain.
The effect of the elastomer mount of this embodiment is verified in a specific experiment as follows.
The width L1 of the elastomer support is 1mm, the height of the elastomer support is 1mm, the distance L2 is 4mm, and the length of the parallel rod is 1.4 cm. The material of the surface acoustic wave device is Lanthanum Gallium Silicate (LGS), the thickness of the surface acoustic wave device is 500um, the wavelength is 6.6um, and the surface acoustic wave device is a single-end resonance type sensor. Aluminum oxide is sputtered on the bottom of the surface acoustic wave device of the surface wave sensor, and the adhesion with high-temperature ceramic adhesive is improved. The high-temperature glue is high-temperature ceramic glue, and the main component of the high-temperature glue is aluminum oxide. The object to be measured is a 301 stainless steel sheet with the width of 4cm, the length of 14cm and the thickness of 1 mm. The test structure is shown in fig. 8, a sensor is welded in the middle of a steel sheet through electric welding, one end of the steel sheet is fixed through a clamping device, the other section of the steel sheet applies specified displacement to the specified direction, the specified displacement point is 13cm away from the fixed end, a surface acoustic wave sensor is arranged at the position 3cm away from the fixed end, and the strain of the steel sheet and the strain of the surface acoustic wave device are tested. And testing the strain of the surface acoustic wave device again after adjusting the height of the elastomer support.
When the measured object is deformed in the transverse direction, the strain caused by the deformation is transferred from the measured object to the surface acoustic wave device along the elastomer support structure of the embodiment. The elastic body bracket of the surface acoustic wave device can relieve the huge deformation generated by a measured object, and the deformation finally transmitted to the surface acoustic wave device 3 is limited in a smaller range, so that the strain borne by the surface acoustic wave device is greatly reduced. Meanwhile, the distance L2 between the elastic body supports is reasonably adjusted, so that the surface acoustic wave device can be subjected to uniform strain, frequency change and good linearity of the measured strain. In addition, the size of the structure of the embodiment is adjusted, the strain transmission proportion can be adjusted, and the range adjustment range is flexible.
Because the elastic body support structure reduces the strain transmitted to the surface acoustic wave device by the steel sheet, the same surface acoustic wave device can sense larger strain by utilizing the elastic body support structure. The strain on the steel sheet can be obtained by only dividing the strain on the surface acoustic wave device by the strain transfer ratio by an algorithm.
As shown in fig. 9, the experimental results of this embodiment show that, with the structural parameters of this embodiment, the strain on the steel sheet has reached 3966 μ epsilon when one end of the steel sheet to be tested is displaced to 6cm, while the strain of the surface acoustic wave device of this embodiment is reduced by only 440 μ epsilon due to the reduction of the strain by the elastomer mount structure, which is 9 times reduced. That is to say, when the strain borne by the saw device is 440 μ ∈, the true strain on the steel sheet can be read by the sensor only by correcting the reading of the sensor in this embodiment with an algorithm, and the final strain reading of the sensor is 3966 μ ∈. The corresponding range is also enlarged by about 9 times. Compared with a sensor consisting of a pure surface acoustic wave device, the measuring range is greatly enhanced.
In addition, the size of the structure is changed, the expanded measuring range can be changed, and the maximum measuring range can be adjusted to a required range, so that the maximum measuring range can be ensured to adapt to an actual testing environment and has good testing precision. As shown in fig. 9, when the height of the elastic body support is reduced and the steel sheet to be tested in the control group is bent to 6cm under other conditions, the strain applied to the surface acoustic wave device of the invention is about 1222 μ ∈, the applied strain is reduced by 3.2 times, and the corresponding range is enlarged by about 3.2 times. Adjusting other parameters can make the strain transfer ratio reach the ideal range to seek higher precision.
The elastomer mount height H1 is increased to maximize the strain transfer ratio. Increase elastomer support interval L2, can increase the transmission proportion of meeting an emergency, need rationally adjust elastomer support interval L2 simultaneously for the surface acoustic wave device can receive even strain, frequency variation and measured strain size and have good linearity. The thickness of the surface acoustic wave device can be reduced to obtain larger range and test precision.
In addition to the three embodiments, a person skilled in the art may also have other deformations of the elastic body support as long as "the strain sensor is attached to the surface of the object to be measured through the elastic body support; the elastic body support transmits the strain of an object to be detected to the surface acoustic wave device, so that the strain sensor generates uniform strain, and the elastic body support keeps the frequency change of the surface acoustic wave device and the measured strain in a linear transmission proportion within the protection range of the invention.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.
Claims (9)
1. A high-temperature-resistant wide-range surface acoustic wave strain sensor is characterized by comprising an elastomer support and a surface acoustic wave device arranged on the elastomer support;
the surface acoustic wave device comprises a piezoelectric substrate layer, an interdigital electrode and a reflection grid, wherein the upper surface of the piezoelectric substrate layer is a polished surface, the interdigital electrode and the reflection grid are arranged on the polished surface, and the reflection grid is symmetrically arranged on two sides of the interdigital electrode; sputtering a layer of alumina ceramic film with the thickness of 1nm-1um on the lower surface of the piezoelectric substrate layer; the elastomer bracket and the lower surface of the surface acoustic wave device are bonded together through high-temperature ceramic glue; the main component of the high-temperature ceramic adhesive is alumina;
the strain sensor is attached to the surface of an object to be measured through the elastomer support; the elastic body support transmits the strain of the object to be measured to the surface acoustic wave device, so that the strain sensor is subjected to uniform strain, and the linear transmission proportion of the frequency change of the surface acoustic wave device and the measured strain is kept.
2. The high temperature resistant wide range surface acoustic wave strain sensor according to claim 1, wherein the elastomer holder is an arch bridge shaped elastomer holder, is an inverted U-shaped, and includes an upper plate, and side plates located on both sides of the upper plate and supporting the upper plate, the surface acoustic wave device is bonded to the upper plate, and the thickness of the upper plate of the arch bridge shaped elastomer holder is equal to the thickness of the surface acoustic wave device, and the area of the upper surface of the upper plate of the arch bridge shaped elastomer holder is not smaller than the area of the surface acoustic wave device; the thickness of the side plate of the arch bridge-shaped elastomer support is not less than that of the upper flat plate, and is positively correlated with the thickness of the upper flat plate.
3. A high-temperature-resistant wide-range surface acoustic wave strain sensor as claimed in claim 2, wherein the arch bridge-shaped elastomer support is in a shape of a Chinese character 'ji', and the arch bridge-shaped elastomer support is attached to the surface of a measured object through bending at two sides of the bottom.
4. The high temperature resistant wide range SAW strain sensor of claims 2 or 3, whereinThe material of the arch bridge-shaped elastomer bracket meets the tensile strength sigma within 0-800 DEG C b Not less than 400MPa, conditional yield strength sigma 0.2 ≥180Mpa。
5. A high temperature resistant and wide range SAW strain sensor as claimed in claim 4, wherein said elastomer support is made of high temperature elastic alloy mainly composed of Ni and Cr.
6. A high temperature resistant wide-range surface acoustic wave strain sensor as claimed in claim 1, wherein the elastomer support is two parallel supporting rods, and assuming that the width of the parallel supporting rod is L1, the height is H1, the length is A1, the distance between the two parallel supporting rods is L2, and the length of the surface acoustic wave device is B1, and the width is L3, the following conditions should be satisfied:
（1）L2+2L1<L3，A1>B1；
(2) the Poisson ratio of the parallel supporting rods is more than 0.25, and the Young modulus is less than 300 Gpa.
7. A high temperature resistant wide range surface acoustic wave strain sensor as claimed in claim 6, wherein L2= (0.1-0.8) = L3, A1= (1-3) = B1.
8. A high temperature resistant wide range saw strain sensor as claimed in claim 1, wherein said saw device electrodes are made of platinum or platinum alloy.
9. A high temperature resistant wide range surface acoustic wave strain sensor as claimed in claim 1, wherein said piezoelectric substrate layer of surface acoustic wave device is selected from high temperature resistant piezoelectric crystals including langasite and its doped crystals, aluminum nitride and its doped crystals, with a thickness of 1um-1 mm.
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