JP2003240505A - Distortion measuring apparatus and measurer thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distortion measuring apparatus capable of measuring high distortion, which plastically deforms a sensing part of a distortion gage even over a small number of distortion measuring, over a larger number of distortion measuring. <P>SOLUTION: The distortion measuring apparatus comprises a first sensor 10, a storing means 82, and a distortion calculating means 83. The first sensor 10 is indirectly attached to an object (x) through an intermediate member 30 capable of transmitting, while dampening, distortion generated in the object (x). The storing means 82, when distortion occurs in the object (x), stores relational data concerning the relation between a change in resistance of the first sensor 10 and a change in resistance of the first sensor 10 when it is directly attached to the object (x). The distortion calculating means 83 calculates distortion of the object (x) based on the change in resistance of the first sensor 10 and the relational data stored in the storing means 82. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the strain generated in an object using a strain gauge having a sensing section that exhibits a resistance change according to the strain of the object, and the strain measurement of the object. Strain gauge used in.

[0002]

2. Description of the Related Art In the fields of machinery, civil engineering, construction, etc., strains of objects such as machinery and structures are measured by various methods such as 1 gauge method, 2 gauge method and 4 gauge method using strain gauges. ing.

A general strain gauge is provided with a sensing section, a gauge base, a gauge lead and, if necessary, a cover film.

The sensing portion is formed into a substantially comb shape having a predetermined size, and a copper-nickel alloy foil (for example, about 0.005 mm in thickness) adjusted to a predetermined resistance value (for example, 120Ω, 350Ω) or (for example, φ0). (.025 mm) wire or the like. The gauge base (for example, has a thickness of about 0.015 to 0.
It is a plate-shaped member made of an insulating hard material (for example, 030 mm) of polyester, epoxy, polyimide resin film material or the like, on which the sensing portion is adhered. The gauge lead is connected to the sensing unit and is provided to connect the sensing unit to the outside. In addition, the cover film is provided to cover and protect the entire sensing unit adhered to the gauge base.

The strain gauge is attached to the object by attaching the gauge base to the object with the same adhesive as the gauge base. When a strain (expansion / contraction) occurs in an object, this strain is transmitted to the sensing unit via the adhesive and the gauge base, whereby the sensing unit stretches and its resistance value changes. Then, the strain generated in the object is measured based on the change in the resistance value of the sensitive portion. Normally, the change in resistance value of the strain gauge when the strain ΔL occurs in the object having the total length L is proportional to ΔL / L.

[0006]

According to a general strain gauge, a low strain measurement (on the order of 1,000 μm / m) can be repeatedly used about 10 ⁸ times. On the other hand, in high strain measurement (on the order of 10,000 μm / m), plastic deformation occurs in the sensitive part and the resistance value of the sensitive part fluctuates when used several times and in severe cases once. With this, even if the strain of the object is reduced thereafter, the resistance value of the sensing unit is maintained at the value after the change and does not return to the original value, and it is erroneously measured that the strain still occurs. When the measurement of high strain is repeated in such a state,
Resistance value fluctuations accumulate, and the error between the strain actually generated in the object and the measured strain gradually increases.

Therefore, when high strain measurement is repeated, it is conceivable to appropriately replace the strain gauge in use with a new strain gauge in which no plastic deformation has occurred in the sensitive portion. However, as mentioned above, the strain ΔL
The change in the resistance value of the sensitive portion of the strain gauge in the case of occurs basically in proportion to ΔL / L. For this reason, when the strain ΔL ′ is further generated in the object thereafter, the change in the resistance value of the sensitive portion of the strain gauge is proportional to (ΔL + ΔL ′) / L. However, if the strain gauge is replaced when strain ΔL is generated in the object and strain ΔL ′ is further generated in the object, the resistance change of the sensitive part of the strain gauge is proportional to ΔL ′ / (L + ΔL). Will be done. This makes the strain measurement complicated compared to the case where the same strain gauge is used without plastic deformation of the sensitive portion. In addition, when a new strain gauge is attached to the measurement site where the original strain gauge was attached, strain may occur due to changes in various conditions such as ambient temperature and humidity at the time of attachment, amount of adhesive, and habit of attachment by the operator. There is a risk that the degree of change in the resistance value of the sensitive portion of the gauge will vary and the measurement error will increase.

Therefore, the present invention provides a strain gauge and a strain gauge, which can measure a high strain such that the sensitive portion of a strain gauge undergoes plastic deformation by a large number of strain measurements a large number of times. Is a problem to be solved.

[0009]

A strain measuring device of the present invention for solving the above-mentioned problems is a device which is indirectly attached to an object through an intermediate member capable of transmitting while attenuating the strain generated in the object. 1 Sensing part and resistance change of the 1st sensing part indirectly attached to the object through the intermediate member when strain occurs in the object and directly attached to the object Storage means for storing relational data relating to a change in the resistance value of the first sensing portion in the case of a change, and a resistance value change in the first sensing portion indirectly attached to the object via the intermediate member. And strain calculation means for calculating the strain of the object based on the relational data stored by the storage means.

According to the present invention, the first sensing unit is indirectly attached to the object through the intermediate member, and the strain generated in the object is attenuated by the intermediate member and then transmitted to the first sensing unit. It Therefore, when the first sensing unit is directly attached to an object, the sensing unit of the first sensing unit may be plastically deformed due to high strain such that the sensing unit immediately plastically deforms. It can be avoided. Moreover, the strain of the object can be measured in consideration of the degree of strain attenuation by the intermediate member. Therefore, according to the present invention,
As compared with the case where at least the first sensing unit is directly attached to the object, the high strain generated in the object can be measured more accurately and more times.

The sensing unit directly attached to the object when acquiring the "relationship data" may be of the same type as the first sensing unit or of a different type. When the sensing unit is of the same type as the first sensing unit, the “relationship data” can be directly acquired from the relationship of the resistance value changes of both strain gauges. On the other hand, when the sensing unit is of a type different from the first sensing unit, the resistance value change of the sensing unit is “change in resistance value of the first sensing unit when directly attached to object”. It is possible to indirectly obtain this “relational data” by correcting the “relationship data”.

[0012] Also, "sensing part is attached directly to an object" means that the sensing part is attached to the object without an intermediate member, and the sensing part is attached without any object. In addition to being attached to the object, it also includes being attached to the object through a member different from the intermediate member such as a strain gauge. On the other hand, that the sensing unit is indirectly attached to the object means that the sensing unit is attached to the object via the intermediate member.

Further, in the strain measuring apparatus of the present invention, the intermediate member is made of an elastic body.

According to the present invention, the high strain generated in the object can be attenuated by the elasticity of the intermediate member to such an extent as not to cause plastic deformation of the first sensing portion, and then transmitted to the first sensing portion. .

Further, the strain measuring apparatus of the present invention is characterized in that the first sensing portion is attached to the intermediate member via a gauge base that is harder than the intermediate member.

According to the present invention, it is possible to use an existing strain gauge in which a sensing portion is provided on a hard gauge base when measuring strain.

Further, the strain measuring apparatus of the present invention is such that the second sensing section directly attached to the object and the second sensing section indirectly attached to the object via the intermediate member when the object is distorted. The relationship data stored in the storage means is obtained by measuring the change in resistance value of the first sensing unit and the change in resistance value of the second sensing unit directly attached to the object. And a data acquisition means for performing the data acquisition.

According to the present invention, it is possible to acquire the relational data by utilizing the relation of the resistance value change of the first and second sensitive portions in the state where there is no plastic deformation. The relational data is the resistance change of the first sensing unit indirectly attached to the object via the intermediate member when the object is distorted, and the first sensing unit when directly attached to the object. It is related to the change in the resistance value of. In addition, when a high strain is generated, the second sensing portion directly attached to the object is likely to be plastically deformed, while the first sensing portion is indirectly connected to the object through the intermediate member. Since it is attached to, the plastic deformation is suppressed. Therefore, even after the second sensing portion is plastically deformed by the high strain of the object, the high strain of the object can be accurately and many times measured based on the relational data and the change in the resistance value of the first sensing portion. it can.

The first and second sensitive portions may be attached to different places, but in the case of an object having a relatively low hardness, the correlation of strain between two points may change. In this case, the relationship in which the resistance values of the first and second sensing units change is different from the relationship associated with the previously acquired relationship data, and as a result, the strain measurement accuracy of the present device decreases. To do.

Therefore, the strain measuring apparatus of the present invention is characterized in that the first and second sensing portions have the same shape and are provided in parallel symmetry with the intermediate member interposed therebetween.

According to the present invention, the first and second sensing portions are indirectly and directly attached to the same position of the object. Therefore, the relationship of the change in the resistance value of the first and second sensing portions becomes constant according to the mounting position regardless of the change in the correlation of the strain between the two points. Therefore, even when the first and second sensing units are attached at different positions and a correlation of strain between two points occurs in the object,
It is possible to prevent the situation where the strain measurement accuracy becomes low.

The strain gauge head of the present invention for solving the above-mentioned problems includes an intermediate member capable of attenuating a stress received on one side and transmitting the stress to the other side, and a first sensation attached to one surface of the intermediate member. And a second sensing section attached to the other surface of the intermediate member.

According to the strain gauge of the present invention, by attaching the other surface to the object, the first sensing unit can be indirectly attached to the object via the intermediate member, and the second sensing unit can be attached. The sensitive part can be directly attached to the object.

Then, the above-mentioned "relationship data" can be obtained by utilizing the relationship of the resistance value changes of the first and second sensing portions in the absence of plastic deformation. Further, when a high strain is generated, the first sensing unit is indirectly attached to the object via the intermediate member, so that the plastic deformation of the sensing unit is suppressed. Therefore, even after the second sensing section is plastically deformed by the high strain of the object, the high strain of the object can be accurately and many times measured based on the relevant data and the change in the resistance value of the first sensing section. it can.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a strain measuring device of the present invention and a strain gauge head applied to the device will be described with reference to the drawings. FIG. 1 is a configuration explanatory view of a strain measuring device of the present embodiment, FIG. 2 is a configuration explanatory diagram of a strain gauge of the present embodiment, and FIG. 3 is an effect explanatory diagram of the strain measuring device of the present embodiment. FIG. 4 is a configuration explanatory view of a strain gauge head of another embodiment.

The strain measuring apparatus shown in FIG. 1 comprises a first sensing section 10, a second sensing section 20, first and second sensing sections 10 and 2.
Three resistors 41 that form a Wheatstone bridge circuit (hereinafter referred to as “bridge circuit”) 40 together with 0,
A bridge power supply circuit 50 that applies a constant voltage V between one diagonal point of the bridge circuit 40 and a voltage Δe between the other diagonal points of the bridge circuit 40, that is, a measurement signal corresponding to the distortion of the object is amplified. It includes an amplifier 60, an A / D converter 70 for converting the output of the amplifier 60 into digital data representing its level, and a control unit 80.

The strain gauge shown in FIG. 2 has a substantially rectangular plate-shaped intermediate member 30 capable of attenuating and transmitting the stress received on one side to the other side.
And the first sensing unit 1 attached to the upper surface of the intermediate member 30.
0 and the second sensing unit 20 attached to the lower surface of the intermediate member 30.

The first sensing section 10 and the second sensing section 20 shown in FIG. 2 are made of a copper-nickel alloy foil or a wire material having a substantially comb shape, have the same shape, and have a resistance value. Adjusted to the same.

The first sensing section 10 is adhered to the upper surface of a substantially rectangular plate-shaped hard gauge base 12 with the same adhesive as the gauge base 12, and is covered with a cover film (not shown). The gauge base 12 is bonded to the upper surface of the intermediate member 30 having a substantially rectangular plate shape. On the lower surface of the intermediate member 30, the second sensitive portion 20 is bonded to the first sensitive portion 10 so as to be parallel and symmetrical to each other with the intermediate member 30 and the cover film (not shown) interposed therebetween. The second sensing unit 20 is adhered to the upper surface of the hard gauge base 22 with the same adhesive as the gauge base 22. One or both of the gauge bases 12 and 22 may be omitted.

The gauge bases 12 and 22 are made of a hard material such as polyester, epoxy or polyimide resin film material. The intermediate member 30 is made of an elastic body such as elastic rubber or low elastic modulus plastic. The elasticity and shape of the elastic body are such that the first sensing unit 10 is plastic when the object x is highly strained as described later. The strain is adjusted so as to be attenuated by the intermediate member 30 and transmitted to the first sensing unit 10 to the extent that the strain is not deformed and the strain measurement accuracy is not deteriorated.

Gauge leads 14 and 24 forming a part of the bridge circuit 40 are connected to the first and second sensing units 10 and 20, respectively. The resistance value of each of the resistors 41 is, for example, the first and second sensing units 1 at a stage where no plastic deformation occurs.
The resistance values of 0 and 20 are the same.

The control unit 80 has a data acquisition means 81.
And a storage means 82 and a strain calculation means 83. Further, the control unit 80 switches the first and second sensing units 10 and 20 as the sensing units configuring the bridge circuit 40 through the switch 84.

When the object x is distorted, the data acquisition means 81 directly changes the resistance value of the first sensing unit 10 indirectly attached to the object x via the intermediate member 30 and the object x. By measuring the change in the resistance value of the second sensing unit 20 attached to, the “relationship data” relating to the relationship between the two is acquired. The storage unit 82 includes a ROM, a RAM, and the like, and the related data described later acquired by the data acquisition unit 81 and the first sensing unit 1 in a state where no plastic deformation occurs.
For strain calculation relating to the relationship between the level of the digital signal output from the A / D converter 70 and the strain of the object x when 0 (or the second sensing unit 20) is directly attached to the object x Store data etc. The strain calculating means 83 is the first
The strain of the object x is calculated based on the change in the resistance value of the sensing unit 10 and the relational data stored in the storage unit 82.

The function of the strain measuring device having the above configuration will be described.

First, the second sensing section 20 covered with the coating material is attached to the object x to be strain-measured through the gauge base 22. As a result, the first sensing unit 10 includes the gauge base 22, the second sensing unit 20, and the intermediate member 3.
0, it is indirectly attached to the object x via the gauge base 12 made of a hard material.

Next, a constant frequency (1 to 15 Hz) is applied to the object x.
1) by the switching device 84 under the condition that external force
A bridge circuit 40 is configured using the sensing unit 10. Then, the data acquisition unit 81 receives from the A / D converter 70 a digital signal having a level corresponding to the output Δe ′ of the bridge circuit 40 due to the change in the resistance value of the first sensing unit 10. Similarly, the bridge circuit 40 is configured by the switching unit 84 using the second sensing unit 20 in the state where the external force having a common constant frequency is intentionally applied to the object x. Then, the data acquisition unit 81 outputs a digital signal A of a level corresponding to the output Δe of the bridge circuit 40 due to the change in the resistance value of the second sensing unit 20.
It is received from the / D converter 70.

Then, the data acquisition means 81 causes the level ratio r (= the output ratio Δe 'of the bridge circuit 40 of both digital signals.
/ Δe = (change in resistance value of first sensing unit 10) / (change in resistance value of second sensing unit 20) is acquired as “relational data”. The storage means 82 also stores this relational data.
This prepares for strain measurement.

When measuring the strain of the object x, the control unit 80 uses the switching unit 84 to configure the bridge circuit 40 using the first sensing unit 10, and does not use the second sensing unit 20. When strain occurs in the object x, the strain is transmitted to the first sensing unit 10 via the intermediate member 30, and the resistance value of the first sensing unit 10 changes. As a result, the bridge circuit 40
From the A / D converter 70, an output corresponding to the resistance value change is given to the amplifier 60, and the data acquisition unit 81 receives a digital signal of a level corresponding to the output.

Then, the strain calculating means 83 and the level of the digital signal acquired by the data acquiring means 81 and the relational data (level ratio r) stored in the storing means 82.
And the strain calculation data are used to calculate the strain.
Specifically, the bridge circuit 4 including the first sensing unit 10 is included.
When 0 is configured, the level obtained by dividing the level of the digital signal received by the data acquisition unit 81 by the level ratio r is the object x at the position of the second sensing unit 20 by the first sensing unit 10.
It corresponds to the level of the digital signal acquired by the data acquisition means 81 when directly attached to the. The data for strain calculation is obtained when the first sensing unit 10 is directly attached to the object x at the position of the second sensing unit 20.
1 relates the level of the digital signal acquired and the distortion of the object x. Therefore, the data acquisition means 8
The strain of the object x can be calculated by using the strain calculation data after dividing the level of the digital signal received by 1 by the level ratio r.

According to the strain measuring apparatus of this embodiment, the first sensing unit 10 is indirectly attached to the object x via the intermediate member 30, and the strain generated in the object x is attenuated by the intermediate member 30. It is transmitted to the first sensing unit 10 above. FIG. 3 shows how the force is transmitted to the first sensing unit 10 via the intermediate member 30 when a periodic external force having an amplitude a ₁ is applied to the object x. It can be seen from FIG. 3 that the periodic external force applied to the object x with the amplitude a ₁ is attenuated to the force with the amplitude a _{2 in} the same cycle.

The force attenuation rate (a ₁ -a ₂ ) / a ₁ can be adjusted by the elasticity of the elastic body forming the intermediate member 30 and its shape. If the damping ratio (a ₁ −a ₂ ) / a ₁ is too small, the plastic deformation of the first sensing unit 10 cannot be sufficiently suppressed,
The number of measurements by the same first sensing unit 10 is limited to a low value. On the other hand, if the attenuation rate (a ₁ −a ₂ ) / a ₁ is too large, sufficient force is not transmitted to the first sensing unit 10 and the strain measurement accuracy decreases. Therefore, the elasticity and the shape of the elastic body forming the intermediate member 30 can sufficiently suppress the plastic deformation of the first sensing unit 10, and a sufficient force is transmitted to the first sensing unit 10. It is adjusted so as to prevent a decrease in strain measurement accuracy. According to the knowledge obtained by the inventor of the present application, as an example, the object x is 5,000 [μ
When a high strain of about [m / m] occurs, the first sensing unit 10
The strain measured "directly" from the change in resistance of
The elasticity and shape of the intermediate member 30 may be determined so as to be 0 [μm / m].

As a result, it is possible to prevent the situation where the sensitive portion of the first sensitive portion 10 is plastically deformed due to the high strain generated in the object x. Further, the strain of the object x can be measured in consideration of the degree of strain attenuation by the intermediate member 30 reflected in the relational data. Therefore, the high strain generated in the object x can be measured more accurately and many times, compared with the case where at least the first sensing unit 10 is directly attached to the object x.

Further, the first and second sensing portions 10 and 20 have the same shape and are provided in parallel symmetry with the intermediate member 30 interposed therebetween. As a result, the first and second sensing units 10 and 20 are indirectly and directly attached to the same position of the object x, and the resistance value changes of the first and second sensing units 10 and 20 are related to each other. It will be constant depending on the mounting position. Therefore, even when the first and second sensing units 10 and 20 are attached at different positions and a correlation of strain between two points occurs in the object x, it is possible to prevent a situation in which the strain measurement accuracy decreases. You can

Although the 1-gauge method is adopted as the strain measuring method in this embodiment, the 1-gauge 3-wire method, 2-gauge method, 2-gauge 3-wire method, opposite-side 2-gauge method, opposite-side 2 is adopted as another embodiment. Various other methods such as the gauge 3-wire method and the 4-gauge method may be adopted.

In the present embodiment, the second sensing unit 20 is used for obtaining the "relational data", but in another embodiment, when the "relational data" has been obtained, the second sensing unit 20 is omitted. However, the strain of the object x may be measured based on the relevant data and the change in the resistance value of the first sensing unit 10 indirectly attached to the object x via the intermediate member 30.

In the present embodiment, the intermediate member 30 has a substantially rectangular plate shape, but in another embodiment, when the object x is highly strained, the strain is applied to such an extent that the first sensing portion 10 is not plastically deformed. Any shape other than the rectangular plate shape may be used as long as it can be attenuated and transmitted to the first sensing unit 10. For example, as shown in FIG. 4A, the intermediate member 30 may have a rectangular saddle shape in cross section so that the intermediate member 30 can be attached to the object x while being floated from the second sensing unit 20.

In this embodiment, the first and second sensing units 10 and 2 are
Although 0 is provided in parallel symmetry, as another embodiment, FIG.
As shown in (b), the second sensing unit 20 may be bonded to the object x near the position where the first sensing unit 10 is indirectly attached to the object x via the intermediate member 30. First,
The second sensing units 10 and 20 are attached at different positions. For example, when the rigidity of the object x is large and the relative relation of strain between the attaching positions does not change and is constant, strain does not occur even by such an attaching method. High measurement accuracy can be maintained. On the other hand, the rigidity of the object x is small,
When the correlation of the distortion between the two points varies, the first and second sensing units 10, as in the above-described present embodiment,
20 is preferably provided in parallel symmetry with the intermediate member 30 interposed therebetween.

In the embodiment shown in FIGS. 4 (a) and 4 (b), the second sensing portion 20 may be attached to the object x via a hard gauge base.

In the present embodiment, the first sensing section 10 is attached to the intermediate member 30 via the hard gauge base 12, but as another embodiment, the first sensing section 10 is the intermediate member 30.
May be directly adhered to.

In this embodiment, the first and second sensing units 10 and 2 are
Common bridge circuit 4 for measuring 0 resistance change
Although 0 was used, a separate bridge circuit dedicated to each strain gauge 10, 20 may be used in other embodiments.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of a strain measuring device according to this embodiment.

FIG. 2 is an explanatory diagram of the configuration of the strain gauge head of the present embodiment.

FIG. 3 is an effect explanatory diagram of the strain measuring device according to the present embodiment.

FIG. 4 is an explanatory diagram of a configuration of a strain gauge head according to another embodiment.

[Explanation of symbols]

10 ... 1st sensing part, 12 ... Gauge base, 14 ... Gauge lead, 20 ... 2nd sensing part, 22 ... Gauge base, 24
・ ・ ・ Gauge lead, 30 ・ ・ ・ Intermediate member

Claims (6)

[Claims] 1. A device for measuring a strain generated in an object using a strain gauge having a sensing section that exhibits a change in resistance value according to the strain of the object, wherein the strain generated in the object is attenuated. A first sensing section indirectly attached to the object via an intermediate member that can be transmitted, and a first sensing section indirectly attached to the object via the intermediate member when distortion occurs in the object. Storage means for storing relational data relating to a change in resistance value of the sensing unit and a change in resistance value of the first sensing unit when directly attached to the object, and via the intermediate member Strain calculation means for calculating the strain of the object based on the resistance value change of the first sensing section indirectly attached to the object and the relational data stored by the storage means is provided. A strain measuring device characterized in that 2. The strain measuring device according to claim 1, wherein the intermediate member is made of an elastic body. 3. The strain measuring device according to claim 1, wherein the first sensing section is attached to the intermediate member via a gauge base that is harder than the intermediate member. 4. A second sensing section directly attached to the object, and a first sensing section indirectly attached to the object via the intermediate member when the object is distorted. Data acquisition means for acquiring the relational data stored in the storage means by measuring a resistance value change and a resistance value change of the second sensing section directly attached to the object. The strain measuring device according to claim 1, 2 or 3, characterized in that. 5. The strain measuring device according to claim 4, wherein the first and second sensing portions have the same shape and are provided in parallel symmetry with the intermediate member interposed therebetween. 6. A strain gauge used for strain measurement of an object, comprising: an intermediate member capable of attenuating a stress received on one side and transmitting the stress to the other; and a first receiving member attached to one surface of the intermediate member. A strain gauge having a sensitive part and a second sensitive part attached to the other surface of the intermediate member.