JPH0769226B2 - Tube flat stress estimation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides stress in the vicinity of a welded portion between a curved pipe portion and a straight pipe portion, for example, when a pipeline is looped on the backside of an abutment. The present invention relates to a flat stress estimating method for a pipe, which estimates the stress due to the flattening generated in the straight pipe portion near the curved pipe portion from the measured value of the magnetostrictive sensor because the concentration is concentrated.

[Prior Art] As a method of 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. As a method for measuring the stress of a cylindrical material such as a magnetizable round bar or pipe using this magnetostrictive sensor, there is a magnetostrictive stress measuring method disclosed in Japanese Patent Application No. 63-153622 filed previously.

In the magnetostrictive stress 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 convenient.

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 measured surface by a certain distance, but in this case, the magnetostrictive sensitivity decreases, so the setting of the magnetostrictive sensor There was another problem that required very subtle adjustments.

In the invention of the prior application, a device for solving the problems in the non-contact measurement and developing a magneto-striction stress measuring method for a columnar material such as a magnetizable round bar or a pipe by a non-contact method, and measuring device therefor have been 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 signal detected by the magnetostrictive sensor 2 at each angular position between 0 ° and 360 ° is continuously measured by making one rotation along the circumferential direction.

FIG. 2 is a diagram for explaining the SIN approximation method based on the magnetostrictive stress measurement method of FIG. 1, and FIG. 2A shows the angle indicating the orientation of the magnetostrictive sensor 2 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 the 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 pipe material disclosed in Japanese Patent Application No. 63-153622 is suitable for measuring a bending stress of a straight pipe portion of the pipe material. However, in the straight pipe part near the curved pipe part, there is an effect due to flattening of the curved pipe part, and even in the straight pipe part, the stress distribution is a good SI for the angle θ in the pipe circumferential direction.
It does not become an N curve. Therefore, there is a problem that the previously applied SINθ approximation method cannot be applied to the straight pipe portion near the curved pipe portion of the pipe.

FIG. 3 (a) is a diagram showing a stress state when the pipe is flat, and in FIG. 3 (a), the angle in the pipe circumferential direction is 0 °.
It is shown that the compressive stress −σ works at the 180 ° position and the tensile stress + σ works at the 90 ° and 270 ° positions.

FIG. 3 (b) is a diagram showing the magnetostrictive sensor output in the flat stress state of the pipe of FIG. 3 (a), where the horizontal axis is the clockwise rotation of the magnetostrictive sensor on the outer peripheral surface of the pipe perpendicular to the central axis of the pipe material. It is an angle indicating the azimuth on the pipe circumference of the sensor when it is rotated once. The vertical axis represents the magnetostrictive sensor output (unit: volt), and the measured value of the sensor is indicated by a + mark in the figure.

From FIG. 3 (b), it has been clarified that the SINθ approximation method is not applicable even in the straight pipe portion in the vicinity of the curved pipe portion of the pipe.

The present invention has been made to solve such a problem, and estimates the stress value due to flattening generated in the straight pipe portion based on the magnetostrictive sensor output measured in the straight pipe portion near the curved pipe portion of the pipe material. The purpose of the present invention is to obtain a method for estimating the flat stress of a pipe.

[Means for Solving the Problems] A method for estimating a flat stress of a pipe according to the present invention uses a measuring device in which a magnetostrictive sensor relatively moves on an outer peripheral surface or an inner peripheral surface of the pipe material in a non-contact state, In the method of estimating the stress distribution in the pipe circumferential direction by approximating with the SIN curve, from the magnetostrictive sensor output measured in the straight pipe part near the curved pipe part of the pipe material
The deviation value obtained by subtracting the SINθ approximate value is approximated by the SIN2θ curve, and the flat stress of the pipe is estimated from the signal amplitude value of the approximated SIN2θ curve to estimate the stress value due to the flattening that occurs in the corresponding straight pipe section. It is equipped with an estimation means.

[Operation] In the present invention, the stress distribution in the pipe circumferential direction of the pipe material is approximated by a SIN curve by using a measuring device in which the magnetostrictive sensor relatively moves on the outer peripheral surface or the inner peripheral surface of the tubular article in a non-contact state. In this method, the deviation value obtained by subtracting the approximate value of SINθ from the magnetostrictive sensor output measured in the straight pipe section near the curved pipe section by the flat stress estimation means of the pipe is SIN2
It is approximated by a θ curve, and the stress value due to the flattening generated in the corresponding straight pipe portion is estimated from the signal amplitude value of the approximated SIN2θ curve.

[Embodiment] FIG. 4 is a block diagram of a pipe stress measuring device to which the pipe flat stress estimating 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. Reference numeral 14 denotes a motor driver, which supplies a traveling drive signal to the traveling vehicle 12 to cause the traveling vehicle 12 to travel, and an encoder signal is returned as position information of the traveling result. 15 is an A / D converter, 16
Is an interface such as RS232C, 17 is a personal
A computer (hereinafter referred to as a personal computer), 18 is a data display unit using a CRT or liquid crystal.

The operation of FIG. 4 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 product on a plane perpendicular to the central axis of the pipe material, and a holder is mounted on this rail or / and gear. Mount the traveling device unit 10 so that it can travel. Next, the personal computer 17 gives a running command for one rotation to the motor driver 14 via the interface 16, and the motor driver 14 sends the running command to the rail or / 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 output 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 flat stress estimation processing of the pipe according to the present invention can be performed based on the data displayed on the data display unit 18 of the present measurement device or the hard copy data output by the printer.

5 (a) to (c) show the flat stress of the pipe according to the present invention as SI.
It is a figure explaining the method of approximating with a N2 (theta) curve.

FIG. 5 (a) is a diagram showing the magnetostrictive sensor output in the flat stress state of the pipe, and each magnetostrictive sensor output (unit is bolt) with respect to the angle indicating the azimuth on the pipe circumference of the magnetostrictive sensor is indicated by + mark. Shows.

Fig. 5 (b) shows SINθ from the magnetostrictive sensor output of Fig. 5 (a).
It is a figure which shows the deviation value obtained by subtracting an approximate value, and each deviation value (a unit is a volt) with respect to the same angle as FIG.

FIG. 5 (c) is a diagram showing the deviation value shown in FIG. 5 (b) and the SIN2θ approximation curve approximated to it, and FIG.
For the same angle as, the + sign shows each deviation value (unit is bolt)
The solid line indicates the SIN2θ approximate curve. Fig. 5 (c)
The deviation value obtained by subtracting the approximate value of SINθ from the stress measurement value in the flat state of the pipe is the periodic value for every 1/2 rotation of the magnetostrictive sensor when the magnetostrictive sensor makes one rotation along the pipe circumferential direction. It can be seen that it can be approximated by the SIN2θ curve changing to.

6 (a) and 6 (b) are diagrams for explaining general flat stress and the SIN2θ approximate curve according to the present invention. FIG. 3A shows a flat stress state in a general case where the azimuth of the maximum value of the flat stress differs from that of FIG. 3A by an angle φ. Further, FIG. 2B shows the SIN2θ in the flat stress state of FIG.
It shows an approximated curve, A · sin2 (θ + φ). Here, A is the maximum signal amplitude value, and φ is the angular difference between the flat axis and the reference axis (angle 0 °) of the magnetostrictive sensor.

FIG. 7 is a diagram showing an example of each measurement position in the straight pipe portion near the curved pipe of the pipe, which is 345 mm from the welding position near the curved pipe now.
It shows that there is a fixed position to bridge the abutment or the like at a distant position, and the measurement positions and are provided at the four positions shown in the figure from the welding position to the fixed position.

FIGS. 8A to 8D are views showing magnetostrictive sensor outputs at the respective measurement positions shown in FIG.
In the figure, (a) is a measurement position, (b) is a measurement position,
(C) is the measurement position, (d) is each measurement value of the magnetostrictive sensor at each position of the measurement position (unit is volts)
Are indicated by + marks corresponding to the angles indicating the azimuth on the tube circumference on the horizontal axis.

FIGS. 9 (a) to 9 (d) are diagrams showing results obtained by approximating deviation values obtained by subtracting SINθ approximate values from the respective magnetostrictive sensor outputs of FIGS. 8 (a) to (d) by SIN2θ curves. Is. (A) to (d) of the same figure show the above deviation values for the same angle as the horizontal axis of FIG. 8 at the measurement positions up to +, and the solid line shows the SIN2θ approximation curve approximating this deviation value. Shown respectively.

FIGS. 10 (a) to 10 (d) are diagrams showing results obtained by approximating deviation values obtained by subtracting SIN2θ approximate values from the respective magnetostrictive sensor outputs shown in FIGS. 8 (a) to (d) by SINθ curves. Is. (A) to (d) of the same figure respectively show the above deviation values for the same angle as the horizontal axis of FIG. 8 at the measurement positions up to +, and the solid line approximates this deviation value.
The respective SINθ approximate curves are shown.

As can be seen from FIGS. 9 (a) to 9 (d) and FIGS. 10 (a) to 10 (d), there is a SIN2θ component due to the influence of flattening at the measurement position in the straight pipe section near the curved pipe. Therefore, as shown in FIGS. 9A and 9B, it is clear that the deviation value (deviation value between the measured value and the SINθ approximate value) can be sufficiently approximated by the SIN2θ approximate curve.

In the present invention, the flattening stress in the straight pipe portion in the vicinity of the curved pipe is measured in advance by a strain gauge or the like, and a calibration curve (not shown) in which the measured value and the SIN2θ approximate value are associated with each other.
Is created. Therefore, it is possible to calculate the SIN2θ approximate value from the magnetostrictive sensor output in the vicinity of the curved pipe, and to estimate the stress associated with the flattening of the corresponding pipe from the calculated value and the calibration curve.

Also, the effect of flattening becomes smaller as the distance from the curved pipe increases,
At the measurement position of the straight pipe section, as shown in FIGS. 10 (c) and 10 (d), the deviation value (measurement value and SIN2θ
It is understood that the deviation value from the approximate value) can be approximated by the SINθ approximate curve. This is because the bending stress component has a SINθ component.

Similar to the case of the estimation of the flat stress, the stress in the straight pipe part slightly apart from the curved pipe is measured by a strain gauge or the like, and a calibration curve (not shown) in which the measured value and the SINθ approximate value are associated with each other. If it is created in advance, the SINθ approximate value can be calculated from the magnetostrictive sensor output in the straight pipe portion, and the corresponding bending stress can be estimated from the calculated value and the calibration curve.

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.

EFFECT OF THE INVENTION As described above, according to the present invention, the stress in the pipe circumferential direction of the pipe material is measured by using the 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 estimating the distribution by approximating with the SIN curve, the deviation value obtained by subtracting the magnetostrictive sensor output SINθ approximate value measured in the straight pipe part near the pipe bending part is approximated with the SIN2θ curve, and the approximation Since it is possible to estimate the stress value due to the deviation generated in the corresponding straight pipe section from the signal amplitude value of the SIN2θ curve, the flat stress that could not be measured by the SIN approximation method using the conventional magnetostrictive sensor Measurement is possible, and the effect of expanding the measurement range of the magnetostrictive sensor is obtained.

[Brief description of drawings]

1 (a) and 1 (b) are diagrams for explaining the magnetostrictive stress measurement method according to the prior application, and FIGS. 2 (a) and 2 (b) are diagrams for explaining the SIN approximation method by the magnetostrictive stress measurement method of FIG. FIG. 3 (a) is a diagram showing a stress state when the pipe is flat, FIG. 3 (b) is a diagram showing a magnetostrictive sensor output in the state of FIG. 3 (a), and FIG. Block diagram of a pipe stress measuring device to which the pipe flat stress estimation method is applied, FIG.
(C) is a diagram for explaining a method of approximating the flat stress of the pipe according to the present invention by a SIN2θ curve, and FIGS. 6 (a) and 6 (b) are general flat stress and a SIN2θ approximate curve according to the present invention. FIG. 7 is a diagram showing an example of each measurement position in a straight pipe portion near the curved pipe of the pipe, and FIGS. 8A to 8D are magnetostrictive sensors at each measurement position shown in FIG. 7. Figures showing outputs, respectively, and Figures 9 (a)-(d) are Figures 8 (a)-(d).
SINθ approximate value is subtracted by each magnetostrictive sensor output, and the result is approximated by the SIN2θ curve. FIGS. 10 (a) to 10 (d) are shown in FIGS. 8 (a) to 8 (d). It is a figure which shows the result of having subtracted the SIN2 (theta) approximate value from the magnetostrictive sensor output, respectively, and approximating the result by the SIN (theta) curve. 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 converter. , 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 stress distribution in the pipe circumferential direction of the pipe material is approximated by a SIN curve and estimated by using a 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, the deviation value obtained by subtracting the approximate value of SINθ from the magnetostrictive sensor output measured in the straight pipe section near the curved pipe section is SIN2
A flattened stress estimating method for a pipe, which comprises approximating with a θ curve and estimating a stress value due to flattening occurring in the corresponding straight pipe portion from a signal amplitude value of the approximated SIN2 θ curve.