JP2000028588A - Ultrasonic flaw detecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily detect material flaws for a complicated shape of a testing body, for which angle beam flaw detection and surface wave flaw detection are difficult to be applied in a normal method, in particular the material flaw generated in a cylindrical face. SOLUTION: In this ultrasonic flaw detecting method, in which a flaw detection signal is output to a submerged probe 1 from an ultrasonic flaw detector 40, and in which an ultrasonic wave is made incident into a flaw-detected object existing in water via the water to detect a flaw, the ultrasonic wave is emitted making the probe 1 made to face to an inflection point 3, where the variations of a surface shape of a material comes to a prescribed amount or more discontinuously so as to get incident into a testing body 8, ultrasonic waves of plural vibration modes generated simultaneously in an incident point of the ultrasonic wave are propagated inside the testing body 8, and echoes reflected in a propagation process therein are detected to conduct flaw detection for a surface of a curved surface part 8a.

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 which is a kind of nondestructive inspection, and more particularly to an ultrasonic flaw detection method for detecting a flaw in a flaw-detected object such as a steel material in water.

[0002]

2. Description of the Related Art In a conventional ultrasonic flaw detection method, a flat and smooth surface of a test material (object to be flawed) is selected as much as possible, and an ultrasonic probe is applied to the surface. Ultrasonic waves are made to enter from the surface on which the probe is applied, and the ultrasonic waves reach a target position by using refraction or mode conversion of the ultrasonic waves at the incident point. For this reason, in the case of a material having a curved surface or the like, the ultrasonic wave may not be able to reach the detected ultrasonic wave.

[0003]

FIG. 6 is a diagram showing an example of a conventional water immersion type ultrasonic flaw detection method. In the drawing, for example, in a flaw detection for a test object (a flaw detection target) 60 in which a flaw 62 exists in a part of a cylindrical surface 61, the water immersion probe 1 is set at a predetermined angle with respect to a flat surface 63. The ultrasonic wave is emitted at an angle, and the ultrasonic wave is incident from the flat surface 63. In this case, in the conventionally known oblique flaw detection method, since the ultrasonic wave propagates along a path indicated by reference numeral 64 in FIG. 6, the incident point of the ultrasonic wave on the test body 60 is limited. The echo 65 from the flaw 62
In addition, an echo 66 from the cylindrical surface 61 is generated,
2 was sometimes difficult to identify.

On the other hand, when a creeping wave 67 propagating just below the flat surface 63 of the flaw-detected object is used, the ultrasonic wave incident point is limited to the same flat surface 63 as described above, and furthermore, the inflection in shape is caused. Since the propagation of the sound wave is stopped at the point 68, the flaw 62
In some cases, ultrasonic waves could not reach.

[0005] On the other hand, there is also known a direct injection method in which ultrasonic waves are directly incident on the surface of the cylindrical surface 61 through a path indicated by reference numeral 70 to perform flaw detection. In this method, light is incident from the opening side of the flaw 62. However, in the case of the flaw 62 having a small opening width, since the echo reflected at the flaw opening is small, it is difficult to determine whether the flaw is a flaw or noise. Detection was difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances of the prior art, and has as its object to provide an ultrasonic flaw detection method capable of detecting a flaw in a curved surface of a test piece having a complicated shape.

[0007]

In order to achieve the above object, a first means is a probe for transmitting and receiving ultrasonic waves in water, a pulse transmitting means for supplying a pulse voltage to the probe, Using an ultrasonic flaw detector equipped with a receiving and amplifying means for amplifying a signal received by the probe and a waveform display means for displaying a received signal waveform of the received signal. In the ultrasonic flaw detection method in which ultrasonic waves are incident through water to perform flaw detection, the probe is opposed to an inflection point where a material surface shape discontinuously changes by a predetermined amount or more, and the probe is used to perform the deformation. The ultrasonic wave is made incident on the object to be probed from a curved point, and ultrasonic waves of a plurality of vibration modes simultaneously generated at the incident point of the ultrasonic wave are propagated into the object to be detected, and are reflected in the course of the propagation. It is characterized by detecting and detecting an echo.

The second means is characterized in that, in the first means, out of the ultrasonic waves mode-converted at the inflection point, a defect is detected based on the ultrasonic wave propagating in the surface layer of the material.

[0009] A third means is the first means, wherein the inflection point, which changes discontinuously by a predetermined amount or more, has a change amount such that propagation of a sound wave is prevented at least at the time of flaw detection using a creeping wave. Characterized by having an inflection point.

The fourth means is characterized in that in the first means, the pass / fail of the flaw detection object is determined based on the presence or absence of a remaining signal obtained by subtracting a previously stored echo waveform of a sound part from the echo waveform. I do.

The present invention is characterized in that the point of incidence of the ultrasonic wave on the test piece is an inflection point, which is a discontinuous portion having a shape that has not been found in the past. The principle of this detection will be described with reference to FIG.

As shown in FIG. 5, when the water immersion probe 1 is tilted by an arbitrary angle θ and the ultrasonic wave (longitudinal wave) 2 is made incident on the inflection point 68 of the shape of the test body 60, the ultrasonic wave 2 propagates in the specimen 60 as a longitudinal wave, while another part is converted into several vibration modes, one of which is along the cylindrical surface (curved surface) 61 of the specimen 60. To become an ultrasonic wave 69 that propagates. This phenomenon is a new finding confirmed by an experiment, and is used to detect a material flaw generated on the surface of the curved surface 61. The inflection point 68 at which the ultrasonic wave is incident is a portion where a discontinuous surface change having a change amount such that the propagation of the sound wave is prevented when the creeping wave 67 described in the related art is used is generated. It is enough.

[0013]

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

FIG. 1 is a system configuration diagram for explaining an ultrasonic flaw detection method according to one embodiment of the present invention. In this figure, the ultrasonic flaw detection system includes an ultrasonic flaw detector 40,
It is basically composed of the water immersion probe 1 connected to the ultrasonic flaw detector 40 and transmitting and receiving ultrasonic waves. The ultrasonic flaw detector 40 is mainly composed of a pulse transmitter 41, a reception amplifier 42, a waveform display unit 43, and the like.
Outputs a pulse to the immersion probe 1 from the
And emits ultrasonic waves through the water, and enters the specimen 8 through water,
The reflected echo is detected by the water immersion probe 1 and input to the receiving amplifier 42, and the amplified received waveform is displayed on a waveform display 43 composed of, for example, a CRT to detect the position and size of the flaw. It is supposed to.

In this example, when detecting the flaws 6 on the surface of the curved surface portion 8a of the test body 8, the water immersion probe 1 is tilted by about 5 degrees to emit ultrasonic waves, and to the inflection point 3 of the shape. An ultrasonic beam (longitudinal wave) 2 was incident. The incident ultrasonic wave 2 is converted into several vibration modes at the inflection point 3 and propagates through the material, but the ultrasonic wave 5 in one of the modes propagates through the surface layer of the curved surface portion 8a and the defect 6 is detected. Is done. The incident angle θ of the ultrasonic wave from the probe 1 depends on the change amount and the surface shape of the inflection point 3 at an angle at which the ultrasonic wave 5 can propagate along the surface of the curved surface portion 8a. Is set as appropriate.

At this time, a waveform display section (hereinafter simply referred to as "CRT") 4 composed of a CRT of the ultrasonic flaw detector 40.
FIG. 2 shows the signal waveform displayed in FIG. In FIG. 2, the position of the starting point of the horizontal axis of the CRT 43 is adjusted to be the inflection point 3 of FIG. 1, that is, the position of the ultrasonic wave incident point.
The time axis of the RT 43 is adjusted so as to be a time for reciprocating 50 mm at the speed of sound of the shear wave.
Is an echo directly from the incident point of the ultrasonic wave, that is, the inflection point 3, and an echo 11 from the flaw 6 is displayed at a position delayed by a time corresponding to a distance of 12.5 mm therefrom.
The actual position of the flaw 6 is measured from the inflection point 3 to 11.
Since it was at a position of 5 mm, the echo 11
Is displayed at a position 1 mm farther from the position.

The sound speed of the ultrasonic wave 5 generated at this time is (11.5 mm / 12.5 mm) × 3230 m / s = 230 m / s, where the sound speed of the transverse wave used for calibrating the time axis of the CRT 43 is 3230 m / s.
970 m / s, which is almost equal to the sound speed of the surface wave. .

In FIG. 2, in addition to the above, the ultrasonic wave 5 in which the ultrasonic wave 5 is mode-converted into a shear wave by the flaw 6 is echo-reflected by the bottom surface 9 of the test piece 8 and the ultrasonic wave 7 is mode-converted into the shear wave by the inflection point 3. Ultrasound 4 can also see echo 12 reflected on bottom surface 9.

FIG. 3 shows a signal waveform obtained by flaw-detecting a so-called flawless test piece whose shape cannot be the same as that of the test piece 8 and does not include the test piece 6. Here, the flaw 6 and the mode conversion echo 13 at the flaw 6 which are clearly displayed in FIG. 2 are not detected, and the direct echo 10 from the inflection point 3 and the mode conversion echo at the inflection point 3 are also detected. Only 12 are measured.

FIG. 4 is a diagram showing a system configuration of an ultrasonic flaw detection system according to another embodiment. This embodiment is an example provided with a pass / fail judgment device 50 for making a pass / fail judgment of the test body 8 using the difference between the waveforms of the flaw portion and the healthy portion shown in FIGS. This pass / fail determination device 50
, Only the configuration different from the configuration of FIG. 1 will be described, and the description of the overlapping parts will be omitted.

The pass / fail judgment device 50 includes a sound waveform storage unit 52 for storing a waveform of a sound portion (for example, FIG. 3) in advance, and a flaw detection waveform recording unit for recording a flaw detection waveform including flaw echoes (for example, FIG. 2). 51, and a comparison device 53 for comparing the waveforms of the two, an output from the receiving amplifier of the ultrasonic flaw detector 40 is input, and a comparison output from the comparison device 53 is output as a pass / fail signal 54. ing.

The comparison device 53 subtracts the sound part waveform 52 stored in advance from the flaw detection waveform (FIG. 2) recorded every moment. If there is no remaining signal, it passes. As a flaw signal, that is, reject. This makes it possible to automatically determine the presence or absence of the flaw 6 on the surface of the curved surface 61 of the test body 8.

[0023]

As described above, according to the present invention, the probe is made to face the inflection point where the surface shape of the material changes discontinuously by a predetermined amount or more, and the ultrasonic wave is emitted and incident on the inspection object. Then, ultrasonic waves of multiple vibration modes generated simultaneously at the point of incidence of the ultrasonic wave are propagated into the object to be detected, and the echo reflected during the propagation is detected and flaw-detected, which hinders the propagation of the ultrasonic wave. It is possible to easily detect a flaw in a curved surface portion of a test piece having a complicated shape having such an inflection point.

Further, since the pass / fail of the test specimen is determined based on the presence or absence of the remaining signal obtained by subtracting the waveform of the echo of the sound part stored in advance from the waveform of the detected echo, the pass / fail judgment of the test specimen can be automatically performed. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of an ultrasonic inspection system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a flaw detection waveform of a test piece having a flaw.

FIG. 3 is a diagram showing a flaw detection waveform of a test piece having no flaws.

FIG. 4 is a diagram showing a system configuration of an ultrasonic inspection system according to another embodiment of the present invention.

FIG. 5 is a diagram for explaining the principle of the ultrasonic flaw detection method of the present invention.

FIG. 6 is a view for explaining a conventional ultrasonic flaw detection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Immersion probe 2 Ultrasonic wave (longitudinal wave) 3 Inflection point of shape 4 Ultrasonic wave (transverse wave) 5 Ultrasonic wave 6 Flaw 7 Ultrasonic wave (transverse wave) 8 Specimen 9 Bottom surface 10, 11, 12, 13 echo Reference Signs List 40 ultrasonic flaw detector 41 pulse transmitter 42 reception amplifier 43 waveform display unit 50 pass / fail judgment device 51 flaw detection waveform recording unit 52 sound part waveform storage unit 53 comparison device 54 pass / fail signal

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shiro Miura 3-1-1, Sachimachi, Hitachi-shi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Isao Nemezawa Sachimachi, Hitachi-shi, Ibaraki 1-chome F-term (reference) in Hitachi, Ltd. Hitachi Works 2G047 AA07 AB01 BA03 BB06 GG33

Claims (4)

[Claims] A probe for transmitting and receiving ultrasonic waves in water; a pulse transmitting means for supplying a pulse voltage to the probe; a receiving and amplifying means for amplifying a signal received by the probe; An ultrasonic flaw detector which performs ultrasonic flaw detection by using an ultrasonic flaw detector having a waveform display means for displaying a received signal waveform of a received signal and irradiating an ultrasonic wave through water to an object to be detected existing in water. In the above, the probe is opposed to an inflection point at which a material surface shape discontinuously changes by a predetermined amount or more, and the probe causes the ultrasonic wave to enter the object to be inspected from the inflection point, An ultrasonic flaw detection method in which ultrasonic waves of a plurality of vibration modes simultaneously generated at the point of incidence of a sound wave are propagated through a flaw-detected object, and an echo reflected during the propagation is detected for flaw detection. 2. The ultrasonic flaw detection method according to claim 1, wherein a flaw is detected by an ultrasonic wave propagating through a surface layer of a material among the ultrasonic waves mode-converted at the inflection point. 3. The inflection point that discontinuously changes by a predetermined amount or more is an inflection point having an amount of change that at least prevents propagation of a sound wave during flaw detection using a creeping wave. The ultrasonic flaw detection method according to claim 1. 4. The ultrasonic flaw detection method according to claim 1, wherein the pass / fail of the flaw detection object is determined based on the presence or absence of a remaining signal obtained by subtracting the prestored echo waveform of the sound part from the echo waveform.