JPH09145696A - Method and apparatus for measuring depth of flaw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the depth of flaw conveniently with high detection sensitivity without varying the shape of an object. SOLUTION: A flaw 4 generated in an object 3 to be inspected is measured by an ultrasonic method. A longitudinal wave vertical probe 1 is set directly above the flaw 4 generated in an object 3 and a transverse wave oblique probe 2 is set oppositely thereto. These probes 1, 2 are used, respectively, for transmission and reception in two probe method. Both probes 1, 2 are positioned at such points as the end echo propagating while being subjected to mode conversion at the forward end of flaw 4 has maximum energy and then the distance between the incident points of probe is measured. The measurements are substituted into a calculation formula derived from the propagation route of ultrasonic beam determined geometrically thus determining the depth of flaw.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention determines the depth (size) of a defect required for evaluating the life of a defect (also called a crack) which is found by nondestructive inspection of a structure. The present invention relates to a defect depth measuring method using an ultrasonic method for measuring and a device therefor.

[0002]

2. Description of the Related Art In non-destructive inspection of a structure, the detection sensitivity and pass / fail of a defect are determined in comparison with a simulated defect of a size that is allowable in terms of strength. However, if a defect is found in a critical structure that is within the acceptable range, or if a defect cannot be repaired immediately even if it is detected as a defect, the size of the defect is measured to evaluate the life of the structure. There was a need.

As the defect size measuring method, for example, as disclosed in JP-A-54-55493 and JP-A-3-146859, the edge portion in the eddy current flaw detection, the electric resistance method and the ultrasonic flaw detection is disclosed. The echo method and the like are known. The eddy current flaw detection method and the electric resistance method have the drawback that measurement cannot be performed unless there is a flaw on the flaw detection surface side, and the measured values vary widely.

Further, in the end echo method capable of measuring the depth of a defect generated from the side opposite to the flaw detection surface,
As shown in FIG. 10 (a), the reflection component of the end echo obtained by irradiating the tip of the defect 4 generated in the inspection object 3 with the ultrasonic wave, that is, the transverse wave incident beam 7 from the transverse wave oblique angle probe 2. 6a is detected by the original transverse wave bevel probe 2 and the diffraction component 6 of the end echo is detected by the other transverse wave bevel probe 2 as shown in FIG. 10 (b). There is a two-probe end echo method.

Since these end echoes are extremely weak, the S / N ratio with crystal grain boundary noise, etc. is very poor, and the ultrasonic mode and refraction angle are selected, and ultrasonic waves are applied to the end of the defect 4. Various studies have been made to improve the S / N ratio, such as the use of a focus type flaw detector for focusing.

[0006]

Particularly in a material with large attenuation such as austenitic stainless steel, it is difficult to correctly recognize the signal from the defect end due to the interference of noise echo, and the end echo cannot be detected. There were quite a few cases. Therefore, it is impossible to measure the defect profile by measuring the depth in the length direction of the defect at a pitch of several millimeters.

When the inventors of the present invention irradiate the tip of the defect 4 with a longitudinal ultrasonic wave from a direction parallel to the defect plane, the direction of the tip of the defect 4 is about 45 ° below the defect plane. It is confirmed that the reflection component (reference numeral 6a in FIG. 10) or the reflection component (reference numeral 6 in FIG. 10) that is used in the conventional end echo is more than 10 times stronger than the end component and is emitted after being converted into a transverse wave. I found it.

This phenomenon occurs in the opposite route, that is, when a transverse ultrasonic beam is applied to the tip of the defect 4 from a direction that makes an angle of about 45 ° with the defect surface, the defect 4 surface starts from the tip of the defect 4. A strong end echo mode-converted into a longitudinal wave is emitted in a direction parallel to and away from the tip of the defect 4.

Heretofore, this mode-converted end echo has not been paid attention because of a difference in sound velocity due to mode conversion, a complicated reflection path, and the like. As described above, according to the conventional end echo method, the measurement is performed even when the S / N ratio is bad, and there is a problem that it is difficult to identify the tip echo of the defect.

The present invention has been made to solve the above-mentioned problems, and it is simple and has a high detection sensitivity without changing the shape of the object to be inspected with respect to a defect generated in the object to be inspected.
An object of the present invention is to provide a defect depth measuring method using an ultrasonic method and a device therefor capable of measuring a good ratio and measuring the depth of a defect.

[0011]

According to the present invention, in a method for measuring the depth of a defect generated in an object to be inspected by an ultrasonic method, a longitudinal wave vertical probe is located directly above the defect generated in the object to be inspected. And a transverse wave bevel probe facing the longitudinal wave vertical probe, one of these probes for transmitting and the other for receiving, and mode conversion at the tip of the defect. The two echoes are positioned at the position where the end echo propagating as a result has the maximum energy, the distance between the incident points of the probes at this time is measured, and the ultrasonic wave geometrically obtained the measurement result. The feature is that the defect depth is obtained by applying the calculation formula derived from the beam propagation route to the calculation.

According to the present invention, a sensor holder provided on an object to be inspected for attaching at least one of a vertical wave vertical oscillator and a transverse wave oblique angle oscillator, a guide screw for attaching at least one of the both oscillators, and this guide It is characterized by comprising a drive motor for driving the screw, a position detector attached to the sensor holder or the guide screw, a pressing mechanism provided on the sensor holder, and a scanner arm to which the pressing mechanism is attached.

Further, according to the present invention, at least one of a vertical-wave vertical oscillator and a transverse-wave oblique-angle oscillator provided on an object to be inspected is constituted by a linear array type probe, and a sensor holder to which these oscillators are attached, The present invention is characterized in that a pressing mechanism provided on the sensor holder and a scanner arm to which the pressing mechanism is attached are provided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of this embodiment, the principle of the present invention will be described with reference to FIG. FIG.
In FIG. 1, the longitudinal wave vertical probe 1 is arranged directly above the defect 4 generated in the inspected object 3, and the transverse wave bevel probe 2 is arranged at a position facing the probe 1. The longitudinal ultrasonic wave beam 5 incident from directly above the defect 4 toward the tip of the defect 4 by the longitudinal vertical probe 1 has an end echo 6b that is mode-converted into a transverse wave when hitting the tip of the defect 4. It is emitted to both sides of the defect at an angle of about 45 °.

The mode-converted end echo 6b is shown in FIG.
Since the echo component is considerably stronger than the reflection component 6 of the end echo described above and the diffraction component 6 of the end echo, the transverse wave bevel probe 2 produces a sufficiently strong echo even if it is reflected once at the bottom surface. Since it is received, the S / N ratio with the grain boundary noise and the like is extremely good.

In FIG. 10, when the plate thickness of the inspection object 3 is t, the defect depth is d, and the refraction angle of the transverse wave oblique angle probe is θ, the transverse wave end emitted after mode conversion at the defect tip. Part echo 6b
The angle at which the light is reflected on the bottom surface of the inspection object 3 is also θ.

In this case, the distance between the center point (hereinafter referred to as an incident point) of the ultrasonic wave which exits (or enters) the vertical wave vertical probe 1 and the incident point of the transverse wave oblique angle probe 2 is set to 1. For example, l = dtan θ + nt tan θ ・ ・ ・ (1) where n is the number of times the transverse ultrasonic waves are reflected on the surface of the object to be inspected. From this equation, the depth d of the defect is d = 1 / tan θ-nt ・ ・ ・ (2). , The known angle of refraction θ of the transverse wave oblique probe 2, the thickness t of the object 3 to be inspected, and the measured inter-probe incidence point distance l.

Although the longitudinal wave vertical probe 1 is used as the transmitting side and the transverse wave bevel probe 2 is used as the receiving side for the principle of measuring the depth of defects according to the present invention, the transverse wave bevel probe 2 is transmitted. side,
The same applies to the case where the longitudinal wave vertical probe 1 is used as the receiving side.
Therefore, hereinafter, the longitudinal wave vertical probe 1 will be described as the transmitting side, and the transverse wave oblique angle probe 2 will be described as the receiving side.

FIGS. 2 (a) and 2 (b) show an example of measurement in the case where a defect is present on the flaw detection surface (the surface where the probe can come into contact) and the number of surface reflections of transverse waves is 0 or 2. Since the end echo 6b to be detected in the present invention is considerably strong, even if the vertical longitudinal wave component is reflected by the bottom surface of the DUT 3 as shown in the figure, it can be detected as a sufficiently strong echo. Defect depth can be measured with the same theory.

Next, referring to FIGS. 2 (a) and 2 (b), a first method of measuring a defect depth by an ultrasonic method according to the present invention will be described.
An embodiment will be described. The first embodiment is an example in which the depth of the defect 4 is measured when the defect 4 is formed below the upper surface of the inspection object 3. 2A shows an example in which the depth of the defect 4 is shallow, and FIG. 2B shows an example in which the depth of the defect 4 is deep.

2A and 2B, a longitudinal wave vertical probe 1 is provided directly above the defect 4, and the transverse wave oblique angle probe 2 is kept away from the probe 1 in the case of FIG. 2A. In the case of (b), they are provided close to each other.

In the first embodiment, as shown in FIG.
(B) Since the end echo 6b to be detected together is quite strong, even if the vertical longitudinal wave component 6b is reflected on the bottom surface of the DUT 3 as shown in the figure, it can be detected as a sufficiently strong echo and the depth of the defect 4 can be detected. Can be measured.

That is, when a longitudinal ultrasonic wave parallel to the defect 4 is incident from the probe 1 through the opening end of the defect 4, a strong transverse ultrasonic wave is generated 45 ° below the tip of the defect 4, so that the ultrasonic wave is generated at the bottom surface. The transverse-wave ultrasonic wave reflected once is detected by the transverse-wave oblique-angle probe 2. At this time, the depth 1 of the defect 4 can be obtained by measuring the distance 1 between the incident points of the longitudinal wave vertical contactor 1 and the transverse wave bevel probe 2 and calculating it by the above-mentioned formula (2).

Next, the first embodiment of the defect depth measuring apparatus according to the present invention will be described with reference to FIG. In FIG.
The longitudinal-wave vertical probe 1 and the transverse-wave oblique-angle probe 2 are placed on the device under test 3, but the longitudinal-wave vertical probe 1 is fixed to the tip end mounting member 9 of the sensor holder 8. , Is located on the vertical line of the defect 4. The transverse wave bevel probe 2 is fixed to a moving member 11 of a screw 10. The screw 10 is directly connected to the bevel probe driving motor 12 fixed to the sensor holder 8,
By the drive of this motor 12, it rotates to move the transverse wave bevel probe 2 left and right.

A position detector 13 is provided at the tip of the sensor holder 8.
Is attached. The sensor holder 8 is attached to the scanner arm 15 via a pressing mechanism 14 such as a coil spring. The scanner arm 15 is provided in an automatic ultrasonic flaw detector (hereinafter referred to as a UT device).

Next, the procedure from the usual flaw detection for the presence or absence of a defect to the measurement of the defect depth by the apparatus having the above-mentioned structure will be described. First, the defect depth measuring apparatus according to the present embodiment is pattern-driven by the UT apparatus, and at this time, flaw detection for defects is performed from the transverse wave bevel probe 2 in the same manner as normal automatic flaw detection. If a defect (crack) is confirmed by this flaw detection, the position of the defect is obtained from the beam path of the defect echo obtained at that time and the refraction angle θ of the transverse wave bevel probe 2 obtained in advance.

Then, while keeping the position of the transverse wave oblique angle probe 2 unchanged, the oblique wave probe driving motor 12 of the UT device and the defect depth measuring apparatus is driven to drive the longitudinal wave vertical probe. Position 1 directly above defect 4.

Next, the UT device is switched from the pulse echo to the pitch catch, and the longitudinal wave vertical probe 1 is reconnected to the transmitting side, and the transverse wave oblique angle probe 2 is reconnected to the UT device. Thereafter, the bevel probe driving motor 12 is driven to move the transverse wave bevel probe 2 in a direction away from the longitudinal wave vertical probe 1,
The longitudinal wave incident beam 5 hits the tip of the defect, and the transverse wave oblique probe 2 is monitored while monitoring the echo on the CRT of the UT device at a position where the energy of the transverse ultrasonic wave 6b generated by mode conversion is maximized. To position.

The distance between the incident point of the longitudinal wave vertical probe 1 and the incident point of the transverse wave oblique angle probe 2 at this time is detected by the position detector 13 using a potentiometer or the like. The defect depth can be obtained by calculating from the detected distance between the incident points.

The switching from the pulse echo of the UT device to the pitch catch, the detection of the maximum height of the echo, the drive positioning of the transverse wave bevel probe 2, and the detection of the distance between the incident points, and this value. It is also possible to electronically control the defect depth calculation and the like.

Next, a second embodiment of the defect depth measuring device according to the present invention will be described with reference to FIG. Since the second embodiment is based on the first embodiment, FIG.
The same parts as those in FIG. 3 are denoted by the same reference numerals, and the description of the overlapping parts will be omitted.

The difference of the present embodiment from the first embodiment is that the tip end mounting member 9 to which the longitudinal wave vertical probe 1 is fixed is attached to the second guide screw 16, and the second guide screw 16 is attached. Is directly connected to the vertical probe driving motor 12a, and the position detector 13 is attached to the sensor holder 8 between the longitudinal wave vertical probe 1 and the transverse wave oblique angle probe 2. The vertical probe driving motor 17 is provided at the end of the sensor holder 8.

According to this embodiment, the longitudinal wave vertical probe 1 is used.
A vertical probe drive motor 12a for finely adjusting the position of the probe 1 by moving it back and forth can also be provided on the side to improve the defect depth measurement accuracy.

That is, after the defect depth measuring operation is performed in the same manner as the procedure described in the first embodiment, the vertical probe driving motor 12a is further driven to move the vertical wave vertical probe 1 to the vertical wave vertical probe 1. It is moved back and forth, and finely adjusted to a position where the echo whose mode is converted at the top of the defect becomes higher. As a result, the calculated defect top position is corrected to the correct position, so that a more accurate defect depth value can be obtained.

Next, a third embodiment of the defect depth measuring device according to the present invention will be described with reference to FIG. In the present embodiment, a linear array type probe 16 is provided in place of the transverse wave bevel probe 2 in each of the above-described embodiments, and the linear array type probe 16 is electrically scanned to obtain the structure shown in FIG. This is because the mechanical drive parts such as the screw 10 and the drive motor shown in FIG. 4 are deleted.

That is, the longitudinal wave vertical probe 1 is attached to the tip end attachment member 9 of the sensor holder 8, and the intermediate portion drive member 17
The linear array type probe 16 is attached to the rear end attachment member 18. The sensor holder 8 is attached to the scanner arm 15 via the pressing mechanism 14.

The linear array type probe 16 is shown in FIGS.
As shown in FIG. 2, a plurality of fine vibrators 19 are arranged in a line, and each vibrator 19 is electrically connected to each delay circuit 20. FIG. 6 shows the principle of electron deflection and focusing of the linear array type probe 16, and FIG. 7 shows the scanning method.

By changing the timing of the ultrasonic transmission pulse given to each transducer, the refraction angle of the ultrasonic wave can be freely set, and the transmission pulse in which the timing is changed to a part of the group of transducers 19 arranged in plural. , The ultrasonic wave is transmitted (or, conversely, received), and then the same element is moved to the adjacent position and repeated, and the same operation is repeated. Can be moved.

In the present embodiment, since the electrical scanning of the linear array type probe 16 is used in place of the transverse wave bevel probe 2, a mechanical drive unit is not required, and therefore the defect depth measuring apparatus itself. Can be downsized, the load on the scanner arm 15 of the UT device can be reduced, and the applicable parts can be expanded.

Next, a fourth embodiment of the defect depth measuring device according to the present invention will be described with reference to FIG. In this embodiment, a linear array type probe 16 is used in place of the longitudinal wave vertical probe 1 in the first embodiment, and a transverse wave bevel probe 2 is the same as in the first embodiment. is there. That is, as shown in FIG. 8, the linear array type probe 16 is attached to the tip attachment member 9 and the intermediate attachment member 17 of the sensor holder 8, and the transverse wave bevel probe 2 is attached to the rear end attachment member 18. It is attached. The other parts are the same as in the third embodiment.

According to the present embodiment, the normal flaw detection for the presence or absence of a defect is performed by the normal transverse wave bevel probe 2, and the defect is detected.
Until the depth measurement is performed, it can be performed in the same manner as an ordinary system.

Next, a fifth embodiment of the defect depth measuring device according to the present invention will be described with reference to FIG. In this embodiment, a linear array type probe 16 is used in place of the longitudinal wave vertical probe 1 and the transverse wave bevel probe 2 in the first embodiment. That is, as shown in FIG. 9, a large linear array type probe 16 is integrally attached to the sensor holder 8 and the sensor holder 8 is attached to the scanner arm 15 via the pressing mechanism 14.

In this embodiment, the defect depth measuring device portion attached to the tip of the scanner arm 15 of the UT device is a single linear array type probe 16, which is very compact.
Also, the longitudinal ultrasonic wave 5 is incident on the top of the defect from the normal oblique flaw detection. The strongest detectable position of the transverse ultrasonic wave 6b generated by mode conversion at the defect length is detected, and the optimum incident position of the longitudinal ultrasonic wave 5 is detected. Fine adjustment, longitudinal wave ultrasonic wave 5 incident position and transverse wave ultrasonic wave 6b
Since the detection of the distance between the detection positions and the calculation of the defect depth from this distance can all be electrically controlled, the defect depth can be accurately measured without mechanical loss.

By using the linear array type probe 16 in this way, it is possible to efficiently perform the point of electrically controlling the scanning of ultrasonic waves and the refraction angle. It can be stopped and all can be covered by one linear array type probe 16.

[0045]

According to the present invention, when longitudinal ultrasonic waves parallel to the defect are incident on the tip of the defect, a downward direction 45
Since a strong transverse ultrasonic wave is generated in the direction of °, this transverse wave reflected once by the bottom surface is detected by the transverse wave oblique probe. The depth of the defect can be accurately measured by measuring and calculating the distance between the incident points of the longitudinal wave vertical probe and the transverse wave bevel probe at this time. As a result, it is possible to evaluate the safety of the container and the structure, estimate the remaining life, and the like, and the effect is great.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view for explaining the principle of a defect depth measuring method according to the present invention.

FIG. 2 (a) is a schematic cross-sectional view for explaining the first embodiment of the defect depth measuring method according to the present invention, and FIG. 2 (b) is (a).
Sectional drawing which shows the other example in FIG.

FIG. 3 is a schematic sectional view showing a first embodiment of a defect depth measuring apparatus according to the present invention.

FIG. 4 is a schematic cross-sectional view showing a second embodiment of the defect depth measuring apparatus according to the present invention.

FIG. 5 is a schematic cross-sectional view showing a third embodiment of the defect depth measuring device according to the present invention.

FIG. 6 is a schematic diagram for explaining the principle of electron deflection and focusing of the linear array type probe in FIG.

FIG. 7 is a schematic diagram for explaining a scanning method of the linear array type probe in FIG.

FIG. 8 is a schematic sectional view showing a fourth embodiment of the defect depth measuring apparatus according to the present invention.

FIG. 9 is a schematic cross-sectional view showing a fifth embodiment of the defect depth measuring device according to the present invention.

10A is a schematic sectional view for explaining a conventional defect depth measuring method, and FIG. 10B is a schematic sectional view showing another example in FIG. 10A.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Longitudinal wave vertical probe, 2 ... Transverse wave oblique angle probe, 3 ... Inspected object, 4 ... Defect, 5 ... Longitudinal wave incident beam, 6 ... End echo,
6a ... Reflection component of end echo, 6b ... End echo after mode conversion, 7 ... Transverse wave incident beam, 8 ... Sensor holder, 9
... Tip mounting member, 10 ... Screw, 11 ... Moving member, 12
... bevel probe driving motor, 13 ... position detector, 14 ... pressing mechanism, 15 ... scanner arm, 16 ... linear array type probe, 17 ... intermediate mounting member, 18 ... rear end mounting member, 19 ... Oscillator, 20 ... Delay circuit.

Claims (3)

[Claims] 1. A method of measuring the depth of a defect generated in an inspection object by an ultrasonic method, wherein a longitudinal wave vertical probe is provided directly above the defect generated in the inspection object, and the longitudinal wave is generated. A transverse wave bevel probe is provided opposite to the vertical probe, one of these probes is used for transmission, and the other is used for reception, and an end echo that propagates after mode conversion at the tip of the defect. Position the both probes at the position where the maximum energy is, measure the distance between the incident points of the probe at this time, and derive the measurement result from the propagation route of the ultrasonic beam obtained geometrically. A defect depth measuring method characterized in that a defect depth is obtained by applying a calculation formula to the calculation. 2. A sensor holder, which is provided on an object to be inspected, for attaching at least one of a vertical wave vertical oscillator and a transverse wave oblique angle oscillator, a guide screw for attaching at least one of the both oscillators, and the guide screw is driven. Defect depth measuring device, comprising: a drive motor for driving, a position detector attached to the sensor holder or the guide screw, a pressing mechanism provided on the sensor holder, and a scanner arm to which the pressing mechanism is attached. . 3. A sensor holder to which at least one of a vertical-wave vertical oscillator and a transverse-wave oblique-angle oscillator provided on an object to be inspected is composed of a linear array type probe, and these transducers are mounted, and this sensor holder. 2. A defect depth measuring device comprising: a pressing mechanism provided in the above and a scanner arm to which the pressing mechanism is attached.