JP3189136B2 - Method and apparatus for measuring material deterioration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring deterioration of a material, and more particularly to a method and an apparatus for detecting a change in the material of a conductive material such as metal or ceramics and the presence or absence and the degree of a crack.

[0002]

2. Description of the Related Art For example, if a crack occurs due to fatigue in a boiler header, a turbine rotor, a turbine casing, or the like of a thermal power plant, a serious accident may occur. When there is a crack on the surface of such a metal or the like, an AC or DC current can flow between the two points sandwiching the crack in the metal material, and the voltage across the crack can be measured. It is known to know the presence or absence of a crack and the depth of a crack.

FIG. 4 is an explanatory view of a conventional method for measuring the deterioration of a material, wherein 1 is a conductive material, 2 is a crack generated therein,
Indicates an AC or DC power supply of several volts, for example, and 4 indicates two sets of detection electrodes which are brought into contact with the material 1 at positions separated from each other by, for example, 5 to 10 mm. In this method, material 1
For example, a voltage of the power supply 3 is applied between two points separated by, for example, several cm to several tens of cm via a voltage application electrode (not shown), and a current of, for example, several to several tens of amperes is caused to flow through the material 1. The voltage between the detection electrodes 4 and 4 is detected by a voltmeter 5 and the value of the voltage detected by one set of the detection electrodes 4 is, for example, several to several tens of times smaller than the value of the voltage detected by the other set of the detection electrodes 4. When the voltage is larger by microvolts, it is determined that the crack 2 exists between the one set of the detection electrodes 4, and the depth of the crack 2 is determined from the ratio of the two voltages.

FIG. 5 is an explanatory view of another conventional deterioration measuring method. In this method, instead of flowing an electric current directly to the material 1, an alternating current is applied to a coil 6 having a diameter of 1 cm, for example. A magnetically induced eddy current is generated in the material 1 by the magnetic field generated by the magnetic field, and the presence or absence of a crack is detected based on the change in the voltage generated in the coil 6 and the phase of the current and the voltage when the crack occurs. I have.

[0005]

However, in the method shown in FIG. 3, when a voltage is applied between two points of the material 1 by the voltage applying electrode, the current is uniformly applied not only through the crack 2 but also around the crack 2. Flows, the voltage generated at both ends of the crack 2 decreases, and in order to increase this voltage, an unnecessarily large voltage must be applied to the material 1, and therefore, a large current flows. The material 1 has various disadvantages such as generating heat.

Further, every time the area to be detected is changed, it is necessary to attach and detach the voltage application electrode to / from the material 1, which has a disadvantage that efficiency is poor.

The method shown in FIG. 5 has the advantage that the voltage application electrode and the detection electrode 4 for the material are not required, but the range that can be detected by one measurement is small, and the crack 2
When the crack did not appear on the surface of the material 1, it took a long time to detect the place where the crack had occurred, and it was impossible to measure the state of the crack extending inside the material 1. .

The present invention has been made to eliminate the above disadvantages.

[0009]

According to the method for measuring deterioration of a material according to the present invention, a detection conductor is linearly arranged along a conductive material to be measured, an alternating current is passed through the detection conductor, and the detection conductor extends along the detection conductor. Detecting a voltage between a plurality of points of the material, and judging deterioration of the material from the detected voltage.

The current is supplied from a variable frequency AC power supply, and the frequency is arbitrarily changed to detect the voltage.

According to the apparatus for measuring deterioration of a material of the present invention, a body, a detection conductor arranged on the bottom surface of the body, and a detection conductor exposed on the bottom surface along a line along the detection conductor are provided.
A plurality of sensing electrodes spaced apart from each other, and means for detecting a voltage between the sensing electrodes, wherein the sensing conductor is arranged along the conductive material to be measured, and an alternating current is passed through the sensing conductor. And

[0012] The detection electrode can protrude outside the bottom surface of the body.

The bottom surface of the body is flexible and can be deformed into an arbitrary curved surface.

[0014]

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

In the method for measuring deterioration of a material according to the present invention,
As shown in FIG. 1, an insulation detecting conductor 7 such as an enameled wire having a length of, for example, 10 to 20 cm is linearly arranged along the surface of the conductive material 1 where a crack is to be detected. 3, an alternating current of, for example, about several amperes is caused to flow, so that a magnetically induced current is generated in the material 1 along the detection conductor 7, and between two points on the material 1 along the detection conductor 7. Is detected by the detection electrodes 4 and 4 that are in contact with the material 1. Then, when the detection conductor 7 and the detection electrodes 4 and 4 are moved in an arbitrary direction, the voltage between the detection electrodes 4 and 4 is detected. If the voltage increases, it detects that the crack 2 exists between the detection electrodes 4 and 4.

The voltage at the crack 2 is
The frequency of the electric wire 3 is changed, for example, from 0.3 K to 100 KHz for measurement, and the form of the crack 2 in the material 1 in the depth direction is determined based on the measurement result.

Since the method for measuring the deterioration of the material of the present invention is as described above, the detection conductor 7 and the detection electrodes 4 and 4 are made of the material 1
The detection area can be easily changed simply by moving on the upper side. Further, since the magnetically induced current flows intensively only in the portion along the detection conductor 7 in the material 1, a crack 2 is generated. Where you can get a sufficiently large voltage,
Sensitivity increases.

If the frequency of the power supply is changed, for example, if the frequency is increased, the induced current can be caused to flow only along the surface of the material by the skin effect to detect cracks only on the surface. Measurement can detect information about cracks in the center of the material, and consequently not only the presence or absence of a crack, but also how the crack extends in the material. Become.

In the above description, the case where the crack 2 of the material 1 is detected has been described. However, the voltage between the two detection electrodes 4 and 4 differs depending on the material of the material 1 regardless of the presence or absence of the crack 2. Therefore, if the voltage of a known material is measured in advance, it is possible to detect a material of an unknown material or a secular change of the known material with reference to the voltage.

FIG. 2 shows a device for measuring the deterioration of a material according to the present invention. The vertical hole 10 of
The compression spring 11 and the detection electrode 4
Are inserted in this order, and the tips of the detection electrodes 4 and 4 are made to protrude out of the bottom surface 9 of the body. When the tips of the detection electrodes 4 and 4 are pressed against the surface of the material 1 where the crack is to be detected, It is pushed by this surface and pushed into the vertical hole 10 against the compression spring 11 so that its tip can coincide with the bottom surface 9 of the body 8.

On the bottom surface 9 of the body 8, the detection conductor 7 is buried in an insulated state on a line connecting the two detection electrodes 4 and 4, and the variable frequency power supply 3 is connected to both ends thereof. A voltmeter 5 is connected between the detection electrodes 4 and 4. Note that the detection conductor 7 is detoured along the outer periphery of the detection electrode 4 at a portion where the detection conductor 7 intersects with the detection electrodes 4 and 4.

Further, it is preferable to cover the outer peripheral surface of the body 8 with a shield such as a metal net, if necessary, in order to prevent radio wave interference or the like.

In the device for measuring deterioration of a material according to the present invention, if the bottom surface 9 of the body 8 is made of a flexible material such as rubber, even if the surface of the material on which the detection conductor 7 is to be measured is a curved surface, And accurate detection is possible.

Further, the method and apparatus for measuring deterioration of a material according to the present invention can be applied to a ferromagnetic material such as ferrite, non-magnetic metal such as aluminum, austenitic steel, and titanium;
It can be widely applied to materials such as ceramics having low conductivity.

Further, a conductor foil may be used as the detection conductor 7, a hole may be formed in the foil, and the detection electrodes 4 and 4 may contact the material 1 through the hole.

In another embodiment of the present invention, FIG.
2, two sets of detection electrodes 4 and 4 are arranged along the detection conductor 7.

In this way, the depth of the crack can be immediately measured by the ratio of the detection voltages of the two sets of detection electrodes 4 and 4 as in the prior art.

[0028]

As described above, according to the present invention, the presence / absence of a crack in a material, the deterioration of the material and the secular change, etc. can be detected very easily with sensitivity several tens of times as compared with the conventional case. There are great benefits.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method for measuring deterioration of a material according to the present invention.

FIG. 2 is an explanatory diagram of a material deterioration measuring device of the present invention.

FIG. 3 is an explanatory diagram of a deterioration measuring device according to another embodiment of the present invention.

FIG. 4 is an explanatory view of a conventional method for measuring deterioration of a material.

FIG. 5 is an explanatory view of a conventional method for measuring deterioration of a material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive material 2 Crack 3 AC or DC power supply 4 Detecting electrode 5 Voltmeter 6 Coil 7 Detecting conductor 8 Body 9 Bottom 10 Vertical hole 11 Compression spring

Claims (6)

(57) [Claims] 1. A detection conductor is linearly arranged along a conductive material to be measured, an alternating current is passed through the detection conductor, and a voltage between a plurality of points of the material along the detection conductor is detected. A method for measuring deterioration of a material, comprising determining deterioration of the material from the detected voltage. 2. The method according to claim 1, wherein the current is supplied from a variable frequency AC power supply, and the frequency is arbitrarily changed to detect the voltage. 3. A body, a sensing conductor disposed on the bottom surface of the body, two or more spaced sensing electrodes exposed on the bottom surface along a line along the sensing conductor, and a gap between the sensing electrodes. Means for detecting the voltage of
The sensing conductor is arranged along the conductive material to be measured,
An apparatus for measuring deterioration of a material, characterized in that an alternating current is applied to the material. 4. The apparatus for measuring deterioration of a material according to claim 3, wherein said detection electrode is protrudable outside the bottom surface of said body. 5. The apparatus according to claim 3, wherein the bottom surface of the body is flexible and deformable into an arbitrary curved surface. 6. The apparatus according to claim 3, wherein said current is supplied from a variable frequency AC power supply.