JPS61228345A - Method for measuring depth of surface aperture flaw of solid by ultrasonic wave - Google Patents

Abstract

PURPOSE:To enable easy and highly accurate measurement in a real time without receiving the effect due to the inclination of a flaw, by measuring the depth of a flaw by using the propagation time of the scattered wave reflected from the leading end of an aperture flaw of an incident ultrasonic wave as an evaluation index. CONSTITUTION:An ultrasonic wave being a longitudinal wave is vertically incident to the surface of an object 1 to be inspected having an aperture flaw 1a so as to be directed to the leading end 1c of said flaw 1a and the propagation time of the scattered wave reflected from the leading end 1c by the incident ultrasonic wave is used as an evaluation index to measure the depth of the flaw 1c. By this method, highly accurate measurement can be performed easily without being affected by the depth, inclination, shape and size of the flaw 1a and the size of the aperture width of said flaw 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of measuring the depth of surface opening defects generated in various solids using ultrasonic waves.

The solid surface opening defect referred to here is a defect that occurs in parts or members that constitute equipment in various industrial fields, such as electrical equipment, 2m mechanical equipment, chemical equipment, etc. Refers to all linear (including cylindrical) and planar defects that open on the surface of a member, including the depth/shallowness of the defect, the inclination of the defect, the shape/dimensions of the tip of the defect, and the size of the opening width. There is no time for such things. In addition, the solids referred to in the present invention include metals and nonmetals (glass, ceramics,
(concrete, synthetic resin, rubber, etc.) that can transmit ultrasonic waves.

Further, the depth of the surface open defect referred to herein refers to the vertical distance from the surface of the solid where the defect is open to the tip of the defect.

[Background of the invention]

In the field of application of the present invention, parts or members constituting a device are investigated for the presence or absence of defects, and if a defect occurs, the location and shape of the defect are determined.

Detailed defect information is required depending on the nature and type of the defect, such as dimensions. Information regarding these defects is essential for strength analysis and life calculation of not only parts or members but also the entire device. For this reason, various flaw detection methods have been developed and put into practical use depending on the nature and type of the defect.

For linear or planar defects opening on the surface of a solid, that is, surface opening defects, the location of the defect.

A method for non-destructively detecting the distribution and approximate size is through the transmission of radiation such as X-rays and γ-rays.

Various flaw detection methods using physical energy, such as magnetism, electric induction, solution penetration, and ultrasonic methods described below, are available, and are used depending on the material, shape, and dimensions of the object to be inspected. However, at present, no method has been developed that can easily measure the depth of surface opening defects with high accuracy and in real time.

Incidentally, surface opening defects are defects generally referred to as cracks or cracks, and there are many types and properties thereof. For example, weld cracks that occur in the weld metal or heat affected zone, fatigue cracks in the stress concentration area of a member, quench cracks during heat treatment,
Each type is classified according to the conditions and environment in which it occurs, such as placement cracking in members that retain residual stress, intergranular cracking that occurs at relatively high temperatures, and stress corrosion cracking that tends to occur in austenitic stainless steel. Conventionally, as a method for measuring the depth of these various surface opening defects, the radiographic inspection method using the above-mentioned radiographic transmission has been widely used. However, in this method, a transparent photograph of the subject is required, and since the results of the examination depend on the quality of the photograph, high-resolution prints must be created. However, depending on the shape and size of the subject, it may not be possible to take a photograph, and even if photographic imaging is possible, the sensitivity of the film and the strength of the radiation energy must be selected depending on the subject, and depending on the handling. It also has the special safety issue of radiation exposure, and many requirements are required for measurement. For this reason, it is often impossible to measure easily and accurately. On the other hand,
It has been reported that methods using ultrasonic waves are already in practical use (■ ``Ultrasonic Flaw Detection Test B J 1979 Publication of the Japan Nondestructive Inspection Association, pp. 117-118, ■ ``Nondestructive Inspection'' No. 32 Volume 2, February 1983, page 110~
(Page 111), but the methods are few and limited. The above report will be explained below with reference to FIGS. 11 to 14.

In the above report, both (1) and (2) are methods called edge peak echo methods, and the outline of these methods will be explained with reference to FIGS. 11 and 12. In the figure, reference numeral 1 denotes an object to be inspected, and a planar defect 1a with an opening and a depth d is provided on the surface of the object. 1
b is the flaw detection surface of the test object 1, IC is the tip of the defect 1a, and 1d is the bottom surface (anti-deep flaw surface) of the test object 1. Reference numeral 20 denotes a normal bevel probe or a point focusing bevel probe (hereinafter referred to as bevel probe), which is in contact with the flaw detection surface 1b and is pointed with an arrow so as to capture the echo from the tip 1c of the defect. Emit ultrasonic waves while scanning back and forth in direction A or B. 20a and 20b indicate arbitrary positions when the angle probe 20 is scanned back and forth. If the bevel probe 20 is now scanned in the direction of arrow B from the position 20a, an echo from the defect 1a will appear on the CRTA shown in A-1 in FIG. 12 as the bevel probe 20 moves. The height is displayed as it changes continuously as it gradually decreases.
An echo envelope 5o is obtained. In this case, the angle probe 2
When the zero beam axis 30 enters the tip 1c of the defect, a slight peak echo 60 is obtained at a position on the CRTJ corresponding to the beam path length x, and the position is displayed on the echo envelope 50. In the edge peak echo method, the depth d of the defect is determined geometrically from the beam path length X at the position of the peak echo 60 from the tip 1c of the defect and the refraction angle θ of the angle probe 20, d=x- This is a method of finding it as cos θ. In Report 2, under the measurement condition that the angle α between the incident direction of the ultrasonic wave and the surface of the defect 1a is 10 parts or more, the refraction angle θ = 45° is required to more clearly identify the peak echo 60. It is noted that it is better to use a normal bevel probe, or a point-focusing bevel probe or split-back type probe that can narrow down the sound waves, and the defect depth d
If the depth d is relatively large, the depth d can be determined with an accuracy of about ±2 ml.
It is stated that it is possible to estimate the dimensions of However, it has been reported that measurement accuracy decreases when other defects are attached to the defective tip IC. Report (2) is a report conducted by the inventors of the present invention, in which various experiments were conducted on the influence of the shape and size of the tip of the defect on the height and depth of the defect, as a study on the edge peak echo method. Fig. 13 shows the test object and the experimental procedure, in which a steel plate with a thickness of 65 tm was grooved, a defective weld penetration part of depth d was provided, and CO□ semi-automatic butt welding was performed. The same reference numerals as in FIG. 11 indicate the same things. The flaw detection surface 1b is finished smooth (gv), and the defect depth d is approximately 30
It is made by wm. The experiment was first conducted based on the shape and size of the tip IC of the three types of defects shown in FIG.
]. The shape of the tip of the defect shown in FIG. 14 is a schematic enlargement of 10 portions of the tip of the defect shown in FIG. 13, and its size is 2ρ (unit: 1) defined as shown in the figure.

Experimental results show that there is almost no difference in shape, and when 2ρ is less than about IB, Δd can be measured with an accuracy of about ±3 fl, but when 2ρ exceeds IN, the accuracy suddenly deteriorates. Next, we experimented with the measurement accuracy of the defect height and depth (d) for each type by changing the type of probe. The experimental results are shown in the table below. In the table, n is the average value of the measurement error when the number of samples is 1 layer, and σ is the standard deviation of the measurement error.

For example, when looking at type 1 on a tree table, Ma is ±0
．． 32~-0.60　l, σ is 1.23~1.67　1
Although there is not much difference in measurement accuracy depending on the type of probe, there are differences depending on the type. When the defect depth d is about 30 mm as in this embodiment, this level of accuracy can be put to practical use, but when the depth d is shallow, for example, less than 10 mm, the accuracy is not practical. The above ■ and ■ reports are as follows:
The depth of surface aperture defects can be adjusted from ±2 to ±2 using the edge peak echo method.
Although it is stated that measurement can be performed with an accuracy of about ±31 m, the following basic measurement problems actually exist.

That is, (i) when the depth d of the surface opening defect is shallow,
The heights and positions of the echoes from the surface of the defect and the echoes from the tip of the defect are close to each other, making it impossible to distinguish between them.

(ii) On the other hand, when the depth d is large, the height of the echo from the tip of the defect drops abruptly, making it impossible to measure it. (iii) Since the state of scattering of ultrasonic waves differs depending on the shape and size of the tip of the defect, the measured values vary and the accuracy decreases. (iv) Even if the ultrasonic wave is incident on the tip of the defect at the nominal refraction angle of the probe, a peak echo may not be obtained, and a peak echo may be displayed when the beam axis does not match the tip of the defect. Because there are times when
This destroys the geometric basis for determining the defect depth, and becomes a direct cause of a decrease in measurement accuracy. etc.

As explained above, there are only a few conventional methods for measuring the depth of surface opening defects, which have many problems in measurement, and cannot be easily and precisely measured in real time.

[Purpose of the invention]

The present invention solves the above-mentioned problems of the prior art, and measures the depth of surface opening defects occurring in solids by determining the depth/shallowness of the defect, the inclination of the defect, the shape and size of the tip of the defect, and the depth of the surface opening defect occurring in a solid. An object of the present invention is to provide a method for measuring the depth of a surface opening defect in a solid using ultrasonic waves, which can be easily measured with high precision without being affected by the size of the opening width, and can be measured in real time.

[Summary of the invention]

The present invention is a method of measuring the depth of an open defect on the surface of a solid using ultrasonic waves. By injecting a longitudinal ultrasonic wave almost perpendicularly to the surface and measuring the depth of the surface aperture defect using the propagation time of the scattered wave reflected from the tip of the aperture defect as an evaluation index, electrical equipment and The present invention relates to a method for easily measuring the depth of surface opening defects occurring in parts and members constituting mechanical devices, etc., non-destructively, with high precision, and in real time.

[Embodiments of the invention]

A first embodiment of the present invention will be described with reference to FIGS. 1 to 8. In the figures, the same reference numerals as in FIGS. 11 and 12 indicate the same things. In Fig. 1, 2 is a longitudinal wave vertical probe (hereinafter referred to as vertical probe), and the object 1 is
It is in contact with the flaw detection surface 1b directly above the surface opening defect 1a, and is connected to a pulse reflection type ultrasonic flaw detector (hereinafter referred to as an ultrasonic flaw detector) 3 indicated by A-1 through a high frequency cable.

The surface opening defect in this example is a planar defect that is oriented substantially perpendicularly to the flaw detection surface 1b and has a depth dl with a linear tip.

Now, if a longitudinal ultrasonic wave is incident almost perpendicularly from the vertical probe 2 toward the IC at the tip of the defect, if there is no surface aperture defect 1a, the ultrasonic wave will be emitted as shown in Fig. 2. ,
With the directivity determined by the frequency (wavelength) of the vertical probe 2 and the dimensions of the transducer, the beam 6 shown by the dotted line propagates inside the object 1, reaches the bottom surface 1d of the plate thickness t, is reflected, and then returns to the vertical direction. The signal is received by the probe 2. 7 is an incident wave, and 8 is a bottom reflected wave.

However, when there is a surface opening defect 1a, the tip IC of the defect becomes a sound source or a reflection source of ultrasonic waves, as shown in FIG. 3, and when the incident wave 7 in FIG. 2 reaches the tip IC, it is excited. is scattered two-dimensionally, and the cylindrical wave 9 propagates within the subject 1.

A part of the cylindrical wave 9 is received by the vertical probe 2, and when the echo of the received cylindrical wave 9 is displayed on the CRTd, an echo pattern as shown in FIG. 4 is obtained. That is, C
A transmission pulse T is displayed at the origin on the time axis of RT4, and an echo F of the cylindrical wave 9 is displayed at a position du on the time axis corresponding to the depth dR of the surface aperture defect 1a from the position of the transmission pulse T. A bottom echo B is displayed almost simultaneously at a position tu corresponding to the plate thickness t. In this case, the position of each echo displayed will remain the same, including the slight measurement error described later, and will display the depth dR and plate thickness t of the surface aperture defect 1a, so the depth and shallowness of the surface aperture defect will be , the depth dR of the defect can be measured from the propagation time du of the echo F caused by the cylindrical wave 9 without being affected by the inclination, the shape and size of the tip, the size of the opening width, etc.

Fig. 5 is a diagram showing the shape and dimensions of the test object used in this example, in which a steel plate (material 5S41) with a thickness of 100 m, a length of 300 mm, and a width of 100 fins is placed in the center with a width l, a Q weight x
The slits were formed by electric discharge machining while changing the depth dR. The number of samples is 12, and the depth d8 is 1.0°2
．． 0.3.0.5.0.7.0.10.0.20.0.
There are 12 types: 30.0.40.0°50.0.60.0.70.0. Further, the tip a portion of the slit is machined to R015m as shown in FIG. The depth d of the slit was measured in the manner shown in FIG. 1 described above.

The frequency of the vertical probe used was 5 MHz. First, as shown in FIG. 2, a vertical probe is brought into contact with the surface of the steel plate in a place where there is no slit, and the bottom echo height is taken as the reference sensitivity (OdB) on the CRT. Then move the vertical probe to the third
As shown in the figure, the echo of the cylindrical wave that comes into contact directly above the slit 7) and scattered from the tip of the slit is displayed on the CRT.

FIG. 7 shows the relationship between the echo height h (unit: dB) of the displayed cylindrical wave and the slit depth di (unit: l). In the figure, the horizontal axis is the logarithmic value of the slit depth dR, the vertical axis is the echo height h, and the circles indicate the measured values. Moreover, the dotted line in the figure indicates the noise region, and the sheep value is about -75 dB. When calculating the regression equation for each measured value using the least squares method, h =
-22log dR-19.5. The above equation becomes a straight line shown by the chain line in the figure, and it can be seen that there is a good correlation between the two. This correlation is the distance amplitude characteristic ho of the scattered waves.
It is in good agreement with cl/dIj. Also, the slit depth d
The measurable limit of , I is theoretically up to the point P where the chain line of the regression equation intersects with the dotted line of the noise region, and it can be estimated that it is possible up to about 300 cranes in this example. Next, the measurement accuracy in this example will be explained with reference to FIG. In the figure, the horizontal axis is the actual slit depth di (unit amount), the vertical axis is the slit depth d (unit N) obtained from the regression equation obtained by the method of the present invention, and the ○ mark is the value. . As a result, it can be seen that the two values match very well and that highly accurate measurement can be performed. The average value of error X is +0.058 m, the standard deviation of error σ is o, 2ii Tsuru, and the correlation T between dR and d is 0.
．． It shows a very good correlation with 99997.

The first embodiment described the case where an opening defect with good processing accuracy was artificially provided in the test object, but the ninth embodiment will be described below.
A second example of an opening defect occurring at the weld toe of an actual welded joint will be described with reference to the drawings and FIG. 10. The test objects used in this example were a web with a thickness of 25 cranes, a height of 50++n, a length of 100 mm, and a flange with a thickness of 25 cranes, a width of 250 cranes, and a length of 100 cranes, as shown in Fig. 9. It was T-shaped welded, and a fatigue crack had occurred at the weld toe on the flange side. The material for both the web and flange is 5M50 (JIS G3106). There are 13 types of crack depth dR ranging from 0.8 m to 9.31 m. Since the vertical probe 2 could not be brought into contact directly above the crack, the measurement was carried out by bringing it into contact with the crack as shown in FIG. The measurement results are shown in FIG. In the figure, the horizontal axis is the actual crack depth da (unit: Vm), the vertical axis is the crack depth du (unit: w) measured by the method of the present invention, and the circle marks are measured values. The two agree very well, with the average measurement error x = -0,062m and the standard deviation of error σ = 0.266.
m, the correlation T between dR and d is 0.868, showing a very good correlation.

The surface opening defect in the first and second embodiments described above is a planar defect, and the tip of the defect has a linear length, but the surface opening defect is a linear defect, If the tip of the defect is point-shaped, the scattered waves from the tip of the defect spread three-dimensionally and become spherical waves, part of which is received by the vertical probe, as shown in Figure 4. The difference is that a spherical wave echo is displayed at a position corresponding to the depth of the surface aperture defect from the position of the transmitted pulse T, and a bottom echo is displayed almost simultaneously at a position corresponding to the plate thickness. However, the depth of the defect is measured from the propagation time of the echo caused by the spherical wave, and the other measurement methods are the same.

〔Effect of the invention〕

As explained above, the present invention makes longitudinal ultrasonic waves incident almost perpendicularly to the surface of the solid from the surface of a solid having an aperture defect toward the tip of the aperture defect. Since the depth of the aperture defect is measured using the propagation time of the scattered wave reflected from the tip as an evaluation index, the depth of the surface aperture defect can be determined based on the depth/shallowness of the defect, the inclination of the defect, the shape of the tip of the defect, and It is possible to easily measure with high precision and in real time without being affected by the size or opening width of the defect.

[Brief explanation of the drawing]

1 to 8 are explanatory diagrams of the first embodiment of the present invention, FIG. 1 is a schematic explanatory diagram of the measurement method of the present invention, and FIG. FIG. 3 is an explanatory diagram of the scattered waves scattered from the tip of the surface aperture defect. FIG. 4 is a diagram showing the echo pattern on the CRT obtained in the case of FIG. 3. Fig. 5 is a diagram showing the shape and dimensions (unit amount) of the test object used in this example, Fig. 6 is an enlarged view of part a of Fig. 5, and Fig. 7 is a defect of the test object shown in Fig. 5. FIG. 8 is a diagram showing the relationship of echo height with depth and measurable limits, and is an explanatory diagram of measurement accuracy in this embodiment. 9 and 10 are explanatory diagrams of a second embodiment of the present invention. FIG. 3 is an explanatory diagram of measurement accuracy of values measured by the method shown in the figure. 11 to 14 are explanatory diagrams of the conventional edge peak echo method. FIG. 11 is a schematic explanatory diagram of the edge peak echo method for measuring the depth of surface aperture defects, and FIG. 12 is an explanatory diagram of the conventional edge peak echo method.
Figure 13 is a diagram showing the echo pattern on a CRT obtained by the method shown in Figure 1. Figure 13 is an explanatory diagram showing the effect of the shape and size of the tip of a defect on the depth of the defect in the edge peak echo method. The figure schematically defines the tip shape and size of the defect. 1...Object to be inspected, 1a...Surface opening defect, 1b...
Flaw detection surface, IC...tip of defect, 1d...bottom surface, 2.
...Vertical probe, 3...Ultrasonic flaw detector, 4...CR
T, 9...scattered waves, 20...angle probe, 30...
・Beam axis, 50...envelope, 60...beak echo. Patent Applicant Hitachi Construction Machinery Co., Ltd. Agent Patent Attorney Tadashi Akimoto Fig. 1 Fig. 2 Fig. 6/c Id Fig. 4 Fig. 5 I Taku no 4g-: 7Lyn 6th Ward Q of convulsions: myn No. 8 figure real P! If o Surin 1 - Kiyoshi'! (dp)
yn, yyb Figure 10 back piece f)! Pear red capsule dp) myin fossa Il Figure 72 Figure 13 Figure 14

Claims (1)

[Claims] 1. A longitudinal ultrasonic wave is incident from the surface of a solid having an aperture defect toward the tip of the aperture defect almost perpendicularly to the surface of the solid, and the ultrasonic wave is applied to the aperture defect. A method of measuring the depth of surface opening defects in solids using the propagation time of scattered waves reflected from the tip as an evaluation index. 2. From the surface of a solid body having a point-like opening defect, a longitudinal ultrasonic wave is incident almost perpendicularly to the surface of the solid body toward the tip of the opening defect, and the ultrasonic wave is A method of measuring the depth of a surface aperture defect in a solid by using the propagation time of a spherical wave reflected from the tip of the aperture defect as an evaluation index. 3. A longitudinal ultrasonic wave is applied almost perpendicularly to the surface of the solid from the surface of a solid having an opening defect whose tip shape is linear, toward the tip of the opening defect, and the ultrasonic wave is A method of measuring the depth of a surface aperture defect in a solid by using the propagation time of a cylindrical wave reflected from the tip of the aperture defect as an evaluation index. 4. A vertical probe is brought into contact with the surface of a solid having an aperture defect, and a longitudinal ultrasonic wave is incident from the probe toward the tip of the aperture defect almost perpendicularly to the surface of the solid. The propagation time of the scattered wave reflected from the tip of the ultrasonic aperture defect,
A method for measuring the depth of a surface opening defect in a solid according to claim 1, characterized in that a correlation with the depth of the opening defect is used as an evaluation index.