CN105698664A - Detecting device and detecting method suitable for strain of concrete - Google Patents

Abstract

The invention relates to the field of strain detection, and particularly to a detecting device and a detecting method suitable for strain of concrete. The detecting device comprises the components of a metal base plate which is bonded at a detecting position of the concrete; and a strain sensor which is fixedly arranged at the center of the metal base plate, wherein the strain sensor comprises a Wheatstone bridge which is provided with four electric resistance strain gauges which are vertical to one another, and furthermore a buffer layer is arranged between the two electrical resistance strain gauges and the metal base plate. The detecting method comprises the steps of supplying the metal base plate which is provided with the strain sensor in a fixed manner, wherein the strain sensor comprises the Wheatstone bridge which is provided with the four electric resistance strain gauges that are vertical to one another, and a buffer layer is arranged between the two electrical resistance strain gauges and the metal base plate; binding the metal base plate on the to-be-detected concrete; detecting change value of output voltage of the Wheatstone bridge, and calculating strain change value of the concrete according to the change value of the output voltage.

Description

Device and method suitable for detecting strain of concrete

Technical Field

The invention relates to the field of strain detection, in particular to a strain detection device and method suitable for concrete.

Background

The existing method for detecting the strain of the heterogeneous material such as concrete generally adopts a strain sensor for detection, and due to the influence of factors such as temperature, the heterogeneity of the material of an object to be detected and the like, the detection value of the strain sensor has the problems of zero drift and large error, and the accuracy of the detected strain value cannot be ensured.

Disclosure of Invention

In view of the problems in the prior art, a device and a method for detecting strain of concrete are provided, which can detect stress change of non-homogeneous materials such as concrete.

The specific technical scheme is as follows:

a detection device suitable for detecting the strain of concrete is applied to the strain detection of the concrete, and comprises:

the metal bottom plate is bonded on the detection position of the concrete;

a strain sensor fixedly arranged at the center of the metal bottom plate, wherein,

the strain sensor includes:

the device comprises a Wheatstone bridge with four resistance strain gauges which are vertical to each other in pairs, wherein a buffer layer is padded between the two resistance strain gauges and the metal bottom plate.

Preferably, the metal bottom plate is square.

Preferably, the four resistance strain gauges have the same resistance value.

Preferably, the buffer layer is made of heat-conducting grease.

Preferably, the two resistance strain gauges padded with the buffer layer are two resistance strain gauges on a diagonal line.

Preferably, the metal bottom plate is made of aluminum alloy.

Preferably, the stress variation has a value of:wherein,

delta U is the variation value of the output voltage of the Wheatstone bridge; k is the sensitivity coefficient of the resistance strain gauge; and E is the working voltage of the Wheatstone bridge.

Preferably, the upper surface of the strain sensor is covered with a waterproof layer.

Preferably, the waterproof layer is made of silica gel.

A method for detecting strain in concrete, comprising:

providing a metal base plate fixedly provided with a strain sensor, wherein the strain sensor comprises: the device comprises a Wheatstone bridge with four pairwise vertical resistance strain gauges, wherein a buffer layer is padded between the two resistance strain gauges and a metal bottom plate;

bonding the metal bottom plate on the concrete to be tested;

and detecting the change value of the output voltage of the Wheatstone bridge, and calculating the stress change value of the concrete according to the change value of the output voltage.

The beneficial effects of the above technical scheme are:

according to the technical scheme, the strain sensing between the two resistance strain gauges and the concrete in the Wheatstone bridge is cut off, so that the resistance strain gauges cannot sense the stress change, the sensitivity of the Wheatstone bridge is improved, and the accuracy of the stress change is further improved.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of a stress variation detection apparatus according to the present invention;

FIG. 2 is a circuit diagram of an embodiment of a Wheatstone bridge according to the invention;

FIG. 3 is a flowchart illustrating a method for detecting a stress variation according to an embodiment of the present invention.

Detailed Description

In the following embodiments, the technical features may be combined with each other without conflict.

The following further describes embodiments of the present invention with reference to the drawings:

as shown in fig. 1, the present embodiment provides a strain detection device suitable for a heterogeneous material such as concrete, which is applied to the detection of concrete, and the strain detection device includes:

the metal bottom plate is adhered to the detection position of the concrete by adopting an adhesive;

a strain sensor fixedly arranged at the center of the metal bottom plate, wherein,

the strain sensor includes:

the Wheatstone bridge is provided with four resistance strain gauges which are vertical to each other in pairs, wherein a buffer layer is padded between the two resistance strain gauges and the metal bottom plate.

In the embodiment, the two resistance strain gauges are isolated from the metal base plate through the buffer layer, so that the two isolated resistance strain gauges cannot feel the change of stress to improve the sensitivity of the Wheatstone bridge, and meanwhile, the Wheatstone bridge can compensate the temperature change.

In a preferred embodiment of the present invention, the metal base plate has a square shape.

The concrete is a mixture composed of broken stones and mortar, the broken stones and mortar have different elastic moduli, the strain distribution of the surface is complex, and the square metal bottom plate is adhered to the surface of the concrete to form a whole body due to the non-uniformity of the strain of the surface of the concrete. The strain on the concrete surface causes the metal floor to strain. The metal bottom plate has certain rigidity, the strain of the central part of the surface of the metal bottom plate reflects the average value of the strain of a concrete area covered by the metal bottom plate, and the error caused by the fact that the rectangular bottom plate senses the longitudinal and transverse non-uniformity of the stress change of the concrete is overcome.

Furthermore, the metal bottom plate is a square metal bottom plate with the side length being 3 to 5 times larger than the maximum diameter of the concrete gravel and the thickness being 2 millimeters, so that the non-uniformity of the concrete detection direction is overcome, and errors caused by transverse non-uniformity are overcome.

In a preferred embodiment of the present invention, the four resistive strain gauges have the same resistance.

In a preferred embodiment of the present invention, the buffer layer is made of thermal grease.

In a preferred embodiment of the present invention, the two resistance strain gauges padded with the buffer layer are two resistance strain gauges on a diagonal line.

As shown in fig. 2, the strain sensor of the present embodiment is a wheatstone bridge composed of 4 identical resistive strain gauges. The 4 identical resistance strain gauges are perpendicular to each other in pairs and are respectively a resistance strain gauge R1, a resistance strain gauge R2, a resistance strain gauge R3 and a resistance strain gauge R4. The resistance strain gauge R1 and the resistance strain gauge R3 are directly adhered to the metal base plate. The resistance strain gauge R2 and the resistance strain gauge R4 are adhered to the metal base plate by using heat-conducting grease.

In a preferred embodiment of the present invention, the metal base plate is made of aluminum alloy.

In this embodiment, the aluminum alloy base plate has good thermal conductivity, and when the temperature of the aluminum alloy base plate changes, the 4 resistor discs adhered to the aluminum alloy base plate can synchronously change at the same temperature, and drift of the reference point caused by the temperature change can be automatically eliminated through the wheatstone bridge.

In a preferred embodiment of the present invention, the stress variation values are:wherein,

delta U is the variation value of the output voltage of the Wheatstone bridge; k is the sensitivity coefficient of the resistance strain gauge; and E is the working voltage of the Wheatstone bridge.

In this embodiment, in fig. 2, the following equation is provided according to the bridge balance equation:

$\mathrm{\Δ}U=\[\frac{R1\·R2}{{(R1+R2)}^2}*(\frac{\mathrm{\Δ}R1+Rt}{R1}-\frac{\mathrm{\Δ}R2+Rt}{R2})+\frac{R3\·R4}{{(R3+R4)}^2}*(\frac{\mathrm{\Δ}R3+Rt}{R3}-\frac{\mathrm{\Δ}R4+Rt}{R4})\]*E;$

where Δ R1 is a change value of the strain-affected resistive strain gauge R1, Δ R2 is a change value of the strain-affected resistive strain gauge R2, Δ R3 is a change value of the strain-affected resistive strain gauge R3, Δ R4 is a change value of the strain-affected resistive strain gauge R4, and Rt is a change in resistance of the strain-affected resistive strain gauge due to temperature.

Since the four resistance strain gauges have the same resistance, i.e., R1 ═ R2 ═ R3 ═ R4 ═ R, the above formula can be simplified as follows:

$\mathrm{\Δ}U=\[\frac{R^2}{4R^2}*\left(\frac{\mathrm{\Δ}R1+Rt-\mathrm{\Δ}R2-Rt}{R}\right)+\frac{R^2}{4R^2}*\left(\frac{\mathrm{\Δ}R3+Rt-\mathrm{\Δ}R4-Rt}{R}\right)\]*E;$

further simplifying the above formula, obtain:

$\mathrm{\Δ}U=\[\frac{1}{4}*\left(\frac{\mathrm{\Δ}R1-\mathrm{\Δ}R2}{R}\right)+\frac{1}{4}*\left(\frac{\mathrm{\Δ}R3-\mathrm{\Δ}R4}{R}\right)\]*E;$

the resistance variation Rt caused by the temperature variation is eliminated, i.e. the strain sensor is not subjected to temperature variations and the wheatstone bridge is capable of temperature compensation. Since the strain sensor is subjected to unidirectional strain, and the resistance strain gauges R2 and R4 are not affected by stress variation, Δ R4 is Δ R2 is 0, Δ R1 is Δ R3 is Δ R, and the above formula may be changed as follows:

$\mathrm{\Δ}U=\[\frac{1}{4}*\left(\frac{\mathrm{\Δ}R}{R}\right)+\frac{1}{4}*\left(\frac{\mathrm{\Δ}R}{R}\right)\]*E$

further simplifying the above formula, obtain:

$\mathrm{\Δ}U=\frac{\mathrm{\Δ}R}{2R}*E;$

according to the relationship between the resistance change and the sensitivity coefficient K and the strain of the resistance strain gauge, the following formula is provided:

$K=\frac{\mathrm{\Δ}R}{R}*\frac{1}{\mathrm{\ϵ}};$

by substituting the value of the stress change into the formula:

$\mathrm{\ϵ}=\frac{2*\mathrm{\Δ}U}{E*K}$

from the above formula, the value of the coefficient of sensitivity is more accurate by reducing the two resistance sensing stress changes in the present embodiment and the temperature compensation of the wheatstone bridge in the present embodiment is not affected.

In a preferred embodiment of the present invention, a waterproof layer is covered on the upper surface of the strain sensor.

In a preferred embodiment of the present invention, the waterproof layer is made of silica gel.

The surface of the strain gauge is covered with silica gel for waterproof treatment, so that the strain sensor can be protected from water, and the precision of strain detection is improved.

The embodiment also provides a method for detecting a stress variation, as shown in fig. 3, including:

providing a metal base plate fixedly provided with a strain sensor, wherein the strain sensor comprises: the device comprises a Wheatstone bridge with four pairwise vertical resistance strain gauges, wherein a buffer layer is padded between the two resistance strain gauges and a metal bottom plate;

bonding a metal bottom plate on the concrete to be tested;

and detecting the change value of the output voltage of the Wheatstone bridge, and calculating the stress change value of the concrete according to the change value of the output voltage.

In summary, in the above technical solution, the strain sensing between two of the resistance strain gauges in the wheatstone bridge and the concrete is cut off, so that the resistance strain gauges cannot sense the change of the stress, thereby improving the sensitivity of the wheatstone bridge and further improving the accuracy of the stress change.

While the specification concludes with claims defining exemplary embodiments of particular structures for practicing the invention, it is believed that other modifications will be made in the spirit of the invention. While the above invention sets forth presently preferred embodiments, these are not intended as limitations.

Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims should be considered to be within the intent and scope of the present invention.

Claims (10)

1. A device for detecting the strain of concrete, which is used for detecting the strain of concrete, and comprises:

the metal bottom plate is bonded on the detection position of the concrete;

a strain sensor fixedly arranged at the center of the metal bottom plate, wherein,

the strain sensor includes:

the device comprises a Wheatstone bridge with four resistance strain gauges which are vertical to each other in pairs, wherein a buffer layer is padded between the two resistance strain gauges and the metal bottom plate.

2. The apparatus for detecting strain applied to concrete according to claim 1, wherein the metal bottom plate has a square shape.

3. The apparatus for detecting strain applied to concrete according to claim 1, wherein the four resistance strain gauges have the same resistance value.

4. The device for detecting strain applied to concrete according to claim 1, wherein the buffer layer is made of heat-conducting grease.

5. The apparatus for detecting strain applied to concrete according to claim 1, wherein the two resistance strain gauges padded with the buffer layer are two resistance strain gauges on a diagonal line.

6. The apparatus for detecting strain applied to concrete according to claim 1, wherein the metal bottom plate is made of aluminum alloy.

7. The apparatus for detecting the strain applicable to concrete according to claim 3, wherein the value of the stress variation is:wherein,

delta U is the variation value of the output voltage of the Wheatstone bridge; k is the sensitivity coefficient of the resistance strain gauge; and E is the working voltage of the Wheatstone bridge.

8. The apparatus for detecting strain in concrete according to claim 1, wherein the strain sensor is covered with a waterproof layer on its upper surface.

9. The apparatus for detecting strain of concrete according to claim 8, wherein the waterproof layer is made of silica gel.

10. A method for detecting strain applied to concrete, comprising:

providing a metal base plate fixedly provided with a strain sensor, wherein the strain sensor comprises: the device comprises a Wheatstone bridge with four pairwise vertical resistance strain gauges, wherein a buffer layer is padded between the two resistance strain gauges and a metal bottom plate;

bonding the metal bottom plate on the concrete to be tested;

and detecting the change value of the output voltage of the Wheatstone bridge, and calculating the stress change value of the concrete according to the change value of the output voltage.