JPH10311804A - Method and device for measuring defect of material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge the presence, position and size of a defect in no contact by carrying an alternating current to a detecting conductor linearly arranged along a material to be measured, and detecting the electromagnetic wave change from the material through an antenna. SOLUTION: A dipole antenna element 7 is arranged opposite to a material to be measured 1 in such a manner as to be horizontally movable through a thin insulating sheet such as paper or plastics. A detecting means 9 comprising a field intensity detector including an amplifier and a phase detector is connected to the antenna element 7 through, for example, a 500 Ω-coaxial cable 8. A detecting conductor 6, for example, consisting of a copper wire 2 nm wide and 36 μm thick is arranged along the material, and a high frequency current of frequency 100 kHz and 1.5 A, for example, is carried thereto from an ac power source 3 to induct an induction current in the material. Since the electric field generated on the material 1 by this induction current is minutely changed by the part of a crack 2, it can be detected by the antenna element 7. Thus, the crack 2 can be easily detected in no contact without breaking the material 1.

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 a defect of a material, and more particularly to a method and a method for detecting a change in the material of a conductive material such as a metal or a ceramic, a paramagnetic material and a ferromagnetic material, and the presence or absence and degree of a crack. It concerns the device.

[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. If there is a crack on the surface or inside of such a metal or the like, it is known to know the presence or absence of the crack and the depth of the crack.

FIG. 3 is an explanatory view of a conventional method and apparatus for measuring a defect of a material, wherein 1 is a conductive and paramagnetic material, 2 is a crack generated therein, 3 is an AC power supply of, for example, several volts,
Are, for example, two pairs of detection electrodes 5-5 mm in contact with the material 1 at positions separated from each other, 5 is a voltmeter for measuring the voltage between the detection electrodes 4 and 4, and 6 is a conductive electrode for detecting a crack. And a detection conductor such as an enameled wire having a length of, for example, 10 to 20 cm, which is linearly arranged along the surface of the paramagnetic material 1.

In this method and apparatus, the power supply 3 is connected to the sensing conductor 6.
, An alternating current of, for example, about several amperes is caused to flow, and as a result, a magnetically induced current is generated in the material 1 along the detection conductor 6, and between the two points on the material 1 along the detection conductor 7. A voltage is detected by the detection electrodes 4 and 4 that are in contact with the material 1. Then, when the detection conductor 6 and the detection electrodes 4 and 4 are moved in an arbitrary direction, the voltage between the detection electrodes 4 and 4 is detected. Is increased, the presence of the crack 2 between the detection electrodes 4 and 4 is detected.

[0005]

However, in such a conventional method, it is necessary to keep the detection electrode 4 in contact with the material 1, which has various drawbacks in quickness and reproducibility of measurement. there were.

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

[0007]

According to a method of measuring a defect of a material according to the present invention, a detection conductor is linearly arranged along a material to be measured.
An alternating current is passed through the detection conductor, and electromagnetic waves from the material are detected by the non-contact detection means via the antenna without destroying the material. Based on the detected electromagnetic wave output, the presence / absence, position, and size of the material defect are detected. Is determined.

According to the defect measuring apparatus for a material of the present invention, a detection conductor disposed on a non-measurement material, a high-frequency power supply for supplying an alternating current to the detection conductor, and the detection conductor are moved along the material to be measured. And an electromagnetic wave detecting means having an antenna.

The antenna is a dipole antenna or a loop antenna, and the electromagnetic wave detecting means is an electric field intensity or a magnetic field intensity detecting means.

[0010]

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

In the present invention, instead of using the detection electrode 4 and the voltmeter 5 which are brought into contact with the material 1 shown in FIG. 3, as shown in FIG. Non-contact detection means comprising two dipole antenna elements 7 having a length of 25 mm and a horizontal length of 12 mm, and an electric field strength detector including an amplifier and a phase detector connected to the antenna elements 7 via, for example, a 50Ω coaxial cable 8. 9, the antenna element 7 is brought into contact with the material 1 via a thin insulating sheet (not shown) such as paper or plastic, and is moved in the X and Y directions by XY moving means (not shown). At the same time, a copper wire having a width of 2 mm and a thickness of 35 μm is used as the detection conductor 6, for example.
Then, from the power supply 3, for example, a frequency of 100 kHz, 1.5
A high-frequency current of ampere is applied.

The coaxial cable 8 preferably has a grounded metal jacket, for example, a semi-rigid coaxial cable.

Further, instead of moving the detection conductor 6 and the antenna element 7 integrally as one probe, the antenna element 7 may be moved relatively to the detection conductor 6.

Since the method and apparatus for measuring a defect of a material according to the present invention are as described above, when a high-frequency current is applied to the detection conductor 6, the electric field generated on the material 1 by the induced current flowing through the material 1 is caused by the crack 2 The small change is detected when the dipole antenna element 7 moves to the crack 2 portion, so that the crack 2 can be detected very easily without contact and without breaking the material 1. become.

When the direction of the two dipole antenna elements 7 matches the direction of the crack 2, the detection output becomes maximum. Thus, it can also be determined how the crack 2 extends in the material 1.

Further, since the peak of the detection power decreases as the depth of the crack 2 increases, the depth of the crack 2 can also be estimated.

In the above description, the case where the crack 2 of the material 1 is detected has been described. However, regardless of the presence or absence of the crack 2, the detection output varies depending on the material of the material 1. If the output is measured, it is possible to detect a material of an unknown material or a secular change of a known material by referring to the output.

In another embodiment of the present invention, as shown in FIG. 2, instead of using a dipole antenna element 7 and an electric field intensity detector, a loop antenna element 10 having a 3 mm-diameter loop-shaped tip and a magnetic field intensity are used. Non-contact detecting means 11 using a detector is used.

This embodiment has the same operation and effect as the above embodiment.

If the antenna according to the present invention is capable of receiving electromagnetic waves, the coaxial cable core may be bent into an L-shape outside the coaxial cable, or a core extending outside without being bent into an L-shape. A tear-shaped element may be connected to the end of the line.

[0021]

As described above, according to the present invention, there is a great advantage that the presence or absence of a crack in a material, the defect of the material and the secular change can be detected very easily in a completely non-contact and non-destructive manner. There is.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method and an apparatus for measuring a defect of a material according to the present invention.

FIG. 2 is an explanatory view of a method and an apparatus for measuring a defect of a material according to another embodiment of the present invention.

FIG. 3 is an explanatory view of a conventional method and apparatus for measuring a defect of a material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Material 2 Crack 3 AC power supply 4 Detecting electrode 5 Voltmeter 6 Detector conductor 7 Dipole antenna element 8 Coaxial cable 9 Detecting means 10 Loop antenna element 11 Detecting means

Claims (4)

[Claims] 1. A method in which a detection conductor is linearly arranged along a material to be measured, an alternating current is passed through the detection conductor, and electromagnetic waves from the material are destroyed by a non-contact detection means via an antenna. A method for measuring the defect of the material, wherein the defect of the material is determined from the detected electromagnetic wave output. 2. A sensing conductor disposed on a non-measurement material,
An apparatus for measuring a defect of a material, comprising: a high-frequency power supply for supplying an alternating current to the detection conductor; and an electromagnetic wave detection means having an antenna, which is moved along the material to be measured. 3. An apparatus according to claim 2, wherein said antenna is a dipole antenna, and said electromagnetic wave detecting means is electric field intensity detecting means. 4. The antenna according to claim 1, wherein the antenna is a loop antenna,
3. The apparatus according to claim 2, wherein said electromagnetic wave detecting means is a magnetic field intensity detecting means.
Defect measuring device for the described material.