JPH0128340B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel ultrasonic flaw detection method based on waveform observation of reflected ultrasonic waves. One of the ultrasonic flaw detection methods is the pulse reflection method, in which ultrasonic pulses emitted from a probe are applied to the inspection area such as a weld or inside a metal material, and the reflected waves are received by the probe again. I know. The problem here is that among such pulse reflection methods, the transmitter and the receiver belong to the same one-probe method, and also belong to the oblique angle method. By the way, in the conventional general pulse reflection method, by displaying a signal obtained by detecting (rectifying) the reflected wave, it is possible to check whether there are defects such as scratches or the interface between the metal material and the air. know the location,
Furthermore, the defect indication length is simply determined by scanning the probe. In other words, in the conventional pulse reflection method, only the envelope information is extracted by detecting (rectifying) the reflected wave, so the direct waveform (that is, high-frequency waveform) of the reflected wave does not include the properties of the boundary surface. Despite the fact that phase inversion occurs due to this, such important information is lost due to detection (rectification). For this reason, with conventional methods, it is not possible to distinguish between reflections from the corners that remain due to insufficient penetration and reflections from the plane that is the interface of the deposited metal in the weld, and the It has been found that there is a risk of missing the corner where the For example, in the conventional pulse reflection method, as shown in Fig. 1, a steel column 1 and a beam 2 are welded together with a backing metal 3. 5, it is difficult to distinguish between the boundary between the base body 1 and the backing metal 3 in a normal weld as shown in A, and the weld with poor penetration as shown in B. In case A, weld metal 4a and base material 1
In contrast, in case B, the weld metal 4a and the base body 1 are not sufficiently fused, and full penetration welding is performed at the corner part. This results in the defect 7 in which the corner portion is not formed and the corner portion remains. In such a case, the directly displayed waveform of the reflected wave obtained from the probe 5, that is, the waveform directly displayed as it is without detecting or rectifying the output from the probe 5, is ) Defect 7 where reflected waves and corners remain from
It has become clear from the study results of the present applicant that the reflected waves from the two parts have different shapes and therefore have phases inverted from each other. However, in the conventional method using the probe 5, both cases A and B are displayed in the same manner, making it difficult to distinguish between them. This invention has been made in consideration of the above points, and provides a completely new ultrasonic flaw detection method that can reliably find defects such as those described above that were overlooked by conventional methods. In the method according to the present invention, when an ultrasonic wave is transmitted with a refraction angle of 45 degrees toward the interface of the deposited metal of the welded part of the object to be inspected, the normal penetration occurs from the bottom surface (interface) of the six parts as described above. This was based on the discovery that the reflected waves from the defect 7 and the reflected waves from the defect 7, which remains at the corner due to poor penetration, have phases inverted from each other in their respective directly displayed waveforms. That is, this invention detects defects by emitting ultrasonic waves with a refraction angle of 45 degrees toward the boundary surface of the weld metal of the welded part of the object to be inspected, and by receiving the reflected waves from the boundary surface. When doing,
The present invention is characterized in that the presence of a defect in which a corner remains on the boundary surface is detected by detecting that the phase of the directly displayed waveform of the reflected wave is reversed. First, the principle of this invention will be clarified by explaining an experimental example that served as the starting point for this invention. Ultrasonic waves reflected from the plane 8 shown in FIG. 2A,
For each high-frequency waveform of the ultrasound reflected from the corner 9 shown in FIG.
When an experiment was conducted with the angle of refraction (refraction angle θ) at 45°, the results shown in Table 1 and Figure 3 were obtained.

[Table] In Figure 3, A is the waveform when the reflected wave from the plane 8 is received and directly displayed, and B is the waveform when the reflected wave from the corner 9 that exists due to the defect is received and directly displayed. It is a waveform. Here, direct display means directly displaying the received reflected wave without detecting or rectifying it. The waveforms of A and B differ by a phase angle of 180°, that is, a difference in waveform due to phase inversion. Next, the effectiveness of this invention will be clarified by setting up an actual flaw detection example. Example of flaw detection (see Figures 4 and 5) When the welded portion 13 of flat plates 11a and 11b butt welded together with the backing metal 12 was detected, defect 14 was found due to poor penetration.
As shown in FIG. 5, a clear difference was found in the waveforms of the reflected waves between the case where this occurred and the case where the weld metal boundary formed a curved surface 12 in a normal weld. In other words, Fig. 5A shows the high-frequency waveform of the reflected wave from the bottom of the curved surface 12 when the weld metal forms the curved surface 12 (boundary surface) during normal welding with sufficient penetration, and Fig. 5B shows the high-frequency waveform of the reflected wave from the bottom of the curved surface 12 (boundary surface). This is a high-frequency waveform of a reflected wave from a corner in a weld with a defect 14 remaining in the corner, and a phase reversal is observed in both. Therefore, by such a phase inversion of the waveform, it was possible to clearly determine whether or not the defect 14 in which the corner portion remained in the butt joint portion had occurred. In addition, horizontal scale of A: 0.2μsec/
1 scale, vertical scale: 50 mV/1 scale, horizontal scale B: 0.5 μsec/1 scale, vertical scale 50 mV/1 scale. By the way, in the above flaw detection example and the preliminary experiment described above, the probe 5 as shown in FIG.
A flaw detector 15 consisting of a pulsar receiver 15a and a synchroscope 15b was used, the specifications of which are shown in Table 2 below.

[Table] Regarding the flaw detection device used in the present invention, a wide-band probe 5 is preferable. This is because the ultrasonic waves emitted from a broadband probe (FIG. 7A) have a smaller wave number than those from a normal probe (FIG. 7B), making it easier to observe changes in waveform. Further, in order to make full use of the performance of such a broadband probe 5, it is preferable that the flaw detector 15 has a band that is five times or more the nominal frequency of the probe 5. Here, one from 1KHz to 35MHz was used.
In addition, as shown in FIG. 8, in addition to the detection signal display 16 of the existing flaw detector, the flaw detector also has the function of a high frequency display 17 that magnifies and directly displays the reflected wave portion 16a of the display 16. If so, it is extremely preferable for the use of this invention. As explained in detail above, according to the present invention, ultrasonic waves are emitted toward the boundary surface of the deposited metal of the welded part with a refraction angle of 45 degrees, and the waveform of the reflected wave from the boundary surface is directly displayed. When observed, by inverting the phase of this directly displayed waveform, it is possible to reliably detect defects that remain at corners at the interface of the deposited metal of the weld, which could not be done using conventional flaw detection methods. That is, the locations where the defects 7, 14 that remain at the corners are likely to occur can be roughly estimated in advance, and
Probe 5 is used to emit ultrasonic waves toward this location.
Since the position at which the probe should be placed can be determined in advance based on the refraction angle and the thickness of the object to be measured, the probe 5 is moved back and forth (or left and right) around this position, and the weld metal of the welded part is measured on the time axis. If you observe the directly displayed waveform of the reflected echo at the position where the reflected echo from the boundary surface should be displayed (this can also be determined in advance based on the sound speed, thickness, and refraction angle of the object being measured), you will know that the ultrasound is The phase of the directly displayed waveform of the reflected echo is inverted when it is emitted towards the defects 7 and 14 that have the remaining corners, and thereby the presence of the defects 7 and 14 that have the remaining corners can be detected. At the same time, its location can also be specified. In addition, the presence or absence of defects 7 and 14 remaining at the corners can be determined based on extremely extreme and easy-to-discern waveform changes such as whether or not the phase of the reflected wave appearing at a specific position has been reversed. Anyone can reliably detect defects 7, 14 that remain at corners and pinpoint their positions, regardless of the experience or intuition of the operator. In other words, it is not only possible to detect defects with residual corners that could not be detected by conventional ultrasonic flaw detection methods, but also the detection of these defects is reliable, simple, and quick. Needless to say, this is a very suitable flaw detection method in construction sites and other sites where it is difficult to secure a homogeneous workforce.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the object to be inspected according to the present invention;
Figure 2 is a diagram for explaining the experiment that became the starting point of this invention, Figure 3 is a waveform diagram showing the experimental results,
4 and 5 show an example of application of this invention,
Fig. 4 shows the object to be inspected, Fig. 5 shows its waveform, Fig. 6 is a block diagram showing the flaw detection device used in this invention, Fig. 7 shows the waveform of the ultrasonic waves emitted from the flaw detector, and Fig. 8 The figure shows a preferred display example of the flaw detection device. 4, 13... Welded part (part to be inspected), 5... Probe, 7, 14... Defect forming a corner, 8... Plane, 9... Corner, 12... Boundary surface.

Claims (1)

[Claims] 1. Emit ultrasonic waves from the probe at a refraction angle of 45 degrees toward the boundary surface of the weld metal of the welded part of the object to be inspected, and receive the reflected waves from the boundary surface with the probe. When detecting defects, by detecting that the phase of the directly displayed waveform of the reflected wave is reversed,
An ultrasonic flaw detection method for detecting the presence of defects that have corners remaining on the boundary surface.