JP4552013B2 - Magnetostriction distribution measuring method by elastic wave standing wave method and stress inspection method using the method - Google Patents

Description

The present invention, by generating a standing wave elastic wave in the elastic body, for measuring the magnetostriction in the magnetic various parts, magnetic strain distribution measuring method according to the elastic wave standing wave method, and the magnetic strain distribution measuring method The present invention relates to a stress inspection method used.

Magnetic rods typified by iron bars have high mechanical strength and are low in cost, and are used, for example, in parts with extremely high mechanical loads such as train axles. However, as is well known, if it continues to be used in a state where the mechanical load is large, metal fatigue progresses, leading to destruction such as a sudden fracture. For this reason, a method for inspecting the degree of fatigue of the magnetic rod in a nondestructive manner is necessary.
As a conventional inspection method of this type, there is an ultrasonic pulse method. In addition, since ultrasonic waves are longitudinal waves, that is, stretching waves, if the object to be inspected is a magnetic structure such as steel, magnetostriction occurs at the expansion and contraction points due to the ultrasonic waves, and the inverse magnetostriction effect due to this magnetostriction occurs. An anisotropic magnetic field is generated based on Focusing on this phenomenon, a standing wave is formed by the incident elastic wave from the elastic wave generator arranged at one end of the magnetic material and the reflected elastic wave from the other end of the magnetic material, and stress is applied to the node of the standing wave. There is known a method for measuring the magnetostriction of a magnetic material from an oscillating anisotropic magnetic field generated by the inverse magnetostriction effect of this stress by utilizing the occurrence of this phenomenon (Patent Document 1 and Non-Patent Document 1).
In addition, by applying a bias magnetic field to the surface of the steel sheet and applying an induction magnetic field so as to be orthogonal to and opposite to each other in the same plane, magnetostriction is generated, and surface waves generated by this magnetostriction in two directions. It is also known to evaluate internal stress from the difference in propagation speed (Patent Document 2).

JP 2003-287565 A JP-A-7-286916 Hiroshi Kanofuku, IEEJ Transactions Volume 121, No. 8, pp 739-744, 2001

However, the ultrasonic pulse method is effective when fatigue has progressed and cracks have occurred, but replacement or repair after cracks have occurred may not ensure safety. There is a problem that is not.
Moreover, although the method of patent document 2 can test | inspect the generation | occurrence | production of the internal stress which is a state just before a crack occurs, since the surface wave is generated with an induced magnetic field, the generation efficiency is not good. Also, when measuring the residual stress of a measured object that has been fatigued, the hardness of the object to be measured increases due to fatigue, and since the elastic modulus generally increases as the hardness increases, the propagation speed of surface waves increases. Because the fatigue point is not uniform over the entire surface, it is difficult to accurately measure the difference in the propagation velocity of the surface wave in two directions based only on the underlying stress. There is a problem that it is difficult to do.
Furthermore, in the method disclosed in Patent Document 1, it is necessary to measure each induced electromotive force curve using a plurality of magnetic bodies having different magnitudes of inherent stresses, which takes time.

  Under such circumstances, the present inventor can further improve the technical contents disclosed in Patent Document 1 and Non-Patent Document 1, and can easily calculate the magnetostriction of each part along the longitudinal direction of the magnetic rod, I came up with the idea of magnetostriction by the elastic wave standing wave method.

The present invention has been made in view of the above problems, by utilizing the acoustic wave standing waves caused in the magnetic body, accurate, and can determine the magnetostriction of any sites conveniently magnetic, acoustic wave It is an object of the present invention to provide a magnetostriction distribution measurement method by a standing wave method and a stress inspection method using the method.

In order to solve the above-mentioned problem, the magnetostriction distribution measuring method by the elastic wave standing wave method of the present invention performs induction while changing the applied magnetic field at the position of the central node equidistant from both ends of the magnetic material to be measured. Determining the effective magnetic field dependency of the electromotive force; determining the effective magnetic field dependency of magnetostriction while changing the applied magnetic field at the position of the central node equidistant from both ends of the measured magnetic material; In a state where a constant magnetic field is applied along the longitudinal direction of the magnetic material, an elastic wave is propagated and reflected in the magnetic material to form a standing wave in the magnetic material to be measured to generate an oscillating magnetic field . From the step of measuring the induced electromotive force at each part in the longitudinal direction of the magnetic substance to be measured while changing the position of the coil in the propagation axis direction, and the distribution of the induced electromotive force at each position in the longitudinal direction of the magnetic substance to be measured, Standing wave Obtain the envelope of the measured value of the belly, and determine the value of the induced electromotive force at each position obtained from this envelope, the effective magnetic field dependency of the induced electromotive force, and the effective magnetic field dependency of magnetostriction. Obtaining a magnetostriction and obtaining a magnetostriction distribution .

  According to this method, it is possible to measure the amount of magnetostriction at an arbitrary position of the magnetic body in a predetermined bias magnetic field applied along the longitudinal direction of the magnetic body. That is, since the induced electromotive force measured by the elastic wave standing wave method is not affected by the demagnetizing field effect based on the shape of the magnetic substance to be measured, the relationship between the induced electromotive force and the previously measured induced electromotive force and effective magnetic field The magnetic field actually applied to the position of the node of the standing wave formed on the magnetic body, that is, the effective magnetic field can be obtained, and from the relationship between the magnetic field strength applied to the magnetic body and magnetostriction, The amount of magnetostriction at the node of the magnetic material is known. Further, since the position of the node of the standing wave can be selected by selecting the frequency of the elastic wave, the amount of magnetostriction at an arbitrary position can be measured.

In addition, the stress inspection method of the present invention uses the magnetostriction distribution measurement method based on the elastic wave standing wave method for the magnetic material in the initial state and the magnetic material in a fatigue state by applying mechanical stress. Measuring the longitudinal magnetic strain distribution of the magnetic material, comparing the magnetic strain distribution of the magnetic material in the initial state with the magnetic strain distribution of the magnetic material in the fatigued state, and determining the degree of fatigue state And

According to this inspection method, the fatigue state of the magnetic material can be accurately determined. That is, when a mechanical stress is applied to the magnetic material, the stress is inherent in the magnetic material, and if the stress exceeds a certain value, breakage such as breakage is likely to occur. The fatigue state of the magnetic material can be known before destruction. When stress is present in the magnetic material, the magnetostriction characteristics change. Therefore, it is possible to determine the degree of fatigue by applying a magnetic field to the magnetic material and measuring the expansion and contraction due to the magnetostriction of the entire magnetic material. However, depending on the type of stress applied to the magnetic material, the direction of the stress varies depending on the part of the magnetic material, and the expansion and contraction of the entire magnetic material may not necessarily be proportional to the degree of fatigue.
Therefore, the inspection method of the present invention is not the expansion and contraction due to the magnetic strain of the entire magnetic body, but the fatigue level is inspected by comparing the expansion and contraction of each part of the magnetic body, that is, the distribution of the magnetic strain of the magnetic body. Even when the direction of the internal stress is different, it can be accurately inspected.

The best mode for carrying out the present invention will be described below with reference to the drawings.
According to the method of the present invention, an elastic wave is propagated and reflected in a magnetic material in a state in which a constant bias magnetic field is applied along the longitudinal direction of the magnetic material to be measured as described in Patent Document 1. A method is used in which a standing wave is generated to generate an oscillating magnetic field, and the effective magnetic field is measured by measuring the oscillating magnetic field at the position of the node of the standing wave as an induced electromotive force. For details, please refer to Patent Document 1 for details.
Stressed σ in the magnetic, the addition of mechanical strain epsilon the magnetic, epsilon is accompanied by an equivalent strain in the magnetostrictive lambda, as a result, the anisotropic magnetic field H _e occurs. Since this effect is the opposite of mechanically distorting a magnetic material by applying a magnetic field, it is called an inverse magnetostriction effect.
Next will be described the magnitude and direction of the anisotropic magnetic field H _e. By applying the stress σ, magnetoelastic energy _Ke is generated in the stress field of the magnetic material. This effect is called an inverse magnetostriction effect, and is expressed by equation (1) in the case of an isotropic magnetic material.
K _e = − (3/2) λσcos ² φ (1)
Here, λ is the amount of magnetostriction, and φ is the angle between the stress σ and the magnetization I. The magnitude of the anisotropy field H _e is expressed by the following equation.
H _e = 2K _e / I (2)
Direction of the anisotropic magnetic field H _e is (1) a direction magnetoelastic energy K _e is the smallest, magnetic moment per unit volume, i.e. the magnetization (magnetic moment) I becomes the K _e is minimum rotates in the direction, the direction of the rotated magnetization I becomes the direction of the anisotropic magnetic field H _e.

FIG. 1 is a diagram for explaining a phenomenon when a bias magnetic field is applied to a magnetic body and an elastic wave is propagated from one end of the magnetic body. In the figure, an elastic wave generator 12 is disposed at one end 11 of the magnetic body 10, and an absorber 15 that absorbs an elastic wave 14 is disposed at the other end 13 of the magnetic body 10. Arrows in the figure represent the magnetic moment 16 of the magnetic body 10 are oriented in the direction of the outline bias field H _DC.

When the elastic wave 14 is generated from the elastic wave generator 12, the elastic wave 14 propagates in the magnetic material. In the figure, 14a indicates the tension portion of the propagating elastic wave, and 14b indicates the pressure portion.
When the stress σ is positive (stress in the state where tension is applied), the magnetic material has a positive magnetostriction (magnetic material that increases the magnetic field due to the inverse magnetostriction effect), that is, the magnetic material has a positive magnetostriction constant. Since the angle φ formed by the stress σ at which the magnetoelastic energy K _e is minimum and the magnetic moment 16 is φ = 0 or π from the above equation (1), as shown in 14a of FIG. In addition, the magnetic moment 16 is parallel to the propagation direction of the elastic wave. Similarly, the angle φ at which the magnetoelastic energy _Ke is minimum when the stress σ is negative (stress that is contracted by pressure) is φ = π / 2 or 3π / 2. As indicated by 14b of 1, the magnetic moment 16 is perpendicular to the propagation direction of the elastic wave. Since the elastic wave 14 propagates, the magnetic moment 16 oscillates in time in the parallel and vertical directions at one point of the magnetic body 10, and an oscillating magnetic field can be generated in the magnetic body.
In the case of a magnetic material having a negative magnetostriction constant, the magnetic moment of the portion where the stress σ is negative is parallel, and the magnetic moment of the portion where the stress is positive is perpendicular.

In FIG. 1, reference numeral 17 denotes a coil formed by surrounding a magnetic body, which is fixed to one point of the magnetic body 10. Along with the propagation of the elastic wave 14, an oscillating magnetic field is generated by the inverse magnetostriction effect, and this oscillating magnetic flux is interlinked since 17 induced electromotive force is generated, oscillating magnetic field amplitude generated in the magnetic body, i.e., it is possible to measure the anisotropy magnetic field H _e. That is, induced electromotive force is proportional to the anisotropy field H _e and the frequency of the acoustic wave shown in equation (3), the anisotropic magnetic field H _e from the frequency of the measured induced electromotive force and the elastic wave I can know.

However, as a first problem, the elastic wave is attenuated as it propagates, and an equivalent stress cannot be applied to each part of the magnetic material.
As a second problem, the electromotive force based on the movement of the magnetic field source in the magnetic field gradient is added to the induced electromotive force in addition to the electromotive force based on the time variation of the magnetic flux. Can not measure only. That is, the electromotive force e induced in the coil 17 is expressed as follows: Φ is a magnetic flux interlinking with the coil 17, t is time, x is a position coordinate, and v is a speed at which the oscillating magnetic field passes through the coil.
e = − (∂Φ / ∂t) − (∂Φ / ∂x) · v (3)
It is represented by When an external magnetic field is applied to the magnetic body 10, a magnetic pole is generated on the end face of the magnetic body, and a magnetic flux gradient (∂Φ / ∂x) exists near the end face of the magnetic body due to the demagnetizing field effect. ) Is unknown, the magnetic flux Φ cannot be obtained from the electromotive force e. Therefore, an accurate effective magnetic field cannot be obtained in the vicinity of the end face of the magnetic material.
These problems can be solved as follows.

FIG. 2 is a diagram showing a configuration in which a standing wave is formed by resonating an elastic wave in a magnetic material. FIG. 2A shows the configuration of the measurement system, in which an elastic wave generator 12 is disposed at one end 11 of the magnetic body 10, and a needle-like mechanical fixed end 30 is disposed at the other end 13 of the magnetic body 10. Is attached. In the figure, reference numeral 31 represents an incident elastic wave generated by the elastic wave generator 12, and reference numeral 32 represents a reflected elastic wave reflected by the other end 13 of the magnetic material.
According to this configuration, the one end 11 and the other end 13 of the magnetic body 10 function as free ends of elastic waves, and a standing wave is formed in which the one end 11 and the other end 13 are antinodes. The coil 17 is configured to surround the magnetic body 10. The coil 17 moves along the traveling axis of the elastic wave, and is different due to the inverse magnetostrictive effect generated in the nodes of the standing waves generated in the magnetic body 10. The induced electromotive force based on the isotropic magnetic field is measured.

FIG. 2B schematically shows a standing wave formed in the configuration of FIG. 2A. The vertical line 33 represents an atomic plane, and the portion where the density of the vertical line 33 is high is as follows. It represents that the magnetic body 10 is contracted by receiving a compressive force from the standing wave, and a portion where the density of the vertical lines 33 is small indicates that the magnetic body is stretched by receiving tension from the standing wave. The atoms located at the antinodes of the standing wave are displaced in the same direction all at once, so no stress is generated. In FIG. N. (Compression node) and T.W. N. As shown by (tensile node), the node (CN) in which the magnetic material is compressed and the node (TN) in which the magnetic material is pulled are alternately arranged.
FIG. 2C shows the distribution of the stress σ generated by the standing wave in the magnetic body 10, where the positive region represents compressive stress and the negative region represents tensile stress.
As shown in the figure, since the standing wave is formed by combining the incident wave 31 and the reflected wave 32, the standing wave is not affected by the attenuation in the magnetic body due to the propagation of the elastic wave, but at any part in the magnetic body. Equivalent stress can be generated. Therefore, the first problem is solved.
Furthermore, although the electromotive force e induced in the coil is expressed by the above equation (3), since the standing wave is used in the present invention, the velocity v at which the oscillating magnetic field passes through the coil 17 is zero, and the magnetic flux Only the electromotive force based on the temporal change (∂Φ / ∂t) of the magnetic flux can be measured without being affected by the gradient (∂Φ / ∂x), and the second problem is solved.

Therefore, a method for measuring magnetostriction by the elastic wave standing wave method of the present invention using the above elastic wave standing wave method will be described. The method of the present invention comprises the following steps.
(1) With respect to the magnetic substance to be measured, the magnetostriction and effective are effective under the condition that the demagnetizing field effect is negligible and the applied magnetic field is equal to the effective magnetic field or the demagnetizing factor is known and the effective magnetic field can be calculated from the applied magnetic field. The relationship with the magnetic field, that is, the magnetostriction characteristic is measured.
(2) With respect to the magnetic substance to be measured, the demagnetizing effect can be ignored, and therefore, the induced electromotive force can be calculated under the condition that the applied magnetic field is equal to the effective magnetic field or the demagnetizing factor is known and the effective magnetic field can be calculated from the applied magnetic field. Measure the relationship with the effective magnetic field.
(3) An induced electromotive force is measured at an arbitrary portion of the magnetic substance to be measured, and an effective magnetic field is obtained from the relationship between the induced electromotive force and the induced electromotive force obtained in (2) and the effective magnetic field. The magnetostriction amount is obtained from the magnetostriction characteristics obtained in 1).
That is, the (1), as can be seen from equation (2), the anisotropic magnetic field H _e, i.e., in order to obtain the effective magnetic field, it is necessary to know the magnetostriction λ and the magnetization I. In Patent Document 2, the magnetostriction curve and the magnetization curve are measured under conditions where the demagnetizing field effect can be ignored and the applied magnetic field is equal to the effective magnetic field or the demagnetizing factor is known and the effective magnetic field can be calculated from the applied magnetic field. However, in order to measure the magnetization curve, a dedicated measuring device is required, which is not simple. Therefore, in the method of the present invention, instead of the magnetization curve, the demagnetizing field effect can be ignored, so that the applied magnetic field is equal to the effective magnetic field, or the demagnetizing coefficient is known and the effective magnetic field can be calculated from the applied magnetic field. The relationship between the induced electromotive force and the effective magnetic field is obtained for one point of the measured magnetic body, and in actual measurement, the effective magnetic field is obtained from the measured induced electromotive force and the relationship, and the effective magnetic field and the previously obtained magnetostriction are calculated. The amount of magnetostriction is obtained from the curve.
The magnetostriction curve can be measured relatively easily using a general strain gauge.

Next, an example is shown.
An iron square bar having a square section of 5 mm on a side and a length of 100 m was heat-treated to obtain a magnetic substance to be measured, and measurement was performed with the measurement system shown in FIG. The measurement position is the center position of the square bar. At this position, the demagnetizing field effect can be ignored, and the applied magnetic field is equal to the effective magnetic field. For the acoustic wave generator 12, an ultrasonic transducer (resonance frequency: 1 MHz) was used, which was brought into close contact with one end of the magnetic material to be measured. The other end was an open end.

First, the effective magnetic field dependence of the induced electromotive force due to the magnetostriction curve and the standing wave in the magnetic material to be measured was obtained. The effective magnetic field dependence of the induced electromotive force is measured by the coil 17 while changing the applied magnetic field at the position of the central node at the same distance from both ends of the magnetic material in the measurement system of FIG. I went and asked. In addition, the magnetostriction curve is obtained by measuring the magnetostriction by the strain gauge method while changing the applied magnetic field at the position of the central node at the same distance from both ends of the magnetic material in the measurement system of FIG. Asked.
FIG. 3 is a diagram showing a result of the effective magnetic field dependence of the magnetostriction curve and induced electromotive force of the magnetic substance to be measured in the example of the present invention. The left vertical axis is magnetostriction, the right vertical axis is induced electromotive force [mV], and the horizontal axis is effective magnetic field.

Next, in the measurement system of FIG. 2A, a constant magnetic field is applied to the magnetic material to be measured where a standing wave is formed, and the position of the coil 17 is changed in the direction of the propagation axis of the elastic wave. The induced electromotive force of each part of the magnetic material was measured. At this time, the externally applied magnetic field was 13.4 kA / m. Since the frequency of the elastic wave was 354 kHz and the wave number was 6.5 m ⁻¹ , the wavelength was 15.4 mm and the velocity was 5450 mm / s. A coil having a diameter of 7.2 mm, a thickness of 1 mm, and a winding number of 100 was used as the coil 17.

  FIG. 4 is a diagram showing the distribution of the induced electromotive force at each position in the longitudinal direction of the magnetic substance to be measured in the example of the present invention. In the figure, the horizontal axis represents each part of the magnetic substance to be measured, that is, the position [mm] of the detection coil 17 when one of the longitudinal directions of the magnetic substance to be measured is positive and the center is zero. The vertical axis represents the induced electromotive force [mV]. Moreover, the arrows in the figure are 1.75 wavelengths from the center in the longitudinal direction of the magnetic substance to be measured, that is, ± 27 mm, and the sign of the standing electromotive force of the node of the standing wave is inverted. It is a place.

FIG. 5 shows the envelope of the measured value of the antinode of the standing wave of the measurement data of FIG. The horizontal axis represents each position of the magnetic body when one of the longitudinal directions of the measured magnetic body is the positive direction and the center is zero, that is, the position [mm] of the detection coil 17, and the vertical axis represents the induction Electric power [mV]. FIG. 5 shows the induced electromotive force at a desired position of the magnetic material, and the effective magnetic field is found from the relationship between the induced electromotive force and the induced electromotive force and the effective magnetic field in FIG. 3, and the effective magnetic field and the magnetostriction in FIG. From the relationship with the effective magnetic field, the amount of magnetostriction at a desired position of the magnetic material can be found.
For example, an induced electromotive force of 0 mV corresponds to an effective magnetic field of about 4 kA / m, and an effective magnetic field of 4 kA / m corresponds to a magnetostriction of about 3 × 10 ⁻⁶ , so that the magnetostriction at a portion 27 mm from the center of the magnetic substance to be measured is It can be determined that the elongation is about 3 × 10 ⁻⁶ .
The induced electromotive force of 120 mV corresponds to an effective magnetic field of about 20 kA / m, and the effective magnetic field of 20 kA / m is required to be about 5 × 10 ^−6. Therefore, at the center of the measured magnetic material, the magnetostriction is about 5 × 10 ^-6 shrinkage can be obtained.
Thus, the magnetostriction can be obtained for each node. Also, various stresses such as tension and compression at each part can be evaluated with the wavelength of the standing wave as a unit.

Next, the stress inspection method of the present invention using the magnetostriction measuring method by the elastic wave standing wave method will be described.
This measurement method uses the magnetostriction measurement method based on the elastic wave standing wave method for the magnetic material in the initial state and the magnetic material in a fatigued state by applying mechanical stress. The magnetic strain distribution in the direction is measured, the magnetostriction distribution of the magnetic material in the initial state is compared with the magnetic strain distribution of the magnetic material in the fatigued state, and the degree of the fatigued state is determined.

According to this inspection method, the fatigue state of the magnetic material can be accurately determined. That is, when a mechanical stress is applied to the magnetic material, the stress is inherent in the magnetic material, and if the stress exceeds a certain value, breakage such as breakage is likely to occur. The fatigue state of the magnetic material can be known before destruction. When stress is inherent in the magnetic body, the magnetostriction characteristics change. Therefore, the degree of fatigue can also be determined by applying a magnetic field to the magnetic body and measuring the expansion and contraction due to the magnetostriction of the entire magnetic body. However, depending on the type of stress applied to the magnetic material, the direction of the stress varies depending on the part of the magnetic material, and the expansion and contraction of the entire magnetic material may not necessarily be proportional to the degree of fatigue.
Therefore, the inspection method of the present invention is not the expansion and contraction due to the magnetic strain of the entire magnetic body, but the fatigue level is inspected by comparing the expansion and contraction of each part of the magnetic body, that is, the distribution of the magnetic strain of the magnetic body. Even when the direction of the internal stress is different, it can be accurately inspected.

As can be understood from the above description, the relationship between the effective magnetic field of the magnetic substance to be measured, the magnetostriction, and the induced electromotive force is obtained, and the induction in each part in the longitudinal direction of the magnetic substance to be measured placed in a constant magnetic field. By detecting the magnetic field, the magnetostriction of each part in the longitudinal direction of the magnetic substance to be measured can be evaluated based on the above relationship. Therefore, it is possible to obtain the expansion / contraction at each part of each magnetic substance to be measured, not the amount of expansion / contraction of the whole magnetic substance to be measured.
Therefore, it is extremely useful when used for nondestructive inspection of various magnetic materials.

It is a figure explaining the phenomenon when a bias magnetic field is applied to a magnetic body and an elastic wave is propagated from one end of the magnetic body. It is a figure which shows the structure which resonates an elastic wave in a magnetic body, and forms a standing wave, (a) is a block diagram of a measurement system, (b) is a schematic diagram of the standing wave formed, (c) is It is a distribution map in the magnetic body of the stress generated by standing waves. It is a figure which shows the magnetostriction curve of the magnetic body in the Example of this invention, and the effective magnetic field dependence of an induced electromotive force. It is a figure which shows distribution of the induced electromotive force in each position of the longitudinal direction of a to-be-measured magnetic body in the Example of this invention. It is a figure which shows the envelope of the induced electromotive force in the position of the antinode of a standing wave in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic body 11 One end 12 Elastic wave generator 13 Other end 14 Elastic wave 14a Elastic wave tension | tensile_strength part 14b Elastic wave pressure part 15 Elastic wave absorber 16 Magnetic moment 17 Coil 30 Mechanical fixed end 31 Incident elastic wave 32 Reflective elasticity Wave 33 Atomic plane C.I. N. Compressed clauses N. Pulled node H _DC external magnetic field

Claims (2)

Determining the effective magnetic field dependence of the induced electromotive force while changing the applied magnetic field at the position of the central node equidistant from both ends of the magnetic substance to be measured;
Obtaining the effective magnetic field dependence of magnetostriction while changing the applied magnetic field at the position of the central node equidistant from both ends of the magnetic substance to be measured;
In a state where a constant magnetic field is applied along the longitudinal direction of the magnetic substance to be measured, an elastic wave is propagated and reflected in the magnetic substance to form a standing wave in the magnetic substance to be measured to generate an oscillating magnetic field. Measuring the induced electromotive force in each part in the longitudinal direction of the magnetic substance to be measured while changing the position of the coil in the propagation axis direction of the elastic wave;
From the distribution of the induced electromotive force at each position in the longitudinal direction of the magnetic substance to be measured, the envelope of the measured value of the antinode of the standing wave is obtained, and the value of the induced electromotive force at each position obtained from the envelope, From the effective magnetic field dependence of the induced electromotive force and the effective magnetic field dependence of the magnetostriction, obtaining a magnetostriction at each position to obtain a magnetostriction distribution;
A magnetostriction distribution measuring method by an elastic wave standing wave method. The magnetic body in an initial state and the magnetic body in a fatigued state by applying mechanical stress, respectively, using the magnetostriction distribution measuring method by the elastic wave standing wave method according to claim 1, Measuring the longitudinal magnetostriction distribution and comparing the magnetostriction distribution of the magnetic substance in the initial state with the magnetostriction distribution of the magnetic substance in the fatigued state to determine the fatigued state. Stress inspection method using magnetostriction distribution measurement method by standing wave method.

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