JPH02223834A - Probe for stress measurement - Google Patents

Abstract

PURPOSE:To measure two-axial stress by applying a sound elastic method to a measurement principle by arranging a longitudinal wave probe coil and two transversal wave probe coils so that two transversal ultrasonic waves and a longitudinal ultrasonic are generated having nearly equal levels at the same time. CONSTITUTION:A magnet 1 has an N pole and an S pole whose magnetic pole surfaces 1a and 1b are close to each other on the same plane and is arranged facing the surface of a material 2 to be inspected. Therefore, the longitudinal wave probe coil 3 which has only a superposition part nearby and along the border between both the magnetic poles is positioned in an intense parallel magnetic field. Almost the whole of the superposition part of a transversal wave probe coil 4 which has the superposition part perpendicularly to the arrangement direction of both the magnetic electrodes and the majority of the superposition part of the transversal wave probe coil 5 which has the superposition part in the arrangement direction of both the magnetic poles are positioned in an intense vertical magnetic field at a distance from the border. Consequently, two transversal ultrasonic waves whose deflection direction cross each other at right angles and the longitudinal ultrasonic wave traveling in the same direction with them are generated at nearly the same positions and at the same time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method of measuring each axial stress of a material to be inspected in a state of biaxial stress.
This invention relates to a stress measurement probe that measures using the anoelastic method as the measurement principle.

[Prior art]

As a method of measuring each axial stress of a material to be inspected which is in a state of biaxial stress, the sound velocity of two transverse waves VTl+vT2 which are deflected in the two directions of the principal stress inside the fragrance material to be tested, and which travel in the same direction as these waves is used. There is an asono-elastic method that uses the sound velocity of longitudinal waves.

To briefly explain the principle of this anoelastic method, first, the material to be tested whose stress is to be measured is a material having orthogonal anisotropy, and the axis of anisotropy and the principal stress If the directions match, the two principal stresses σ1. The difference between σ2 is the sound velocity of the transverse wave VTI, v, □
In proportion to the difference between the two, the following relationship, which is called the birefringence law of acoustic elasticity, holds true between the two.

= α + CA (σ1 - σ2) ... (11 However, VTI, v, □. are the sound speeds of the two transverse waves in the stress-free state, CA is the acoustic elastic constant, and α is the tissue effect. Yes, it can be calculated using the following formula.

In addition, when the material to be inspected is a material having weak orthotropy, the ratio between the sound speed V of the longitudinal wave and the average sound speed of both the transverse waves (sound speed ratio), and the principal stress σ1. The relationship shown in the following equation, which is called the sonic law of sound-stopping elasticity, holds true between the sum of σ2 and the sum of σ2.

(VTI + VT2) / 2 = Ro + CR (σ1 + σ2) ... (
3) However, CR is the sound velocity ratio constant, and Ro is the sound velocity ratio in a stress-free state, which is determined by the following formula.

It is difficult to directly measure the sound velocity ■Tl+VTRrv, and these sound velocities in equations +1) and (3) can be calculated using the respective propagation times T inside the flavoring material to be tested.
The following equation obtained by replacing t r , T tz , and T L is actually used in place of equations (11 and (3)).

(TTI+T?□)/2 ζα+CA (σ1-σ2) ...(5)
TL'RO+CM(σ, +σ2)...(6)
That is, in the acoustoelastic method, the measured values of the propagation times Tt+, TT□, and TL in the material to be inspected are expressed by equations (5) and (
6) Substitute them into the equations respectively, and convert both equations into σ1. By solving the equation as a two-dimensional simultaneous equation with σ2 as an unknown, the principal stress of each axis inside the tested fragrance material which is in a state of biaxial stress can be determined. Therefore, this anoelastic method can be used when the material to be tested satisfies the conditions for formula +11 and equation (3) above, that is, the material to be tested is a material with weak orthogonal anisotropy, and the two directions of principal stress are This method is applicable only when the axes of anisotropy coincide with each other.

A rolled material having anisotropic axes in the rolling direction and a direction orthogonal thereto is a material that satisfies the above conditions, and in the inspected material made of rolled material, the stress in each axis is measured by the anoelastic method described above. is possible.

Therefore, when measuring the axial stress generated in a railway rail due to thermal expansion and predicting the bending of the rail, it is also possible to measure the circumferential stress generated in a wheel for a railway vehicle manufactured by press rolling. When measuring and predicting breakage of the wheel, it is effective to apply the acousto-elastic method, and it is possible to measure the stress on each axis, so it is possible to measure the stress on each axis. This has the excellent effect of making it possible to correct errors occurring in the measurement results of the axial stress or circumferential stress.

[Problem to be solved by the invention]

As described above, the application of the acousto-elastic method is effective for inspected materials made of rolled material that are in a state of biaxial stress, and its application is strongly desired. However, in order to measure each axial stress by applying the acousto-elastic method, as mentioned above, two transverse ultrasonic waves deflected in the directions of the two principal stresses, and a longitudinal wave traveling in the same direction as these are required. It is necessary to propagate ultrasonic waves into the material to be inspected, and it has traditionally been difficult to achieve this at approximately the same location in the material to be inspected. At present, the application of the elastic method has not been realized.

The present invention has been made in view of such circumstances, and includes two transverse ultrasonic waves deflected in two directions perpendicular to each other,
It is possible to generate these and longitudinal ultrasound waves traveling in the same direction alternately at approximately the same location and at the same time with a simple configuration, and in the biaxial stress field using the acousto-elastic method. It is an object of the present invention to provide a stress measurement probe that can be effectively used to measure stress in each axis.

[Means to solve the problem]

The stress measurement probe according to the present invention has positive and negative magnetic poles whose respective magnetic pole surfaces are in the same plane and are close to each other within the plane, and both magnetic pole surfaces are opposed to the surface of the material to be inspected. A magnet is disposed between both the magnetic pole faces and the surface of the material to be inspected, and in a range overlapping with the magnetic poles in plan view, near the boundary between the magnetic poles, a probe coil for longitudinal waves having only a portion along the boundary; and a first probe coil for transverse waves having a straight portion that overlaps with one of the magnetic poles at a position away from the vicinity of the boundary and is orthogonal to the direction in which the magnetic poles are arranged side by side. and a second transverse wave probe coil that overlaps the two magnetic poles and has a straight portion along the direction in which the two magnetic poles are arranged side by side.

[Effect]

In the present invention, near the boundary between both magnetic poles of the magnet, a synergistic effect of a magnetic field formed parallel to each magnetic pole surface and an electric field formed by the longitudinal wave probe coil causes longitudinal wave ultrasonic waves to be generated. A sound wave is generated, and a reflected wave of the longitudinal ultrasound wave from the inspected material is received by the probe coil,
This is converted into a current flowing through it. Further, in a portion other than the vicinity of the boundary, a magnetic field is formed in a direction perpendicular to the magnetic pole face of each of the magnets, and a magnetic field is formed in a direction perpendicular to the magnetic pole face of each of the magnets. Due to the synergistic effect with the electric field formed by the second transverse wave probe coil, two transverse ultrasonic waves deflected in mutually orthogonal directions are generated,
The reflected waves of the transverse ultrasonic waves from the inspected material are received by the probe coils and converted into electric currents flowing therethrough.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. 1 and 2 are schematic side views of a stress measuring probe according to the present invention.

The stress measurement probe according to the present invention has each magnetic pole surface 1a
, lb have a positive pole (N pole) and a negative pole (S pole) that are close to each other in the same plane, and both magnetic pole faces la and lb are placed on the surface of the material 2 to be inspected whose stress is to be measured. On the other hand, magnets 1 are arranged so as to face each other substantially parallel to each other with an appropriate distance apart, and are parallel to the magnetic pole faces la and lb, respectively,
The magnet 1 and the material to be inspected 2 are stacked on each other in the thickness direction.
A longitudinal wave probe coil 3 and two transverse wave probe coils 4 and 5 are provided.

As shown in FIG. 1, the magnet 1 is made up of two permanent magnets 10 and 11 in the shape of a rectangular bar, which are attached to each other in such a manner that the positive pole of the former and the negative pole of the latter are adjacent to each other in the same plane. As shown in FIG. 2, an excitation coil 13 is wound around an iron core 12 having both end portions adjacent to each other in the same plane, and each end surface is a positive pole. It may have any configuration, such as one configured as an electromagnet serving as a negative electrode. Both magnetic poles of the magnet 1 are preferably placed in close contact with each other as shown in FIG. 1, but may be placed close to each other with an appropriate gap as shown in FIG. is a very small value that does not exceed a predetermined range (for example, within 2+ nm).Also, the stacking order between the longitudinal wave probe coil 3 and the transverse wave probe coil 4.5 is as shown in FIGS. 1 and 2. Not limited to the order shown.

FIG. 3 is a plan view showing the positional relationship of the longitudinal wave probe coil 3 with respect to the magnet 1, and FIGS. 4 and 5 are plan views showing the positional relationship of the transverse wave probe coil 4.5 with respect to the magnet 1. It is a diagram.

As shown in the figure, the longitudinal wave probe coil 3 has a pair of semicircular parts 3a and 3a facing each other on their concave sides, and straight parts 3b and 3c connecting both ends of these parts, and has a long length. It has an annular planar shape, and one straight portion 3b overlaps the magnet 1 in a plan view near the boundary between both magnetic poles of the magnet 1 in a manner along the boundary, and the other portion, i.e. The other straight portion 3c and semicircular portion 3a.

3a and the magnet 1 are arranged so that no overlapping portion occurs. Each of the sections of the longitudinal wave probe coil 3 has a narrow width so that the straight section 3b can be overlapped. In FIG. 3, since the boundary between the two magnetic poles of the magnet 1 is a straight line, the part that overlaps the magnet 1 along the boundary is also a straight part 315, but it is assumed that the boundary is curved. In this case, the overlapping portion of the longitudinal wave probe coil 3 with the magnet 1 is also configured to have a curved shape corresponding to the boundary shape. Further, the planar shape of the longitudinal wave probe coil 3 is not limited to the oval shape shown in FIG.
(b), as long as it has only a portion near the boundary between both magnetic poles of the magnet l and along the boundary, it may have another planar shape.

Further, as shown in FIG. 4, the first transverse wave probe coil 4 includes a pair of semicircular portions 4a, 4a and a straight portion 4b connecting both ends of these, similarly to the longitudinal wave probe coil 3. . The other linear portion 4c is arranged to overlap the positive pole and the negative pole at a position outside the vicinity of the boundary between both magnetic poles. It is desirable that each part of the transverse wave probe coil 4 has a wide width as shown in the figure so that the above-mentioned overlapping state with the magnet 1 can be realized over a wide range. An essential requirement for the transverse wave probe coil 4 is that it overlaps with the magnet 1 in a portion outside the boundary between both magnetic poles and is perpendicular to the direction in which both magnetic poles are arranged in parallel, that is, at least one of the straight portions 4b and 4c. The planar shape of the transverse wave probe coil 4 is not limited to the oval shape shown in FIG. 4 as long as it satisfies this requirement.

Furthermore, as shown in FIG. 5, the second transverse wave probe coil 5, like the longitudinal wave probe coil 3 and the transverse wave probe coil 4, has a pair of semicircular parts 5a, 5a and a space between the respective ends thereof. It has linear parts 5b and 5c connected to each other, and has an elliptical planar shape, and the straight part 5b is arranged so as to overlap these along the direction in which both magnetic poles of the magnet 1 are arranged side by side. ing. Like the transverse wave probe coil 4, each part of the transverse wave probe coil 5 is desirably wide in order to realize the above-mentioned superimposed state over a wide range. An essential requirement for the transverse wave probe coil 5 is that it has a portion that overlaps with the magnet 1 along the direction in which both magnetic poles are arranged side by side, that is, the straight portion 5b, and the plane of the transverse wave probe coil 5 is The shape is not limited to the oval shape shown in FIG. 5 as long as it satisfies this requirement.

The operation of the stress measurement probe according to the present invention constructed as described above will be explained next.

FIG. 6 is a graph showing the measurement results of the magnetic field formed on the side of the material to be inspected 2 by the magnet work having the above-mentioned configuration. In the present invention, as a result of the positive pole surface 1a and the negative pole surface 1b of the magnet 1 being placed close to each other in the same plane,
In the magnet 1, as shown in FIG. 6, a strong magnetic field parallel to the magnetic pole faces 1a and 1b is applied near the boundary between the two magnetic poles, and a strong magnetic field perpendicular to the area other than the vicinity of the boundary is applied. are formed respectively. Therefore, the longitudinal wave probe coil 3 having only an overlapping part along the vicinity of the boundary is located in a strong parallel magnetic field, while a probe coil 3 for longitudinal waves having only an overlapping part along the vicinity of the boundary is located in a strong parallel magnetic field. substantially all of the superimposed part in the first transverse wave probe coil 4 having the superimposed part, and most of the superimposed part in the second transverse wave probe coil 5 which has the superimposed part along the direction in which both magnetic poles are arranged side by side. will be located within a strong vertical magnetic field. Therefore, when the longitudinal wave probe coil 3 is energized, the synergistic effect of the electric field thus formed and the parallel magnetic field causes a direction perpendicular to the magnetic pole faces 1a and Ib, that is, as shown in FIGS. In the arrangement shown in FIG. 2, longitudinal ultrasonic waves are generated that travel toward the surface of the material 2 to be inspected in a direction substantially perpendicular thereto. Further, when the transverse wave 7" tel-ficoil 4.5 is energized, different transverse ultrasonic waves are generated due to the synergistic effect of the electric field formed by each of them and the vertical magnetic field, and these two transverse wave ultrasonic waves are Sound waves are first and second
Since the superimposed portions of the probe coils 4.5 are orthogonal to each other, they have deflection directions that are orthogonal to each other, and their traveling directions are similar to the longitudinal ultrasound.
This is a direction perpendicular to the magnetic pole faces 1a and lb. The direction of deflection of the transverse ultrasound by the first transverse wave probe coil 4 is parallel to the direction in which both magnetic poles of the magnet 1 are arranged in parallel, and the direction of deflection of the transverse ultrasound by the second transverse probe coil 5 is as described above. Needless to say, it is perpendicular to the direction of parallel arrangement.

As described above, the stress measurement probe according to the present invention has a simple configuration and can transmit longitudinal ultrasound and two types of transverse ultrasound, which are necessary for implementing the sound intensity method, at substantially the same position. They can be generated simultaneously and alternately, and the reflected waves of the longitudinal ultrasonic waves and the two types of transverse ultrasonic waves from the inspected material 2 are transmitted through the longitudinal wave probe coil 3 and the first . When the probe coil 4.5 for transverse waves reaches the second transverse wave probe coil 4.5, it is converted into the respective energizing currents and received. The propagation time of the transverse ultrasonic wave of the species, that is, the f51. (TL, 'rye, and TT□ in Equation 61 are recognized, and using these, it is possible to obtain the two principal stresses σ1σ2 inside the fragrance material 2 to be tested. In this way, the principal stresses σ1 and σ2 are obtained. In order to do this, as mentioned above, it is necessary that these directions and the deflection directions of the two types of transverse ultrasonic waves coincide with each other. is realized by aligning the parallel direction of both magnetic poles of the magnet 1 or the direction orthogonal to this with the longitudinal direction of the rail, and when measuring residual stress in the circumferential direction in wheels for railway vehicles. This is realized by making the juxtaposition direction and the direction perpendicular thereto coincide with the circumferential direction and the radial direction of the wheel, respectively.

FIG. 7 is a block diagram showing the configuration of a biaxial stress measuring device using the stress measuring probe according to the present invention.

The stress measuring probe according to the present invention is disposed as described above close to the surface of the inspected material 2, which is the object to be measured, and includes a longitudinal wave probe coil 3 and two transverse wave probe coils 4. , 5 are separate pulse generating circuits 23 .
24 and 25, respectively, and the short-time pulse current generated by these is applied. The pulse generation circuits 23, 24, and 25 are respectively connected to the trigger circuit 20 via the changeover switch 21.
The trigger signal emitted by the pulse generating circuits 23, 24.
5, each of which outputs one pulse current in response to the 1-IJ signal. Then, the longitudinal ultrasonic waves emitted from the longitudinal wave probe coil 3 as described above due to the application of this pulse current are reflected on the back surface of the fragrance material 2 to be tested, and are returned to the installation position of the longitudinal wave probe coil 3. The two types of transverse ultrasonic waves that are received by the transverse wave probe coils 4 and 5 and separately emitted from the two transverse wave probe coils 4 and 5 as the pulse current is applied are also reflected on the back surface of the fragrance material 2 to be tested. After that, the signals are received by both probe coils 4 and 5, respectively. The reception signal emitted by the longitudinal wave probe coil 3 in response to this reception is sent to the reception amplification circuit 26, and
Similarly, the reception signals emitted by the transverse wave probe coils 4.5 are given to the reception amplifier circuit 27 via the changeover switch 28, and these reception signals amplified by the reception amplifier circuit 26 or 27 are used for timekeeping. Part 3o is given.

A trigger signal generated by the trigger circuit 2° is also applied to the timer 30, and the timer 30 measures the time from when the trigger signal is applied to when the corresponding received signal is applied. .

The time point at which the trigger signal is generated is determined by the pulse generation circuit 23.
．． 24 or 25, in other words, substantially coincides with the generation time of the ultrasonic wave from the longitudinal wave probe coil 3 or the transverse wave probe coil 4 or 5, and furthermore, the received signal is a longitudinal wave The time measured by the timer 30 corresponds to the round-trip propagation time of the longitudinal ultrasonic wave inside the fragrance material 2. TL, and the round trip propagation time of the two types of transverse ultrasonic waves ′F
Corresponds to AtTTZ. These timing results in the timer 30 are given to the calculation unit 31, and the calculation unit 31 uses the values of Ta, TT□, and TL to calculate the above-mentioned (5).
) The principal stresses σ1 and σ2 inside the fragrance material 3 to be tested are calculated using the following equation obtained by modifying equation (6).

...(7) ...(8) As is clear from equations (2) and (4), α and Ro in these equations are the sound velocities of the two types of transverse ultrasonic waves in a stress-free state, respectively. ■Tl' + 'VT□, and the sound velocity of longitudinal ultrasound ■. Since this value is determined by
It is only necessary to input it to the calculation unit 31.

Furthermore, CA and CR in equations (7) and (8) are constants as described above, and these values are also
1 has been entered in advance. Note that the calculation result by the calculation unit 31 is given to the display unit 32 and displayed there.

FIG. 8 is a graph showing the results of measuring the residual stress in the circumferential direction of a railway vehicle wheel using the biaxial stress measuring device configured as described above. The vertical axis of this figure shows the measurement results by the above device, and the horizontal axis shows the results of circumferential stress measured using a strain gauge attached to the wheel simultaneously with the above measurements.

As is clear from this figure, there is a good relationship between the stress measurement results by the acousto-elastic method performed using the stress measurement probe according to the present invention and the measurement results using a strain gauge. A good agreement was obtained, and the acousto-elastic method is a much simpler method than the stress measurement method using strain gauges. Therefore, when using the stress measurement probe according to the present invention, it is possible to The stress state can be measured accurately and easily.

〔effect〕

As detailed above, the stress measurement probe according to the present invention has
With a simple configuration, the two deflection directions are perpendicular to each other.
Since two transverse ultrasonic waves and a longitudinal ultrasonic wave traveling in the same direction can be generated simultaneously at approximately the same position, it is possible to measure biaxial stress using the acousto-elastic method as the measurement principle. 2
The present invention has excellent effects such as being able to measure each axial stress of a material to be inspected in a state of axial stress easily and with sufficient accuracy.

[Brief explanation of the drawing]

1 and 2 are schematic side views of the stress measurement probe according to the present invention, FIGS. 3 to 5 are schematic plan views showing the arrangement of the probe coil, and FIG. 6 is the magnet. 7 is a block diagram showing the configuration of a biaxial stress measuring device using the stress measuring probe according to the present invention, and FIG. 8 is a graph showing the results of stress measurement by the device. This is a graph showing. 1... Magnet 1a, lb... Magnetic pole surface 2...
Inspected material 3...Longitudinal wave probe coil 4.5...
・Probe coil agent for transverse waves Patent attorney Noboru Kono Condolence diagram Condolence diagram Condolence diagram Condolence diagram Condolence diagram! 00 Funeral map

Claims (1)

[Claims] 1. A magnet having positive and negative magnetic poles whose respective magnetic pole faces lie in the same plane, adjacent to each other within the plane, and with both of the magnetic pole faces facing the surface of the material to be inspected. and disposed between both the magnetic pole faces and the surface of the material to be inspected, and having only a portion along the boundary in the vicinity of the boundary between the magnetic poles, in a range that overlaps with the magnetic poles in plan view. a probe coil for longitudinal waves; a first probe coil for transverse waves that overlaps one of the two magnetic poles at a position away from the vicinity of the boundary and has a straight line portion perpendicular to the direction in which the two magnetic poles are arranged side by side; A stress measurement probe comprising: a second transverse wave probe coil superimposed on the second transverse wave probe coil having a straight line portion along the direction in which both the magnetic poles are arranged side by side.