JP7655082B2 - Ultrasonic testing specimen and method for producing same - Google Patents

Description

The present invention relates to an ultrasonic test piece used when adjusting the sensitivity of an ultrasonic testing device, and a method for manufacturing the same.

In this type of ultrasonic test piece, a so-called flat-bottom hole is provided as an artificial flaw, and ultrasonic testing waves are emitted toward the flat-bottom surface of the flat-bottom hole, and the sensitivity of the ultrasonic testing device is adjusted so that the reflected ultrasonic wave has a defect echo signal strength of a predetermined value or more (for example, Patent Document 1). When testing for surface flaws or surface layer flaws in a round bar material, as shown in Figure 7, a cylindrical flat-bottom hole 2 of a predetermined length is formed on the surface of a cylindrical test piece body 5 of the same material and diameter as the round bar material to be tested. The flat-bottom hole 2 is angled so that its flat-bottom surface 21 is perpendicular to the direction in which the ultrasonic testing waves are incident.

That is, when inspecting for surface or subsurface flaws in a round bar material, oblique angle inspection is performed so that the refraction angle θ of the inspection ultrasonic waves is, for example, 45° to 55°. The flat-bottom hole 2 is formed at an angle such that the flat-bottom surface 21 is perpendicular to the inspection ultrasonic waves incident on the test piece S from the inspection probe 4 at such a refraction angle θ, and the round bar material is rotated to adjust the sensitivity of the ultrasonic inspection device so that the defect echo of the reflected ultrasonic waves is equal to or greater than a predetermined value.

Patent Publication 2019-78558

In the conventional ultrasonic test piece S, the reflected ultrasonic waves from the flat-bottomed hole 2 formed in the test piece body 5 include not only defect echoes Ed that are reflected back from the flat-bottomed surface 21 of the flat-bottomed hole 2, but also double-reflected echoes En that are reflected from the peripheral surface of the round bar material and the side of the flat-bottomed hole 2 close to it, because the ultrasonic waves for flaw detection have a certain degree of spread.

In this case, when testing small-diameter round bar material, the test piece S is also made smaller in diameter accordingly. In this case, the defect echo Ed from the flat-bottom hole 2 and the double-reflection echo En return to the flaw detection probe 4 close in time, and as shown in Figure 8, in addition to the defect echo signal Eds, the double-reflection echo signal Ens appears within the detection window (time width) T of the ultrasonic flaw detection device, making it impossible to distinguish between them. This creates a problem in that the intended purpose of rotating the round bar material and adjusting the sensitivity of the ultrasonic flaw detection device so that the reflected ultrasonic defect echo signal Eds is equal to or greater than a predetermined value cannot be achieved.

The present invention is intended to solve such problems, and aims to provide an ultrasonic test piece for use in ultrasonic testing of round bar materials, which is capable of eliminating the influence of double-reflection echoes and reliably adjusting the sensitivity of the ultrasonic testing device.

In order to achieve the above object, the first invention provides a test piece for ultrasonic testing used when detecting defects present on the surface or surface layer of a round bar material by ultrasonic waves, the test piece (S) being a columnar body made of the same material as the round bar material, an artificial flaw (2) being provided on the surface of the test piece (S), the test piece (S) having a main body (1) with a circular cross section of the same diameter as the round bar material, and a protrusion (11) having a cross section defined by a partial arc of the circular cross section, a straight line connecting one end point (c) of the partial arc and a point on a tangent to the one end point (c), and a line connecting the point on the tangent to the other end point of the partial arc and perpendicular to the straight line, the artificial flaw (2) being a hole formed in a surface (111) of the protrusion (11) corresponding to the line, the hole penetrating the protrusion (11), and a part of the hole including a tip (21) being formed in the main body (1) .

According to the first invention, the reflection path of the flaw detection ultrasonic wave from the protrusion is made longer than the reflection path from the artificial flaw, so that the defect echo and the double-reflected echo return to the flaw detection probe with a sufficient time separation between them. Therefore, the ultrasonic flaw detection device can reliably distinguish between the defect echo and the double-reflected echo, and the sensitivity of the ultrasonic flaw detection device can be reliably adjusted so that the defect echo signal is equal to or greater than a predetermined value without being affected by the double-reflected echo.

In the second invention, the hole (2) is a cylindrical flat-bottomed hole, and an extension portion (22) of constant cross-sectional thickness is formed between the straight line of the protrusion (11) and the side of the flat-bottomed hole (2) .

According to the second invention, by forming an extension portion, the defect echo of the flaw detection ultrasonic wave is reflected back by the flat bottom surface of the flat bottom hole, and the twice-reflected echo is reflected back by the tip of the extension portion, which is sufficiently far away from the flat bottom surface. Therefore, the defect echo and the twice-reflected echo return to the flaw detection probe with a sufficient time separation between them, so that the ultrasonic flaw detection device can reliably distinguish between them and reliably adjust the sensitivity of the ultrasonic flaw detection device so that the defect echo signal is equal to or greater than a predetermined value without being affected by the twice-reflected echo.

In the third invention, the radius (r) of the main body, the diameter (D) of the flat-bottom hole, and the thickness (W) of the extension portion have the following relationship:
W=r-(rsinθ+D/2)
Here, W>λ, λ is the wavelength of the ultrasonic wave for flaw detection, and θ is the refraction angle of the ultrasonic wave for flaw detection.

The symbols in parentheses above are for reference purposes only and indicate the corresponding relationship with the specific means described in the embodiments below.

As described above, according to the ultrasonic test piece and manufacturing method thereof of the present invention, when ultrasonic testing is performed on a round bar material using a flat-bottom hole as an artificial flaw in the ultrasonic test piece, the effect of double-reflection echoes can be eliminated and the sensitivity of the ultrasonic testing device can be reliably adjusted.

1 is a cross-sectional view of a test piece for ultrasonic flaw detection, showing one embodiment of the present invention. FIG. 2 is an overall perspective view of a test piece body used in manufacturing a test piece for ultrasonic flaw detection. FIG. 2 is a side view and an end view of the test specimen body. FIG. 2 is a partially enlarged side view of a test piece body having a flat-bottom hole formed therein. 4 is a diagram showing changes over time in a reflected ultrasonic signal received by an ultrasonic flaw detector. FIG. FIG. 4 is a cross-sectional view of a test piece for ultrasonic inspection showing another embodiment of the present invention. FIG. 1 is a cross-sectional view of a conventional ultrasonic testing specimen. 4 is a diagram showing changes over time in a reflected ultrasonic signal received by an ultrasonic flaw detector. FIG.

The embodiment described below is merely an example, and various design improvements made by those skilled in the art that do not deviate from the gist of the present invention are also included in the scope of the present invention.

Figure 1 shows an example of a cross section of the ultrasonic test piece S of the present invention. In Figure 1, the body 1 of the ultrasonic test piece S is columnar and has a circular cross section with the same diameter as the round bar material to be tested. A cylindrical flat-bottom hole 2 is formed as an artificial flaw, with its flat bottom surface 21 perpendicular to the direction of incidence of the ultrasonic wave, which is incident on a point a on the periphery of the test piece body 1 from a flaw-detection probe (not shown) and propagates through the body 1 at a refraction angle θ.

In this embodiment, the flat-bottomed hole 2 is drilled in a protrusion 11 formed on a portion of the circumferential surface of the test piece body 1. As a result, an extension 22 is formed at the upper edge of the opening of the flat-bottomed hole 2 on the side surface close to the (imaginary) circumferential surface of the test piece body 1. This extension 22 extends outward from the circumferential surface of the test piece body 1 along the axis m of the flat-bottomed hole 2 with a constant thickness W, and its tip 221 is flat.

In addition, the symbols r, D, W, and H in FIG. 1 indicate the dimensions of the following parts.
r: radius of test piece body D: diameter of flat-bottom hole W: thickness of extension H: extension amount of extension (= depth of flat-bottom hole)

Here, there is a relationship of W = r - (r sinθ + D/2), and the larger W is made, the smaller the effect of the double-reflected echo can be, but D becomes smaller accordingly, and the defect echo reflected by the flat bottom surface 21 becomes weaker. Therefore, taking this into consideration, the sizes of W and D must be appropriately adjusted. Note that, when the wavelength of the flaw detection ultrasonic wave is λ, W must be greater than λ.

The larger H is, the better the separation of defect echoes and double-reflection echoes will be. The magnitude of H must be set to be greater than or equal to the pulse duration of the flaw detection ultrasonic wave. As an example, if the sound speed of the flaw detection ultrasonic wave is 3000 m/s, the frequency is 10 MHz, and the wave number is 3, the magnitude of H must be 0.9 mm or greater.

The above-mentioned test piece S with the extension 22 formed is manufactured, for example, as follows. That is, a columnar body of a certain length X made of the same material as the round bar is formed by machining or the like into a test piece body 1 as shown in a perspective view in Figure 2, and in side and end views in Figures 3 (1) and (2), respectively. The length X of the test piece body 1 need only be longer than the length of the flaw detection probe 4 used (the length perpendicular to the paper surface in Figure 1).

The test piece body 1 has a circular cross section with the same diameter as the round bar material for the most part, and a protruding portion 11 that protrudes radially outward at a portion of the circumference. The cross section of this protruding portion 11 is bounded by a tangent line from a point c on the circumference above the circular cross section, and a line that runs perpendicularly from the tangent line to another circumference below the circular cross section. Then, at one point in the longitudinal direction of this protruding portion 11, a cylindrical flat-bottomed hole 2 is drilled in the lower inclined surface 111 of the protruding portion 11, parallel to the upper inclined surface 112, as shown in Figure 4. This forms the above-mentioned extension portion 22 of a predetermined thickness W at the upper edge of the opening of the flat-bottomed hole 2.

By forming such an extension 22, as shown in FIG. 1, the defect echo Ed of the flaw detection ultrasonic wave is generated by reflection on the flat bottom surface 21 of the flat-bottom hole 2, while the double-reflection echo En is generated by reflection on the flat surface of the tip 221 of the extension 22, which is separated from the flat bottom surface 21. As a result, the defect echo Ed and the double-reflection echo En return to the flaw detection probe with sufficient time separation, and as shown in FIG. 5, only the defect echo signal Eds appears within the detection window T of the reflected ultrasonic signal received by the ultrasonic flaw detection device. This makes it possible to reliably adjust the sensitivity of the ultrasonic flaw detection device so that the defect echo signal Eds of the reflected ultrasonic wave is equal to or greater than a predetermined value.

The protrusion formed on the test piece body does not necessarily have to have the cross section as described above, and the method of forming the extension on the opening edge of the flat-bottom hole of the test piece is not limited to the above method. In this case, depending on the formation method, the extension amount of the extension may not be the same as the depth of the flat-bottom hole, unlike the above example. The thickness of the extension does not necessarily have to be constant, and may be gradually increased toward the tip. Furthermore, the tip of the extension does not necessarily have to be flat. More specifically, for an artificial flaw 6 that does not have a flat bottom surface as shown in FIG. 6(1) or an artificial flaw 7 formed at a certain depth from the surface as shown in FIG. 6(2), the same effect as the above embodiment can be obtained by forming the extensions 61 and 71 as shown in the figures. In addition, the test piece of the present invention can be used with either a single-transducer or phased array type flaw detection probe.

DESCRIPTION OF SYMBOLS 1... Main body, 11... Protrusion part, 2... Flat bottom hole, 21... Flat bottom surface, 22... Extension part, S... Test piece for ultrasonic flaw detection.

Claims (3)

An ultrasonic test piece used for ultrasonically detecting defects on the surface or surface layer of a round bar material,
The test piece is a columnar body made of the same material as the round bar material,
An artificial flaw is provided on the surface of the test piece,
The test piece is
A main body having a circular cross section with the same diameter as the round bar material;
a protrusion having a cross section defined by a contour of a partial arc of the circular cross section, a straight line connecting one end point of the partial arc and a point on a tangent to the one end point, and a line connecting the point on the tangent to the other end point of the partial arc and perpendicular to the straight line;
having
The artificial flaw is
a hole formed in a surface corresponding to the line of the protrusion;
The hole penetrates the protrusion, and a portion of the hole, including the tip, is formed in the main body . 2. The ultrasonic test piece according to claim 1, wherein the hole is a cylindrical flat-bottomed hole, and an extension portion of a constant cross-sectional thickness is formed between the straight line of the protrusion and a side surface of the flat-bottomed hole. 3. The ultrasonic test piece according to claim 2, wherein the radius (r) of the body, the diameter (D) of the flat-bottom hole, and the thickness (W) of the extension portion have the following relationship:
W=r-(rsinθ+D/2)
Here, W>λ, λ is the wavelength of the ultrasonic wave for flaw detection, and θ is the refraction angle of the ultrasonic wave for flaw detection.