JPH0762636B2 - Magnetostrictive stress measurement method for cylindrical materials - Google Patents

Description

TECHNICAL FIELD The present invention relates to a non-contact magnetostrictive stress measuring method for a cylindrical material such as a round bar and a pipe.

[Prior Art] When bending stress or axial stress is applied to a steel pipe or the like, in order to know the distribution state of the stress, in the conventional case,
For example, the X-ray stress measurement method is used. In this X-ray stress measurement method, when the crystal plane distance is d, and when the X-ray of wavelength λ is incident at an angle of θ with the plane, nλ = 2dsinθ when the direction of the diffracted X-ray is also θ Since there is a relationship of (n is a positive integer), if θ is measured by an X-ray with a known λ, then d can be obtained from this formula, and from this change of d, the stress is calculated by a calculation method. .

However, in this X-ray stress measurement method, it takes at least 1 hour to measure one point, and in the case of a steel pipe,
Since it is necessary to measure at least 4 points at 90 ° in the circumferential direction, it takes a long time to measure and the operation is complicated, so it is practically difficult to provide a large number of points.
Therefore, the number of data obtained was naturally limited.

On the other hand, regarding a general structure, the material is not uniform when viewed microscopically. Therefore, the stress data obtained by such point measurement cannot always be evaluated as the stress acting on the structure, and human or economic judgment is required.

Therefore, it is conceivable to use a magnetostrictive stress measuring method that is simpler than the X-ray stress measuring method.

In the magnetostrictive stress measurement method, when a load acts on a cylindrical material, anisotropy occurs in the magnetic permeability, the magnetic permeability in the load direction increases, and on the contrary, the magnetic permeability in the direction perpendicular to the load direction decreases. This is a method of measuring the direction and magnitude of the principal stress by detecting the difference with a magnetostrictive sensor having an exciting core and a detecting core. According to this measuring method, the measuring time for one point is 10 to 100 msec, and the handling is extremely convenient.

However, since the conventional magnetostrictive stress measurement method is generally performed by bringing the magnetostrictive sensor into contact with the non-measurement surface, the magnetic resistance at the contact surface greatly differs depending on the state of the measurement surface. Therefore, there is a drawback that the measurement error becomes large.

Therefore, the idea is to measure in a non-contact state, that is, in a state where the magnetostrictive sensor is separated from the surface to be measured by a certain distance, but in this case, the magnetostrictive sensitivity decreases, so when setting the magnetostrictive sensor. It has not been put to practical use because it requires extremely delicate adjustment.

[Problems to be Solved by the Invention] Therefore, the present invention has developed a device capable of performing a magnetostrictive stress measuring method for a cylindrical material in a non-contact method, and using the measuring device, a stress distribution at an arbitrary cross-sectional position of the cylindrical material. It is an object of the present invention to provide a method capable of highly accurately measuring.

[Means for Solving the Problem] In the magnetostrictive stress measuring method for a columnar material according to the present invention, a magnetostrictive sensor moves relative to the outer peripheral surface or the inner peripheral surface of the columnar material in a non-contact state while maintaining a constant distance. Using a measuring device, determine the output voltage of the magnetostrictive sensor at any cross-sectional position of the columnar material, and further approximate the output voltage to a sin curve, of the bending stress and bending moment acting on the cross section at that position. The feature is that the direction of action is obtained.

[Operation] Generally, the stress distribution when a bending load is applied to a cylindrical material as shown in Fig. 8 (a) is a sin curve as shown in Fig. 8 (b) when considering material mechanics. . When an axial load is applied in addition to the bending load, the neutral position of this sin curve moves upward or downward depending on whether the axial load is tensile or compressive. In the case of FIG. 8 (b), a tensile load is applied.

A similar sin curve can be obtained by measuring the magnetic anisotropy, that is, the magnetostriction of the cylindrical material over the entire circumference. If this is expressed by an equation, it can be expressed as follows.

V = Asin (θ + ω) + B (1) where V: Magnetostrictive sensor output voltage A: Amplitude B: Offset amount θ: Circumferential angle of cylindrical material ω: Phase shift Amplitude A in this equation is the magnitude of bending stress The offset amount B is a stress that is unrelated to the circumferential angle θ,
That is, it is considered to be a value that changes depending on the axial stress.
Further, the phase shift ω indicates the relative positional relationship between the measurement start point and the material mechanics neutral axis.

The diagram of the output voltage of the magnetostrictive sensor thus obtained usually contains ripples due to the non-uniformity of the material to be measured, so the statistical processing of the measurement data is carried out to smooth the ripple component. It is approximated to the above equation (1).

For example, when a moment is applied to a cylindrical material of a structural member such as a steel pipe and bending stress is generated, if the surface is measured with a magnetostrictive sensor, the output voltage of the magnetostrictive sensor will include the bending stress due to the bending moment of the external force. Will randomly include components due to residual stress. However, by approximating the measured value over the entire circumference to a sin curve as shown in equation (1), the bending stress distribution with periodicity and its direction (phase), the axial stress component without periodicity, or It can be decomposed and extracted into residual stress components.
Here, the amplitude A of the equation (1) is the bending stress acting on the cylindrical material (the maximum value of the stress generated by the bending moment).
Value, which is an important parameter for evaluating the safety of the material in terms of stress. Also, the phase ω
Is a parameter for judging the direction of bending (direction of action of bending moment) acting on the material. Therefore, the safety of the cylindrical material can be evaluated by evaluating the values of the amplitude A and the phase ω in the expression (1).

[Examples] Hereinafter, the present invention will be specifically described with reference to the drawings.

FIG. 1 is an explanatory view showing a non-contact type magnetostrictive stress measuring method for a cylindrical material such as a steel pipe. In the figure, 1 is a columnar material, 2 is a magnetostrictive sensor of the measuring device according to the present invention, which moves vertically to the columnar material 1 and in the circumferential direction while maintaining a constant height h from its outer peripheral surface 11. It has become.

2A to 2E are diagrams of the output voltage of the magnetostrictive sensor 2 thus obtained. In addition, each line diagram V _-20 , V
_As shown in FIG. 3, the stress values at ₋₁₀ , V ₀ , V ₊₁₀ , and V ₊₂₀ are such that one end of the steel pipe 1 is fixed to the rigid wall 3 and the other end is connected to the rod 5 of the hydraulic cylinder 4. It is a value obtained by the strain gauge 6 attached to the uppermost point of the steel pipe 1, that is, the 0 ° position when the lever rod 5 is moved up or down. Magnetostrictive sensor 2
Makes one round around the steel pipe 1 in the vicinity of the strain gauge 6.

As can be seen from FIG. 2, the output voltage of the magnetostrictive sensor 2 shows the same sign corresponding to the sign of the stress in the upper half part and the lower half part of the steel pipe 1, and its amplitude value changes with the magnitude of the stress value. Is changing. That is, this output voltage generally shows a tendency of a sin curve, and well shows the change of the amplitude due to the bending stress difference. However, since many ripples due to the non-uniformity of the measured material are recognized, it is necessary to remove this ripple component. For that purpose, statistical processing of data is performed using a micro computer or the like. For example, data for every 1 ° is extracted from the above measurement data, processed by the least square method, and the ripple component is smoothed by approximating the above equation (1).

The sin curve thus obtained is shown in FIG.
Curves A _-20 , A _-10 , A ₀ , A ₊₁₀ , A ₊₂₀ respectively added to (e)
Is.

As described above, the stress actually acting on the cylindrical material 1 as the structural member can be continuously and highly accurately measured over the entire circumference.

It is needless to say that the magnetostrictive sensor 2 and the cylindrical material 1 may be in relative motion, but the magnetostrictive sensor 2 is often moved to measure the actually used cylindrical material. Seem.

Next, a non-contact type measuring device used for carrying out the method of the present invention will be specifically described with reference to FIGS.

FIG. 4 is a vertical side view of the measuring device, FIG. 5 is a front view showing a part of the traveling device, FIG. 6 is a front view showing a part of the carrying device, and FIG. 7 is a plan view of FIG. Is.

As shown in these drawings, the measuring device 10 includes a traveling device 12 installed so as to orbit the outer peripheral surface 11 of the columnar material 1.
And a carrying device 13 that is attached to the traveling device 12 and accompanies the outer peripheral surface 11 together.

In the configuration of each part, the traveling device 12 includes a traveling carriage 15 having a plurality of rubber wheels 14, and a frame 151 of the traveling carriage 15.
An elevating body 16 provided so as to be able to ascend and descend by engagement of the dovetail groove 152 and the dovetail 161; A rotary shaft 18 rotatably supported by the lifting body 16, a chain wheel 19 mounted on the rotary shaft 18 and a non-slip chain 20 wound around the columnar material 1, and a transmission gear mechanism 21. Servo motor 23 with encoder 22 for driving the chain wheel 19 via
It consists of and.

In the pressing device 17, a stud bolt 171 is fixed to the upper end of the lifting body 16, a nut 172 is screwed into the tip of the bolt 171 projecting upward from the bogie frame 151, and a compression spring 173 is provided between the nut 172 and the bogie frame 151. It is through the.

The servo motor 23 is attached to the lifting body 16 and is connected to the transmission gear mechanism 21 via the speed reducer 24. This transmission gear mechanism 21 is a small gear 2 attached to the output shaft 241 of the speed reducer 24.
It is configured by engaging 11 with a large gear 212 attached to a rotary shaft 18. Both ends of the rotating shaft 18 are bearings 181
It is pivotally supported by the lifting body 16 via.

The non-slip chain 20 that is wound around the chain wheel 19 of the rotating shaft 18 is an ordinary non-slip L chain.
The rubber plates 201 are attached to both sides. Then, the rubber plate 201 of the chain 20 which is strained by the pressing device 17 comes into close contact with the outer peripheral surface 11 of the columnar material 1, and the traveling device 1
2 is pressed and held on its outer peripheral surface 11 by the wheel 14 in the direction of the half cylinder of the columnar material 1. Further, when the size of the cylindrical material 1 changes as shown in FIG. 5, a chain 20 with a slip stopper having a length corresponding to the size is used.

Next, as shown in detail in FIGS. 6 and 7, the carrying device 13 has a carrying carriage 26 which vertically holds the magnetostrictive sensor 2 and has a plurality of wheels 25, and a carrying carriage 26. A rectangular frame 27 provided around 26, a connecting arm 29 swingably pivoted by first horizontal shafts 28 on both sides in the longitudinal direction of the frame 27, and a carrying carriage 26 in the frame 27. A second horizontal shaft 30 that is pivotally supported and is provided at a right angle to the first horizontal shaft 28, and an upper block 31 of the connecting arm 29 is moved up and down via dovetail grooves 321 and 311. Mounting guide 32 that can be freely engaged and this connecting arm
It is composed of a compression spring 33 that constantly urges 29 toward the outer peripheral surface 11 side.

The attachment guide 32 is attached to the side surface of the bogie frame 151. Further, the compression spring 33 is interposed between the upper block 31 of the connecting arm 29 and the upper plate 321 of the attachment guide 32, and is fitted to the rod 312 on the upper block 31 penetrating the upper plate 321. The wheels 25 of the carrying carriage 26 are made of rubber like the wheels 14 of the traveling carriage 15 described above.

The magnetostrictive sensor 2 is fixed to the carrying carriage 26 with a set screw 34 so that the lower end surface of the magnetostrictive sensor 2 maintains a constant minute height h from the outer peripheral surface 11.

The measuring apparatus 10 is configured as described above, and its operation will be described next.

First, the traveling device 12 is set on the outer peripheral surface 11 of the cylindrical material 1 of a pipe or a round bar. In this case, when the nut 172 of the pressing device 17 is screwed in against the elastic force of the compression spring 173, the dolly frame 151 is pushed down toward the columnar material 1 side, and on the contrary the lifting body 16 is pulled up. Tension the non-slip chain 20 wrapped between 1 and the chain wheel 19. As a result,
The traveling carriage 15 is supported by its wheels 14 on the outer peripheral surface 11 of the cylindrical material 1.
It is pressed and held radially on top of it. Further, the gum plate 201 of the non-slip chain 20 is also wound so as to be in close contact with the outer peripheral surface 11 of the columnar material 1.

On the other hand, the carrying device 13 causes the wheel 25 of the carrying cart 26 to move in the same manner as the outer peripheral surface of the cylindrical material 1 due to the pressing operation of the traveling device 12.
11 Stick it on top. The pressing force at this time is performed by the compression spring 33. That is, the compression spring 33 is connected to the connecting arm 29.
Is pressed against the outer peripheral surface 11 side along the attachment guide 32, and the carrying carriage 26 connected to the lower end of the connecting arm 29 is brought into close contact with the outer peripheral surface 11 as described above. Moreover, the carrying cart 26 is the first
In a rectangular frame 27 pivotally supported on the connecting arm 29 by a horizontal axis 28 of the frame 27, which is pivotally supported by a second horizontal axis 30 which is arranged at a right angle to the first horizontal axis 28.
Automatically adjusts the inclination of the first horizontal axis 28 in the direction parallel to the outer peripheral surface 11, and the carrying cart 26 automatically adjusts the inclination of the second horizontal axis 30 in the direction perpendicular thereto. further,
Since the magnetostrictive sensor 2 is vertically held by the carrying carriage 26 that is automatically adjusted as described above, and is held at a constant height h from the outer peripheral surface 11, the holding state is changed by the subsequent movement of the carrying carriage 26. There is nothing to do.

With the above, the preparation for the measurement work is completed. Next, the servomotor 23 is driven to move the traveling device 12 to the cylindrical material 1.
Turn around. In this case, when the chain wheel 19 is rotated by the rotation of the rotating shaft 18, the non-slip chain 20 wound around the chain wheel 19 is in close contact with the outer peripheral surface 11 of the columnar material 1 as described above, and therefore the rubber plate 20 thereof is provided.
Since there is no slip due to the frictional force due to 1,
After all, the chain wheel 19 is this non-slip chain
20 is used as a kind of bending guide to make a planetary motion around the cylindrical material 1. Therefore, the traveling device 12 orbits the outer peripheral surface 11 of the columnar material 1 in a state of being closely adhered thereto. Along with this, the carrying device 13 also moves the magnetostrictive sensor 2 together with the traveling device 12 while maintaining the above-mentioned holding relationship, so that the magnetostrictive stress of the outer peripheral surface 11 can be measured continuously in a contacted manner, and the accuracy is extremely high. Measurement data can be obtained.

The magnitude of the principal stress difference is obtained by detecting the position where the output of the magnetostrictive sensor 2 is maximum by the encoder 22 and the detected angle and the output value.

Further, although the outer peripheral surface of the columnar material has been described in the above-mentioned embodiment, it is obvious that the inner peripheral surface can be similarly used in consideration of the basic principle of the present invention.

[Effects of the Invention] As described above, according to the present invention, the magnetostrictive sensor is moved relative to the outer peripheral surface or the inner peripheral surface in a non-contact state at an arbitrary cross-sectional position of the columnar material so as to make one round. Since the stress distribution can be obtained as a continuous sin curve, the stress of the cylindrical material can be measured in a short time, and the stress state actually acting on the cross section can be measured with high reliability and high accuracy. It can be measured and its practical value is extremely large.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the measuring method of the present invention, and FIG.
(E) is an output voltage diagram of the magnetostrictive sensor obtained by the measuring method of the present invention, FIG. 3 is an explanatory diagram showing a test method for a steel pipe, and FIG. 4 is a measurement used for carrying out the measuring method of the present invention. FIG. 5 is a front view showing a part of the traveling device, FIG. 5 is a side view showing a part of the carrying device, and FIG. 7 is a plan view of FIG. FIG. 8 (a),
(B) is an explanatory view when a bending stress acts on the columnar material and a stress distribution diagram at that time. 1 …… Cylinder material 2 …… Magnetic strain sensor 10 …… Measuring device

Claims (1)

[Claims] 1. A magnetostrictive sensor is used to measure the magnetostriction at an arbitrary cross-section position of a columnar material by using a measuring device which relatively moves on an outer peripheral surface or an inner peripheral surface of a cylindrical material in a non-contact state while maintaining a constant distance. A method for measuring magnetostrictive stress of a cylindrical material, which comprises obtaining an output voltage of a sensor, further approximating the output voltage to a sin curve, and obtaining an action direction of a bending stress and a bending moment acting on a cross section at that position.