JPH11352111A - Polarized wave flaw detection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a flaw detection method by which the evaluation of the defects and the judgement of the kind can be easily performed by utilizing the polarization phenomenon in the angle ultrasonic wave flaw detection by 'straddle scanning', and checking the change of the sensitivity in a case when the polarization axes of a transmitter and a receiver are relatively changed. SOLUTION: A SV wave vibrating in the direction vertical to a plane of incidence of the ultrasonic wave is transmitted by a transmitter 6, and the SH wave vibrating in the direction horizontal to the plane of incidence of the ultrasonic wave is received by a receiver 7 to detect the flat defect 4a by the ultrasonic wave angle beam method by 'straddle scanning method' with an angle of refraction of 45 deg. and a straddle angle of 70 deg.. On this occasion, the SV wave reflected by the flat defect 4a is polarized by 90 deg. and converted into the SH wave, so that it can be efficiently received by the receiver 7. In a case when a spherical defect 4b is detected by the same method, the SV wave reflected by the flat defect 4a is not polarized, so that the SH wave can not be detected by the receiver 7. Accordingly the evaluation of the defect properties and the judgement of the kind can be performed by two kinds of flaw detections and checking the relative change of the defect detecting sensitivity in both flaw detections.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method, and more particularly to an ultrasonic flaw detection method suitable for evaluating defect properties and determining the type of the defect.

[0002]

2. Description of the Related Art Conventional ultrasonic flaw detection measures the size and position of a flaw by measuring the reflection, refraction, attenuation, and scattering of ultrasonic waves incident on a material due to discontinuities (flaws) in the material. However, it has not been considered that the polarization phenomenon occurs when the ultrasonic wave is reflected.

[0003]

In the above-described ultrasonic flaw detection, there are still some remaining technical improvements, one of which is a problem of improving the accuracy of flaw type discrimination.

An object of the present invention is to provide an ultrasonic flaw detection method that can more easily evaluate the defect properties and determine the type.

[0005]

In order to detect a flaw in a direction perpendicular to a welding line such as a lateral crack in a welded portion, FIG.
As shown in (b), one bevel probe is placed on each side of the welding line, one is used as a transmitter, and the other is used as a receiver. Has been done. In this method, the angle between the incident direction of the transmitting probe and the receiving direction of the receiving probe (a stride angle) is determined by the ultrasonic wave polarization phenomenon described below with respect to the planar defect. A phenomenon in which the defect detection sensitivity changes is known.

FIG. 2 is a diagram for explaining a change in defect detection sensitivity due to a polarization phenomenon in step scanning. In this figure, ← → indicates the direction of the deflection axis which is the vibration direction of the ultrasonic wave, but if the polarization phenomenon does not occur, the direction of the deflection axis of the reflected wave from the defect is the deflection axis of the incident wave as shown by the dotted line. Is obliquely symmetric.
In this case, since the signal is received by the receiver having the same polarization axis as the transmitter, no polarization loss occurs, and no change in the defect detection sensitivity due to the step angle occurs.

On the other hand, when the polarization phenomenon occurs and the direction of the deflection axis of the reflected wave from the defect is not obliquely symmetric with respect to the deflection axis of the incident wave as shown by the solid line, the receiver having the same deflection axis as the transmitter is used. When receiving by wave element, the defect detection sensitivity decreases according to the amount of polarization. The amount of polarization changes depending on the step angle. The theoretical consideration of such a phenomenon is reported by Lovelace (Materials Evaluation, Vol. 38, No. 12, (1980)), and A and B of the following equations are derived as the amount of polarization.

[0008]

(Equation 1)

[0009]

(Equation 2)

The transmission / reception sound pressure ratio of the reflected echo indicating the defect detection sensitivity in step scanning is expressed by the following equation.

[0011]

(Equation 3)

[0012]

2χ = 2 tan ⁻¹ (D / C ₁ ) (Equation 4)

[0013]

(Equation 5)

[0014]

D = (1-2 sin ² β) ² (Equation 6)

[0015]

Β = cos ⁻¹ ((sin θcos (γ / 2)) (Expression 7) θ: refraction angle, γ: step angle, 2 °: phase shift, β: incident angle to the reflection source C _S : transverse wave Sound velocity, C _L : longitudinal wave velocity, A, B and | P _r / P _i when the refraction angle is 45 °
The relationship | is shown in FIG. In particular, when the stride angle is 70 °, A = B = 0.5, and the amount of polarization of the reflected wave is 90 °, so that the transmission / reception sound pressure ratio | P _r / P _i | is the lowest. This is explained as follows.

In the general oblique flaw detection method, flaw detection is performed using a so-called SV wave that vibrates in a direction perpendicular to the ultrasonic wave incident surface, out of the transverse waves. In the case of a steep angle of 70 °, when the wave incident on the planar defect as an SV wave is reflected by the defect, SH vibrates in a direction horizontal to the ultrasonic incident surface.
This shows that the wave is converted into a wave that cannot be received by a general angle beam probe called a wave.

When the crossing angle becomes 70 ° or more, the transmission / reception sound pressure ratio | P _r / P _i | rises again because the amount of polarization of the ultrasonic wave becomes 90 ° or more, and the SV wave component is included in the reflected wave. This is because it occurs.

The sensitivity change when the polarization axes of the transmitter and the receiver are relatively changed using the polarization phenomenon in the oblique ultrasonic flaw detection by the "crossover scanning" described above can be examined. .

That is, the transducer capable of rotating the polarization axis measures the change of the polarization axis due to the reflection of the ultrasonic wave, and provides information for discriminating the type of the flaw.

[0020]

FIG. 4 shows an embodiment of the present invention.
This will be described with reference to FIGS. 9 (a) and 9 (b) to FIGS. 9 (a) and 9 (b). FIG.
(A) shows the transmission of ultrasonic waves in a direction perpendicular to the plane of incidence of ultrasonic waves in order to detect planar defects by ultrasonic oblique flaw detection by the “crossover scanning method” at a refraction angle of 45 ° and a crossover angle of 70 °. 1A and 1B are a plan view and a cross-sectional view of a first embodiment of the present invention in which an SV wave transmitter vibrating in the direction shown in FIG. In the figure, ，, 及 び and ← → indicate the vibration direction of the ultrasonic wave, ○ and ○ indicate that the vibration is in a direction perpendicular to the paper surface, and ← → indicates that the vibration is in the paper surface direction. In this case, the SV wave oscillating in the direction of the paper surface reflected by the planar defect is polarized by 90 ° and converted into an SH wave oscillating in the vertical direction of the paper surface. We can receive waves well.

On the other hand, FIGS. 4A and 4B show a case where a spherical defect is detected by the same method as described above. in this case,
The SV wave reflected by the planar defect is not polarized and remains as an SV wave oscillating in the direction of the paper surface, and thus cannot be detected by the SH wave receiver oscillating in the direction perpendicular to the paper surface. on the other hand,
In the conventional method of transmitting and receiving ultrasonic waves using SV waves, the defect detection sensitivity is poor for planar defects and conversely for spherical defects under the conditions of a refraction angle of 45 ° and a stride angle of 70 ° as described above. Good. Therefore, by performing the above two types of flaw detection and examining the relative change in the defect detection sensitivity of both,
It is possible to evaluate the defect properties and determine the type.

FIGS. 5A and 5B show a second embodiment in which the polarization axis of the ultrasonic transmitter can be rotated with respect to the first embodiment.
In the embodiment of the present invention, by rotating the polarization axis, it is possible to switch and transmit the SV wave and the SH wave from the same probe. By examining the actual change, it is possible to evaluate the defect property and determine the type. Fig. 6 (a), (b)
Is a third embodiment in which the polarization axis of the ultrasonic wave receiver can be rotated with respect to the first embodiment. By rotating the polarization axis, the SV probe and the SH Since the waves can be switched and received, the same effects as in FIGS. 5A and 5B can be obtained.

In the above embodiment, for simplicity, the transmission and reception of ultrasonic waves has been described as simple SV waves and SH waves. However, in principle, both transmission and reception waves have an SV wave component and an SH wave component. If it has a wave axis and the direction of the polarization axis of the receiver is different from the direction of the polarization axis of the transmitter, the defect property is evaluated and the type is determined using the polarization phenomenon at the planar defect. be able to. Also, the description has been made on the assumption that the refraction angle is 45 ° and the crossover angle is 70 °. However, in the case of a combination of different refraction angles and crossover angles, as described above, the polarization phenomenon at the planar defect is used. Thus, it is possible to evaluate the defect properties and determine the type.

In the above embodiment, a two-probe ultrasonic transducer having two ultrasonic transducers, of which the first transducer is used as a transmitter and the second transducer is used as a receiver. Although the description has been given on the premise of the flaw detection method, a dual-probe ultrasonic wave having two ultrasonic probes, and both the first transducer and the second transducer act as a transmitter and a receiver. In the flaw detection method,
Similarly, the evaluation of the defect property and the type determination can be performed. FIGS. 7 (a) and 7 (b) show a polarization flaw detection method in which the first transducer is an SV wave transducer and the second transducer is an SH wave transducer in the dual probe ultrasonic flaw detection method. FIG. 8 (a),
(b) is a fifth embodiment in which the polarization axis of the first vibrator and / or the second vibrator can be rotated.

Also, instead of rotating the transmitter or the receiver as in the second, third and fifth embodiments, FIG.
As shown in (b), in the sixth embodiment in which a plurality of receivers are provided and the polarization axes thereof are set in different directions, the evaluation of the defect properties and the type determination can be similarly performed.

[0026]

The sensitivity change when the polarization axes of the transmitter and the receiver are relatively changed by utilizing the polarization phenomenon in the oblique ultrasonic flaw detection by the "crossover scanning" described above. I made it.

[Brief description of the drawings]

1 (a) and 1 (b) are a plan view and a side view of FIG. 1 (a) for explaining oblique ultrasonic flaw detection by a conventional step scanning method.

FIG. 2 is an explanatory diagram of a change in defect detection sensitivity due to a polarization phenomenon in the step scanning in FIG. 1;

FIG. 3 is a cross-sectional angle and A and B when the conventional refraction angle is 45 °.
FIG. 4 is a characteristic diagram showing the relationship between | P _r / P _i |.

4 (a), (a) ′ and (b), (b) ′ are a plan view and a sectional view of a polarization flaw detection method in a two-probe ultrasonic flaw detection method according to an embodiment of the present invention.

FIGS. 5A and 5B are a plan view and a cross-sectional view of a second embodiment according to the first embodiment in which the polarization axis of the ultrasonic wave transmitter can be rotated.

FIGS. 6A and 6B are a plan view and a cross-sectional view of a third embodiment according to the first embodiment in which the polarization axis of the ultrasonic wave receiver can be rotated.

FIGS. 7A and 7B are a plan view and a cross-sectional view of a polarization inspection method according to a fifth embodiment of the present invention.

FIGS. 8 (a) and (b) are plan views of a fifth embodiment in which the polarization axes of the first vibrator and / or the second vibrator of the fourth embodiment can be rotated. Figures and sectional views.

FIGS. 9A and 9B are a plan view and a cross-sectional view of a sixth embodiment of the first or fourth embodiment in which the number of ultrasonic wave receivers is plural.

[Explanation of symbols]

1 ... Transmission ultrasonic probe, 2 ... Reception ultrasonic probe, 3
... welding line, 4 ... defect, 4a ... planar defect, 4b ... spherical defect, 5 ... ultrasonic beam, 6 ... transmitter, 7 ... receiver, 8 ...
Transmitting and receiving ultrasonic probe, 9 ... Transmitter and receiver.

Claims (6)

[Claims] 1. A two-probe ultrasonic flaw detection method having two ultrasonic probes, of which a first transducer is used as a transmitter and a second transducer is used as a receiver, An ultrasonic flaw detection method, wherein the direction of the polarization axis of the receiver is different from the direction of the polarization axis of the transmitter. 2. The ultrasonic flaw detection method according to claim 1, wherein the polarization axis of the transmitter can be rotated. 3. The ultrasonic flaw detection method according to claim 1, wherein the polarization axis of the receiver can be rotated. 4. A dual-probe ultrasonic flaw detection method comprising two ultrasonic probes, wherein the first transducer and the second transducer both act as a transmitter and a receiver. An ultrasonic flaw detection method wherein the directions of the polarization axes of the first vibrator and the second vibrator are different. 5. The ultrasonic flaw detection method according to claim 4, wherein the polarization axis of the first vibrator and / or the second vibrator can be rotated. 6. The ultrasonic flaw detection method according to claim 1, wherein the number of the transducers is plural.