CN105424238A - Stress strain sensor - Google Patents

Abstract

The embodiment of the present invention provides a stress strain sensor, which includes a sensitive element and a cladding covering the sensitive element, wherein at least a portion of the cladding is made of a composite material. The sensor improves the durability and maintainability of the sensitive element of the sensor on the one hand, and on the other hand, when measuring a composite material test piece, it can improve the compatibility of the contact surface between the sensor and the test piece, and better transmit the strain of the composite material test piece.

Description

Stress and strain sensor

technical field

The invention relates to the field of measurement technology, in particular to a stress and strain sensor.

Background technique

With the wide use and particularity of wind turbine blades and nacelles, strain gauges (medium temperature foil resistance strain gauges) are commonly used to measure the stress and strain of composite nacelle and blades, but strain gauges often include the following three deficiencies Where:

First, the implementation requirements are high, the installation process and process are complicated, and the efficiency is low, so it is not suitable for batch use (the installation of strain gauges requires professional skills, so if it is to be used in large-scale batches, it is necessary to train a large number of professional installers to implement) . In addition, due to the uneven skills of the technicians, the test results are quite different.

Second, the maintainability is poor and the maintenance cost is high. If problems occur during the operation of the unit, professionals are required to deal with them, which increases the time cost and personnel maintenance cost.

Third, the scope of application is limited. The strain gauges currently on the market are not suitable for pre-embedding when processing composite components due to their own structural characteristics.

Contents of the invention

The purpose of the present invention is to provide a stress and strain sensor to solve the problems of high implementation requirements, poor maintainability and limited application range of the strain gauges in the prior art.

An embodiment of the present invention provides a stress-strain sensor, which includes a sensitive element and a cladding covering the sensitive element, at least a part of the cladding is made of composite material.

Preferably, the cladding includes a protective cladding and a working cladding, the protective cladding or the working cladding is provided with a groove, and the sensitive element is fixedly arranged in the groove.

Preferably, the side of the working cladding away from the protective cladding is the working surface matched with the measured piece, the protective cladding is provided with a groove, the sensitive element is arranged in the groove, and at least one side of the sensitive element is in contact with the working package. Layer fit.

Preferably, a temperature compensation sheet is also provided in the groove, the temperature compensation sheet is arranged side by side with the sensitive element, and at least one side of the temperature compensation sheet is bonded to the working cladding.

Preferably, a groove is provided on the protective cladding, an electromagnetic shielding protective layer is provided between the groove and the sensitive element, and the electromagnetic shielding protective layer covers the surface of the sensitive element away from the working surface.

Preferably, the sensor further includes test leads protruding outside the cladding.

Preferably, the claddings are composite material claddings, and the composite material is glass fiber reinforced plastics.

Preferably, an installation datum line is provided on the protective cladding and on the shell corresponding to the tested object.

Preferably, a plurality of mounting holes are provided on the cladding.

Preferably, the protective cladding and the working cladding are bonded by an adhesive.

Preferably, the stress and strain sensors are installed on the nacelle and/or the blades of the wind power generating set for measuring the stress and strain values of the nacelle and/or the blades.

According to the stress-strain sensor provided by the embodiment of the present invention, since the sensitive element is packaged with at least a part of the cladding made of composite material, on the one hand, the durability and maintainability of the sensitive element of the sensor are improved; When the measured piece of composite material is measured, the compatibility of the contact surface between the sensor and the tested piece can be improved, and the strain of the composite material tested piece can be better transmitted.

Description of drawings

Fig. 1 is the schematic diagram of the sensor installation surface of the embodiment of the present invention;

Fig. 2 is a schematic diagram of a protective cladding of a sensor according to an embodiment of the present invention;

Fig. 3 is a schematic cutaway view of the internal structure of the sensor according to an embodiment of the present invention;

Fig. 4 is a schematic side sectional view of a sensor according to an embodiment of the present invention.

Explanation of reference signs:

1. Working surface; 2. Lead wire; 3. Installation reference line; 4. Protective cladding; 5. Sensitive components; 6. Electromagnetic shielding protective layer; 7. Adhesive; 10. Working cladding.

detailed description

Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The invention relates to a strain gauge sensor, which generally consists of two parts, a resistance strain gauge and a measurement conversion circuit. The working principle of the resistance strain gauge is: when the resistance strain gauge is used, it is glued to the tested piece. When the tested piece is deformed by force, the length and cross-sectional area of the metal wire in the strain gauge also change with the tested piece. , and then the change of resistance occurs. Since the change of strain and the relative change of resistance have a linear correspondence relationship, the corresponding strain increment can be calculated by measuring the change value of the output voltage of the bridge by using the Wheatstone bridge.

As shown in Fig. 3 and Fig. 4, the embodiment of the present invention provides a stress-strain sensor, including a sensitive element 5 and a cladding layer covering the sensitive element 5, wherein the sensitive element 5 is a sensor that can directly sense the measured The part of the variable, it can sensitively sense the measured variable, and convert the stress and strain into an electrical signal output. The role of the cladding outside the sensitive element 5 is to prevent the sensitive element 5 inside the sensor from being damaged and deformed by mechanical force, and at the same time reduce the process of using the sensitive element 5 and improve the use efficiency. At least a portion of the cladding is made of composite material.

The stress-strain sensor of the present embodiment encapsulates the sensitive element 5 by at least a part of the cladding made of a composite material. On the one hand, the durability and maintainability of the sensitive element 5 of the sensor are improved, and the reliability of the traditional strain gauge measurement is overcome. The defects of poor maintainability, high maintenance cost and not suitable for repeated use improve the protection level of the sensor. On the other hand, because at least a part of the packaging material of the sensor in the embodiment of the present invention is a composite material, when the test piece of the composite material is measured, the compatibility of the contact surface between the sensor and the test piece can be improved (sensor's The working surface 1 and the surface of the tested piece are made of the same material), which can better transmit the strain of the composite material tested piece and ensure that the sensor can measure the strain of the composite material.

As shown in FIG. 4 , specifically, the cladding of the sensor includes a protective cladding 4 and a working cladding 10 , and the protective cladding 4 and the working cladding 10 are bonded with an adhesive 7 to ensure its sealing performance. The protective cladding 4 is mainly used to form an effective protection outside the sensitive element 5 together with the working cladding 10, so that the sensitive element 5 inside the sensor is prevented from being damaged and deformed by mechanical force, and the protective cladding 4 and the working cladding 10 also have Anti-corrosion and moisture-proof functions, in this way, the protection level of the sensor can be improved, so that the protection level of the sensor can reach IP54. For the convenience of placing the sensitive element 5, a groove is provided on the protective cladding 4 and/or the working cladding 10, and the sensitive element 5 is fixedly arranged in the groove, so that the fixing and positioning of the sensitive element 5 inside the sensor can be realized, ensuring The sensitive element 5 will not move freely in the sensor, and it is convenient for the sensitive element 5 of the sensor to be aligned with the object under test for measurement.

Preferably, a groove is provided on the protective cladding 4 , and the sensitive element 5 is disposed in the groove of the protective cladding 4 . Such an arrangement can securely fix the sensitive element 5 without damaging the working cladding 10 . The working cladding 10 of the sensor is directly attached to the side of the sensitive element 5, and the side of the working cladding 10 of the sensor away from the protective cladding 4 is the working surface 1 that cooperates with the measured object, that is, when the sensor is used, the working surface of the sensor The working surface 1 of the cladding 10 is in contact with the surface of the measured object and performs strain measurement.

In order to improve the measurement accuracy of the sensor and effectively reduce the influence of the ambient temperature on the measured value, a temperature compensation sheet is also arranged in the groove, and the temperature compensation sheet and the sensitive element 5 are arranged side by side, and at least one side of the temperature compensation sheet is in contact with the working cladding 10 fit. The temperature compensation sheet should be made of materials that are not sensitive to temperature, such as Karma alloy or constantan. When in use, since the temperature compensation sheet has been preset between the sensitive element 5 and the protective cladding 4, the steps of performing temperature compensation processing in the existing use process can be omitted, reducing the difficulty of use and the setting time.

Specifically, the sensitive element 5 is made of the same material as the temperature compensation sheet, and the sensitive element 5 is made of Karma alloy or constantan.

In order to further improve the measurement accuracy of the sensor and improve the anti-electromagnetic interference capability of the sensor, an electromagnetic shielding protective layer 6 is provided between the groove on the protective cladding 4 and the sensitive element 5, and the electromagnetic shielding protective layer 6 covers the part of the sensitive element 5 that is far away from the place. The surface of the working face. When the temperature compensation sheet and the electromagnetic shielding protection layer 6 are simultaneously arranged in the stress strain sensor, the temperature compensation sheet and the sensitive element 5 are arranged side by side in the groove of the protective cladding, and at least one side of the temperature compensation sheet is connected to at least one side of the sensitive element 5 One side is all bonded with the working cladding 10 . At this time, the electromagnetic shielding protection layer 6 needs to cover the sensitive element 5 and the surface of the temperature compensation sheet away from the working surface at the same time. The electromagnetic shielding protection layer 6 is used to realize the shielding function of electromagnetic interference, and at the same time, it is anti-corrosion and moisture-proof. The electromagnetic shielding protective layer 6 is made of metal material, specifically tin foil.

As shown in Fig. 1, in order to fix the sensor conveniently and improve the efficiency of measuring the DUT, the test lead 2 of the sensor protrudes out of the cladding. And according to the actual situation of the DUT, sometimes in order to connect the test lead 2 to the test equipment more conveniently, the length of the test lead 2 can also be extended appropriately (the lead 2 has been reserved before packaging), so that it is easier to access the test equipment.

Specifically, the lead 2 mark can be set on the cladding to facilitate the wiring of the staff, and a mark can also be set on the lead 2 to identify the type and function of the lead 2. The signal lead 2 of the sensor is marked as follows, which can be identified according to the following lead 2, Directly connected to the test equipment, the measurement can be realized.

EX+ - incentive "+";

IN+——signal input "+";

EX--encouragement "-";

IN--signal input "-";

GND - ground terminal;

Compared with the traditional strain gauge wiring method (traditional strain gauges need to glue the terminal and weld the lead wire 2), the lead wire 2 of the sensor in the embodiment of the present invention is more convenient to use and more suitable for practical engineering applications.

In order to solve the stress-strain measurement problem of composite material components (such as the nacelle and blades) of wind turbines, the working cladding 10 of the sensor is made of glass fiber reinforced plastic composite material. The protective cladding 4 is also made of fiberglass composite material. In this way, the fiberglass sensor is made of fiberglass composite material because of its working cladding 10, so the sensor is suitable for the measurement of the measured parts such as polyester fiberglass, epoxy fiberglass, phenolic fiberglass, etc. (the working surface 1 of the sensor and the measured part The material is the same, the two have better compatibility and improve the measurement accuracy), not only can be applied to the stress and strain measurement of the wind turbine nacelle and/or blades (when used, the stress and strain sensor is installed on the wind turbine cabin and/or blades, used to measure the stress and strain values of the cabin and/or blades), it can also be used in other fields, as long as the material of the tested part is a glass fiber reinforced plastic composite material. Of course, in the same way, the working cladding 10 of the sensor can also be replaced with other materials as required, as long as the material is the same as that of the measured object, the measurement can be realized.

In order to meet the insulation technical requirements, the cladding material of the sensor should be an insulating material, so the insulation can be improved by a level compared with the traditional strain gauge.

As shown in FIG. 2 , in order to further facilitate the use of the sensor, an installation datum line 3 is provided on the protective cladding 4 of the sensor and on the shell corresponding to the tested part. The installation reference line 3 is mainly used to assist in determining the installation direction of the sensor. Specifically, when using, first determine the force direction of the tested piece, and mark the surface of the tested piece. When fixing the sensor, you only need to match the installation reference line 3 with the marked line on the tested piece surface to determine The orientation of the sensor is installed, and then the measurement is performed.

Specifically, the connection between the sensor and the tested object may be directly glued, or a plurality of mounting holes may be provided on the cladding of the sensor. Preferably, the four corners of the sensor are provided with holes, and the sensor is tightly connected with the measured object by fixing parts such as bolts or rivets, and the measured object is measured.

The installation method of the sensor in the embodiment of the present invention greatly simplifies the process and reduces the difficulty for operators. The installation method of the traditional strain gauge has high requirements on the surface roughness, and the surface of the measured part needs to be finely ground and cleaned. In addition, sticking strain gauges has high requirements for installation process, such as sticking method, installation direction, moisture-proof, anti-corrosion, insulation treatment, anti-interference shielding treatment, etc. The process is complicated, and the operation during installation directly affects the measurement results. For the reasons mentioned above, traditional strain gauge installation requires professionally skilled staff. If strain gauges need to be used in large quantities, a large number of professional installers need to be trained to implement them. Due to the differences in the skills of technicians, the test results are quite different. However, the sensor of the embodiment of the present invention omits these operation steps. When in use, the installer only needs to clean the working surface 1 of the sensor with acetone or 95% ethanol, apply special glue evenly on the surface, and then make Simply clean or polish to ensure that the glue between the sensor and the tested part is firm and reliable. The installation process is simple and easy to use in engineering. For example, the sensor can be pre-embedded in the test piece for measurement as required (the structural characteristics of the traditional strain gauge are not suitable for pre-embedding in the process of the test piece).

The measurement process of the sensor of the embodiment of the present invention is also relatively simple. During the test process, due to the firm bonding between the tested piece and the working surface 1 of the sensor, the deformation of the tested piece is effectively transmitted to the working surface 1 of the sensor, through the sensitive element 5 Perceive the deformation on the working surface 1, thereby sensing the deformation of the tested piece, and then convert this deformation into an electrical signal and output it to the acquisition device to calculate the stress and strain value of the tested piece. In use, ensuring the firm bonding between the working surface 1 and the surface of the tested piece can ensure the effective transmission of the measured piece's deformation.

Of course, other suitable sensors can also be selected according to the form of the measured physical quantity (such as tension, pressure, shear force and torsion) and the structure of the measured object, which is not limited in this embodiment of the present invention.

The sensor provided by the embodiment of the present invention is also reusable. Traditional strain gauges are disposable and cannot be reused, which is not conducive to saving resources and costs. Because of its optimized design structure, the sensor of the embodiment makes it possible to remove the sensor by cleaning the glue on the surface 1 and the surface of the tested object with a special solvent after the sensor finishes the test, and then clean the residual solvent and glue on the working surface 1 of the sensor , In this way, the sensor will not be damaged, and it can be reused, which greatly reduces the cost consumption.

In addition, the sensor provided by the embodiment of the present invention also has good maintainability. In use, if the sensor or line is damaged, just clean up the damaged sensor and line, and reinstall the spare sensor at the original measuring point.

The stress-strain sensor provided by the embodiment of the present invention has the following technical effects:

It can be more convenient to measure the components of composite materials, and reduce the implementation requirements, simplify the installation process and installation process, thus expanding the application range and application scale; improving maintainability, reducing maintenance costs, and can be repeated Use; small size, light weight, and integrated packaging, high protection level (up to IP54), easy to transport and store; with anti-electromagnetic interference, temperature supplement and insulation protection technology processing, improve the measurement accuracy.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (11)

1. a stress strain gauge, is characterized in that, comprises sensitive element (5) and is coated on described sensitive element (5) covering outward, described covering at least partially for compound substance is made.

2. stress strain gauge according to claim 1; it is characterized in that; described covering comprises protection covering (4) and work covering (10); described protection covering (4) or described work covering (10) are provided with groove, and described sensitive element (5) is fixedly installed in described groove.

3. stress strain gauge according to claim 2; it is characterized in that; the one side away from described protection covering (4) of described work covering (10) is the workplace (1) coordinated with measured piece; described protection covering (4) is provided with described groove; described sensitive element (5) is arranged in described groove, and at least one side of described sensitive element (5) and described work covering (10) are fitted.

4. stress strain gauge according to claim 3, it is characterized in that, temperature compensation sheet is also provided with in described groove, described temperature compensation sheet and described sensitive element (5) are arranged side by side, and at least one side of described temperature compensation sheet and described work covering (10) are fitted.

5. stress strain gauge according to claim 3; it is characterized in that; described protection covering (4) is provided with described groove; be provided with electromagnetic screen protective layer (6) between described groove and described sensitive element (5), described electromagnetic screen protective layer (6) covers the surface away from described workplace of described sensitive element (5).

6. stress strain gauge according to claim 1, is characterized in that, also comprises test lead (2), and it is outside that described test lead (2) extend out to described covering.

7. stress strain gauge according to claim 1, is characterized in that, described covering is Composite materials Clad, and described compound substance is fiberglass.

8. stress strain gauge according to claim 2, is characterized in that, the upper shell corresponding with measured piece of described protection covering (4) is provided with installation reference line (3).

9. stress strain gauge according to claim 1, is characterized in that, described covering is provided with multiple mounting hole.

10. stress strain gauge according to claim 2, is characterized in that, by bonding agent (7) bonding between described protection covering (4) and described work covering (10).

11. stress strain gauges as claimed in any of claims 1 to 10, is characterized in that, on the cabin that described stress strain gauge is installed on wind power generating set and/or blade, for measuring the ess-strain value of described cabin and/or blade.