JP2007093311A - Ultrasonic flaw detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect flaws in materials to be inspected and having a complicated shape such as a rail head part without being affected by interfering echo due to sidelobes different from defects. <P>SOLUTION: An array type probe 3 is opposed to materials 1 and 2 to be inspected to detect flaws inside the materials 1 and 2 to be inspected by electronic scanning in this ultrasonic flaw detection method. The center axis of the array type probe 3 is tilted, and the location of the array type probe 3 is determined and arranged in such a way that interfering echo from a section 6, which is present inside the materials 1 and 2 to be inspected and causes interfering echo, may not return to the array type probe 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for ultrasonic flaw detection using an array type probe for internal defects of a specimen having a complicated shape such as a rail.

  Shaped steel such as rails are produced by rolling a heated steel piece through a hole mold between upper and lower rolling rolls called a caliber. The rolled rail is cut into a predetermined length, and after cooling, the bend is corrected by a roller straightener. The rail manufactured in this way is inspected for internal defects by ultrasonic flaw detection during conveyance.

  For example, Non-Patent Document 1 describes an ultrasonic inspection method for rails during manufacturing. An example is shown in FIG. Using a single-type ultrasonic probe, a total of 17 rail heads, 2 from the left and right, 3 from the top, 7 from the left from the web, and 3 from the bottom from the base By doing so, internal defects are vertically detected. However, the flaw detection method using such a single type ultrasonic probe has the following problems. That is, in order to increase the coverage of the ultrasonic beam in order to reduce flaw detection, a large number of ultrasonic probes are required, resulting in an increase in equipment cost. In the example of FIG. 6, there are 17 in total, but there are also examples of 20 or more. In addition, in order to adjust the incident angle of each of these probes, the holding mechanism of the ultrasonic probe becomes very complicated, the equipment cost increases, and it is easy to break down, and adjustment work is troublesome. There is also a problem that it takes.

  On the other hand, by using an array-type probe and electronically scanning the ultrasonic beam for flaw detection, the number of ultrasonic probes is reduced, the mechanism is simplified, and the above problems are avoided. An example is known.

  In Patent Document 1, an example of a square steel slab is shown, but an array type probe is set at a predetermined angle with respect to the surface of the material in a plane perpendicular to the axial direction of the square steel slab and at a predetermined angle with respect to the material surface. By performing sector scanning, vertical flaw detection and oblique flaw flaw detection are performed at the same time so that internal defects and surface layer defects can be detected with a small number of probes.

  In Patent Document 2, each element of the array-type probe is selected according to the beam direction to be set, and ultrasonic waves from these elements are interfered to transmit side lobes in a predetermined direction, thereby widening the flaw detection area. Like to do.

In Patent Document 3, as shown in FIG. 7, a sector scan is performed on the rail, particularly the head portion, using an array-type probe, and a defect gate is detected every time an ultrasonic wave is irradiated in accordance with the shape of the test object. The setting is made.
JP 59-116543 A Japanese Patent Laid-Open No. 62-032356 Japanese Patent Laying-Open No. 2005-037407 V.Deutsch et al., "New developments concerning ultrasonic testing of rails in production line", 14th World Conference on Non Destructive Testing (14th WCNDT), 1996, p.207-213

  However, the ultrasonic flaw detection method using these array-type probes still has the following problems. The ultrasonic beam by the array type probe is formed as a composite from a plurality of small elements. At this time, as the sound field of the synthesized beam becomes finer and more elements, a beam equivalent to a single-type ultrasonic probe can be obtained. I can't do much. In this case, in the ultrasonic beam, in addition to the main lobe in the main direction, a sub beam called a side lobe is generated at another angle. The angle θ generated by the side lobe is expressed by the following equation with respect to the main lobe, where λ is the wavelength of the ultrasonic wave and d is the pitch between the elements.

  Here, considering flaw detection with an array type probe disposed on the side surface of the head portion of the rail, as shown in FIG. 2, the side lobe may hit the web portion near the head portion and be reflected. Since the web is in front of the head portion facing surface located on the opposite side of the head portion side surface on which the array probe is arranged, echoes from the web portion in the vicinity of the head portion enter the flaw detection gate and are fixed echoes. Will end up as noise. Therefore, there are limited parts to which the ultrasonic flaw detection method using an array type probe can be applied.

  The present invention has been made to solve the above-mentioned problems, and its object is to obstruct a specimen having a complicated shape such as a head part of a rail by side lobes different from defects. It is an object of the present invention to provide an ultrasonic flaw detection method using an array type probe capable of flaw detection without the influence of echo.

(1) An ultrasonic flaw detection method according to the present invention is an ultrasonic flaw detection method in which an array-type probe is arranged opposite to a surface of a test material, and the inside of the test material is detected by electronic scanning. The central axis of the array probe is tilted and the position of the array probe is determined so that the disturbing echo from the part where the disturbing echo is present does not return to the array probe. The main feature is that they are arranged.
(2) An ultrasonic flaw detection method according to the present invention is an ultrasonic flaw detection method in which an array-type probe is disposed opposite to the surface of a rail head portion, and the inside of the rail head portion is flawed by electronic scanning. The array-type probe is inclined while the central axis of the array-type probe is inclined so that the interference echo from the boundary portion between the head portion and the web portion inside the rail does not return to the array-type probe. Is arranged at a position near the web portion of the head portion.

  The internal inspection of a specimen with a complicated shape such as the head of a rail can be performed without an interference echo problem using an array type probe with a small number of elements. Can improve the internal quality of the product.

  Here, the case where the test material is a rail and the measurement site is the head portion of the rail will be described. FIG. 1 shows an embodiment of the present invention, in which 1 and 2 are rails as test materials, 1 is a head portion, and 2 is a web portion. 3 is an array type probe, and 4 is an ultrasonic beam. Note that the ultrasonic beam 4 shown in FIG. 1 shows the entire angular range that is sequentially scanned by sector scanning, and does not transmit the ultrasonic beam in the angular range shown in FIG. 1 at the same time. Here, the array-type probe 3 is arranged in the vicinity of the outer peripheral surface of the head portion 1 of the rail so that flaws can be detected from the outside, and the side of the head portion 1 that is closer to the web portion 2 than the center of the side surface. Is located. Further, the central axis of the array-type probe 3 is tilted upward from the horizontal so that the entire head unit 1 to be measured falls within the ultrasonic electronic scanning range. The array-type probe 3 and the test materials 1 and 2 are connected by water 5 as an acoustic contact medium.

  When the array-type probe 3 is disposed on the side surface of the head unit 1, the array-type probe is positioned at a height approaching a part that emits an interference echo in the test material, that is, the boundary part 6 between the web part and the head part. 3 and the central axis of the array-type probe 3 is tilted upward from the horizontal, so that the side lobe is in the web portion 2 (including the boundary portion 6 between the web portion and the head portion). You will not win. Alternatively, even if it hits the web portion 2, it enters at an oblique angle, so that the disturbing echo does not return to the array type probe 3. Therefore, ultrasonic flaw detection can be performed without the problem of interference echo.

  Here, the position at which the array-type probe 3 is arranged is preferably lower than the center of the side surface of the head unit 1 and more than the position A where the perpendicular N from the boundary portion 6 between the web unit and the head unit intersects the side surface of the head unit. The web part 2 side is more preferable. If the perpendicular line N from the boundary part 6 between the web part and the head part is on the web part 2 side from the position A where the head part 1 crosses the side surface, the ultrasonic wave directed toward the web part 2 is always transmitted to the web part 2 ( This is because it does not become a disturbing echo because it is incident obliquely with respect to (including the boundary portion between the web portion and the head portion).

  The angle at which the central axis of the array-type probe 3 is inclined from the horizontal should be oriented toward the center of the head unit 1 and should be larger than the directivity angle of one element of the array-type probe 3. Is desirable. This is because the side lobe intensity is proportional to the directivity of one element, and therefore, if tilted as described above, the side lobe has no intensity in the direction in which the disturbing echo is emitted.

  FIG. 4 and FIG. 5 show an example of the interference echo reduction effect depending on the position of the array-type probe 3 and the angle of the central axis. FIG. 4 shows the result of examining the relationship between the position of the array-type probe 3 and the interference echo due to the side lobe. Conditions other than the position of the array-type probe 3 were in accordance with a comparative example of FIG. From the results shown in FIG. 4, it is clear that the interference echo is reduced by arranging the array-type probe below the position where the perpendicular from the web hits the side surface of the head. On the other hand, FIG. 5 shows the result of examining the relationship between the angle of the central axis of the array-type probe 3 and the interference echo due to the side lobe. Conditions other than the angle of the central axis of the array-type probe 3 are described later. According to 2 comparative examples. From the result shown in FIG. 5, it is clear that the interference echo is reduced by setting the angle larger than the directivity angle of one element.

  Also from these results, by appropriately selecting and combining the angle and position of the central axis of the array-type probe 3 with respect to the test material, the influence of the interference echo is minimized, and the inside of the product material is detected. It is clear that it is possible.

  Next, a comparison between the prior art and the present invention will be described with reference to FIGS. The size of the head part to be measured is 75 mm wide and 40 mm high. The same components as those described in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 2 shows the case of the comparative example, in which the array type probe 3 is located at the center of the side surface of the head unit 1 and the central axis of the array type probe 3 is horizontally arranged. One main lobe of the ultrasonic beam 4 is denoted by 41, and a side rope for the ultrasonic beam 41 is denoted by 43. Here, in order to perform sector scanning so as to detect almost the entire cross section of the head portion 1 within the angle range of the ultrasonic beam 4, the range of the electronic scanning angle is the relationship between the width and height of the head portion 1. From the horizontal direction to the reference (0 °), it is necessary to make the direction about -14 ° to + 14 °. Therefore, according to Snell's law, the angle range in the water 5 that is the acoustic contact medium of the array type probe is in the −3.5 ° direction to the + 3.5 ° direction with respect to the horizontal direction (0 °). The angle θ of the side lobe 43 in the water 5 with respect to the main lobe 41 is calculated based on the formula (1). For example, when the frequency is 3 MHz and the element pitch is 3 mm, the speed of sound in the water 5 is Considering 1480m / s, θ is 9.5 °. Therefore, the side lobe 43 in the water 5 of the ultrasonic beam 41 in FIG. 2 is in the −6.0 ° direction with respect to the horizontal direction (0 °), and thus in the −25 ° direction in the head 1 of the subject. As shown in FIG. 4, there is a surface that is perpendicularly incident on the boundary portion 6 between the web portion and the head portion. Here, when the time setting of the flaw detection gate of the ultrasonic beam 41 is expanded so that it can be input to the right end of the head portion 1, the side lobe 43 reflected at the boundary portion 6 between the web portion and the head portion is set to the flaw detection gate time. This is a disturbing echo that falls within range and is difficult to distinguish from a defect. Although an example has been described here, the angle θ of the side lobe 43 with respect to the main lobe 41 varies depending on the frequency λ and the element pitch d. However, as long as the sector scan is performed as shown in FIG. Side lobes cause interference echoes.

  FIG. 3 shows the case of the present invention. The array type probe 3 is positioned at the lower end closest to the web part 2 on the side surface of the head part 1 and is supervertically emitted vertically from the oscillation surface of the array type probe 3. The central axis of the array-type probe is tilted 3.5 ° upward from the horizontal so that the sound beam 4 passes through the center of the head unit 1, and the angle range in water 5 is 0 ° with respect to the horizontal direction (0 °). It is set to 7 °. In this way, in the head unit 1, the electronic scanning range is from 0 ° to + 28 ° with the horizontal direction as the reference (0 °). As in the comparative example, when the direction of the side lobe 43 of the ultrasonic beam 41, which is one of the ultrasonic beams 4, is calculated, it becomes -11 °, and as shown in FIG. It does not enter the boundary portion 6 of the head portion). Further, with respect to the ultrasonic beam 42 adjacent to the ultrasonic beam 41, the side lobe 44 is incident on the web part 2 (including the boundary part 6 between the web part and the head part), but oblique to the web part 2. Echo does not return to the probe. As described above, in the example of the present invention, since the array-type probe 3 is positioned near the web portion 2 on the side surface of the head portion 1, the frequency λ and the element pitch d are changed, and any side lobe of the ultrasonic beam 4 is changed. Even if the direction of is changed from the above, no disturbing echo is generated.

  As described above, according to the present invention, even when an electronic scanning ultrasonic flaw detection method using an array type probe is performed on a specimen having a complicated shape such as a rail, the specimen is not affected by side lobes. It was confirmed that a wide cover range can be obtained with a small number of probes by using an array type probe.

  In the present embodiment, the case where the test material is a rail has been described. However, the present invention is not limited to this, and may be a combination of a shape steel or a complicated shape by welding. The electronic scanning method is not limited to sector scanning, and linear scanning may be used.

The figure which showed typically an example of embodiment of the ultrasonic flaw detection method concerning this invention. The figure which showed the conventional method typically. The figure explaining the mechanism which can reduce the detection of the interference echo in this Embodiment. The figure which showed the relationship between the position of an array type probe, and the interference echo by a side lobe. The figure which showed the relationship between the angle of an array type probe, and the interference echo by a side lobe. The figure which showed an example of the ultrasonic flaw detection method of the rail shown by the nonpatent literature 1 (conventional method). The figure which showed the example which performed the sector scan with respect to the rail by the array type probe (conventional method).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Head part of test material 2 Web part of test material 3 Array type probe 4 Ultrasonic beam 41, 42 Ultrasonic beam (main lobe)
43, 44 Side lobes of ultrasonic beams 41, 42 5 Water (acoustic contact medium)
6 Boundary part of the web part and the head part A A position where the perpendicular of the boundary part of the web part and the head part intersects the side surface of the head part d Element pitch of the array type probe N N perpendicular of the boundary part of the web part and the head part λ Ultrasound Frequency θ Angle formed by main lobe and side lobe of ultrasonic beam

Claims (2)

An ultrasonic flaw detection method in which an array-type probe is disposed opposite to the surface of a test material, and the inside of the test material is detected by electronic scanning,
The array-type probe is inclined while the central axis of the array-type probe is inclined so that the disturbing echo from the part that generates the disturbing echo existing inside the test material does not return to the array-type probe. An ultrasonic flaw detection method characterized by determining and arranging the position. An ultrasonic flaw detection method in which an array type probe is arranged opposite to the surface of the rail head portion, and the inside of the rail head portion is flawed by electronic scanning,
The array-type probe is inclined while the central axis of the array-type probe is inclined so that the interference echo from the boundary portion between the head portion and the web portion inside the rail does not return to the array-type probe. Is disposed at a position near the web portion of the head portion.

Images