JP3147271B2 - Defect size measurement method in ultrasonic flaw detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a defect size in an ultrasonic flaw detector.

[0002]

2. Description of the Related Art An ultrasonic measuring apparatus which outputs a portion having an echo level equal to or higher than a predetermined value in ultrasonic flaw detection to a CRT or the like as an image of a defect is generally commercially available. Has conventionally been estimated. That is, conventionally, using the dimensions of the cross-sectional image or planar image obtained by flaw detection, for example, in the case of precision flaw detection of welding defects, from the dimensions of the image obtained by the detection level of the echo corresponding to each of the defect classification, The actual size of the defect is calculated by the following estimation formula. (Refer to the JGA finger-104-89 Spherical Gas Holder Guidelines Technical Committee for Gas Machinery, etc. of the Gas Association of Japan) H = a ・ h + b (H: actual dimensions, h: image dimensions,
a, b: Coefficients a, b are coefficients obtained from a number of test results. In the above reference, for example, when the defect classification is a jig mark defect or a vertical crack in a weld line, a: 0.746 b: -1.77 + 4.50, and when the defect category is a lateral crack in the weld line, it is shown as a: 0.231 b: 8.86 + 7.78.

As shown in FIG. 1, the ultrasonic beam emitted from the probe 1 to the object to be inspected is diffused by the directional angle α, so that the distribution curve of the sound pressure level becomes gradually lower and wider according to the propagation distance. go. In figure 1, the sound pressure level on the central axis of the ultrasonic beam is decreased from P ₁ in the propagation distance X _1, a P ₂ in X _2.

Therefore, in the conventional ultrasonic flaw detection, the sensitivity is adjusted according to the distance so that the sound pressure level on the central axis of the ultrasonic wave is constant at any distance. For example the sound pressure level in the propagation distance X ₂ as shown in FIG. 2, is equal to the sound pressure level P ₁ in the propagation distance X _1.

[0005]

[SUMMARY OF THE INVENTION In the state of performing the distance sensitivity adjustment as described above, when the flaw detection with a constant detection level P _0, fault coverage W ₁ in the propagation distance X ₁ in the propagation distance X ₂ spread in W _2. That is, when flaw detection is performed at a fixed detection level, the defect detection range spreads at a fixed angle γ. Therefore, the actual size of a defect far from the probe is larger than that of a defect near the probe.
The image will be displayed larger in proportion to the propagation distance.

However, in the conventional ultrasonic flaw detector,
The proportional relationship between the propagation distance and the image size as described above is not taken into account, and the dimension is not corrected for the sound wave propagation distance. Therefore, an object of the present invention is to solve this point.

[0007]

In order to achieve the above-mentioned object, according to the present invention, a portion having an echo level equal to or higher than a predetermined value is displayed as a defect image, and a defect size is calculated from the image size. in the method, the ultrasound central axis
Distance so that the sound pressure level of the
In addition to adjusting the sensitivity according to the above , the correspondence between the image size and the actual size of the defect is obtained in correspondence with the reference position of the defect, and the image size is converted by the ratio of the reference position to the measured position of the defect. Then, it is proposed to calculate the actual size of the defect from the correspondence.

[0008] In the present invention, in the defect size measuring method for calculating and displaying a predetermined or more portions of the echo level from the back surface of the test object blemished as a defect image, the actual dimensions of the defect from the size of the image, the ultrasonic center The sound pressure level on the axis
Adjust the sensitivity according to the distance so that the distance is constant.
At the same time , the correspondence between the dimensions of the image and the actual dimensions of the defect is determined in accordance with the reference plate thickness, and the image dimensions are converted by the ratio of the reference plate thickness to the plate thickness at the time of measurement, and It is proposed to calculate the actual size of the defect from the relation.

[0009]

As described above with reference to FIG. 2, when the sensitivity is adjusted in accordance with the distance of the defect, the propagation distance and the defect detection range, that is, the image size of the defect are in a proportional relationship. To convert image dimensions.

Since the propagation distance is the product of the elapsed time and the sound speed, when a defect existing at the propagation distances X ₁ and X ₂ is detected by the reflection method, the time position of the defect echo, that is, the time between the incident wave and the echo, is detected. Assuming that the time difference is t ₁ and t ₂ and the sound velocity is c, 2
Since X ₁ = t ₁ · c ₂ X ₂ = t ₂ · c, the position of the defect can be detected from the temporal positions t ₁ and t ₂ of the defect echo, and thus the position or the position of the defect thus derived. The above conversion can be performed using the previous temporal position.

That is, the reference position (or reference time position)
Assuming that H = a · h ₀ + b (where h ₀ is an image size in the flaw detection at the reference position t ₀ ) based on the above-described equation for estimating the actual size H of the defect existing at t ₀ , The equation for estimating the actual size H of the defect at the position (or the temporal position of the defect echo) t ₁ is given by H = a · (t ₀ / t ₁ ) h ₁ + b (where h ₁ is the image of the defect at the position t ₁ ) Correcting as (dimensions) allows accurate estimation of actual dimensions from image dimensions.

Accordingly, the above-mentioned estimation formula is derived in advance from the test result for the reference position t ₀ which is set in advance using the reference test piece, and the above-mentioned estimation formula which uses the defect position t ₁ measured in the actual measurement as an input condition is obtained. By storing the defect in the flaw detector, the actual dimensions of the defects existing at various positions can be easily measured.

When the object to be inspected is the back surface of the plate as the object to be inspected, the reference position t ₀ of the defect is replaced by the reference plate thickness t ₀ , and the measured position t _{1 of} the defect is By storing in the flaw detection device the above estimation formula, which has been replaced with the thickness t ₁ of the flaw-detected object in the actual measurement, the flaw detection on the back surface of the flaw-detected object having a different thickness allows accurate detection from the image size of the defect. Estimation of actual dimensions can be performed.

[0014]

Since the present invention has been described above, a portion having an echo level higher than a predetermined level is displayed as a defect image.
In the defect size measuring method for calculating the actual size of a defect from the size of an image, there is an effect that the actual size of the defect can be accurately measured by converting a change in the image size due to a difference in the position of the defect.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a diffusion state of an ultrasonic beam in ultrasonic inspection.

FIG. 2 is an explanatory diagram showing a change in a defect detection range when the detection sensitivity in ultrasonic flaw detection is adjusted according to a distance.

[Explanation of symbols]

 1 Probe

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-58-88651 (JP, A) JP-A-5-126808 (JP, A) JP-A-61-96461 (JP, A) JP-A-1- 227056 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 29/00-29/28

Claims (2)

(57) [Claims] [Claim 1] to display the portion of the predetermined or more echo levels as an image of the defect, the defect size measuring method for calculating the actual dimension of the defect from the size of the image, the sound on the ultrasound central axis
Make sure that the pressure level remains constant at any distance.
In addition to the sensitivity adjustment, the correspondence between the dimensions of the image and the actual dimensions of the defect is determined in accordance with the reference position of the defect, and the image dimension is calculated as the ratio of the preset reference position to the measured defect position. And calculating the actual size of the defect from the correspondence described above. 2. A defect size measuring method for displaying a portion having an echo level equal to or higher than a predetermined value from a back surface of a flaw-detected object as a defect image and calculating an actual defect size from the image size.
The sound pressure level on the ultrasonic center axis is constant at any distance.
So that the sensitivity is adjusted according to the distance, and the correspondence between the dimensions of the image and the actual dimensions of the defect is determined in accordance with the reference thickness, and the image dimensions are compared with the reference thickness. A defect size measuring method in an ultrasonic flaw detector, wherein the actual size of a defect is calculated from the correspondence by converting the ratio with the plate thickness.