JPH09274019A - Evaluation method for scale of defect by ultrasonic waves - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an evaluation methods in which the size of a defect can be evaluated precisely even regarding a spherical defect which is larger than the width of a beam by a method wherein an ultrasonic probe is scanned and the scale of the defect is evaluated on the basis of the distance between peaks in the intensity distribution of reflected waves. SOLUTION: When an ultrasonic array probe 1 is scanned in the X-direction, the center line 4 of a focused beam at an angle of -θ is passed through the center pi of a defect on the left side of a perpendicular line N when it comes to a position A. At this time, an ultrasonic beam perpendicularly hits the outside of the defect 10, and the intensity of reflected waves indicates an intensity distribution in which a peak is situated in the scanning position A. In addition, the center line 5 of a beam at an angle of θ. is passed through the center p1 of the defect 10 on the right side of the perpendicular line N. At this time, the beam perpendicularly hits the outside of the defect 10, the intensity distribution of reflected waves becomes a peak in a position A', and the distance between peaks becomes X1 . On the other hand, in a large defect 20, the distance B-B' between peaks in the intensitity distribution of reflected waves becomes X2 . Naturally, X1 (X2 , the distance between the peaks is changed according to the size of a defect, and the size of the defect can be estimated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic defect size evaluation method for evaluating the size of a defect by a reflected wave received by irradiating an ultrasonic wave.

[0002]

2. Description of the Related Art Conventionally, the following two methods, for example, are known as methods for evaluating the scale (width, length, etc.) of defects in an object to be inspected. One is a method of estimating the intensity of the reflected wave from the defect from the characteristic that the intensity increases as the defect becomes larger, and the other is that the intensity of the reflected wave is larger than a certain value when the probe is scanned. This is a method (for example, 6 dB down method) of estimating from the scanning width in which a defect is detected by the intensity of the reflected wave. The former is effective when the beam width is larger than the size of the defect, such as a spherical defect, and the latter is effective when the beam width is smaller than the size of the defect, which is targeted for the planar defect.

[0003]

By the way, in the case of detecting a small defect inside an object with high resolution, a focused beam obtained by narrowing an ultrasonic beam is often used. When such a beam is used, for a spherical defect larger than the focused beam width, the defect size cannot be accurately evaluated by the former method of estimating the defect size from the intensity of the reflected wave. Further, since the spherical defect has almost the same directivity of reflection regardless of the size of the defect, there is a problem that it cannot be evaluated from the scanning width of the probe.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to accurately evaluate the size of a defect even in a spherical defect larger than the focused beam width from the intensity of the reflected wave. It is to provide a defect size evaluation method that can be performed.

[0005]

In order to achieve the above-mentioned object, the present invention scans an ultrasonic probe for a defect,
Ultrasonic beams were applied from two different left and right directions of the defect, and the size of the defect was evaluated from the peak-to-peak distance in the intensity distribution of the reflected wave from each defect obtained.

Alternatively, a vertical line directed to the flaw detection surface or the ultrasonic probe scanning plane is detected in advance from the defect, and one of the two lines is detected on the upstream side and the downstream side in the scanning direction of the ultrasonic probe with respect to this vertical line. The ultrasonic probe is scanned to apply an ultrasonic beam to the defect, the intensity distribution of the reflected wave from the defect of the received ultrasonic beam is detected, and the peak of the intensity distribution of the detected reflected wave and the perpendicular line are detected. The size of the defect was evaluated from the distance.

In these cases, an ultrasonic focused beam in which the ultrasonic waves are narrowed down is used, and it is preferable to use an array probe as a means for generating the ultrasonic beam.

With this configuration, fluctuations in the peak position of the reflected wave intensity distribution obtained when the ultrasonic probe is scanned while the ultrasonic beam is emitted at a certain angle from the flaw detection surface with respect to the defect inside the object to be inspected. Therefore, the size of the defect can be evaluated. That is, the peak position of the reflected wave intensity distribution is
When the center of the defect coincides with the center line of the ultrasonic beam, the ultrasonic beam impinges on the defect surface perpendicularly.
Therefore, as the defect diameter increases, the defect center moves deeper, and the peak position moves accordingly.

Further, by focusing the focused beam on the defect, the peak of the reflected wave intensity distribution becomes sharp, and the peak position can be confirmed more accurately.

Further, since the array probe electronically switches the ultrasonic beam, the scanning speed of the ultrasonic beam can be made high and the angle of the ultrasonic beam can be freely set by changing the delay time.

[0011]

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

FIG. 1 is an explanatory view showing the principle of ultrasonic flaw detection according to an embodiment of the present invention. As can be seen from the figure, the diameter d1 centered on p1 is now inside the inspection body 15.
It is assumed that there are a spherical defect 10 and a spherical defect 20 having a diameter d2 centered on p2. Inspection body 1 having such a defect
The ultrasonic probe, in this case, the array probe 1 is scanned in the X direction along the flaw detection surface 3 of 5. Here, for convenience, a perpendicular line extending from the center of the defect 10 to the flaw detection surface 3 perpendicularly is set as N. In this case, ultrasonic waves are emitted from the defect 10 at an angle −θ on the left side of the perpendicular N and at an angle + θ on the right side.

First, a small defect 10 having a depth F from the flaw detection surface 3 to the defect surface and a diameter d1 will be described.
When the array probe 1 is scanned in the X direction, on the left side of the vertical line N, the center line 4 of the focused beam of the angle −θ sent from the array probe 1 passes through the center p1 of the defect 10 when it reaches the position A. . At this time, the ultrasonic beam hits the outer surface of the defect vertically, and the reflected wave intensity shows an intensity distribution that peaks at the scanning position A as shown in FIG. Further, on the right side of the vertical line N, when the center line 5 of the focused beam of the angle + θ sent from the array probe 1 comes to the position A ′, the center p1 of the defect 10
Pass through. At this time, the ultrasonic beam hits the outer surface of the defect 10 vertically, and the reflected wave intensity shows an intensity distribution that peaks at the scanning position A ′ as shown in FIG. The peak-to-peak distance AA ′ at this time is X1.

On the other hand, in the case of a large defect 20 having a depth F from the flaw detection surface 3 to the defect surface and a diameter of d2, the center of the focused beam of the angle −θ sent from the array probe 1 on the left side of the normal line N. When the line 6 comes to the position B, it passes through the center p2 of the defect 20. At this time, the ultrasonic beam perpendicularly hits the outer surface of the defect 20, and the reflected wave intensity shows an intensity distribution that peaks at the scanning position B as shown in FIG. Also, the vertical line N
On the right side of, the center line 7 of the focused beam of the angle + θ emitted from the array probe 1 passes through the center p2 of the defect 20 when it reaches the position B ′. At this time, the ultrasonic beam hits the outer surface of the defect 20 vertically, and the reflected wave intensity shows an intensity distribution that peaks at the scanning position B ′ as shown in FIG. The peak-to-peak distance BB ′ at this time is X2. Of course, X1
<X2, and the peak-to-peak distance changes depending on the size of the defect.

As described above, when the ultrasonic beam is scanned at a certain angle, the peak position of the reflected wave intensity varies depending on the size of the defects 10 and 20. Therefore, if the peak-to-peak distance X is measured, on the contrary, the defect size d can be estimated.

That is, the diameter d of a defect can be calculated by d = (X-2Ftan θ) / tan θ (1), where X is the peak-to-peak distance, F is the defect depth, and θ is the ultrasonic beam angle. The peak-to-peak distance X and the defect size d are shown in FIG.
The relationship is as shown in.

FIG. 4 shows that the array probe 1 is actually used.
It is a figure which shows the state which has carried out the flaw detection of the hole 30 opened with the drill of 1 mm in diameter in the steel of depth 20.14 mm. In this case, the ultrasonic beam has an angle of about ± 20 degrees and is focused near the surface of the hole 30. First, the array probe 1 is mechanically scanned while radiating an ultrasonic beam of -20 degrees right above the holes 30, and the reflected waves from the holes 30 are received. On the right side of the hole 30, the reflected wave from the hole 30 is similarly received while radiating the ultrasonic beam of +20 degrees. FIG. 5 is a diagram in which the intensities of the reflected waves at this time are plotted. The vertical axis represents the reception intensity, and the horizontal axis represents the scanning position of the array probe. From FIG. 5, the distance between the respective peaks is 14.5 mm. By substituting these values into the equation (1) and evaluating the diameter d of the holes, the value is 0.9.
8 mm.

FIG. 6 shows a diameter of 1 to 3 mm and a depth of 30 m.
These are the results of the evaluation of four types of holes of m or less, and from this result, the evaluation can be performed with an error of ± 20%.

In the above, the array probe 1 is mechanically scanned to transmit and receive ultrasonic waves. However, the long array probe 1 is used, and the array probe is electronically controlled by the ultrasonic beam. It is also possible to carry out transmission / reception without moving and to perform defect size evaluation. That is, the array probe 1 is mechanically moved (scanned) until a defect is detected, and the array probe 1 itself is not mechanically moved at the position where the defect is detected.
It is also possible to electrically scan the array probe 1 for transmission and reception.

In the above embodiment, the size of the defect is evaluated by detecting the peak-to-peak distance as described above. However, even if the distance between one peak and the perpendicular is measured, the defect The size can be evaluated. In this case, for example, the incident angle θ of the ultrasonic beam is set to 0 and the array probe 1
Is mechanically scanned to detect the peak position. Since this incident angle is 0, this peak position almost corresponds to the position of the perpendicular line N. When the position of the vertical line N is detected in this way, the array probe 1 is fixed to the detected peak position and electrically scanned at a preset incident angle θo to detect the peak position at the incident angle θo. When the distance from the perpendicular N to the peak at this time is Xo, F is the defect depth, and θo is the incident angle of the ultrasonic beam, the defect diameter is d = 2 (Xo-Ftanθo) / tanθo (2 ) Can also be calculated as

In this embodiment, when detecting the position of the vertical line N, scanning is performed with the incident angle θ of the ultrasonic beam emitted from the array probe 1 set to 0, but this is one example. It goes without saying that the position of the vertical line N may be detected by specifying the defect position by known ultrasonic flaw detection.

Although the array probe is used in this embodiment, it goes without saying that a normal ultrasonic probe having a single transmitting / receiving unit can also be used.

[0023]

As is apparent from the above description, according to the present invention, an ultrasonic beam is applied to a defect and the peak-to-peak distance of the intensity distribution of the reflected wave thereof, or the flaw surface or the ultrasonic probe from the defect. Since the size of the defect can be evaluated from the distance between the perpendicular to the scanning surface and the peak, it is possible to directly evaluate the diameter of a spherical or cylindrical defect larger than the ultrasonic beam diameter.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an evaluation principle of the present invention.

FIG. 2 is a diagram showing a state of intensity distribution of a reflected wave from a defect.

FIG. 3 is a diagram showing a relationship between a peak distance and a defect size.

FIG. 4 is a diagram showing a flaw detection state in the embodiment of the present invention.

FIG. 5 is a diagram showing an intensity distribution of a reflected wave in the embodiment of the present invention.

FIG. 6 is a diagram showing an experimental result in one embodiment of the present invention.

[Explanation of symbols]

 1 array probe 3 flaw detection surface 4,5,6,7 center line of ultrasonic beam 10,20 spherical defect 15 inspection object 30 hole F defect depth N perpendicular d1, d2 defect diameter p1, p2 defect center Position X1, X2 Peak distance θ, θo Incident angle of ultrasonic beam

Claims (4)

[Claims] 1. A method for irradiating ultrasonic waves to a defect in the inspection object while scanning the surface of the inspection object with an ultrasonic probe, and evaluating the scale of the defect from the state of reflected waves from the received defect. In the defect scale evaluation method by sound waves, the ultrasonic probe on the upstream side and the downstream side in the scanning direction of the ultrasonic probe with respect to the perpendicular from the defect toward the flaw detection surface or the ultrasonic probe scanning surface. Scan and irradiate the defect with an ultrasonic beam, calculate the intensity distribution of the reflected wave from the defect of the received ultrasonic beam, and evaluate the defect size from the peak-to-peak distance of the obtained reflected wave intensity distribution. A method for evaluating defect size by ultrasonic waves, characterized by: 2. A method of irradiating ultrasonic waves to a defect in an object to be inspected while scanning the surface of the object to be inspected with an ultrasonic probe, and evaluating the scale of the defect from the state of reflected waves from the received defect. In the defect scale evaluation method using sound waves, a perpendicular line to the flaw detection surface or the ultrasonic probe scanning plane is detected from the defect, and an upstream side and a downstream side in the scanning direction of the ultrasonic probe with respect to this perpendicular line. On the other hand, the ultrasonic probe is scanned to irradiate the defect with the ultrasonic beam, and the intensity distribution of the reflected wave from the defect of the received ultrasonic beam is calculated. An ultrasonic defect size evaluation method, characterized in that the defect size is evaluated from the distance between the perpendiculars. 3. The ultrasonic defect scale evaluation method according to claim 1, wherein the ultrasonic beam to be irradiated is a focused beam. 4. The ultrasonic defect size evaluation method according to claim 1, wherein the ultrasonic probe is an array probe.