JPH0769228B2 - Calibration and measurement method of bending stress of pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an on-site pipe for a pipe material of unknown magnetostriction sensitivity when the magnetostrictive stress measurement of a structure such as a pipeline is performed on-site. The present invention relates to a method for calibrating / measuring the bending stress of a pipe, in which a magnetostrictive stress measuring device is calibrated by applying a bending load to the pipe.

[Prior Art] In a structure such as a pipeline, when there is a fixed portion such as the back of an abutment, excessive stress may be exerted due to uneven subsidence of the ground. In such a case, quantitatively measuring how much stress acts on a structure such as a pipeline is indispensable for evaluating the safety of this structure.

As a conventional method for measuring the stress and residual stress of a steel material or a steel structure, there is a method using a magnetostriction sensor in addition to X-rays and ultrasonic waves. A round bar that can be magnetized using this magnetostrictive sensor,
As a method for measuring the stress of a cylindrical material such as a pipe, there is a magnetostrictive stress measuring method disclosed in Japanese Patent Application No. 63-153622 filed previously.

In the magnetostrictive pressure measurement method, when a load acts on a magnetic material, anisotropy occurs in the magnetic permeability, the magnetic permeability in the load direction increases, and on the contrary, the magnetic permeability in the direction perpendicular to the load direction decreases. This is a method of measuring the direction and magnitude of the principal stress by detecting the difference by a magnetostrictive sensor (also called a magnetic anisotropy sensor) having an exciting coil and a detecting coil. According to this measuring method, the measuring time for one point is 10 to 100 m.
Only sec, and handling is extremely appropriate.

However, since the conventional magnetostrictive stress measuring method is generally performed by bringing the magnetostrictive sensor into contact with the surface to be measured, the magnetic resistance at the contact surface greatly differs depending on the state of the surface to be measured. Therefore, there is a drawback that the measurement error becomes large.

Therefore, the idea is to measure in a non-contact state, that is, in the state where the magnetostrictive sensor is separated from the surface to be measured by a certain distance, but in this case, the magnetostrictive sensitivity decreases, so the setting of the magnetic floor sensor Another problem was that there was a very slight adjustment required.

In the invention of the prior application, the problems in the non-contact measurement are explained, and a device capable of carrying out a non-contact method for measuring magnetostrictive stress on a cylindrical material such as a magnetizable rod or pipe is developed, and the measuring device is developed. We have provided a method to measure the stress distribution in the circumferential direction of a cylindrical material with higher accuracy than before.

FIG. 1 is a diagram for explaining the magnetostrictive stress measuring method according to the previous application. In FIG. 1 (a), a bending load is applied to the columnar material 1 so that the upper side of the columnar material 1 has a tensile stress + σ and the lower side thereof has a compression stress. Stress-σ
Indicates that is working. Further, FIG. 2B shows the columnar material 1
The magnetostrictive sensor 2 is rotated clockwise from the uppermost point of the cylindrical material 1, that is, the angular position of 0 °, while maintaining a lift-off (gap) at a constant distance h from the central axis of the cylindrical material 1 and its outer peripheral surface. In the figure, a method is shown in which the magnetostrictive sensor 2 continuously measures the magnetostrictive signal detected by the magnetostrictive sensor 2 at each angular position between 0 ° and 360 ° by making one rotation along the circumferential direction.

FIG. 2 is a diagram for explaining the SIN approximation method by the magnetostrictive pressure measurement method of FIG. 1, and FIG. 2 (a) shows the angle at which the magnetostrictive sensor 2 indicates the orientation on the outer circumference of the cylindrical material 1 and its stress distribution. Since the maximum tensile stress occurs at an angle of 0 ° (that is, directly above the columnar material 1) and the maximum compressive stress occurs at an angle of 180 ° (that is, immediately below the columnar material 1,) the stress distribution is similar to the SINθ curve. To do.

FIG. 2 (b) shows the measured value of stress by the strain gauge and the SINθ approximate value when a load of −20 kg / mm ^{2 was} applied to the cylindrical material. From this figure, it can be seen that the actual stress distribution and the SINθ curve are very similar.

[Problems to be Solved by the Invention] The SINθ approximation method based on the magnetostrictive stress measurement method for a cylindrical material, which is disclosed in Japanese Patent Application No. 63-153622, enables stress measurement to be made on a material to be measured while being in contact therewith. Suitable for on-site measurement. However, since the magnetostriction sensitivity differs depending on the material to be measured, it is necessary to know the magnetostriction sensitivity of the material to be measured in order to perform quantitative measurement.

Therefore, when measuring a structure on site, it is necessary to calibrate on site because the magnetostriction sensitivity of the material to be measured is unknown, but there was a problem that there was no good method for simple calibration on site.

The present invention has been made in order to solve such a problem, even for the unknown management of magnetostriction sensitivity in the measurement site, after performing calibration of the magnetostrictive stress measuring device in the field, quantitative stress measurement. The purpose is to obtain a method of calibrating and measuring the bending stress of a pipe that can be implemented.

[Means for Solving the Problems] A bending stress calibrating / measuring method by a public official according to the present invention is a magnetostrictive stress measuring device in which a magnetostrictive sensor relatively moves on an outer peripheral surface or an inner peripheral surface of a pipe material in a non-contact state. In the method of measuring the bending stress distribution of the pipe material in the pipe circumferential direction by approximating it with a SIN curve, when measuring the bending stress of the pipe material of unknown magnetostriction sensitivity, a bending load is applied to the pipe material to be measured. Then, the bending stress based on the addition of the bending load is measured by a standard stress measuring device, and the amplitude deviation value of the SIN curve approximated from the measured value of the magnetostrictive stress measuring device before and after the bending load is calculated is calculated as the standard. Bending stress value measured by the stress measuring device, and correspondingly, to create a bending stress calibration curve of the magnetostrictive stress measuring device from the amplitude deviation value of the SIN approximation curve obtained from the magnetostrictive stress measuring device, and the created Song The present invention is provided with a means for calibrating and measuring the bending stress of a pipe for measuring the bending stress of the pipe by using a bending stress calibration curve.

[Operation] In the present invention, the bending stress distribution in the pipe circumferential direction of the pipe material is measured by using the magnetic floor stress measuring device in which the magnetostrictive sensor relatively moves on the outer peripheral surface or the inner peripheral surface of the pipe material in a non-contact state.
In the method of approximating with a curve, in the case of measuring the bending stress of a pipe material of unknown magnetostriction sensitivity by means of calibration / measurement of the bending stress of the pipe, a bending load is applied to the pipe material to be measured, Bending stress based on load addition is measured by a reference stress measuring device, and the amplitude deviation value of the SIN curve approximated from the measured value of the magnetostrictive stress measuring device before and after applying the bending load is calculated, and by the reference stress measuring device. Bending stress calibration curve of the magnetostrictive stress measuring device is created from the measured bending stress value and the amplitude deviation value of the SIN approximation curve correspondingly obtained from the magnetostrictive stress measuring device, and the created bending stress calibration The curve is used to measure the bending stress of the tube.

[Embodiment] FIG. 3 is a block diagram of a pipe magnetostrictive stress measuring device to which the pipe bending stress calibration / measurement method of the present invention is applied. In the figure, reference numeral 10 denotes a traveling device section, which incorporates a magnetic anisotropy sensor 11 and a traveling carriage 12. The magnetic anisotropy sensor 11 is a sensor for detecting the magnetic anisotropy in the circumferential direction of the pipe material in a non-contact manner, and includes, for example, an exciting coil and a detecting coil that are orthogonal to each other, and a constant exciting current is applied to the exciting coil. Then, the magnetic anisotropy caused by the action of stress is detected as a voltage signal obtained from the detection coil. The traveling carriage 12 is, for example, a traveling mechanism that travels on rails and / or gears provided on the outer circumference of the pipe and moves the magnetic anisotropy sensor 11 in the circumferential direction of the pipe to perform measurement. Reference numeral 13 is a magnetostriction measuring unit, which supplies a constant current to the exciting coil of the magnetic anisotropy sensor 11, and at the same time amplifies the detection signal obtained from the detection coil of the sensor 11 to obtain a voltage signal proportional to the magnetic anisotropy. It is a magnetostriction measuring unit for outputting. 14 is a motor driver,
The traveling drive signal is supplied to the traveling vehicle 12 to cause the traveling vehicle 12 to travel, and the encoder signal is returned as position information of the traveling result. 15
Is an A / D converter, 16 is an interface such as RS232C, 1
Reference numeral 7 is a personal computer (hereinafter referred to as a personal computer), and 18 is a display unit using a CRT or liquid crystal.

The operation of FIG. 3 will be described. To measure the stress in the circumferential direction of the pipe material, for example, a rail or / and a gear (not shown) is attached to the outer peripheral surface of the pipe material on a plane perpendicular to the central axis of the pipe material, and a holder is mounted on the rail or / and the gear. Mount the traveling device unit 10 so that it can travel. Next, the personal computer 17 gives a run command for one rotation to the mote driver 14 via the interface 16, and the motor driver 14 causes the rail or
Also, the traveling device 10 on the gear is caused to travel once along the circumference of the pipe. During this running, the magnetic anisotropy sensor 11 (magnetostriction sensor 2
The same as the above) is detected by the magnetostriction measuring unit 13 at each angular position between 0 ° and 360 ° on the outer peripheral surface of the pipe material shown in FIG. 1 (b). The amplified signal is output, and the output is quantized by the A / D converter 15 and supplied to the personal computer 17. The personal computer 17 displays the sensor measurement value or this SIN curve approximate value for each angle indicating the azimuth on the outer circumference of the magnetic anisotropy sensor 11 on the data display unit 18, and outputs a hard copy by a printer not shown if necessary. . The bending stress of the pipe according to the present invention can be calibrated and measured based on the data displayed on the data display unit 18 of the measuring device or the hard copy data output by the printer.

Further, in the above-described embodiment, the example in which the magnetostrictive sensor is made to travel on the outer peripheral surface of the pipe material in a non-contact manner has been shown, but the magnetostrictive sensor may be made to travel on the inner peripheral surface of the pipe material in a non-contact manner as well. Further, in this case, the magnetostrictive sensor may be fixed by rotating the pipe material with respect to the central axis thereof without running the magnetostrictive sensor. In either case, the magnetostrictive sensor and the pipe member may be moved relative to each other, and the same effect can be obtained by fixing one and moving the other.

FIG. 4 is a diagram showing an installation example of a pipeline installed on the back of the abutment. In the figure, the pipeline is buried underground on the left side of the abutment and exposed on the right side of the abutment.
The position of the pipeline is fixed by the abutment penetration and the right support. The bending stress generated in the pipeline between the abutment and the support due to the ground subsidence on the left side is now calibrated and measured.

In the case of the pipeline installation example shown in FIG. 4, the method for calibrating and measuring the bending stress of the pipe according to the present invention will be described by the following procedure.

(1). First, the magnetostrictive stress measuring device shown in FIG. 3 is used to measure the distribution characteristics of the locations of the bridge connecting tube and the magnitude of bending stress.

In the example of FIG. 4, the bending stress is greatest at the point A near the abutment penetration part, the bending stress is slightly smaller at the point B, and
At the point, the distribution characteristics are obtained so that the bending stress becomes the minimum ground that is closest to zero.

(2). Next, from the stress distribution of the pipeline obtained in (1), at the place where the bending stress level is considered to be sufficiently small (close to zero) (point C), the strain gauge is bent and the axis And 2 places on the ground (both upper and lower).
In addition, the location where the stress is highest near the abutment penetration point of the pipeline (point A) and the bending stress becomes smaller as it goes away from the penetration point, and the location between the highest stress location and the lowest stress location (point B) is at the top. Attach strain gauges to the ground and ground respectively. In FIG. 4, the position where the strain gauge is attached is indicated by an X mark.

(3). When the strain gauge mounting position in the item (2) and the magnetostrictive stress measuring position in the item (1) are different, the magnetostrictive stress measurement is performed again at the same position as the strain gauge measuring position. At this time, the signal amplitude grounds V _AO , V _BO , and V _CO of the SIN approximate curve measured and approximated at the points A, B, and C are stored. In FIG. 4, this magnetostrictive stress measurement position is indicated by a circle.

(4). After that, a reaction force is taken from a part of the abutment, parallel pipes or pipe supports, and a load is applied to the pipes with a chain block or hydraulic jack to add bending stress.
FIG. 4 shows an example in which a hydraulic jack is installed at an intermediate portion between points B and C, and a load is applied from the lower side to the upper side of the pipeline to apply bending stress.

(5). The magnitudes of the bending stresses M _A , M _B , and M _C generated at the points A, B, and C due to the addition of the bending stress in the item (4) are measured by strain gauges. Further, the stress state after the bending stress is applied is measured by the magnetostrictive stress measuring device of FIG. 3, and the signal amplitude of the approximated SIN approximate curve V _AL , V _BL , V is measured at each of points A, B and C. Memorize each _CL .

(6). Before and after the bending stress is applied, the signal amplitude ground difference of the approximated SIN approximate curve measured by the magnetostrictive stress measuring device of FIG. 3 at each point A, B, C is ΔV _A = V _AL −V _AO , ΔV _B = V _BL -V _BO, the ΔV _C = V _CL -V _CO is calculated respectively.

(7). Next, the horizontal axis is the bending stress, and the vertical axis is the signal amplitude value of the SIN approximation curve. First, the signal amplitude change ΔV _{C with} respect to the additional bending stress at the point C where the bending stress is the smallest.
With / M _C as the slope, draw a straight line that passes through the origins of the horizontal and vertical axes.

(8). Change in signal amplitude with respect to additional bending stress at point A where bending stress is the largest from the beginning A line segment with slope ΔV _A / M _A and change in signal amplitude with additional bending stress at point B where intermediate value of bending stress is first Draw a curve so that the line segment with the slope of ΔV _B / M _B is connected to the straight line obtained in (7) with a gentle curve. This curve is the bending stress for the pipe to be measured and is measured by a magnetostrictive stress measuring device,
It is a calibration curve with the signal amplitude of the approximated SIN approximation curve.

FIG. 5 is a diagram for explaining how to make a bending stress calibration curve for a pipe according to the present invention. In the figure, when the calibration curve is created by the procedure described above, the value of the Y-axis is the point B of the first line segment due to the straight line of the inclination ΔV _C / M _C from the origin of the X-axis and the Y-axis at the point C. The line segment until reaching the initial value V _BO of
Is a slope ΔV _B / M at point B from the end of the first line
The straight line of _{B is used as} the line segment until the Y-axis value reaches the initial value V _{AO of the} point A, and the third line segment is the line of ΔV _A / M _A straight line at the point A from the end of the second line segment. The method of obtaining a calibration curve that is approximated by a broken line connecting each line segment is shown.

FIG. 6 is a diagram for explaining how to make a simple calibration straight line for bending stress of a pipe according to the present invention. In the same figure, without considering the non-linearity of the calibration curve (which has a saturation characteristic at a large bending stress), simply one place (point C in this example as a small initial bending stress place) is used. Slope at ΔV _C
An example in which a straight line passing through the coordinate origin is a simple calibration line by / M _C is shown below. Therefore, this simple calibration line can be used in the range where the bending stress does not become too large.

[Effects of the Invention] As described above, according to the present invention, a magnetostrictive stress measuring device in which a magnetostrictive sensor relatively moves in a non-contact state on the outer peripheral surface or the inner peripheral surface of a pipe material is used to measure the pipe peripheral direction of the pipe material. In the method of approximating the bending stress distribution of a SIN curve, for example, when performing magnetostrictive stress measurement on a pipe material of unknown magnetostriction sensitivity such as a structure at the site, the bending load on the measured pipe material at the site is measured. Quantitatively calibrate the measurement value of the magnetostrictive stress measuring device from the reference stress measurement value by adding the bending load and the amplitude deviation value of the SIN approximate curve obtained from the magnetostrictive stress measuring device before and after applying the bending load. Since it is possible to perform various measurements, it becomes possible to measure bending stress of structures such as pipelines, which was difficult to measure quantitatively in the conventional field, and the effect of expanding the field of measurement of magnetostrictive stress measuring devices can be obtained. .

[Brief description of drawings]

1 (a) and 1 (b) are diagrams for explaining the magnetostrictive stress measuring method according to the prior application, and FIGS. 2 (a) and 2 (b) are for explaining the SIN approximation method by the magnetostrictive stress measuring method of FIG. FIG. 3 is a block diagram of a magnetostrictive stress measuring device for a pipe to which the method for calibrating and measuring the bending stress of the pipe according to the present invention is applied, and FIG. 4 shows an example of installation of a pipeline installed on the back of the abutment. FIG. 5 is a diagram for explaining how to make a bending stress calibration curve of a pipe according to the present invention,
FIG. 6 is a diagram for explaining how to make a simple calibration straight line for bending stress of a pipe according to the present invention. In the figure, 1 is a cylindrical material, 2 is a magnetostrictive sensor, 10 is a traveling device section, 11 is a magnetic anisotropy sensor, 12 is a traveling carriage, 13 is a magnetostrictive measuring section, 14 is a motor driver, and 15 is an A / D conversion. Bowl, 16
Is an interface, 17 is a personal computer, and 18 is a data display unit.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Sadaaki Sakai 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (56) Reference JP-A-1-308933 (JP, A)

Claims (1)

[Claims] 1. A bending stress distribution in the pipe circumferential direction of the pipe material is approximated by a SIN curve using a magnetostrictive stress measuring device in which a magnetostrictive sensor relatively moves on the outer peripheral surface or the inner peripheral surface of the pipe material in a non-contact state. In the method of measuring by, when measuring the bending stress of the tube material of unknown magnetostriction sensitivity, a bending load is applied to the tube material to be measured, and the bending stress based on the addition of the bending load is measured by a standard stress measuring device, Further, the amplitude deviation value of the SIN curve approximated from the measurement value of the magnetostrictive stress measuring device before and after applying the bending load is calculated,
Bending stress value measured by the reference stress measuring device,
Corresponding to this, SIN obtained from the magnetostrictive stress measuring device
Calibration of bending stress of a pipe characterized by a method of creating a bending stress calibration curve of a magnetostrictive stress measuring device from an amplitude deviation value of an approximate curve and performing bending stress measurement of the pipe using the created bending stress calibration curve Measuring method.