JP3130111B2 - Measuring method of magnetostriction sensitivity - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring magnetostriction necessary for measuring a magnetostrictive stress generated when a bending moment acts on a pipe such as a steel pipe in a plane including the pipe axis by using a magnetostrictive stress measuring method. It relates to a method for measuring sensitivity.

[0002]

2. Description of the Related Art In a magnetostrictive stress measurement method, when a load is applied to a material such as steel, which is a ferromagnetic material, anisotropy is generated in the magnetic permeability, and the magnetic permeability in the load direction increases, and conversely, the magnetic permeability is perpendicular to the load direction. This method measures the direction and magnitude of the main stress by detecting the difference between the two magnetic permeability by using a phenomenon that the magnetic permeability in the direction becomes small and detecting the difference between the two magnetic permeability. M is the magnetostriction sensitivity, σ is the true stress when a bending moment acts in a plane including the tube axis of the tube, and V is the output of the magnetostriction sensor.
Then, Equation 1 is established.

V = M · σ Magnetostrictive sensitivity M is a physical property value determined by the material and manufacturing method of a steel pipe, and is usually determined by a bending test of an actual steel pipe to be measured. In the prior art, each end of a pipe such as a steel pipe is supported at each fulcrum, and loads are respectively loaded at two points 4 and 5 between the fulcrums, and a plurality of pipes are provided on the outer peripheral surface of the pipe at circumferentially spaced intervals. The true bending stress σ by providing the strain gauge 6
And the output V is measured while moving the magnetostrictive sensor in the circumferential direction along the rail fixed to the outer peripheral surface of the tube, thereby obtaining a graph represented by the true bending stress σ and the output. The magnetostriction sensitivity M is a proportional constant indicated by the slope of the graph. The magnetostriction sensitivity M is measured in advance for each tube, and the magnetostrictive stress of the tube to be measured is measured by a magnetostrictive sensor, whereby the magnetostrictive stress σ can be measured.

[0004]

In such a prior art, when a steel pipe for which the magnetostriction sensitivity M is to be measured has a small diameter, the actual pipe bending test is relatively easy. Nominal diameter 600A, 750A, 9
In the case of 00A, 1000A, 1200A, etc., a large-scale test facility is required, which is a serious problem from the viewpoint of cost and workability.

[0005] It is an object of the present invention to provide a method for measuring the magnetostriction sensitivity so that the magnetostriction sensitivity can be easily obtained.

[0006]

According to the present invention, a tube whose magnetostrictive stress is to be measured is cut out of an elongated test piece 11 along a tube axis 13 of the tube, and is cut in a plane 14 containing the tube axis 13 of the test piece 11. The test piece 11 is supported on two fulcrums 17 and 18 spaced apart in the pipe axis direction, and two loads in the plane 14 at both outer sides of the fulcrums 17 and 18 in the pipe axis direction. Point 1
In steps 9 and 20, by applying forces F1 and F2 perpendicular to the tube axis 13 and applying a bending moment to the test piece 11, the true tensile stress .sigma. Measuring means 15 provided on the outer surface of the
And the test piece 11 is measured by the magnetostrictive sensor 140.
The output V corresponding to the true tensile stress σ caused by the difference in the magnetic permeability between the tube axis direction and the circumferential direction of the outer surface of the outer surface is measured, and the tensile stress σ measured by the stress measuring means is measured.
And measuring the magnetostrictive sensitivity M of the tube from the output V of the magnetostrictive sensor. The present invention also relates to a method for measuring a tube whose magnetostrictive stress is to be measured by using a tube shaft 13 of the tube.
The test piece 11 is cut out along an axis, and the test piece 11 is supported on two fulcrums 21 and 22 spaced apart in the tube axis direction in a plane 14 including the tube axis 13 of the test piece 11 and By applying forces F3 and F4 perpendicular to the tube axis 13 at the two load points 23 and 24 in the plane 14 on both insides of the fulcrums 21 and 22 in the tube axis direction, the test piece 11
With the bending moment acting on the test piece 11, the true compressive stress σ acting on the test piece 11 is measured by the stress measuring means 15 provided on the outer surface of the test piece 11, and the magnetostrictive sensor 14 is measured.
0, the output V corresponding to the true compressive stress σ caused by the difference in the magnetic permeability of the outer surface of the test piece 11 between the tube axis direction and the circumferential direction was measured, and the compression measured by the stress measuring means was measured. This is a method for measuring a magnetostrictive conduit, wherein a magnetostrictive sensitivity M of a tube is obtained from a stress σ and an output V of a magnetostrictive sensor.

Further, the present invention is characterized in that the stress measuring means is a strain gauge.

[0008]

According to the present invention, a tube such as a steel tube whose magnetostrictive stress is to be measured is cut out along the tube axis to form an elongated test piece, and the test piece is placed parallel to the tube axis. In a plane, for example, in a plane 14 including the tube axis 13,
Apply a bending moment. To apply a true tensile stress σ to the test piece 11, the test piece 11 is
And two supporting points 17 and 18 spaced apart in the pipe axis direction, and two load points 19 and 20 in the plane 14 on both outer sides of the supporting points 17 and 18 in the pipe axis direction. Apply forces F1 and F2 perpendicular to the tube axis 13. Test piece 1
To apply a true compressive stress σ to 1, two fulcrums 2
The test pieces 11 are supported on
The forces F3 and F4 act in the same manner as described above at the two load points 23 and 24 on both inner sides in the tube axis direction 22. Thus, the tensile stress σ or the compressive stress σ is measured by the stress measuring means 15 provided on the outer surface of the test piece 11. When the bending moment acts, the true tensile stress σ or the true compressive stress σ caused by the difference in the magnetic permeability between the tube axis direction and the circumferential direction of the outer surface of the test piece 11 using the magnetostrictive sensor 140. Is measured. The tensile stress σ or the compressive stress σ thus obtained and the output V of the magnetostrictive sensor
From this, the magnetostriction sensitivity M of the tube can be obtained. Since the magnetostrictive sensitivity is determined in this way, even for a large-diameter tube, the external force required for bending deformation of the test piece may be relatively small, and therefore, the large-scale test equipment described in connection with the prior art is This is no longer necessary, and both cost and workability are improved.

[0009]

FIG. 1 is a perspective view of a test piece 11 according to one embodiment of the present invention. This test piece 11 is a steel pipe 12 shown in FIG.
Is cut out along the tube axis 13 to be elongated.
Both ends 11 a and 11 b of the test piece 11 are in a plane parallel to the tube axis 13. Both ends 11 c and 11 d in the axial direction of the test piece 11 are in respective planes perpendicular to the tube axis 13.
The steel pipe 12 has, for example, a nominal diameter of 300 mmφ and a thickness of, for example, 5 mm.

FIG. 3 is a plan view of the test piece 11. The length L1 of the test piece 11 along the pipe axis 13 is, for example, 1250 m.
m, and the width L2 perpendicular to the tube axis 13 is 100 mm. In order to measure the true stress on the outer surface of the test piece 11 when a bending moment is applied to the test piece 11 in a plane 14 including the tube axis 13, a stress measuring means is provided. One or more (9 in this embodiment) strain gauges 15 are provided.

FIG. 4 is a side view for explaining a state when a tensile stress is applied to the test piece 11. Test piece 11
Are supported on two fulcrums 17, 18 provided on a flange of a rigid H-section steel 16 and apply forces F1, F2 at load points 19, 20. Support points 17, 18 and load point 1
Reference numerals 9 and 20 are located at the center of the test piece 11 in the width direction. The forces F1, F2 are in the plane 14, parallel to each other and perpendicular to the tube axis 13. Thus, a bending moment is applied to the test piece 11. At this time, the true tensile stress σ acting on the test piece 11 is detected by the strain gauge 15, and the output V of the magnetostrictive sensor 140 is obtained.

In order to apply a compressive stress to the test piece 11, the test piece 11 is supported on fulcrums 21 and 22, and forces F3 and F4 are applied at load points 23 and 24, as shown in FIG. The supporting points 21 and 22 and the load points 23 and 24 are
1 at the center in the width direction. Where the forces F3, F4 are of equal value and in this embodiment are in the plane 14;
Perpendicular to the tube axis 13. Also at this time, the test piece 11
The true compressive stress is measured by the strain gauge 15 provided in the sensor and the output V of the magnetostrictive sensor 140 is obtained.

FIG. 6 is a perspective view of the configuration of the magnetostrictive sensor 140, and FIG. 7 is a simplified plan view of the magnetostrictive sensor 140. In the magnetostrictive sensor 140, an exciting coil 169, which is an exciting coil for measuring magnetostrictive stress, is wound around the inverted U-shaped core 168. The pair of magnetic poles 170 and 171 of the core 168 are connected to the tube axis 13 at an angle θ3 other than 90 ° (θ3 in this embodiment).
(= 45 degrees) at intervals in the direction of a straight line 177 that intersects at an angle. Further, a core 173 is provided, and a detection coil 174 is wound around the core 173. The magnetic poles 175 and 176 of the core 173 are spaced from each other in a direction of a straight line 178 perpendicular to a straight line 177 connecting the pair of magnetic poles 170 and 171 of the core 168. Each magnetic pole 17
The centroids of the end faces of the test pieces 11 of 0, 171; 175, 176 are located at the vertices of a virtual square. The exciting coil 169 is excited by an AC power supply 179, and the induced electromotive force of the detecting coil 174 is measured by a voltage measuring means 1 such as a voltmeter.
80. The true stress σ, the magnetostriction sensitivity M, and the induced electromotive force V of the detection coil 174 have the above-described relationship of Equation 1. The magnetostrictive sensor 140 including the cores 168 and 173 and the coils 169 and 174 is configured to be totally symmetric with respect to one diameter line of the test piece 11 passing through an intersection 185 (see FIG. 7) of the straight lines 177 and 178.

In the magnetostrictive sensor 140, the magnetic poles 170 and 171 of the core 168 are equidistant from the magnetic pole 175 of the core 173, and when the magnetostrictive stress σ is not generated in the tube axis direction of the test piece 11, Have the same magnetic permeability μ in the tube axis direction and in the circumferential direction. Therefore, when the exciting coil 169 is excited by the AC power supply 179, for example, the magnetic flux entering the magnetic pole 175 from the magnetic pole 171 and the magnetic flux exiting from the magnetic pole 175 to the magnetic pole 170. The same is true for magnetic flux, and the same holds for the magnetic pole 176. Therefore, the output V, which is the induced electromotive force of the detection coil 174 detected by the voltage measuring means 180, is zero or a very small value. When the stress σ acts in the tube axis direction, the respective magnetic permeability in the tube axis direction and the circumferential direction of the tube 1 are different, and therefore, the output V, which is the induced electromotive force,
Is a value corresponding to the stress σ and the magnetostriction sensitivity M.

Based on the experiments shown in FIGS. 4 and 5, the true stress σ obtained from each of the plurality of strain gauges 15 is calculated.
And the induced electromotive force V obtained from the detection coil 174 of the magnetostrictive sensor 140, the magnetostrictive sensitivity M can be obtained based on the equation (1). Using the magnetostriction sensitivity M of the test piece 11 thus obtained, and thus of the steel pipe 12, it is possible to measure the stress σ acting on the actual steel pipe 12 using the output V of the magnetostriction sensor 140 as shown in FIG. Will be possible.

Reference numeral 160 in FIG. 6 denotes a coating material for corrosion protection which is coated on the surface of the steel pipe 12 and thus the test piece 11. In FIGS. 1 to 5, such a coating material is shown. 1
The illustration of 60 is omitted. At the time of measurement by the strain gauge 15 and the magnetostrictive sensor 140, the coating material 160 may be removed. In FIG. 8, the magnetostrictive sensor 140
Is moved circumferentially along an annular rail 26 fixed to the outer peripheral surface of the pipe 12, whereby the stress σ acting on the steel pipe 12 can be measured.

FIG. 9 is a graph showing the experimental results of the present inventor. The stress σ measured using the magnetostriction sensitivity M obtained by an actual pipe test with a nominal diameter of 300 mmφ is shown by a line 27. On the other hand, according to the present invention, the test piece 11
Is cut out from the steel pipe 12 as described above, and the magnetostriction sensitivity M is obtained by the above-described procedure. Based on the magnetostriction sensitivity M, the output V of the actual steel pipe 12 is obtained using the magnetostriction sensor 140, and the output V and the magnetostriction sensitivity are obtained. The relationship with the stress σ obtained from M is shown by a line 28. From this, test piece 1
It can be seen that the stress σ can be obtained with relatively high accuracy even when the magnetostriction sensitivity M obtained by using No. 1 is used, as in the case of performing the actual pipe test.

The magnetostrictive sensor 140 may be realized by another configuration. Further, instead of the strain gauge 15, a stress measuring means having another configuration may be used.

[0019]

As described above, according to the present invention, a tube whose magnetostrictive stress is to be measured is cut out along the tube axis to form an elongated test piece, and a bending moment is applied to the test piece. The true tensile stress .sigma. Or the true compressive stress .sigma. Acting on the test piece 11 is measured by the stress measuring means 15, and the true tensile stress .sigma. The output V of the magnetostrictive sensor 140 corresponding to the tensile stress σ or the true compressive stress σ is obtained.
Since the magnetostriction sensitivity is obtained using the output V of 40, the external force for bending and deforming the test piece may be relatively small, so that a large-scale test facility is not required, so that the cost is reduced, and The property becomes good.

[Brief description of the drawings] [Explanation of symbols]

FIG. 1 is a perspective view of a test piece 11 according to one embodiment of the present invention.

FIG. 2 is a perspective view of a steel pipe 12 from which a test piece 11 is cut out.

FIG. 3 is a plan view of a test piece 11;

FIG. 4 is a side view showing an experimental state of the test piece 11 when a tensile stress is applied.

FIG. 5 is a side view showing an experimental state of the test piece 11 when a compressive stress is applied.

FIG. 6 is a perspective view showing a configuration of a magnetostrictive sensor 140.

FIG. 7 is a simplified plan view of the magnetostrictive sensor 140.

FIG. 8 is a side view showing a state where the stress of the steel pipe 12 is measured using the magnetostrictive sensor 140.

FIG. 9 is a graph showing experimental results of the present inventor.

[Explanation of symbols]

 11 Test piece 12 Steel pipe 13 Tube axis 15 Strain gauge 140 Magnetostrictive sensor

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshiaki Sakai 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Masao Shiokawa 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan (56) References JP-A-3-176629 (JP, A) JP-A-3-190635 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 1/00 G01L 1/12

Claims (3)

(57) [Claims] 1. A tube whose magnetostrictive stress is to be measured is cut into an elongated test piece 11 along a tube axis 13 of the tube. The test piece 11 is supported on the two fulcrums 17, 18, which are located outside the fulcrums 17, 18 in the tube axis direction and in the plane 14 at two load points 19, 20. 13
When the bending moment is applied to the test piece 11 by applying forces F1 and F2 perpendicular to the test piece 11, the true tensile stress σ acting on the test piece 11
The true tensile stress σ measured by the stress measuring means 15 provided on the outer surface of the test piece 11 and caused by the fact that the magnetic permeability of the outer surface of the test piece 11 in the tube axis direction differs from that in the circumferential direction by the magnetostrictive sensor 140. A method of measuring a magnetostrictive line, comprising: measuring an output V corresponding to the following equation; and obtaining a magnetostrictive sensitivity M of the tube from the tensile stress σ measured by the stress measuring means and the output V of the magnetostrictive sensor. 2. A tube whose magnetostrictive stress is to be measured is cut out of an elongated test piece 11 along a tube axis 13 of the tube. The test piece 11 is supported on the two fulcrums 21 and 22 which are opened, and the tube axis is formed at two load points 23 and 24 in the plane 14 on both inner sides of the fulcrums 21 and 22 in the tube axis direction. 13
In a state where a bending moment is applied to the test piece 11 by applying forces F3 and F4 perpendicular to the test piece, a true compressive stress σ acting on the test piece 11 is measured on the outer surface of the test piece 11. The output V corresponding to the true compressive stress σ caused by the difference in the magnetic permeability between the tube axis direction and the circumferential direction of the outer surface of the test piece 11 is measured by the magnetostrictive sensor 140 using the magnetostrictive sensor 140. A method for measuring a magnetostrictive sensitivity M of a tube from a compressive stress σ measured by a stress measuring means and an output V of a magnetostrictive sensor. 3. The method according to claim 1, wherein the stress measuring means is a strain gauge.