JPH0815231A - Eddy current flaw detecting testing device - Google Patents

Abstract

PURPOSE:To provide an eddy current flaw detecting testing device, by which the measuring conditions such as a distance between a testing coil and a material to be tested, a gain at the time of amplifying the change of a current flowing through the testing coil to obtain a detection signal and so on can be automatically executed without hands. CONSTITUTION:CPU 6 tests a fitting hole 13 of a calibration testing piece 3 where an artificial damage with a designated depth is formed by a flaw detecting probe 1 including a testing coil 2 on the side of the forward end cylindrical part 1a. The CPU 6 controls the position of the flaw detecting probe 1 and sets a gain of an amplifier in an eddy current flaw detecting part 5 according to a detection signal output from the testing coil 2. A material 4 to be tested and a calibration testing piece 3 are disposed in a designated position on a testing table 8 constructed in such a manner as to move in the directions of X and Y or freely rotate. The movement and rotation of the testing table 8 and the position of the flaw detecting probe 1 are controlled by the CPU 6, and the CPU 6 prints control information on recording paper and writes the same on an optical disc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an eddy current flaw detector for detecting flaws on metal parts and the like.

[0002]

2. Description of the Related Art A so-called eddy current flaw detector is known as a means for finding flaws in an object to be tested. The outline of this eddy current flaw detector is as described below. First, the test coil is brought close to the DUT, and an AC magnetic field passing through the surface of the DUT is generated from the test coil. As a result, an eddy current is generated on the surface of the DUT.

Then, the current flowing through the test coil is measured while moving the test coil in parallel with the surface of the DUT. In the process of moving the test coil, if the DUT has damage, the eddy current flowing on the surface of the DUT changes, and as a result, the current flowing through the test coil changes.
The impedance of the test coil changes. Therefore, the presence or absence of damage to the device under test can be determined by extracting the change in impedance of the test coil as a detection signal.

[0004]

By the way, the width of the change in the current flowing through the test coil depends on the material of the DUT to be inspected, the distance between the test coil and the DUT, and the test coil with respect to the DUT. It changes depending on the moving speed when moving relative. Further, the magnitude of damage to be detected also differs depending on the parts, products, etc. to be inspected. Therefore, in order to detect all the damage to be detected, the measurement conditions such as the distance between the test coil and the DUT, the gain when the change in the current flowing through the test coil is amplified, and the detection signal are obtained. Calibration work is required to optimize.

However, in the conventional eddy current flaw detector, such calibration work must be performed manually,
Its handling was inconvenient. In addition, it is difficult to improve the accuracy of manual calibration, which is also a factor that reduces the measurement accuracy of the eddy current flaw detector.

The present invention has been made under such a background, and measures the distance between the test coil and the DUT, the gain when the change in the current flowing through the test coil is amplified, and the detection signal is obtained. It is an object of the present invention to provide an eddy-current flaw inspection device that can automatically perform conditions without relying on human labor.

[0007]

In order to solve the above-mentioned problems, in a first aspect of the present invention, the test coil is made to face a calibration test object on which artificial damage is formed, and the test coil having a predetermined amplitude is provided. It is characterized in that it has calibration means for setting measurement conditions for obtaining the detection signal so that the detection signal can be obtained.

According to a second aspect of the present invention, the calibration means adjusts a relative positional relationship between the calibration test object and the test coil so that the detection signal having a predetermined amplitude is obtained. After the adjustment by the calibration means, the test coil and the DUT are moved relative to each other to perform the operation of obtaining the detection signal.

According to a third aspect of the present invention, the calibration means adjusts the gain when the detection signal is obtained from the change in the current so that the detection signal having a predetermined amplitude can be obtained.

According to a fourth aspect of the present invention, the calibration test sample has a plurality of artificial damages of different sizes, and the calibration means has an amplitude change width of the detection signal corresponding to each of these damages. The measurement conditions are set so that the distributions are distributed over a predetermined range.

[0011]

According to the first aspect of the present invention, the measurement conditions are set so that a detection signal having a predetermined amplitude can be obtained when an inspected test object is inspected. According to the second aspect of the invention, the relative positional relationship between the DUT and the test coil is initialized so that a detection signal with a predetermined amplitude can be obtained when the damaged test item is inspected. It According to the invention of claim 3, the gain when the detection signal is obtained from the change of the current flowing through the test coil is adjusted so that the detection signal having the predetermined amplitude can be obtained when the test object having the damage is inspected. To be done. According to the invention of claim 4, the measurement condition is set so that the damage having a size within a certain range is detected.

[0012]

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

A. Configuration of Embodiment FIG. 1 is a configuration diagram of an eddy current flaw detector according to an embodiment of the present invention. In FIG. 1, 4 is a test object as an inspection target. As shown in FIG. 1, the DUT 4 has a disc shape, and a plurality of mounting holes 12, 12, ... Are formed therein. The eddy current flaw detector according to this embodiment is for inspecting the wall surface of these mounting holes 12, 12, .... Reference numeral 3 is a calibration test piece used to calibrate this eddy current flaw detector, an example of which is shown in FIG. The calibration test piece 3 has the same material, thickness, and diameter of the mounting hole 13 as those of the DUT 4, but artificial damage of a predetermined depth is formed around the mounting hole 13. . As shown in FIG. 2, assuming an XYZ orthogonal coordinate system having the center of the mounting hole 13 as the origin and having the Z axis in the vertical direction, the artificial hole is placed at a position in the -X direction around the mounting hole 13. Damage 9 is artificial damage 10 in the Y direction.
However, the artificial damage 11 is formed at the position in the X direction. The artificial damages 9, 10 and 11 have different depths, and in the present embodiment, they are 75 [μm] and 150 [μm], respectively.
m] and 225 [μm].

In FIG. 1, 8 is an inspection table,
The calibration test piece 3 and the DUT 4 are the inspection table 8
It is arranged at a predetermined position above and in a predetermined posture. The inspection table 8 has a structure that can be freely moved or rotated in the X direction or the Y direction by numerical control.

Further, in FIG. 1, reference numeral 1 denotes a flaw detection probe, which is driven by a driving means (not shown) to produce the X, Y and Z.
It is designed to be moved and rotated in each axial direction. A cylindrical tip cylindrical portion 1a is attached to the flaw detection probe 1, and a test coil 2 made of a coil is attached to a side surface of the tip cylindrical portion 1a. Further, a touch sensor (not shown) is provided at the tip of the tip cylindrical portion 1a. Reference numeral 5 is an eddy current flaw detection section. The eddy current flaw detection unit 5 has an amplifier capable of gain adjustment, and the amplifier amplifies a change in voltage obtained by a change in impedance of the test coil 2 and outputs it as a detection signal. Further, the eddy current flaw detection unit 5 converts the detection signal into time-series digital data and outputs it, and displays the waveform of the detection signal on a display device (not shown). It is a CPU (central processing unit) 6 that controls each part of the eddy current flaw detector.
The gain of the amplifier that outputs the detection signal in the eddy current flaw detection unit 5 is set by the CPU 6. The movement and rotation of the inspection table 8 and the vertical position control of the flaw detection probe 1 are also controlled according to the control information output by the CPU 6. Reference numeral 7 denotes a recording device, which prints on a recording paper and writes on an optical disc according to control information given from the CPU 6.

B. Operation of Embodiment The operation of this embodiment will be described below. (1) Calibration When a command instructing calibration is input through the input means (not shown), the CPU 6 initializes the position of the inspection table 8 and, as a result, the calibration test piece 3 is transferred to the flaw detection probe 1. It will be located below. Then the CPU
A control signal is sent from 6 to the driving means of the flaw detection probe 1, and the flaw detection probe 1 gradually descends. When the touch sensor detects contact with the calibration test piece 3, the CPU 6 stops the flaw detection probe 1. Next, the CPU 6 controls the X, Y, and Z axes to gradually insert the calibration test piece 3 into the mounting hole 13. As a result, the test coil 2 moves circularly while facing the inner wall of the mounting hole 13 of the calibration test piece 3, and each time the test coil 2 passes through the artificial damages 9, 10 and 11 formed on the inner wall of the mounting hole 13. The impedance of the test coil 2 changes,
The output voltage will change. Then, this change in voltage is amplified by the amplifier in the eddy current flaw detection unit 5, and the detection signal obtained as a result becomes time-series digital data C
It is supplied to PU6.

Here, it is assumed that the tip cylindrical portion 1a rotates in the direction shown by the arrow in FIG. 1, and when the test coil 2 is oriented in the above-mentioned -X direction, θ = 90 [°], Y
If the rotation angle of the tip cylindrical portion 1a is defined so that θ = 180 [°] when facing the direction and θ = 270 [°] when facing the X direction, the tip cylindrical portion is defined. The detection signal shown in FIG. 3 is obtained by the eddy current flaw detection unit 5 by one rotation of 1a. In FIG. 3, θ is 90
The signals appearing at the points of [°], 180 [°], and 270 [°] are due to the influences of the artificial damages 9, 10, and 11 formed on the calibration test piece 3, respectively.

Then, the CPU 6 moves the flaw detection probe 1 in the Z-axis direction so that the amplitude of the detection signal obtained by the eddy current flaw detection unit 5 becomes maximum. As a result of such control, the vertical position of the flaw detection probe 1 is set to the optimum position for eddy current flaw detection.

Next, the CPU 6 makes θ = 90 [°] based on the time-series digital data supplied from the eddy current flaw detection unit 5.
Amplitude values a (90), a (180) and a (270) of the detection signal corresponding to 180 [°] and 270 [°], respectively.
And the ideal value b of each of these amplitude values determined in advance is calculated.
It is determined whether the following expressions (1) to (3) are established between (90), b (180) and b (270). -Dmin≤a (90) -b (90) ≤Dmax ... (1) -Dmin≤a (180) -b (180) ≤Dmax ... (2) -Dmin≤a (270) -b ( 270) ≦ Dmax (3) However, in the above formulas (1) to (3), Dmax and Dmin are values that set the accuracy of calibration, and the smaller these values, the higher the inspection accuracy. Then, when the expressions (1), (2) and (3) are all satisfied, C
The PU 6 records the gain of the amplifier in the eddy current flaw detection unit 5 and the position of the flaw detection probe 1 as calibration data by the recording device 7. On the other hand, if any one of the expressions (1), (2), and (3) does not hold, the CPU 6 determines that S (90) = a (90) / b (90) ... (4) S (180) = a (180) / b (180) ... (5) S (270) = a (270) / b (270) ... (6), and then S The flaw detection probe 1 is moved in the X-axis direction so that (90) = S (270) ± Δ (7). Next, the flaw detection probe 1 is moved in the Y-axis direction so that S (180) = S (90) ± Δ (8). Here, Δ is a value that sets the accuracy of calibration, and the smaller this value, the higher the inspection accuracy.

By repeating such processing, the position of the flaw detection probe 1 in the X direction and the Y direction is adjusted, and the position of the flaw detection probe 1 satisfying all of the expressions (7) and (8) is determined. Desired. When the position adjustment of the flaw detection probe 1 in the X and Y directions is completed,
The CPU 6 adjusts the gain of the amplifier in the eddy current flaw detection unit 5 so that −Dmin ≦ a (90) −b (90) ≦ Dmax (9) holds. The calibration is completed as described above, and the CPU 6 records the gain of the amplifier in the eddy current flaw detection unit 5 and the position of the flaw detection probe 1 as calibration data by the recording device 7.

When the calibration is completed, it corresponds to the relative distance between the first mounting hole to be inspected among the mounting holes 12, 12, ... Of the DUT 4 and the mounting hole 13 of the calibration test piece 3. The inspection table 8 is advanced in the X and Y directions by the distance. As a result, the first mounting hole 12 is located immediately below the flaw detection probe 1.
Then, the mounting holes 12, 12, ...
The flaw inspection is performed. Thereafter, the inspection table 8 is rotated by an angle corresponding to the pitch of each mounting hole, and the flaw detection inspection is performed on each of the second and subsequent mounting holes 12, 12, ....

The scope of application of the present invention is not limited to the above embodiment, but various modifications can be made. For example, it may be applied to a case where a flaw inspection is performed by linearly moving the test coil 2 along the surface of the DUT 4. Also,
The measurement conditions for calibration are not limited to the position of the flaw detection probe 1 and the gain of the amplifier in the eddy current flaw detection unit 5, and items effective for improving the precision of flaw detection inspection may be calibrated as necessary.

[0023]

As described above, according to the present invention, the complicated operation for calibrating the eddy current flaw detector, which has been conventionally performed by a human, is automatically performed without the human being involved. Therefore, it is possible to obtain an effect that the flaw detection inspection can be performed with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an eddy current flaw detector according to the present invention.

FIG. 2 is a diagram showing an example of a calibration test piece used for automatic calibration of the eddy current flaw detector according to the present invention.

FIG. 3 shows an eddy current flaw detector according to the present invention.
It is a figure which shows the signal waveform output from an eddy current flaw detector when the test piece for calibration shown in is inspected.

[Explanation of symbols]

 1 Probe for flaw detection 2 Test coil 3 Test piece for calibration 4 DUT 5 Eddy current flaw detection unit 6 CPU 7 Recording device 8 Inspection table 9 Artificial damage (depth [75 μm]) 10 Artificial damage (depth [150 μm]) 11 Artificial Damage (depth [225 μm]) 12 Mounting hole (DUT) 13 Mounting hole (calibration test piece)

Claims (4)

[Claims] 1. A detection which indicates a damage of the DUT based on a change of a current flowing through the test coil by moving the test coil along the DUT and applying an AC magnetic field to the DUT by the test coil. In an eddy current flaw detection device for obtaining a signal, the test coil is made to face a calibration test object on which artificial damage is formed, and measurement conditions for obtaining the detection signal are set so that the detection signal having a predetermined amplitude can be obtained. An eddy current flaw detector having a calibration means. 2. The calibration means adjusts a relative positional relationship between the calibration test object and the test coil so that the detection signal having a predetermined amplitude can be obtained. The eddy current flaw detector according to claim 1, wherein the test coil and the DUT are moved relative to each other to perform the operation of obtaining the detection signal. 3. The eddy current flaw detection according to claim 1, wherein the calibration means adjusts a gain when the detection signal is obtained from a change in the current so that the detection signal having a predetermined amplitude is obtained. Inspection device. 4. The calibration test article has a plurality of artificial damages of different sizes, and the calibration means has an amplitude change width of the detection signal corresponding to each of these damages within a predetermined range. The eddy current flaw detector according to claim 1, wherein the measurement conditions are set so as to be distributed in a uniform manner.