CN103105124B - Full-bridge type and semibridge system measure foil gauge and the method for shear strain - Google Patents

Abstract

The invention relates to a full-bridge and half-bridge strain gauge and a method for measuring shear strain, belonging to the technical field of "experimental stress analysis". The bridge-type strain gauge for measuring shear strain has a 0-degree sensitive grid, 90-degree sensitive grid, the first 45-degree sensitive grid, and the second 45-degree sensitive grid; the half-bridge strain gauge for measuring shear strain has a 135-degree sensitive grid and 45-degree sensitive grid; the invention can directly carry out the manufacture of shear strain gauges for shear strain measurement. Added new test means in the "Resistance Strain Test" field in "Experimental Stress Analysis".

Description

Full-bridge and half-bridge strain gauges and methods for measuring shear strain

technical field

The invention relates to a full-bridge and half-bridge strain gauge and a method for measuring shear strain, belonging to the technical field of "experimental stress analysis".

Background technique

Internet search shows that in the current "resistance strain test technology" in "experimental stress analysis", the resistance strain gauge is still mainly used to measure the strain of the component when it is under force, and the resistance strain gauge can only measure the strain along the strain gauge grid. The linear strain in the long direction cannot measure the shear strain of the measured point.

Contents of the invention

The purpose of the present invention is to complete the manufacture of shear strain gauges capable of directly measuring shear strain. Added new test means in the "Resistance Strain Test" field in "Experimental Stress Analysis".

A full-bridge strain gauge for measuring shear strain, characterized in that: the strain gauge has a 0-degree sensitive grid, a 90-degree sensitive grid, a first 45-degree sensitive grid, and a second 45-degree sensitive grid; wherein the 0-degree sensitive grid , 90-degree sensitive grid, the first 45-degree sensitive grid, and the second 45-degree sensitive grid form a full-bridge circuit. The specific method is: the second end of the 0-degree sensitive grid and the first end of the first 45-degree sensitive grid The node connected to each other becomes node B; the second end of the first 45-degree sensitive grid is connected to the first end of the 90-degree sensitive grid, and the node connected to the two becomes node C; the second end of the 90-degree sensitive grid is connected to The first end of the second 45-degree sensitive grid is connected, and the node connected between the two becomes the D node; the second end of the second 45-degree sensitive grid is connected to the first end of the 0-degree sensitive grid, and the node connected between the two is called A node.

The method for measuring shear strain using the above-mentioned full-bridge strain gauge for measuring shear strain is characterized in that it includes the following process: the four nodes A, B, C, and D of the strain gauge are drawn out with lead wires, and connected to the strain gauge respectively. A, B, C, D four connection points, then the reading of the strain gauge at this time is the shear strain γ ₀ to be measured.

A half-bridge strain gauge for measuring shear strain is characterized in that: the strain gauge has a 135-degree sensitive grid and a 45-degree sensitive grid; wherein the 135-degree sensitive grid and the 45-degree sensitive grid form a half-bridge circuit, the specific method It is: the first end of the 135-degree sensitive grid is used as node A; the second end of the 135-degree sensitive grid is connected to the first end of the 45-degree sensitive grid, and the node connected between the two becomes node B; the second end of the 45-degree sensitive grid terminal as node C.

The method for measuring shear strain using the above-mentioned half-bridge strain gauge for measuring shear strain is characterized in that it includes the following process: the three nodes A, B, and C of the strain gauge are drawn out with lead wires, and connected to A, B, and C of the strain gauge respectively. There are three connection points B and C, then the reading of the strain gauge at this time is the shear strain γ ₀ to be measured.

The feature of the present invention is that it changes people's traditional concept that the resistance strain gauge can only measure the linear strain of tension and compression, and provides a new type of resistance strain gauge that directly measures the shear strain "γ", and utilizes Hooke's theorem τ =Gγ Calculate the shear stress value of the corresponding unit body. The types of resistance strain gauges are increased, the connotation of resistance strain test technology is improved, the speed and means of testing shear stress are improved, and the application range of resistance strain gauges can be expanded.

Description of drawings

Fig. 1 bridge circuit diagram;

Figure 2 Full bridge strain gauge for measuring shear strain;

Figure 3 The strain gauge diagram of the half-bridge measurement of shear strain;

Label name in the picture: 1-0 degree sensitive grid, 2-90 degree sensitive grid, 3-first 45-degree sensitive grid, 4-second 45-degree sensitive grid, 5-135-degree sensitive grid, 6-45-degree sensitive grid , 7-leader, 8-base.

detailed description

Known by the experts in resistance strain testing technology, the resistance strain gauge can only measure the linear strain. To measure the shear strain γ, it can only measure the linear strain ε _α1 , ε _α2 , ε _α3 in three directions at the place first, and then according to the strain Analysis formula (1)

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; xy</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; xy</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&epsiv;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}_{\mathrm{<span\; class="notranslate">\; xy</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}\end{array}\right\}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Among them: ε _α1 , ε _α2 , ε _α3 are the measured strains in the α1 direction, α2 direction and α3 direction of a certain point on the stressed structure respectively, ε _x is the strain in the X direction of the point, ε _y is the strain in the y direction of the point, γ _xy is the strain at this point. (See "Material Mechanics Testing Principles and Experiments" edited by Cao Yibo, National Defense Industry Press, page 39, 1991 edition) Calculate the shear strain γ _xy . For example: if the three strains of ε ₀ , ε ₄₅ , and ε ₉₀ are measured respectively, the shear strain can be calculated

γ ₀ =ε ₀ +ε ₉₀ -2ε ₄₅ (2)

And the basic characteristics of the readings of the bridge based on the resistance strain testing technique. The bridge circuit diagram 1 is as follows, the two ends of B and D are the output ends of the electric bridge, and the two ends of A and C are the working voltage supply ends of the electric bridge.

There is such a relationship between the reading value of the strain bridge and the sensed strain of the strain gauges on the four bridge arms that make up the bridge, that is, K ₀ ε _d =K(ε _AB -ε _BC -ε _AD +ε _CD ), where K ₀ , K are the gage coefficient value of the strain gauge and the value of the strain gauge respectively, when the gage coefficient K ₀ of the strain gauge is set to be equal to the gage coefficient K value of the strain gauge, the relationship (3) exists

ε _d = (ε _AB -ε _BC -ε _AD +ε _CD ) (3)

(Refer to "Material Mechanics Testing Principles and Experiments" edited by Cao Yibo, National Defense Industry Press, 91 Edition, page 27) Combining (2) and (3) it is not difficult to see that if one ε ₀ strain gauge and one ε ₉₀ strain gauge and Two ε ₄₅ strain gauges are integrated on one substrate to form a full-bridge strain gauge, and leads are drawn from four nodes A, B, C, and D to connect to four connection points A, B, and C of the strain gauge , D, the reading of the strain gauge at this time is the result of formula (2), that is, the shear strain γ ₀ we need (as shown in Figure 2)

Similarly, it can also be calculated according to the strain analysis formula (1)

γ ₀ =ε ₁₃₅ -ε ₄₅ (4)

Then according to the formula (3), a half-bridge strain gauge is formed (as shown in Figure 3, the strain gauge diagram of the half-bridge measuring shear strain) (Note: In the working mode of the strain gauge, there is also a half-bridge working mode, namely In this way, the strain gauge can automatically provide two resistors R, instead of the two resistors R _AD and R _CD in the bridge circuit diagram, as long as A, B, and C of the half-bridge strain gauge measuring shear strain are three Each node is connected to the corresponding nodes A, B, and C of the instrument, so that the two sensitive grids R ₁₃₅ and R ₄₅ on the strain gauge act as the resistors R _AB and R _BC in the bridge circuit, which can be directly read by the instrument The shear strain γ ₀ =(ε ₁₃₅ -ε ₄₅ ) is obtained.

The technical solution of the present invention is that, according to the current manufacturing process of the resistance strain gauge, four sensitive grids are integrated on a substrate, and the four sensitive grids are connected in an appropriate form and drawn out with lead wires. When in use, as long as the The four lead wires are connected to the bridge terminals A, B, C, and D of the strain gauge in the order of A, B, C, and D, and the shear strain "γ" of the patch point can be read directly from the resistance strain gauge ( As shown in Fig. 2, 3, be one of them example of this scheme, be the strain gauge figure of full-bridge measurement shear strain. There can also be the combination form of the sensitive gate of other different directions, as the half-bridge measurement shear strain Strain gauges).

Therefore, in Figures 2 and 3: 1. The full-bridge strain gauge for measuring shear strain has four lead wires A, B, C, and D, of which A and C are connected to the bridge pressure, and B and D are the strain output. end. The half-bridge strain gauge for measuring shear strain has three lead wires A, B, and C. When the sensitivity coefficient of the resistance strain gauge and the sensitivity coefficient of the strain gauge are set to be the same, the indicated strain of the strain gauge is the shear strain value. 2. There are two main combinations of sensitive grids. Of course, other combinations are possible. 3. The substrate is used to fix the sensitive grid and to insulate the sensitive grid from the measured object.

The embodiment of the present invention is: make the strain gauge according to the current process of making the resistance strain gauge, connect several sensitive grids integrated on the same substrate according to the figure, and lead them out with lead-out lines. As shown in Figures 2 and 3, where: the four lead wires in Figure 2 are respectively connected to the four terminals A, B, C, and D of the full bridge of the strain gauge. The three lead wires A, B, and C in Fig. 3 are respectively connected to the three terminals A, B, and C of the plate bridge of the strain gauge.

Claims (4)

1. full-bridge type measures a foil gauge for shear strain, it is characterized in that:

This foil gauge have 0 degree of sensitive grid, 90 degree of sensitive grids, the one 45 degree of sensitive grid, the 2 45 degree of sensitive grid;

Wherein 0 degree of sensitive grid, 90 degree of sensitive grids, the one 45 degree of sensitive grid, the 2 45 degree of sensitive grids form a full bridge circuit, concrete mode is: wherein the second end of 0 degree of sensitive grid is connected with the first end of the one 45 degree of sensitive grid, and the node that both are connected becomes B node; Second end of the one 45 degree of sensitive grid is connected with the first end of 90 degree of sensitive grids, and the node that both are connected becomes C node; Second end of 90 degree of sensitive grids is connected with the first end of the 2 45 degree of sensitive grid, and the node that both are connected becomes D node; Second end of the 2 45 degree of sensitive grid is connected with the first end of 0 degree of sensitive grid, and the node that both are connected is called A node.

2. the foil gauge utilizing the full-bridge type described in claim 1 to measure shear strain measures the method for shear strain, it is characterized in that comprising following process: A, B, C, D tetra-node lead-in wires of foil gauge are drawn, access A, B, C, D tetra-wiring points of strainmeter respectively, then now the reading of strainmeter is the shear strain γ needing to measure ₀.

3. semibridge system measures a foil gauge for shear strain, it is characterized in that:

This foil gauge have 135 degree of sensitive grids and 45 degree of sensitive grids;

Wherein 135 degree of sensitive grids and 45 degree of sensitive grids form a half bridge circuit, and concrete mode is: wherein the first end of 135 degree of sensitive grids is as node A; Second end of 135 degree of sensitive grids is connected with the first end of 45 degree of sensitive grids, and the node that both are connected becomes B node; Second end of 45 degree of sensitive grids is as node C.

4. the foil gauge utilizing claim 3 to utilize above-mentioned semibridge system to measure shear strain measures the method for shear strain, it is characterized in that comprising following process: A, B, C tri-node lead-in wires of foil gauge are drawn, access A, B, C tri-wiring points of strainmeter respectively, then now the reading of strainmeter is the shear strain γ needing to measure ₀.