JPH03186725A - Method and instrument for measuring magnetic stress - Google Patents

Abstract

PURPOSE:To detect and measure the direction and the magnitude of a stress even when the direction of the stress is not shown in advance by constituting the subject instrument so that when an alternating magnetic flux turning around the center point is supplied to a ferromagnetic material sample from a counter magnetic pole of an exciting core, a voltage corresponding to the direction of the magnetic flux to the direction of the stress applied to the sample is induced in a detection coil. CONSTITUTION:An alternating exciting signal is applied from an alternating exciting power source circuit to the exciting coil 17 of a detector main body 10. Thus, from both leg parts of an exciting core 11, an alternating magnetic flux is supplied to the ferromagnetic material sample. Also, a part of the corresponding magnetic flux flows through a path of the leg part and the end part of the core 11, the ferromagnetic material sample, an end part of a leg part of a detection core 12, etc. Consequently, an induction voltage corresponding to the direction of the magnetic flux to the direction of a stress applied to the ferromagnetic material sample is induced in a detection coil 18, and it is detected. Subsequently, a crossing angle of a line for connecting the end parts of both leg parts of the core 11 and the direction of the stress applied to the ferromagnetic material sample is detected by a rotational position detector, and since its induction voltage corresponds to a stress value, the direction of the stress is derived by the crossing angle, and the magnitude of the stress is derived from the induction voltage of a peak.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic stress measuring method and a magnetic stress measuring device.

[Prior art] Measuring and monitoring the stress distribution state of mechanical devices, structures, etc. is extremely important in order to know their strength and durability, and it is important to measure and monitor the stress distribution state of mechanical devices, structures, etc. It is something to respond to.

When stress is applied to a ferromagnetic material, the magnetic anisotropy changes due to the inverse magnetostriction effect, and the magnetic permeability changes depending on the direction. Stress can be measured by detecting changes in this magnetic anisotropy.

In the prior art, magnetic stress measuring instruments generally use a first
It has the same structure as the detector main body IO in the magnetic stress measuring apparatus of the present invention as shown in FIGS.

Then, during measurement by the above-mentioned magnetic stress measuring device, the excitation core 11 and the detection core 12 have ends 13a, 15a; A line connecting the ends 13a and 15a of both legs of the excitation core 11 and the detection core 12
is rotated around the intersection point O with the line connecting the ends 14a and 16a of both legs.

Then, an alternating excitation signal is applied to the excitation coil 17,
An alternating magnetic flux is supplied to the ferromagnetic material sample M from both legs 13.15 of the excitation core 11.

Then, since there is a close relationship between the direction of stress applied to the ferromagnetic material sample M and the magnetic permeability, both legs 14 of the detection core 12
．． The magnetic flux introduced into the magnetic flux 16 changes depending on the intersection angle between the path and the stress direction, that is, the magnetic permeability in the path direction, and a corresponding induced voltage is induced in the detection coil 18.

Therefore, the ends 13a of both legs of the excitation core 11, ! 5a
If the intersection angle between the line connecting the ferromagnetic material sample M and the direction of the stress applied to the ferromagnetic material sample M is θ, then the line connecting the direction of the stress and the ends 13a and 15a of both legs of the excitation core 11 is 0=061800.
, they match, and at θ=90' and 270', the 8th orthogonal
(see FIG. 8(a)), the induced voltage V in the detection coil 18 of the detection core 12 as shown in FIG. 8(b). is detected. This induced voltage Vo is obtained by detecting the alternating voltage induced in the detection coil in synchronization with the exciting current and converting it into a direct current voltage.

Then, when θ=45°+nX90', the induced voltage shows a peak, and the induced voltage corresponds to the stress value, so
The stress acting on the ferromagnetic material sample M is determined from the induced voltage.

[Problem to be solved by the invention]

When the stress is low, the conventional magnetic stress measuring instrument described above is effective in measuring stress because the induced voltage becomes linear, but when the stress range increases beyond a certain point, the stress history and magnetic history become distorted. As a result, the characteristics of the induced voltage corresponding to the stress exhibit hysteresis as shown in FIG. 10, which poses a practical problem.

To solve this problem, there is a method of magnetizing the stress measurement range to saturation magnetization using a magnetization device to reduce the unevenness of magnetic permeability due to residual magnetization and magnetic history in the stress measurement range (Jikko Kosho 6).
2-36149).

The method of applying a DC bias magnetic field to the stress measurement range using a magnetization device can be said to be a method of suppressing detection sensitivity unevenness and hysteresis due to stress history, magnetization history, etc. of the stress measurement range.

However, since the measurement is performed in a small range of magnetic permeability, it is not advantageous for increasing sensitivity. Furthermore, since it is necessary to measure the stress by magnetizing the magnet to the saturation magnetization region, problems such as force applied to the measurement object may occur. Furthermore, there are many problems in practical use, such as the need to demagnetize the magnetized areas in the measurement range after the measurement is completed.

[Means to solve the problem]

The magnetic stress measurement method according to the present invention applies a rotating magnetic field to a ferromagnetic material sample, detects the induced voltage induced by the rotating magnetic field and the rotational position of the rotating magnetic field, and calculates the intensity based on the peak value of the induced voltage. In order to detect the magnitude of the stress acting on the magnetic material sample and to detect the direction of the stress based on the rotational position of the alternating magnetic flux at the time when the induced voltage peaks, the magnetic material rotates concentrically with the rotating alternating magnetic flux. Then, a gradually decreasing demagnetizing alternating magnetic field is applied to the ferromagnetic material sample for a predetermined period of time, and at the end of that time, the peak value of the induced voltage and the rotational position of the alternating magnetic flux at the time of the peak value are detected.

The magnetic stress measuring device according to the present invention includes an excitation core and a detection core, each having a pair of magnetic poles, the magnetic poles being arranged alternately in the direction of rotation around the center point, and integrally driven to rotate around the center point. A detection head consisting of a detection head, an excitation power supply to the excitation coil of the excitation core, a detector body equipped with an excitation core rotational position detector and an induced voltage detector of the detection coil of the detection core, and a rotating alternating box arranged around the detector body. It consists of a demagnetizer consisting of a plurality of magnetic pole pairs that generate a magnetic field.

[For production]

During measurement, the magnetic stress measuring device is placed on the surface of a ferromagnetic material sample, the detector body is driven to rotate around the center point, and the excitation coil of the detector body is supplied with an alternating excitation signal from an alternating excitation power supply circuit. is added. Then, alternating magnetic flux rotating around the center point is supplied to the ferromagnetic material sample from the opposing magnetic poles of the excitation core.

Then, a voltage corresponding to the direction of the magnetic flux relative to the direction of the stress applied to the ferromagnetic material sample is induced in the detection coil, and this voltage is detected.

The intersection angle θ between the line connecting the opposing magnetic poles of the excitation core and the direction of stress applied to the ferromagnetic material sample is detected by a rotational position detector.
When the intersection angle θ is θ=45°+nX90°, the induced voltage shows a peak, and the induced voltage corresponds to the stress value, so θ
The direction of the stress is determined by the peak induced voltage Vma
The magnitude of stress σ can be found from x.

At this time, a demagnetizing signal is inputted from the demagnetizing power supply circuit to the plurality of pairs of demagnetizing coils of the demagnetizing device, and alternating currents having phase differences sequentially flow therethrough. As a result, a rotating alternating demagnetizing field is applied to the stress measurement range in the ferromagnetic material sample. Furthermore, the magnitude of the current is gradually reduced exponentially to zero over a predetermined period of time by the demagnetizing command signal in the demagnetizing power supply circuit, that is, the strength of the demagnetizing magnetic field is gradually reduced. Thereby, the stress measurement range in the ferromagnetic material sample is demagnetized at any timing, regardless of the stress direction and the rotational position of the detector body.

Therefore, the stress/induced voltage relationship hysteresis curve when θ=45° is a single curve that passes through the origin.

Therefore, based on the peak value Vmax of the induced voltage in the detection coil detected by the induced voltage detector, the magnitude of the stress σ can be determined on a previously prepared stress/induced voltage relationship hysteresis curve (passing through the origin).

The above stress/induced voltage relationship hysteresis curve (passing through the origin) is calculated by applying various stresses σ in a predetermined direction to a predetermined ferromagnetic material sample M and measuring the peak value of the induced voltage using the above magnetic stress measuring device. It can be determined by measuring Vmax and calibrating it.

〔Example〕

Embodiments of the invention will be described with reference to the drawings.

The magnetic stress measuring device has a detector main body IO assembled with a demagnetizer 20 as shown in FIGS. 1 to 3.

The detector main body IO is composed of a gate-shaped (eye-shaped) excitation core 11 and a gate-shaped detection core 12 , and both legs 13 . Is is longer than both legs 14.16 of the detection core 12, and is longer than both legs 13.15 of the excitation core 11 and the detection core 12.
The legs 14 and 16 of the excitation core 11 face the same direction, and the ends 13a and 15a of the legs 13 and 15 of the excitation core 11 and the detection core 1
The excitation core 11 is positioned relative to the detection core I2 such that the ends 14a and 16a of both legs 14. It is assembled so as to straddle it. The line connecting the ends 13a and 15a of the legs 13.15 and the leg 1
It is orthogonal to the line connecting the ends 14a and +6a of 4.16 at the intersection, that is, the center point O.

Excitation coils 17 are mounted on both legs 13.15 of the excitation core 11, and detection coils 18 are mounted on both legs 14.16 of the detection core 12.
but.

The winding direction is reversed from one leg 13.14 to the other leg 15.16, so that the winding is harmonious with respect to the flow of magnetic flux.

An alternating excitation power supply circuit (not shown) is connected to the excitation coil 17, and an induced voltage detector (not shown) is connected to the detection coil 18.

On the outside of the assembly of the excitation core 11 around which the excitation coil I7 is wound and the detection core 12 around which the detection coil 18 is wound,
A cylindrical non-magnetic casing 19 is fitted, and the upper part of the non-magnetic casing I9 is formed with a lead wire outlet portion 19a through which the lead wires of each coil having a small diameter cylindrical portion are inserted. .

The demagnetizer 20 has a four-legged table-like excitation core with four excitation coils located at the corners of a square as shown in FIGS. 26.
27, 28, and 29 are wound in the same direction, and the fitting hole 3 into which the lead wire outlet portion 19a of the detector main body 10 fits.
The top plate portion in which the number 1 is perforated serves as a common magnetic path portion 30.

The demagnetizing coils 26, 27, 28, 29 of the demagnetizer 20 include
It is connected to a demagnetizing power supply circuit as shown in FIG. 4 which generates a rotating alternating magnetic field.

Excitation coil 26.27 on each leg 22.23.24.25
．． A cylindrical non-magnetic casing 32 is fitted on the outside of the demagnetizer 20, in which the demagnetizer 28 and 29 are wound. A fitting hole 33 into which is fitted is bored.

In the central space between the legs 22.23.24.25 around which the excitation coils 26.27.28.29 of the demagnetizer 20 are wound,
The detector body 10 is rotatably inserted, and the detector body IO
Lead wire outlet! 9a is rotatably fitted into the fitting hole 31 of the common magnetic path section 30 of the demagnetizer 20 and the fitting hole 33 of the casing 32, protrudes from the casing 32, and is restrained and locked in the axial direction. As a result, in the detector body 10 and the demagnetizer 20, a line connecting the ends 22a, 24a of the legs 22.24 in a diagonal relationship in the demagnetizer 20 connects the ends 23a, 25a of the legs 23.25. The intersecting point with the line coincides with the center point O of the detector body 10, and the detector body IO is rotatably assembled integrally with the demagnetizer 20 in a coaxial relationship, thereby forming a magnetic stress measuring device. is configured.

In the magnetic stress measuring device, the detector main body IO is rotatably driven by a well-known drive device (not shown), and its rotational angle phase is determined by a well-known rotational position detector (not shown). It is now detected. Then, the legs 13 of the excitation core 11 in the detector main body lO.
15 end portions 13a, 15a, leg portions 14 of the detection core 12
．． The ends 14a, 16a of the casing 16 and the end face of the casing 19 are the end faces 22a, 23a of the casing 32 and the ends 22a, 23a of the leg parts 22, 24, 23, 25 in the demagnetizer 20.
, 24a, slightly smaller than 25a (e.g. about 0:5 mm
) retracted inward in the axial direction.

Therefore, when measuring, the legs 22.23.2 of the demagnetizer 20
4°25 ends 22a, 23a, 24a, 25a
is placed in contact with the surface of the ferromagnetic material sample M, and the detector body lO is connected to the end 13 of the leg 13.14.15.16.
a, 14a, 15a, and 16a are ferromagnetic material samples M
The lead wire is held in a position close to the surface of the lead wire with a small gap (for example, about 0.5 mm) therebetween, and is driven by a drive source (not shown) through the lead wire outlet 19a around an axis passing through the center point O parallel to the leg. It is designed to rotate.

The number of legs of the demagnetizer 20 of the magnetic stress measuring device described above is not limited to four as described above, but for example, the number of legs is not limited to four.
As shown in the figure, the ends are in the positional relationship of the corners of a regular triangle 3
In addition, the excitation coil may be connected to an excitation power supply circuit as shown in Figure 6 to simplify the structure, or the end portions may be arranged in a regular hexagonal corner position relationship as shown in Figure 7. It is also possible to use a certain number of six to reduce unevenness in the magnitude of the rotating magnetic field depending on the direction.

The above magnetic stress measuring method will be explained as the operation and operation of the above magnetic stress measuring device.

During the measurement, the magnetic stress measuring device uses a ferromagnetic material sample M
The detector body 10 is rotated by a drive device (not shown) around an axis passing through the center point O, and the excitation coil 17 of the detector body 10 is connected to an alternating excitation power supply circuit. An excitation signal is applied.

Then, from both legs 13.15 of the excitation core 11 to the center point 0
A rotating alternating magnetic flux is supplied to the ferromagnetic material sample M.

Then, a part of the magnetic flux corresponding to the stress is transmitted to the leg portion 13 of the excitation core 11, the end portion 13a, the ferromagnetic material sample M, and the detection core 1.
In the path of the end 14a of the leg 14 of No. 2, the leg 14, the leg 16, the end 16a, the ferromagnetic material sample M, the end 15a of the leg 15 of the excitation core 11, the leg 15, the leg 13. flows.

Therefore, as already described with respect to the conventional magnetic stress measuring device, an induced voltage is induced in the detection coil 18 according to the direction of the magnetic flux with respect to the direction of the stress applied to the ferromagnetic material sample M. it is detected.

The intersection angle θ between the line connecting the ends 13a and 15a of both legs of the excitation core 11 and the direction of the stress applied to the ferromagnetic material sample M is:
Detected by a rotational position detector (not shown), the intersection angle θ
When is 0 = 45° + n The magnitude of the stress σ can be determined from the induced voltage Vmax.

At this time, the demagnetizing coil 26.27.28.2 of the demagnetizing machine 20
9, a demagnetizing signal is input from the demagnetizing power supply circuit shown in FIG. 4, and X5inωt, Xcosωt, -X5inω
A current of t, -XCOSωt flows. Thereby, the stress measurement range in the ferromagnetic material sample M is applied f times per second (ω=
A clockwise rotating alternating demagnetizing field of 2πf) is applied6.
Furthermore, the magnitude of the current X is gradually reduced exponentially to zero in a few seconds by the demagnetizing command signal in the demagnetizing power supply circuit, that is, the strength of the demagnetizing magnetic field is gradually reduced (see FIG. 9).

As a result, the stress measurement range for the ferromagnetic material sample M is
Demagnetization is performed at any timing regardless of the stress direction and the rotational position of the detector body 10.

Therefore, the stress/induced voltage relationship hysteresis curve in the case of θ=45' in FIG. 8 becomes one curve that passes through the origin as shown in FIG. 10.

Note that if the demagnetization direction is not as in the present invention but is in one direction, the angle φ between the stress direction and the demagnetization direction
The characteristics will be as shown in the figure. That is, although the hysteresis shown in FIG. 10 can be eliminated by demagnetization, the induced voltage with respect to stress differs depending on the angle φ.

The above stress/induced voltage relationship hysteresis curve (passing through the origin) is obtained by applying various stresses σ in a predetermined direction to a predetermined ferromagnetic material sample M, and measuring the peak value Vmax of the induced voltage using the above magnetic stress measuring device. It can be determined by measuring and calibrating.

[Effects of the invention j According to this invention, even when the direction of stress is not known in advance, the direction and magnitude of stress can be detected and measured. Since detection is performed within a limited range, detection and measurement can be performed with high sensitivity with a good S/N ratio, and the size of the apparatus can also be reduced.

Moreover, since there is no need to magnetize to the saturation magnetization region to measure stress, there are no problems such as force applied to the measurement object, and furthermore, there is no need to demagnetize the magnetized part of the measurement range after the measurement is completed. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional front view of a magnetic stress measuring device according to an embodiment of the present invention, and FIG. 2 is a bottom view of the magnetic stress measuring device according to an embodiment of the present invention (arrowed by the Introversion, Figure 3 is
1 is a sectional view taken along the line ■-■, FIG. 4 is a power supply circuit diagram of a demagnetizer of a magnetic stress measuring device according to an embodiment of the present invention, and FIG. FIG. 6 is a power supply circuit diagram of the modified demagnetizer of FIG. 4, and FIG. 7 is an explanatory diagram of the magnetic poles of the modified demagnetizer of the measuring device. FIG. 8 is an explanatory diagram of the magnetic poles of porcelain, and is an explanatory diagram of the relationship between the stress direction of the sample for magnetic stress measurement and the positional direction of the detector body of the magnetic stress measuring device in the embodiment of the present invention, and FIG. FIG. 9 is a graph showing the relationship between the position direction and the induced voltage. FIG. 9 is an explanatory diagram of the timing of demagnetizing the demagnetizer for magnetic stress measurement in the embodiment of the present invention and stress value reading. FIG. FIG. 11 is a hysteresis curve diagram of the relationship between induced voltage in magnetic stress measurement and sample stress in an example of the present invention. FIG. It is a graph showing degree. ll: Excitation core 12: Detection core +3a, 14a, 15a, 16a: End portion 18:
Detection coil 19a: Lead wire outlet portions 22, 23, 24, 25 + legs 26, 27, 28, 29: Demagnetizing coils 31, 33: Fitting hole M: Ferromagnetic material sample 1O: Detector body + 3. 14.15.16: Leg I7: Excitation coil 19.32: Casing 20: Demagnetizer 22a, 23a, 24a, 25a: End 30:
Common magnetic path part O: center point

Claims (1)

[Claims] (1) A rotating magnetic field is applied to a ferromagnetic material sample, the induced voltage induced by the rotating magnetic field and the rotational position of the rotating magnetic field are detected, and the voltage applied to the ferromagnetic material sample is based on the peak value of the induced voltage. Demagnetization that rotates concentrically with the rotating alternating magnetic flux and gradually decreases when detecting the magnitude of stress and the direction of the stress based on the rotational position of the alternating magnetic flux at the time when the induced voltage exhibits a peak value. A magnetic stress measurement method in which an alternating magnetic field is applied to a ferromagnetic material sample for a predetermined period of time, and at the end of that time, the peak value of the induced voltage and the rotational position of the alternating magnetic flux at the time of the peak value are detected (2) Each pair of magnetic poles a detection head consisting of an excitation core and a detection core whose magnetic poles are arranged alternately in a rotational direction around a center point and are integrally driven to rotate around the center point; an excitation power supply to an excitation coil of the excitation core; Consists of a detector body equipped with an excitation core rotational position detector and an induced voltage detector of the detection coil of the detection core, and a demagnetizer consisting of a plurality of magnetic pole pairs arranged around the detector body and generating a rotating alternating magnetic field. Magnetic stress measuring device