JPH11201735A - Strain measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately perform the correction to the temperature change even when a local temperature change is generated in an object to be measured without any temperature distribution measuring instrument by fixing a first optical fiber part to the object, continuously arranging a second optical fiber part through a hollow tube, and providing a play between the hollow tubes. SOLUTION: An optical fiber 1 is adhered and fixed to an object 2 to be measured in sections 1a-1b. Then, the optical fiber 1 is returned to pass a hollow tube 9, and juxtaposed in the sections 1c-1d to the sections 1a-1b. Because a play is formed in the sections 1c-1d, the optical fiber becomes independent from the expansion/contraction of the object 2. When only the temperature is changed, the strain distribution in the sections 1a-1b and the sections 1c-1d is measured by a strain distribution measuring instrument 5. The temperature dependent initial strain distribution quantity is subtracted from the respective temperature dependent strain distribution quantity to the sections 1a-1b by an initial strain canceler A6 and to the sections 1c-1d by an initial strain canceler B7, and outputted to a signal processor 8. When the output of the canceler B7 is subtracted from the output of the initial strain canceler A6 by the signal processor 8, the output of the actual strain distribution becomes zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain measuring device, and more particularly to a strain measuring device capable of measuring a strain distribution of an object to be measured using a fiber.

[0002]

2. Description of the Related Art When a building or the like is constructed or used, it is sometimes necessary to measure the amount of distortion. In such a case, various methods are known as methods for measuring the amount of distortion. FIG. 6 shows an example of a conventional strain measuring device using an optical fiber.

Referring to FIG. 6, in a conventional strain measuring device, an optical fiber 1 is laid on an object 2 to be measured, and an adhesive 3
Is bonded to the measured object 2 in all sections. FIG.
Shows a situation where only a part is adhered. Since the optical fiber 1 is fixed to the object 2 to be measured, when the object 2 is distorted, the optical fiber 1 is similarly distorted. Utilizing this, the strain amount of the DUT 2 is measured by the optical fiber strain distribution measuring device 5.

[0004] The optical fiber strain distribution measuring device 5 irradiates the optical fiber 1 with a light pulse, detects the amount of distortion from the frequency shift amount of the Brillouin scattered light returned from each part of the optical fiber 1, and detects the time required for the Brillouin scattered light to return. To detect the scattering position.

This principle of measurement is a well-known fact, and is generally marketed as an optical fiber strain distribution measuring device. However, it is known that the frequency shift of the Brillouin scattered light occurs even when the temperature of the optical fiber changes regardless of the distortion. A temperature change of about 5 ° C. corresponds to a strain of 0.01%.

For this reason, when trying to measure the distribution of the amount of distortion of the measured object 2 outdoors or the like, the measured light of the measured object 2
When the temperature changes, the apparent amount of distortion changes. Therefore, the temperature distribution measuring optical fiber 11 is
The temperature distribution measuring device 22 measures the temperature distribution at various points of the measured object 2, and the signal processor 20 performs a temperature correction operation.

FIG. 4 shows a test situation using the temperature distribution measuring device 22. The constant temperature furnace 24 was kept constant at 100 ° C., and the temperature was measured by the temperature distribution measuring device 22 while changing the length 1 g-1 h of the optical fiber 1 inside the constant temperature furnace 24 from 3 m to 0.5 m. FIG. 5 shows the test results, wherein the horizontal axis indicates the position of the optical fiber with the center of the optical fiber in the constant temperature furnace being 0, and the vertical axis indicates the measured temperature.

The measured data 25 when the optical fiber is inserted 3 m inside the constant temperature furnace 24 shows about 100 ° C. when the horizontal axis is 0, but the measured data 26 when the optical fiber is inserted 0.5 m is about 48 ° C. when the horizontal axis is 0. Becomes This indicates that the more local the temperature change of the measurement target 2, the more difficult it is to perform the correction calculation of the distortion amount due to the temperature.

[0009]

As described above,
In a conventional strain measuring device, a temperature distribution measuring device is required to perform temperature correction. For this reason, there is a problem that the strain measurement device becomes expensive.

[0010] Even if such a temperature distribution measuring device is used, the temperature distribution measuring device is required to have an optical fiber length of 3 m.
However, since only an average temperature of about 5 m is measured, there is a problem that it is difficult to perform a correction operation for a local temperature change.

The present invention has been made in view of the above problems. Accordingly, it is an object of the present invention to provide a low-cost strain measurement device that does not require a temperature distribution measuring device.

Another object of the present invention is to provide a distortion measuring apparatus capable of accurately performing a correction operation for a temperature change even when a local temperature change occurs in an object to be measured.

[0013]

A strain measuring apparatus according to the present invention is an optical fiber comprising a first optical fiber portion and a second optical fiber portion, wherein the first optical fiber portion is fixedly arranged on an object to be measured. The second optical fiber portion is arranged in parallel with the first optical fiber portion, and expands and contracts in accordance with expansion and contraction of the object to be measured in the arrangement direction.
An optical fiber that is provided to be able to expand and contract regardless of the expansion and contraction of the object to be measured and is placed in the same temperature environment as the first optical fiber portion; a strain distribution measuring device that measures a strain amount distribution of the optical fiber; A first strain distribution calculator for calculating a total strain distribution for the optical fiber portion, and a temperature-dependent strain distribution for the first optical fiber portion by calculating a strain distribution for the second optical fiber portion; A second strain distribution calculator; and a processor for calculating an actual strain distribution from the overall strain distribution and the temperature-dependent strain distribution.

Further, the distortion measuring device of the present invention is an optical fiber comprising a first optical fiber portion and a second optical fiber portion, wherein the first optical fiber portion is fixedly disposed on an object to be measured, and The second optical fiber portion extends and contracts in accordance with the expansion and contraction of the object to be measured in the arrangement direction, the second optical fiber portion is juxtaposed to the first optical fiber portion through at least two hollow tubes, and a play is provided between the hollow tubes. An optical fiber, a strain distribution measuring device for measuring a strain distribution of the optical fiber, a first strain distribution calculator for calculating an overall strain distribution for the first optical fiber portion, and a strain distribution calculator for calculating the second optical fiber portion. A second strain distribution calculator for calculating a strain distribution and calculating a temperature-dependent strain distribution for the first optical fiber portion; A processor for calculating an actual strain distribution from the distribution and the temperature-dependent strain distribution.

Further, the strain measuring apparatus of the present invention is provided with a first optical fiber fixed to an object to be measured, which expands and contracts according to the expansion and contraction of the object to be measured in the installation direction, and at least two hollow tubes. A second optical fiber which is provided in parallel with the first optical fiber portion, is provided so as to be able to expand and contract regardless of expansion and contraction of the object to be measured, and is placed in the same temperature environment as the first optical fiber; And a strain distribution measuring device for measuring the strain distribution of the second optical fiber, wherein the strain distributions of the first and second optical fibers measured at the time of reference are respectively referred to as a first reference strain distribution and a second reference strain distribution. And outputs the first and second optical fiber distributions measured during the inspection as a first inspection distortion distribution and a second inspection distortion distribution, respectively. A cloth measuring device; and a distortion amount distribution process for determining a distortion amount in the disposing direction of the object to be measured from the first and second reference distortion amount distributions and the first and second inspection distortion amount distributions. Device.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a distortion measuring apparatus according to the present invention.

FIG. 1 is a diagram showing a configuration of a strain measuring device according to a first embodiment of the present invention. Referring to FIG. 1, the strain measuring device according to the first embodiment includes an optical fiber 1, a strain distribution measuring device 5, an initial strain canceller A6, an initial strain canceller B7, a signal processor 8, and a display device 10. A printing device may be used instead of or together with the display device 10.

The optical fiber 1 is bonded to the strained object 2 with an adhesive in the conventional manner in all sections 1a-1b. FIG. 1 shows a situation where only part 3 is adhered. The optical fiber 1 extends from the end 1b to the end 1
c, the optical fiber 1 is inserted into the two hollow tubes 9 shown in FIG. 2 in sections 1c-1d.

FIG. 2 shows a section 1c-1d of the optical fiber 1.
Is shown. The inside of the hollow tube 9 is hollow,
The optical fiber 1 is inserted into the optical fiber. Arbitrary setting section 1
The play of the optical fiber 1 is provided at e-1f, and the optical fiber 1 can move freely without resistance. Therefore, even if the hollow tube 9 expands in the directions of arrows 12, 13, 14, and 15, no tension or pressure is applied to the optical fiber. Thus, even if the optical fiber 1 expands and contracts due to a temperature change, no distortion other than the distortion due to the temperature change occurs in the optical fiber 1 in the section 1c-1d.

The strain distribution measuring device 5 irradiates the optical fiber 1 with a light pulse and detects the amount of strain from the frequency shift amount of the Brillouin scattered light returned from each part of the optical fiber 1.
The scattering position is detected from the time when the Brillouin scattered light returns. Since the connection between 1b-1c of the optical fiber 1 is established, the strain distribution in the sections 1a-1b and 1c-1d of the optical fiber 1 can be measured by using the strain distribution measuring device 5.

The initial strain canceller A6 is used to cancel the strain distribution of the optical fiber 1 at the time of reference. For example, the initial strain distribution value immediately after the sections 1a-1b of the optical fiber 1 are laid and bonded is held as a reference time, and the initial strain distribution value is later subtracted from the strain distribution value at the time of inspection. Thus, the distortion distribution value at the reference time is canceled.

The initial strain canceller B7 is used to cancel the strain distribution due to the temperature of the optical fiber 1 at the time of reference. For example, the temperature-dependent initial strain distribution value after laying the section 1c-1d of the optical fiber 1 is held as a reference time, and the temperature-dependent initial strain distribution value is later subtracted from the temperature-dependent strain distribution value at the time of inspection. Thus, the temperature-dependent strain distribution value at the reference time is canceled.

The signal processor 8 includes an initial distortion canceller A
The temperature-dependent strain distribution value as the output of the initial strain canceller B7 is subtracted from the strain distribution value as the output from 6. Thereby, it is possible to calculate only the actual strain distribution amount of the DUT 2 without being affected by the temperature change. The calculated amount of strain distribution is displayed on the display device 10.

Next, the operation of the distortion measuring device according to the first embodiment of the present invention will be described.

First, the optical fiber 1 is bonded and fixed to the measured object 2 in the sections 1a-1b. Next, the optical fiber 1 is folded, and is arranged in parallel with the optical fiber sections 1a-1b in the section 1c-1d so as to pass through the hollow tube 9. At this time, the hollow tube 9 may be fixed to the workpiece 2. In the section 1e-1f between the two hollow tubes 9, the optical fiber 1 is slackened and play is created.

In the example shown in FIG. 1, the optical fiber 1 is fixed to the object 2 in a three-dimensional direction, but may be in a one-dimensional direction or a two-dimensional direction.

Since the optical fiber 1 is laid as described above, in the section 1a-1b of the optical fiber 1, when the measured object 2 expands and contracts, the optical fiber 1 expands and contracts accordingly. That is, a force such as tension is applied to the optical fiber 1.
Therefore, the frequency of the light pulse shifts in the section 1a-1b of the optical fiber 1.

In the section 1c-1d, the optical fiber 1
Is passed through the hollow tube 9 and a play is formed. Therefore, in this section 1c-1d, the expansion and contraction of the optical fiber 1
It has nothing to do with expansion and contraction. Thereby, even if the measured object 2 expands and contracts, the frequency does not shift in this section 1c-1d of the optical fiber 1.

However, when the temperature changes,
Since the optical fiber 1 changes as the temperature changes,
The frequency shifts. However, section 1c-1
At d, the optical fiber 1 can move freely, and at this time, a strain distribution amount depending on the temperature is obtained.

After laying the optical fiber 1, an optical pulse is input from the strain distribution measuring device 5 to the optical fiber 1. The strain distribution measuring device 5 is connected to the section 1a- of the optical fiber 1 at this time.
The strain distribution between sections 1a and 1b is measured from the light pulse returned from 1b. At this time, the distortion distribution amount measured in the section 1a-1b is stored in the initial distortion canceller A6 as the initial distortion distribution amount. Similarly, the strain distribution measuring device 5 measures the amount of strain distribution immediately after the section 1c-1d of the optical fiber 1 is laid, and stores it in the initial strain canceller B7 as the temperature-dependent initial strain distribution amount.

After the installation, if there is no temperature change, section 1a-1
The distortion distribution amount of b is, for example, 0. After the installation, if there is no change in strain and temperature, the temperature-dependent strain distribution amount in the section 1c-1d becomes zero. The signal processor 8 performs a subtraction operation between the initial distortion canceller A and the initial distortion canceller B,
Calculate the actual strain distribution value. In the above case, the distortion distribution amount 0 is naturally output.

Next, consider the case where only the temperature changes.
In this case, the sections 1a-1b and 1c of the optical fiber 1
During −1 d, the strain distribution amount depending on the temperature change is measured by the strain distribution measuring device 5. In the initial strain canceller A6, the stored initial strain distribution amount is subtracted from the temperature-dependent strain distribution amount for the section 1a-1b of the optical fiber 1, and the result is output to the signal processor 8. In the initial strain canceller B7, the stored temperature-dependent initial strain distribution amount is subtracted from the temperature-dependent strain distribution amount for the section 1c-1d of the optical fiber 1, and is output to the signal processor 8. When the output of the initial distortion canceller B7 is subtracted from the output of the initial distortion canceller A6 by the signal processor 8, the output of the actual distortion distribution amount becomes zero.

As described above, when only the ambient temperature changes, the output from the initial distortion canceller A6 is corrected by the output from the initial distortion canceller B7, so that the output becomes zero. At this time, in the initial distortion canceller A6 and the initial distortion canceller B7, the stored reference value (the value measured at the time of reference) is subtracted from the measured value, so that the time-dependent change is also canceled.

Next, consider a case where distortion occurs in the object to be measured. At this time, the strain distribution amount corresponding to the strain of the measured object 2 is measured by the strain distribution measuring device 5 in the section 1a-1b of the optical fiber 1. In the initial distortion canceller A6, the stored initial distortion distribution amount is subtracted from the measured distortion distribution amount at the time of inspection, and the subtracted output is output to the signal processor 8.

However, the section 1c of the optical fiber 1
In the case of -1d, although the hollow tube 9 is elongated due to the strain, the tension is not applied to the internal optical fiber 1 due to the play between 1e-1f provided in an arbitrary section. Therefore, the strain distribution amount for the sections 1c-1d from the strain distribution measuring device 5 remains 0. In the initial strain canceller B7, the stored temperature-dependent initial strain distribution amount is subtracted from the temperature-dependent strain distribution amount 0 and output to the signal processor 8. The signal processor 8 outputs the initial distortion canceller B from the output of the initial distortion canceller A6.
When the output of 7 is subtracted, the signal processor 8 outputs only the distortion distribution amount immediately after the optical fiber 1 is laid (reference time).

Next, consider a case where a change in distortion and a change in temperature of the measured object 2 occur simultaneously. In this case, the optical fiber 1
Are output from the strain distribution measuring device 5 to the initial strain canceller A6. The measured strain distribution amount includes the strain of the measured object 2 and the strain due to the temperature change. In the initial distortion canceller A6, the stored initial distortion distribution amount is subtracted from the measured distortion distribution amount at the time of inspection, and the subtracted output is output to the signal processor 8.

On the other hand, since tension is not applied between the internal optical fibers 1c and 1d due to play between 1e and 1f provided in an arbitrary section, only the amount of strain distribution due to a temperature change is included. Therefore, the amount of strain distribution including only the amount of strain distribution due to temperature change is obtained from the strain distribution measuring device 5 by the initial strain canceller B7.
Is output to In the initial strain canceller B7, the stored temperature-dependent initial strain distribution amount at the reference time stored is subtracted from the temperature-dependent strain distribution amount at the time of inspection and output to the signal processor 8.

When the output from the initial distortion canceller B7 is subtracted from the output from the initial distortion canceller A6 by the signal processor 8, the signal processor 8 outputs the temperature-compensated signal immediately after the optical fiber 1 is laid (at the reference time). Only the distortion distribution amount is output.

As described above, the true distortion amount can be measured without being affected by the temperature change of the object 2 to be measured, and it is not necessary to use a temperature distribution measuring device.

Next, a distortion measuring device according to a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the optical fiber 1 is not folded at the ends 1b and 1c, and is provided as an optical fiber 1-1 corresponding to the section 1a-1b and an optical fiber 1-2 corresponding to the section 1c-1d. When measuring the total amount of strain distribution including the amount of strain distribution depending on the temperature and the amount of strain distribution depending on the object to be measured, the strain distribution measuring device 5 is connected to the optical fiber 1-1. After that, the switch 25 is switched so that the strain distribution measuring device 5
Is connected to the optical fiber 1-2, and measures the temperature-dependent strain distribution. Other operations are the same as above,
Description is omitted.

[0041]

As described above, according to the strain measuring apparatus of the present invention, the true strain amount can be measured without being affected by the temperature change of the object 2 to be measured, and the temperature distribution measuring device can be used. No need to do. Therefore, the strain measurement device can be provided at a low price.

Further, in the strain measuring apparatus of the present invention, even if a local temperature change occurs in the object to be measured, a correction operation for the temperature change can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a strain measuring device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a hollow tube and an optical fiber used in the strain measuring device according to the first embodiment.

FIG. 3 is a diagram illustrating a configuration of a strain measurement device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing measurement by a temperature distribution measuring device used in a conventional strain measuring device.

FIG. 5 is a graph showing a result obtained by measuring a temperature distribution of the optical fiber by the method shown in FIG. 4;

FIG. 6 is a diagram showing a configuration of a conventional strain measuring device.

[Explanation of symbols]

 1, 1-1, 1-2: Optical fiber 2: Object to be measured 5: Strain distribution measuring instrument 6: Initial strain canceller A 7: Initial strain canceller B 8, 20: Signal processor 9: Hollow tube 10: Display device 22: temperature distribution measuring instrument 24: constant temperature furnace 25: optical switch

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadashi Sugimura 5-717-1 Fukabori-cho, Nagasaki-shi, Nagasaki Sanishi Heavy Industries Co., Ltd. Nagasaki Research Institute (72) Inventor Masazumi Tsukano 1-1-1, Akunoura-cho, Nagasaki-shi, Nagasaki No.Mitsubishi Heavy Industries, Ltd.Nagasaki Shipyard

Claims (3)

[Claims] 1. An optical fiber comprising a first optical fiber portion and a second optical fiber portion, wherein the first optical fiber portion is fixedly provided on an object to be measured, and the object to be measured is arranged in a direction of the installation. Expands and contracts according to the expansion and contraction of the second
An optical fiber portion is provided in parallel with the first optical fiber portion, is provided so as to be able to expand and contract regardless of expansion and contraction of the object to be measured, and is placed in the same temperature environment as the first optical fiber portion; A strain distribution measuring device for measuring an amount distribution; a first strain distribution calculator for calculating an overall strain amount distribution for the first optical fiber portion; and a strain amount distribution for the second optical fiber portion. A second strain distribution calculator that calculates a temperature-dependent strain distribution for the first optical fiber portion; and a processor that calculates an actual strain distribution from the overall strain distribution and the temperature-dependent strain distribution. Equipped strain measurement device. 2. An optical fiber comprising a first optical fiber portion and a second optical fiber portion, wherein said first optical fiber portion is fixedly arranged on an object to be measured, and said object to be measured in a direction in which said optical fiber portion is arranged. Expands and contracts according to the expansion and contraction of the second
An optical fiber portion is provided in parallel with the first optical fiber portion through at least two hollow tubes, and an optical fiber provided with a play between the hollow tubes, and a strain distribution measuring instrument for measuring a strain amount distribution of the optical fiber. A first strain distribution calculator for calculating a total strain distribution for the first optical fiber portion; and a temperature-dependent strain for the first optical fiber portion by calculating a strain distribution for the second optical fiber portion. A strain measurement device comprising: a second strain distribution calculator that calculates a quantity distribution; and a processor that calculates an actual strain quantity distribution from the overall strain quantity distribution and the temperature-dependent strain quantity distribution. 3. A first optical fiber which is fixed to an object to be measured and which expands and contracts in accordance with the expansion and contraction of the object to be measured in a direction in which the object is arranged, and at least two hollow tubes to the first optical fiber portion. A second optical fiber that is juxtaposed and provided so as to be able to expand and contract regardless of the expansion and contraction of the object to be measured, and is placed in the same temperature environment as the first optical fiber; and a distortion of the first optical fiber and the second optical fiber. A strain distribution measuring device for measuring the amount distribution of the first and second optical fibers measured at the time of reference as a first reference distortion amount distribution and a second reference distortion amount distribution, respectively. And a strain distribution measuring device for outputting the strain distributions of the first and second optical fibers measured at the time of inspection as a first inspection strain distribution and a second inspection strain distribution, respectively; Wherein a reference strain amount distribution of the two first
A strain amount distribution processing device for determining a strain amount of the object to be measured in the arrangement direction from the second inspection strain amount distribution.