JPS6073453A - Ultrasonic flaw detecting method - Google Patents

Abstract

PURPOSE:To easily detect a planar defect such as ''cracking'' and measure its position and shape by comparing an ultrasonic indicator pattern with standard ultrasonic indicator patterns measured previously in various defect states, and measuring various defects. CONSTITUTION:An ultrasonic beam is transmitted from an oblique probe 1 for ultrasonic wave transmission on a plate 3 where X=infinity , namely, where there is no influence of a rib plate 4, and received by an oblique probe 2 ultrasonic wave reception, whose reception sensitivity is regarded as a reference level. The position on the bottom surface of the plate 3 where the ultrasonic beam is reflected is a measurement point. An indication received at sufficient distance from the rib plate 4 is at the reference level, but the amount of the ultrasonic wave beam reflected by the bottom surface of the plate 3 decreases as the position comes closer to the rib plate 4, the indication (of transmission into the rib plate 4) becomes lower than the reference level. A comparison with the standard indication pattern of every structure is made to estimate whether ''cracking'' occurs or not, or its length.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic flaw detection method, which is one of the methods of non-destructive testing.

[Technical background of the invention and its problems] The ultrasonic pulse reflection method using a probe, which is generally used in ultrasonic flaw detection tests to detect defects, uses ultrasonic pulses emitted from a probe. This is a method of estimating the existence, location, size, and properties of a defect by receiving the reflected pulses with the same probe. In this case, since the reflected ultrasonic pulse must be captured at the same position as the transmitted ultrasonic pulse, the defect detection sensitivity is maximized for defects that have a plane perpendicular to the incident acoustic beam.

Among the defects targeted during flaw detection inspection of structures, particular importance is placed on detecting planar "warps" such as "weld curls" and "fatigue cracks," as well as poor fusion of welds and insufficient penetration. Among non-destructive inspection methods, ultrasonic flaw detection is effectively used to detect planar defects such as these "curvatures" that exist inside the interior of the building. ,
As mentioned above, there is a problem in that when these defects exist parallel to each other in an ultrasonic beam, the detectability thereof is extremely small.

In the field of ultrasonic flaw detection technology, research on the effective detection, position measurement, and shape measurement of these defects has been particularly vigorously conducted in recent years.

For example, attempts are being made to differentiate the ultrasonic waveforms caused by these defects from the waveforms of other defects such as weld blowholes and slag entrainment by frequency analysis, and attempts are being made to distinguish between the ultrasonic waveforms caused by these defects and the waveforms of other defects such as weld blowholes and slag entrainment, and planar defects with sharp edges such as "wara". One example of this is research on an edge peak echo detection method that uses ultrasonic scattering near the tip. However, since the frequency analysis method requires frequency analysis for each individual ultrasonic waveform and pattern comparison of these frequency spectra, real-time flaw detection is not easy. In addition, in the edge beak echo method, the energy of the edge beak echo is relatively small compared to the energy of the ultrasonic main beam, so when detecting the edge beak echo, the sensitivity is sufficiently increased. If welding defects exist, the edge beak indication may be obscured by the indications caused by them. In other words, the edge beak echo method has a simple structure, has few welding defects, and is an extremely effective method for precision measurement when the presence of planar defects such as "wavy" is obvious to some extent. Therefore, when trying to detect flaws in a wide area, it takes time to detect flaws, which causes problems in application.

[Objective of the Invention] The object of the present invention is to easily detect planar defects such as "curvature", measure position, and measure shape without being affected by complex structures or welding defects. The objective is to provide an ultrasonic flaw detection method that makes it possible.

[Summary of the Invention] The present invention provides a method for transmitting and receiving ultrasonic beams.
Taking advantage of the fact that the received ultrasonic energy decreases when a defect such as a defect exists in the path of the main beam, one or more pairs of angle probes are used to scan the flaw detection point position and send and receive sound waves. The ultrasonic indication pattern determined by this method was compared with a standard indication pattern that had been determined in advance for various states of defects using the same method. It is characterized by evaluating and measuring the existence, position, or shape of.

In other words, the refraction angle of the ultrasonic transmitting angle probe and the receiving angle probe are determined based on the shape of the 4R structure to be detected and the position and direction where planar defects such as "cracks" are estimated to exist. The refraction angle is selected, and the probe position is determined and fixed so that the ultrasonic beam is reflected near the position where the "crack" or the like exists. The flaw detection point of this pair of oblique probes is the reflection point of the ultrasonic beam, and the flaw detection point is swept while accurately measuring the position of the flaw detection point. Since there is a difference in the degree of ultrasonic beam transmission between a healthy part with no defects and a defect, the indication pattern is measured in advance at various detection point positions and compared to the actual one. By comparing the indication patterns obtained during flaw detection, the presence of planar defects such as ``curvature'' is detected and their positions and shapes are measured.

[Embodiment of the Invention] FIG. 1 shows an embodiment in which the present invention is applied to a T-shaped welded structure with a twist.

FIG. 1(a) shows the structure of the inspection section. In the figure, reference numeral 1 denotes an oblique probe for transmitting ultrasonic waves, which emits an ultrasonic beam at a refraction angle θi as shown. Reference numeral 2 denotes an oblique angle probe for receiving ultrasonic waves, which receives an ultrasonic beam at a refraction angle θ'. Reference numeral 3 denotes a plate having a thickness t, which is an object to be examined, and is welded to a rib plate 4.

Reference numeral 5 indicates a ``curvature'' whose length is δ remaining in the welded portion, and this ``curvature'' 5 is initially generated from the clevis tip 6. 7 is weld metal.

The distance MLθ between the angle probes 1.2 and the refraction angle of the angle probes 1.2, as well as the propagation direction and length of the curve, are selected to be optimal. Fixed by relationship.

Lθ-t (tanθi + tanθr) Here, the center line of the rib plate 4 and the weld metal 7 is assumed to be X=O. X on the plate 3 =■ In other words, an ultrasonic beam is emitted from the ultrasonic transmitting angle probe 1 at a position not affected by the rib plate 4, and is received by the ultrasonic receiving angle probe 2. Sensitivity is the reference level.

The position where the ultrasonic beam is reflected on the bottom surface of the plate 3 (X=X in the figure, that is, the position at a distance of t・1a11θi from the transmitting angle probe 1hX to the receiving angle probe 2) is measured. It is a point. Indication 1.1 received at a position sufficiently distant from the rib plate 4 is at the reference level,
As the ultrasonic beam approaches the ribbed plate 4, the amount of the ultrasonic beam reflected from the bottom surface of the plate 3 decreases (transmits into the inside of the ribbed plate 4), so that the indication becomes lower than the reference level.

Here, we will explain the case where there is no "I" 5, that is, the healthy case when δ-0.

As the measurement point approaches the rib plate 4, the indication level becomes smaller than the reference level, but when it reaches near the tip of the clevis 6, the end peak echo reaches its maximum.
δ−0 of the indication pattern shown in FIG. 1(b)
As in the case of , the indication level partially rises to a peak and then falls again.

When “I” 5 exists, the decrease in the indication level from the standard level compared to the healthy case is X=XO(
It starts from a position where X is larger than the point at which the indication starts to decline in a healthy case, and the degree of attenuation increases.

While δ is small, the peak on the indication attenuation pattern due to the end beak echo from near the tip of the clevis 6 becomes slightly weaker but still exists, but when δ is large, that is, the length of the "curvature" 5 is large. Indeed, the peak becomes smaller and disappears, and the degree of attenuation becomes steeper.

The indication pattern shown in FIG. 1(b) is summarized using the length δ of "I" 5 as a parameter.
This attenuation characteristic data, ie, an indication pattern, is obtained (measured) in advance for each structure and recorded or stored as a standard indication pattern. Then, by comparing the attenuation pattern of the indication obtained during flaw detection with the standard indication pattern obtained in advance, peaks, etc. will be compared)
It is possible to estimate the presence or absence of "we" or its length. This indication pattern is clearly different from the pattern of the healthy part even when the "we" length is small, so
It is also effective for the newly born "I". Furthermore, by accurately measuring the position of the measurement point, for example, the distance from the center of the weld, the position of the "break" can also be estimated.

In addition, it is possible to detect not only the above-mentioned "flaws" but also poor fusion and insufficient penetration of the weld metal 7 using the same method as described above.

As mentioned earlier, in conventional normal flaw detection, due to the influence of the structure of the remaining clevis Ib rib plate 4 of the welded part, the detection of "cracks" that have started to occur, in particular, involves judgment of those indications. Therefore, flaw detection was not easy, requiring a technician with sufficient experience to perform flaw detection. In contrast, the method according to the present invention described above only needs to capture the attenuation pattern of the indication, and anyone can determine the existence of "I" even in the very early stages. In addition, since it is not necessary to evaluate each indication other than "we" during "we" flaw detection, it is possible to reduce the flaw detection time by narrowing down the target to, for example, "curvature" detection. Furthermore, even if a welding defect exists locally in a welded part, the attenuation characteristics are not significantly affected, and inspection can be performed only for detecting "cracks".

In this way, it is possible to detect planar defects such as "cracks" and measure their shapes simply by passing the ultrasonic beam through the estimated initial region of "cracks".

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without changing the gist thereof.

For example, FIG. 2 is intended for the same structure as in FIG. 1, but shows an example in which the approachable surface is the rib plate 4 side of the plate 3. For example, the ultrasonic beam may be reflected three times within the plate 3 to detect the estimated area where the "war" is first formed.

In addition, Figures 3(a) and 3(b) respectively show the configuration of the measuring section and the indication pattern when the plate 3 has a nearly perpendicular "warp" 5 that is difficult to detect in a normal ultrasonic flaw detection test. Then, with respect to the reference bell, at the position where "I" 5 exists, the existence of "I" and its length are measured using the fact that the indication level decreases according to the depth δ of "I" J5.

[Effects of the Invention] According to the present invention, there is no defect between the ultrasonic transmitting angle probe and the receiving angle probe that obstructs the passing ultrasonic beam;
For example, by using the fact that the ultrasonic indication pattern is different depending on when "we" exist and when "we" do not exist,
By comparing the ultrasonic indication pattern measured during inspection with a standard ultrasonic indication pattern that has been measured in advance for various defect conditions, the various defects mentioned above can be measured. It is possible to provide an ultrasonic flaw detection method that is less affected by cracks and welding defects and can easily detect planar defects such as cracks, measure the position, and measure the shape.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of flaw detection according to an embodiment of the present invention in the case where there is a crack in the clevis of a T-shaped welded structure, and Fig. 2 is a diagram showing another embodiment of the present invention (Fig. 1). Figure 1 shows an example of flaw detection from the opposite side, and Figure 3 shows another embodiment of the present invention (an example of flaw detection from the side that is almost perpendicular to the plate).
FIG. DESCRIPTION OF SYMBOLS 1... Bevel probe for ultrasound transmission, 2... Bevel probe for ultrasound reception, 3... Plate, 4... Rib plate, 5...
"Nare", 6... Clevis, 7... Welded metal. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure s3

Claims (1)

[Claims] Ultrasonic wave transmission and reception angle probes transmit and receive sound waves, and the flaw detection point position is scanned to obtain an ultrasonic indication pattern. An ultrasonic flaw detection method that is characterized by evaluating and measuring the presence, position, or shape of defects by comparing them with standard indication patterns that have been prepared for various states of existence of defects using a similar method.