JPS5945928B2 - Principal stress measurement method for magnetic materials - Google Patents

Description

[Detailed Description of the Invention] The present invention combines a plurality of magnetic sensors radially, rotates them around a measurement point on the surface of a magnetic material, and compares the iron loss measured by the sensors for each magnetic material. And the difference in iron loss is o
The present invention relates to a method for measuring principal stress in a magnetic material, in which the direction of the center line of at least two magnetic sensors is measured, and the direction and magnitude of the principal stress at the measurement point are determined.

For magnetic materials such as steel that are conveniently used in assembled structures, there is generally a relationship between the stress that acts on the magnetic material and the iron loss characteristics as shown in Figure 1, and this relationship can be used to calculate the stress that acts on the magnetic material. The direction and magnitude of the stress caused can be measured using a magnetic sensor.

As shown in FIG. 3, the magnetic sensor 2 is constructed by winding a primary coil (excitation coil) 3 and a secondary coil (output secondary voltage coil) 4 around a magnetic sensor 5 having a U-shaped cross section. As shown in FIG. 2, if the center of this magnetic sensor 2 is aligned with the measurement point 6 at which the stress on the surface of the magnetic material 1 is to be measured, and the excitation coil 3 is excited with alternating current, the magnetic flux from the magnetic core 5 is As shown in FIG. 3, the magnetic material 1 forms a closed magnetic path that flows in the direction of the arrow in the magnetic material 1 and returns to the magnetic core 5 again. At this time, the voltage on the primary side is controlled to keep the output voltage induced in the secondary coil constant, and the excitation current of the primary coil is connected to the current terminal of the wattmeter (not shown) to the secondary coil. If the iron loss is measured by connecting the output voltage of the coil to the voltage terminal of the wattmeter, the magnetism acting on the measurement point 6 of the magnetic material 1 can be detected by the sensor 2.
The stress in the center line direction can be determined from the relationship shown in FIG. The direction of the center line of the magnetic sensor 2 may be in the longitudinal direction of the magnetic sensor 2, as shown in FIG. 2, or may be perpendicular to the longitudinal direction. Now, in order to measure the stress at measurement point 6 when the magnetic material is in a certain stress state (tension or compression), it is necessary to find the direction and magnitude of the principal stress acting on measurement point 6.

For this purpose, conventionally, the center of the sensor 2 is aligned with the measuring point 6 using one magnetic field, and the magnetic sensor 2 is rotated around the measuring point 6 to generate a magnetic field that produces the maximum or minimum iron loss. The direction of the center line of Yansa 2 was determined, the iron loss in that direction and the direction perpendicular to that direction was determined, and the magnitude of the principal stress was determined from the iron loss. In this case, if the iron loss of the magnetic material 1 when the stress is 0 is Wo, then as can be seen from FIG. 1, when compressive stress is acting on the magnetic material 1, the iron loss is W.

The iron loss W is larger when tensile stress is applied.
. become smaller. In addition, in order to measure the stress distribution at the measurement point 6 by iron loss, the magnetic sensor 2 is connected to the measurement point 6.
When the iron loss was measured by rotating it around , it was confirmed through experiments that the iron loss was distributed symmetrically with respect to the directions of maximum and minimum iron loss corresponding to the principal stress, as shown in Fig. 4.

As can be seen from this curve, the curve is gentle near the point where the iron loss is maximum or minimum, so one magnetic sensor 2 can directly and accurately measure the direction of the maximum or minimum iron loss and the iron loss in that direction. It is difficult to do so. Therefore, there was a drawback that the direction and magnitude of the principal stress could not be determined accurately. In view of the above points, the present invention compares each iron loss measured by rotating a plurality of magnetic sensors arranged radially around a measurement point on the surface of a magnetic material. Determine the exact direction of the principal stress by measuring the direction of the center lines of at least two magnetic sensors where the difference is 0, and then calculate the direction of the principal stress at that measurement point and the difference and sum of the iron loss in the direction perpendicular to it. The purpose of the present invention is to provide a method for measuring the principal stress of a magnetic material, in which the accurate magnitude of the principal stress is obtained by simple calculation from the difference and sum of the measured iron losses. An embodiment of the method of the present invention will be described below with reference to the drawings.

In the embodiment, a case will be described in which two magnetic sensors are combined. Figures 5A and b are explanatory diagrams of the method for measuring principal stress in magnetic materials of the present invention, Figure 6 is a sectional view of Figure 5Af)A-0-A, and Figure 7 is a primary coil of two magnetic sensors. Figure 8 is a connection diagram of the secondary coils of two magnetic sensors, and Figure 9 is a characteristic curve diagram showing the stress distribution of the magnetic material in terms of iron loss measured with the magnetic sensor shown in Figure 5. be.

In FIG. 5a, two magnetic sensors 8, 8 are mounted on a mounting base 9 made of an insulating material along their longitudinal center lines 11, 11.
A case is shown in which the iron loss measuring device 18 is attached to the surface of the magnetic material 7, and the iron loss measuring device 18 is configured so that the center lines form a 90 angle with each other and the intersection of the center lines '11. be.

Furthermore, as shown in FIGS. 6, 7, and 8, the magnetic sensors 8, 8 have magnetic cores 12, 12, primary coils (excitation coils) 13, 13', and secondary coils (output The primary coils 13, 13 are connected in series, and when the secondary coils 14, 14 open the switch 15 and close the switch 16, the magnetic sensor 8.8 The output voltages El and e2 can be detected individually, and when the switch 15 is closed and the switch 16 is opened, the output voltage e1-E2 of the magnetic sensor 8.8 can be detected. It is connected to the.

Therefore, align the fulcrum 10 of the mount 9 of the iron loss measuring device 18 with the measurement point at which the principal stress on the surface of the magnetic material T is to be measured, close the switch 15 of the secondary coil, and open the switch 16. , when the primary coil 13,''13 is excited with alternating current,
The magnetic flux from the magnetic cores 12, 12 flows through the magnetic material 7 in the direction of the arrow, as shown in FIG.

Now, rotate the iron loss measuring device 18 about the fulcrum 10, connect the primary coils 13, 13 of the magnetic sensor 8,''8 to the current terminal of the wattmeter (not shown), and connect the secondary coil 1
4. Connect 14 to the voltage terminal of the wattmeter.

If the current flowing through the primary coils 13, 13 at this time is I, then 1(e1-E2)=W1-W2 is measured.

In this X, Wl and W2 are used to place the iron loss measuring device 18 at any position.
This is the iron loss measured by the magnetic sensors 8, 8 when rotated.

When finding the positions of the magnetic sensors 8, 8 where W, -W2 become O, as is clear from FIG.
, 8 becomes the direction of the principal stress.

Next, open the switch 15 on the side of the secondary coils 14, 14,
' By closing the switch 16 and measuring the iron loss in the principal stress direction using the magnetic sensors 8, 8, and setting W, = WM, W, 2゛Wm, the principal stress σ can be more easily determined.

Here, α is a coefficient determined by the quality of the magnetic material. Fifth
In Figure b, two magnetic sensors 8, 8/ are mounted on the mounting base 9, and the center lines 17, ``17 in the direction perpendicular to the longitudinal direction thereof form a right angle, and the intersection of the center lines 17, 17 is on the mounting base 9. An iron loss measuring device 19 configured to coincide with the fulcrum 10 is connected to the magnetic material 7.
The case where it is attached to the surface of is shown.

The rest of the configuration is the same as in the case of FIG. 5a, so the same measurement as in the case of FIG. 5a can be carried out while rotating the iron loss measuring device 19 around the measurement point on the surface of the magnetic material 7. In the above embodiment, the case was described in which two magnetic sensors were combined so that their center lines were 90 degrees apart from each other.
There is no need to limit this angle to 90 degrees, and the angles may be combined to form any angle.

In addition, if you use two or more magnetic sensors in combination by arbitrarily changing the angle formed by the center line of each magnetic sensor, you can determine the direction and magnitude of the principal stress more quickly than when using two magnetic sensors. You can ask for it. As described above, according to the method for measuring principal stress of a magnetic material of the present invention, a plurality of magnetic sensors are installed radially on a mounting base, and the intersection of the center lines of each magnetic sensor is aligned with the fulcrum of the mounting base. The fulcrum of the constructed iron loss measurement device is aligned with the measurement point on the surface of the magnetic material whose principal stress is to be measured, and the primary coils of each magnetic sensor are connected in series, and the output of the secondary coil [ヮ沒dpressure is connected so that the output pressure of each magnetic sensor can be detected, and the difference between the output pressures of any two magnetic sensors can be detected.
The primary coil of each magnetic sensor is excited, the iron loss measuring device is rotated around the measurement point, and the measurement is first made from the difference between the excitation current of the primary coil and the output pressure of any two magnetic sensors. If you measure the difference in iron loss at a point and find the position where the difference in iron loss becomes 0, the direction of the center line of any two magnetic sensors where the iron loss becomes 0 will be the direction of the principal stress. . Next, this 2
By switching the connection of the secondary coil so that the individual voltages of the magnetic sensors can be detected and measuring the iron loss WM, wrn in the direction of the principal stress and the direction perpendicular to it, the principal stress can be easily calculated. You can find the size. In particular, as explained in the example, when two magnetic sensors are combined so that their center lines form a 90 degree angle, the direction of the principal stress is determined, and the iron loss in the direction of this principal stress is determined. This is convenient because iron loss in the perpendicular direction can be measured at the same time. Therefore, the direction and magnitude of the principal stress of a magnetic material can be determined more easily and more accurately than conventional methods, and
Since we want to find the point where the difference in iron loss between magnetic sensors becomes 0,
This has great effects, such as being able to eliminate temperature drift in the amplifier used as the excitation power source for the primary coil of the magnetic sensor.

[Brief explanation of drawings]

Figure 1 is a characteristic curve diagram showing the relationship between stress and iron loss of magnetic materials, Figure 2 is an explanatory diagram of the conventional principal stress measurement method using one magnetic sensor, and Figure 3 is A of Figure 2. -A is an enlarged cross-sectional view, Figure 4 is a characteristic curve diagram showing the stress distribution around the measurement point of the surface soil of the magnetic material in terms of iron loss, and Figures 5A and b are explanations of an embodiment of the method of the present invention. Figure 6 is Figure 5Af) A-0-A
A sectional view, FIG. 7 is a connection diagram of the primary coils of two magnetic sensors, and FIG. 8 is a connection diagram of the secondary coils of two magnetic sensors.
Figure 9 shows the stress distribution of a magnetic material where the center line forms 90 continuations.
FIG. 3 is a characteristic curve diagram showing iron loss measured by two magnetic sensors. '7...Magnetic material, 8,8...Magnetic sensor, 9...
Mounting base, 10...Fully point, 12, 12...Single magnetic core, 1
3,″13...Primary coil (excitation coil), 14,1
4...Secondary coil (output [ヮ沒d pressure coil)], 15,1
6...Switch, 18.19... Iron loss measuring device.

Claims (1)

[Claims] 1 Arrange a plurality of magnetic sensors radially so that the center lines of each magnetic sensor intersect at one point, align the point where the center lines intersect with the measurement point on the surface of the magnetic material, and excite each magnetic sensor with alternating current. , rotating the plurality of magnetic sensors around a measurement point and comparing the iron loss measured by each magnetic sensor,
A method for measuring principal stress in a magnetic material, comprising: measuring the direction of the center line of at least two magnetic sensors such that the difference in iron loss is 0; and determining the direction and magnitude of the principal stress at the measurement point.