JPH05172789A - Ultrasonic flaw detector - Google Patents

Abstract

PURPOSE:To enable detecting of the position and dimension of flaws existing in a inspected body of metal material and the like and also the distribution status of neighbouring flaws and indicating on a display. CONSTITUTION:An ultrasonic flaw detector 12 having a pair of horizontal wave slanting angle flaw detection vibrators 131, 132 which emit ultrasonic waves slantingly at a certain refraction angle from the opposit direction with respect to the vertical line into the inspected body 11 surface, is provided. The flaw detection data from each of the horizontal wave slanting angle flaw detection vibrators 131, 132 which is accompanied by the movement of the ultrasonic flaw detector 12 in its flaw detection scanning area, is stored in a wave shape memory 17. An opening synthesize signal processing is made with this flaw detection data stored in the wave shape memory 17 and this result is again processed for synthesizing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detector for detecting the position and size of a defect existing inside an object to be inspected, such as a metallic material, and the distribution of adjacent defects, and displaying the image.

[0002]

2. Description of the Related Art In an ultrasonic flaw detection method for detecting defects such as cracks, cavities and peeling existing inside an object to be inspected, such as a metallic material, using ultrasonic waves, in particular, improvement of measurement accuracy of defect size and proximity defect Is strongly desired, and in addition to this, there is an increasing demand for a technique for displaying and visualizing these results in an easily understandable manner.

As one of the typical techniques for achieving this purpose, the aperture synthetic ultrasonic signal processing method has been conventionally known. This method can be applied to the vertical flaw detection method and the oblique angle flaw detection method. Here, as shown in FIG. 7, the flaw detection apparatus according to the vertical method has a wide sound field characteristic, that is, a relatively small aperture. , A probe 1 capable of detecting flaw detection waveforms including defect information over a wide range inside the object to be inspected, a normal ultrasonic flaw detector 2, and flaw detection waveforms at respective probe positions during probe scanning. Taking as an example a data recording system 3 for recording as a digital value and an analysis processing system 4 for performing signal processing calculation and image display of the waveform data, this should be analyzed by aperture synthesis signal processing calculation. As shown in FIG. 8A, a defect is present on the specified region on an arc C ₁ (that is, an estimated defect existing range) having a radius of the beam path l ₁ of the defect echo at the probe position P _1. The echo amplitude is added, and As a result, the defect echo amplitude is added to the arcs C ₁ to C _{n according} to the flaw detection waveform data in the probe position range P ₁ to P _n where a certain defect is detected. The position of the intersection of the circular arcs C ₁ to C _n is the position of the defect, and the value of the added defect echo amplitude, that is, the strength of the sound pressure distribution after analysis is remarkably higher than the position of the intersection, because the position of the intersection is significantly higher than that around the intersection. If the entire analysis region is standardized by using the maximum value of this sound pressure distribution, a defect image showing a steep rise as shown in FIG. Even if it cuts at the threshold level, the result that the change in the defect size is small is obtained.

However, in the case of oblique flaw detection with a relatively large refraction angle or in the case of oblique flaw detection where the surface to be inspected has a concave curvature, a situation different from that in the case of vertical flaw detection is obtained. Here, as an example of the case of aperture synthesis processing in oblique flaw detection, as shown in FIG. 9A, a flaw detection waveform obtained by scanning from the probe position range P ₁ to Pn where a certain defect is detected. The estimated defect existing position range calculated using the data, that is, the arcs C ₁ to C _n to which the defect echo amplitudes are sequentially added are close to each other with a relatively small angle due to the relationship between the refraction angle and the moving direction of the probe. It will be drawn at the position you did. Also in this case, the intersection of the arcs C ₁ to C _n is defective,
The value of the added defect echo amplitude, that is, the sound pressure distribution after analysis is maximum at this point, but the left and right circular arcs C ₁ to C _{n of} the intersections along the direction perpendicular to the ultrasonic beam are close to each other. In the part, the addition of the defect echo amplitude is relatively dense, although not as much as at the intersection, so if the entire analysis region is normalized by the maximum value of the sound pressure distribution at the intersection, the sound is as steep as the vertical method described above. Instead of the pressure distribution, as shown in FIG. 9B, the foot of the sound pressure distribution on the left and right of the defect position becomes gentle.

This tendency becomes particularly large when the surface to be inspected has a concave curvature in the oblique angle inspection, as shown in FIG.
Based on the relationship between the traveling direction of the ultrasonic beam and the moving direction of the probe, the probe waveform data obtained by scanning from the probe position range P ₁ to P _n where the defect is detected is used as shown in FIG. The calculated estimated defect existing position range, that is, the arcs C ₁ to C _n to which the defect echo amplitudes are sequentially added are drawn on almost the same curve. Therefore, the sound pressure distribution near the defect existing position becomes a similar value along this curve, and FIG. 10B showing the result of normalizing the entire analysis region by the maximum value of the sound pressure distribution is the same as the one described above. The bottom of the sound pressure distribution on the left and right of the defect position becomes gentler than the result of the aperture synthesis calculation processing by oblique angle flaw detection when the inspection surface is flat.

[0006]

As described above, in the case of the plane oblique flaw detection with a relatively large refraction angle or in the case where the surface to be inspected has a concave curvature in the oblique flaw detection, the analysis processing is performed. Unlike the case of vertical flaw detection, the resulting sound pressure distribution becomes gentle, but in such a case, the maximum sound pressure, which is a general method for measuring defect dimensions, is used as a reference.
If a threshold value is set at a level such as 50% and the defect dimension is measured from the distance of the points that cross the threshold value, the sound pressure distribution becomes steep as shown in FIGS. 11 (a) and 11 (b). If the threshold level is set to any value, the defect size does not change much, but if the sound pressure distribution is gentle, the defect size changes significantly at the set threshold level. There was a flaw.

The present invention has been made in view of the above circumstances, and a cross-sectional image of a defect existing inside an object to be inspected is not affected by the incident angle of ultrasonic waves or the polarities of the surface of the object to be inspected having a curved surface. An object of the present invention is to provide an ultrasonic flaw detector that can be reconfigured, is less affected by the height of a threshold value set for defect dimension measurement, and has high defect dimension measurement accuracy.

[0008]

SUMMARY OF THE INVENTION The present invention has a pair of transverse wave oblique flaw detectors which obliquely enter an ultrasonic beam at a constant refraction angle from opposite directions across a normal line on the surface of the object to be inspected. Ultrasonic probe, storage means for storing the flaw detection data from each of the above-mentioned transverse wave oblique angle flaw transducers associated with the movement of the flaw detection scanning range of the ultrasound probe, and flaw detection data stored in this storage means Is subjected to aperture synthesis signal processing, and these results are subjected to synthesis processing again.

[0009]

According to such a flaw detector, the reconstructed defect image can be clearly seen, that is, in the case of a plane oblique flaw detection with a relatively large refraction angle or a flaw surface having a concave curvature in the oblique flaw detection. When the defect size is measured, it is possible to improve the sound pressure distribution after the smooth analysis processing that spreads to the left and right of the defect with a strong tendency to a sharp sound pressure distribution concentrated in the defect. At the point where the sound pressure distribution increases beyond the threshold value,
The defect size calculated from the distance of the points falling below the threshold value has a small fluctuation range even if the threshold level to be set is set high or low, that is, the influence of the threshold level setting value is small. It is possible to improve the accuracy of defect dimension evaluation and the resolution of adjacent defects.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of an ultrasonic flaw detector according to the present invention. In this case, the ultrasonic probe 12 placed on the surface of the device under test 11 has a pair of ultrasonic waves in which the absolute values of the refraction angles are equal and the ultrasonic wave incident directions are opposite to each other with the normal line at the incident point therebetween. Transverse wave bevel transducers 131 and 132 are built in, and are connected to an ultrasonic flaw detector 15 via a probe switching device 14 that selects which of these transducers to use.

The ultrasonic flaw detector 15 applies an excitation pulse for transmitting ultrasonic waves to each transducer in a time-division manner, and converts a reflection echo from a defect inside the object to be inspected into an electric signal. The received flaw detection waveform is the A / D converter 1
Waveform memory 17
Sent to. The waveform memory 17 records the received flaw detection waveform for each probe. The probe 12 is attached to the probe driving device 18, and the position associated with the probe scanning is detected by the probe position detector 19. The output of the probe position detector 19 in this case is also recorded in the waveform memory 17 together with the flaw detection waveform data.

All the flaw detection waveform data recorded in the waveform memory 17 are sent to the arithmetic processing unit 20 and the aperture synthesis processing operation is performed. In this case, the input of the analysis range and the analysis conditions is performed by the input device 21, and the display of the sectional image as the analysis result is performed by the output display device 22 such as a CRT display. Further, initial conditions such as a refraction angle and an incident point position that are slightly different for each probe are input in advance in the probe characteristic memory 23, and this internal data is referred to during analysis. In addition, 24 is a flaw detection control device,
A series of operations of each functional block described above are controlled. Next, the operation of this embodiment will be described.

First, the flaw detection operation will be described with reference to FIG.
First, specify the scanning range of the ultrasonic probe (step A
1). Next, as shown in FIG. 3A, a left ultrasonic beam is output from the oscillator 131, and flaw detection waveform data recording by this ultrasonic beam is recorded (step A2). Similarly, as shown in FIG. 3B, the transducer 132 outputs an ultrasonic beam in the right direction and records flaw detection waveform data by the ultrasonic beam (step A3). Next, the probe position data is recorded in time division (step A4), and the probe is moved to the next flaw detection position (step A5). This operation is repeated over the specified flaw detection range, and if YES in step A6, the flaw detection operation ends.

Next, the analysis operation will be described with reference to FIG.
In this case, after the analysis region is designated (step B1), as shown in FIG. 5 (a), the flaw detection echo is performed on each pixel in the analysis region using all the flaw detection waveform data based on the left ultrasonic beam of the transducer 131. The amplitude value is added together with the signal polarity (step B2, step B3), and similarly, as shown in FIG.
As shown in (b), the processing for adding the flaw detection echo amplitude value to each pixel in the area is performed using all the flaw detection waveform data based on the right direction ultrasonic beam of the transducer 132 (step B).
4, step B5). Then, the addition processing results of the amplitude values using the ultrasonic beams incident on the analysis region from the left and right directions in this way are added to each other (step B).
6) After that, each pixel is squared and converted into an amount corresponding to energy (step B7), and finally the value of each pixel is standardized by the maximum value in the analysis region, and aperture synthesis is performed. The sound pressure distribution is standardized by the processing (step B8). It should be noted that the transducers that generate the leftward ultrasonic beam and the transducers 131 and 132 that generate the rightward ultrasonic beam are slightly different from each other in terms of manufacturing error in the refraction angle, the incident point, the beam path within the shoe, and the like. Therefore, by referring to these values which are input in advance in the probe characteristic memory 23, correction is performed when the analysis results from the left and right directions are added together (step B).
9).

By thus recombining the analysis results from both the left and right directions, the reconstructed image of the defect shown in FIG. 6 (a) is compared with the surroundings in the vicinity of the intersection where the analysis results from the left and right directions intersect. There is a remarkably high portion of the sound pressure distribution, and the rise of the sound pressure distribution becomes steep as shown in FIG. 6 (b), and the influence of the level of the threshold value level when determining the defect size is affected. You can do less.

[0017]

According to the present invention, the threshold value level is set in the aperture synthesis signal processing in the case of flat bevel flaw detection with a relatively large refraction angle or the flaw detection surface having a concave bend, and a defect level is set. A flaw detection waveform in which the gentle sound pressure distribution around the defect image after analysis processing, which is a problem when measuring dimensions, is recorded as data by a transducer that emits ultrasonic beams in both left and right directions incorporated in one probe. By synthesizing and analyzing from, it is possible to improve the sound pressure distribution with a sharp rising edge concentrated in the vicinity of the defect, and it is possible to reduce the influence of the high and low threshold levels set when determining the defect size. It is possible to improve the accuracy of defect dimension evaluation and the resolution of adjacent defects.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure of flaw detection operation in the embodiment shown in FIG.

FIG. 3 is a view for explaining a flaw detection operation in the embodiment shown in FIG.

4 is a flowchart showing a procedure of aperture synthesis calculation processing in the embodiment shown in FIG.

FIG. 5 is a diagram for explaining arithmetic processing in the embodiment shown in FIG.

FIG. 6 is a diagram for explaining an analysis result in the embodiment shown in FIG.

FIG. 7 is a diagram showing a processing system of a general vertical aperture synthesis method.

FIG. 8 is a diagram showing the characteristics of the oblique angle flaw detection aperture synthesis method in the case where the vertical surface, the oblique angle, and the surface to be inspected have a concave curvature.

FIG. 9 is a diagram showing characteristics of the oblique angle flaw detection aperture synthesis method in the case where the vertical surface, the oblique angle, and the surface to be inspected have a concave curvature.

FIG. 10 is a diagram showing the characteristics of the oblique angle flaw detection aperture synthesis method in the case where the vertical surface, the oblique angle, and the surface to be inspected have a concave curvature.

FIG. 11 is a diagram for explaining the influence of the shape of the sound pressure distribution on the defect size measurement according to the conventional technique.

[Explanation of symbols]

11 ... Inspected object, 12 ... Ultrasonic probe, 13 ... Transducer,
14 ... Probe switching device, 15 ... Ultrasonic flaw detector, 16 ... A /
D converter, 17 ... Waveform memory, 18 ... Probe drive device, 19 ... Probe position detector, 20 ... Arithmetic processing device,
23 ... Probe characteristic memory, 24 ... Flaw detection control device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Nagai 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Keihin Office (72) Inventor Taiji Hirasawa 2-4, Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Address inside Toshiba Keihin office

Claims (1)

[Claims] 1. An ultrasonic probe having a pair of transverse-wave oblique-angle flaw-detecting transducers that obliquely enter an ultrasonic beam at a constant refraction angle from opposite directions across a normal line on the surface of the object to be inspected. Storage means for storing the flaw detection data from each of the above-mentioned transverse wave oblique angle flaw detection transducers accompanying the movement of the flaw detection scanning range of the ultrasonic probe, and aperture synthesis signal processing for the flaw detection data stored in this storage means. An ultrasonic flaw detector, comprising: a data processing unit that synthesizes these results again.