Destroy metal tubular objects, such as oil well pipes, line pipes, and metal pipes used as mechanical parts (mechanical tubes used in hollow axles, automotive parts, etc., and stainless steel pipes used in high temperature environments, etc.). As a non-destructive inspection method for inspecting defects that do not exist, an ultrasonic flaw detection method is known by injecting ultrasonic waves into a metal tube and detecting reflection echoes from defects present therein. In order to detect defects in the inner surface, the outer surface, the inside of the metal tube, and the welded portion, an inclination angle flaw detection method in which ultrasonic waves are incident at an angle to the flaw detection surface is used. As is well known, in this inclination angle flaw detection method, a casing for accommodating a vibrator, a sound absorbing material, and a contact medium (wedge made of resin such as acrylic) on the flaw face is usually provided so as to transmit ultrasonic waves at an angle to the flaw face. An inclination angle transducer is used. When water is used as the contact medium, instead of accommodating the contact medium such as wedges in the casing, the metal tube and the inclined angle probe are submerged and inspected.
11 is an explanatory diagram showing the relationship between the incident wave 1 and the refraction waves 2 and 3 in the tilt angle flaw detection method. In addition, the broken line in FIG. 11 and FIGS. 12, 13 mentioned later shows the normal line of the flaw detection surface 0. FIG.
As shown in FIG. 11, when the incident wave 1 of the ultrasonic wave is obliquely incident on the flaw surface 0 of the metal tube (medium II) by the oblique angle flaw detection method, the incident wave 1 of the ultrasonic wave incident from the vibrator, not shown, is shown. Even if the ultrasonic wave is the longitudinal wave, both the refractive wave 2 and the refractive shear wave 3 of the ultrasonic wave propagate inside the metal tube as the refraction wave. Ultrasonic wave in medium II (metal tube that is a tubular object) with the sound velocity of the incident wave 1 of the ultrasonic wave in medium I (generally, a liquid contact medium represented by water or a wedge embedded in the inclination angle transducer) as Vi. The sound velocity of the refractive shear wave 3 of V is set to Vs, the sound velocity of the refractory longitudinal wave 2 of the ultrasonic wave in medium II is set to VL, the incident angle of the incident wave 1 is set to? I, and the If the refraction angle is θ s and the refraction angle of the refraction longitudinal wave 2 is θ L, Snell's law, that is, sin θ i / Vi = sin θ s / V s = sin θ L / between the incident wave 1 and the refraction waves 2, 3. The relationship of the VL is established.
12 is an explanatory diagram showing a situation in which the refraction waves 2 and 3 propagate the inside 5c of the metal tube 5.
As shown in the figure, when the incident wave 1 is incident on the metal tube 5 at the incident angle θ i from the vibrator 4 of the ultrasonic probe, the incident ultrasonic waves 2 and 3 are formed inside the metal tube 5. The inside 5c of the metal tube 5 propagates while repeating the reflection on the surface 5a and the outer surface 5b. If a defect exists in the inner surface 5a, the outer surface 5b of the metal tube 5 and the inside 5c, the reflected echo of the ultrasonic waves reflected by the defect returns to the vibrator 4 and is received as a defect echo. do. In this way, ultrasonic flaw detection of the metal tube 5 is performed.
As described with reference to FIG. 11, since both the refracting longitudinal wave 2 and the refracting transverse wave 3 propagate the inside 5c of the metal tube 5, that is, the medium II, the defect echo received by the vibrator 4 is reduced. It becomes difficult to identify whether it is by the refractive longitudinal wave 2 or by the refractive transverse wave 3. For this reason, the presence position of a defect cannot be specified, or the received signal waveform becomes complicated, and the SN ratio of a defect echo falls.
Therefore, in general, in order to perform ultrasonic flaw detection of the metal tube 5 by the inclination angle flaw detection method, the angle of incidence θ i is set to be larger than the critical angle of the refractive longitudinal wave 2 to propagate the interior 5c of the metal tube 5. Do not mix the refraction longitudinal wave (2) with the refraction wave. For example, when the medium I is water, the sound velocity Vi of the refractive longitudinal wave 2 in the medium I at room temperature is about 1500 m / sec, and the refractive longitudinal wave 2 in the metal tube 5 of the medium II is 2. When the sound velocity VL of) is 5900 m / sec and the sound velocity Vs of the refraction cross wave 3 is 3200 m / sec, the critical angle (θL = 90 °) of the refraction longitudinal wave 2 is obtained from the equation (1). The incident angle θi becomes about 15 °, and the refractive angle θs of the refractive shear wave 3 is about 33 °. For this reason, in principle, when the incident angle [theta] i of the incident wave 1 is set to 15 degrees or more, only the refracted transverse wave 3 exists in the medium II.
In recent years, for steel pipes used as oil well pipes, line pipes, and mechanical parts, the demand for higher strength as well as light weight is increasing. Accordingly, the demand for a metal tube (hereinafter referred to as a "high t / D metal tube") with a large ratio (t / D) of the thickness (t) to the outer diameter (D) of, for example, 15% or more increases, have. However, as shown in FIG. 13, which is an explanatory diagram of a situation in which the high t / D metal tube 6 is inspected by the inclination angle flaw detection method, the inclination angle of the high t / D metal tube 6 by the conventional ultrasonic flaw detection method described above. In the case of flaw detection, even if the ultrasonic wave 1 is incident from the outer surface 6b of the high t / D metal tube 6 at an incident angle θi which is equal to or greater than the critical angle of the longitudinal wave ultrasonic wave, the inside 6c of the metal tube 6 is introduced. The refraction shearing wave 3 which propagates does not reach the inner surface 6a of the metal tube 6, but may follow the propagation path | route to the outer surface 6b. In this case, the defect which exists in the vicinity of the inner surface 6a of the metal pipe 6 cannot be detected.
Thus, for example, Patent Document 1 discloses a first oscillator having a refractive angle θ s of a refractive transverse wave inside a metal tube larger than 35 degrees, for example, and a refractive angle θ s being smaller than 35 degrees, for example. In order to detect a normal ratio (t / D) metal tube 5 by using an ultrasonic probe having a second vibration oscillator together, the first vibrator is used alone, and the high t / D metal tube 6 is used. In the case of flaw detection, the use of a first vibrator and a second vibrator is disclosed.
When the ultrasonic probe disclosed in Patent Document 1 is used, when the high t / D metal tube 6 is scanned, it is certain that the refractive transverse wave generated by the second vibrator reaches the inner surface of the high t / D metal tube 6. It becomes possible. However, when the second oscillator is used, not only the refraction transverse wave but also the refraction longitudinal wave are generated. Therefore, the position at which the defect is present cannot be specified, or the received signal waveform is complicated, and the SN ratio of the defect echo is lowered.
For example, in Non-Patent Document 1, an acoustic lens having a tip end surface having a spherical or cylindrical curved surface is disposed in front of the vibrator, or the tip end surface of the vibrator is processed into a spherical or cylindrical curved surface, and the In the case of detecting short and shallow depths in the tube axis direction, an acoustic lens having a spherical end surface or a vibrator processed into a spherical shape is used, and defects that are shallow in depth but continuous in the tube axis direction are detected. In the case of detection, the ultrasonic wave which enters a metal tube is made into the inside of a metal tube by using the acoustic lens or the oscillator which processed the end surface into the cylindrical shape in which the curved surface of the cylindrical curved surface was the cylindrical curved shape in the front-end surface along the circumferential direction of the metal tube. Focusing on the laser beam, thereby increasing the intensity of the defect echo and detecting it with a good SN ratio, The invention is disclosed for detecting the minute flaws with high accuracy.
FIG. 14 shows a refractive longitudinal wave propagating inside the metal pipes 5 and 6 in the case where the refractive shear wave 3 is focused on the inner surfaces of the metal pipes 5 and 6 according to the invention disclosed by Non-Patent Document 1. FIG. (2) and an explanatory diagram showing the propagation behavior of the refractive shear wave 3, and FIG. 14 (a) shows the refractive shear wave when the high t / D metal tube 6 having a ratio (t / D) of about 15% or more ( 3), and FIG. 14 (b) shows the refractive longitudinal wave 2 when the high t / D metal tube 6 is used, and FIG. 14 (c) shows the ratio t / D of less than about 15% ( 10%), the refractive shear wave 3 in the case of using the metal tube 5 which is about 10%), and FIG. 14 (d) shows the case where this metal tube 5 is used.
As shown in Figs. 14 (c) and 14 (d), in the case of a normal metal tube 5 having a ratio (t / D) of less than about 15%, the refractive shear wave 3 is applied to the inner surface of the metal tube 5. Ultrasonic flaw detection can be performed by simply setting conditions at 5a and not causing the refractory longitudinal wave 2 to occur. On the other hand, in the case of the high t / D metal tube 6 having a ratio (t / D) of about 15% or more, as shown in Figs. 14 (a) and 14 (b), the refractive shear wave 3 is applied to the metal tube ( Attempting to reach the inner surface 6a of 6) also results in a refractive longitudinal wave 2. A part of the generated refractive longitudinal wave 2 reaches the inner surface 6a of the metal tube 6 in the same way as the refractive transverse wave 3, and the reached refractive longitudinal wave 2 reaches the inner surface 6a of the metal tube 6. Since it propagates at an angle approximately close to the normal, it multi-reflects between the inner surface 6a and the outer surface 6b of the metal tube 6.
FIG. 15 is a graph showing an example of the reflected echo observed when the high t / D metal tube 6 is inspected in this manner. As illustrated graphically in FIG. 15, the inner defect echo due to the refractive shear wave 3 is observed as embedded between the multiple reflection echoes of the refractive longitudinal wave 2. Multiple reflection echoes of this refractive longitudinal wave 2 become a noise signal that hinders detection of a defect, and minute defects cannot be detected with a good SN ratio. In addition, depending on the thickness of the metal tube 6, the defect echo is completely buried in the multiple reflection echoes of the refraction longitudinal wave 2 which is large in number, and even a skilled inspector cannot identify the defect echo.
Therefore, Patent Document 2 discloses flaw detection at two frequencies so as to detect defect echoes and multiple reflection echoes by flaw detection at a certain frequency, and detect only multiple reflection echoes by flaw detection at a different frequency from this. Disclosed is an invention in which defect echoes of a high t / D metal tube are obtained by alternately processing the flaw detection waveforms at these frequencies to remove multiple reflection echoes that are noise.
[Patent Document 1: Japanese Patent Application Laid-Open No. 10-90239]
[Patent Document 2: Japanese Patent Application Laid-open No. Hei 6-337263]
[Non-Patent Document 1: "Ultrasonic Scanning Law" Japanese Academic Society, Steelmaking Committee 19, Japan Daily Newspaper, 224-227 pages]
[Problem to Solve Invention]
However, the invention disclosed by Patent Document 2 also has problems (a) to (c) listed and described below.
(a) Since it is necessary to collect flaw waveforms at approximately the same position alternately at two frequencies, it is inevitable that the inspection efficiency is reduced to about half.
(b) When the intensity of the defect echo is equal to or smaller than the intensity of the adjacent multiple reflection echo, or when the appearance position of the defect echo is very close to the appearance position of the multiple reflection echo, Even if the difference processing is performed, most of the defect echoes are removed, and the defect echoes cannot be detected based on the waveform after the difference processing.
(c) Since it is necessary to use a special ultrasonic flaw detector capable of flaw detection at a plurality of frequencies, the inspection cost inevitably increases.
This invention is made | formed in order to solve these problems (a)-(c) which the prior art has, For example, a well tube, a line pipe, a mechanical tube (mechanical tube used for a hollow axle, an automobile part, etc.) The outer surface of a metallic tubular test object used as a stainless steel pipe used in a high temperature environment, especially a metal pipe having a ratio (t / D) of thickness t to the outer diameter D, for example, 15% or more. It is an object of the present invention to provide an ultrasonic probe, an ultrasonic flaw detection method, and an ultrasonic flaw detector capable of reliably flaw- ing microscopic defects existing on the inner surface, inside, or the like with inclination angle flaw detection.
[Means for solving the problem]
MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the above-mentioned subject, this inventor acquired the knowledge (A) and (B) listed below and described, and completed this invention.
(A) As described with reference to Figs. 14A and 14B, the incident wave 1 from the vibrator 7 whose front end surface is spherical or cylindrically curved, that is, the longitudinal end shape of the front end is arc-shaped. When the flaw detection is attempted while conducting the flaw detection while focusing on the refractive transverse wave 3 on the inner surface 6a of the high t / D metal tube 6, the refraction longitudinal wave 2 simultaneously generated is the metal tube 6 Reaches the inner surface 6a of. The refractory longitudinal wave 2 reaching the inner surface 6a of the metal tube 6 is located at the propagation direction side of the ultrasonic wave (the left side of the paper in FIG. 14) as viewed from the center of the metal tube 6. Is generated by the incident wave 1 which is transmitted from the light beam and is incident at a small angle of incidence to the outer surface 6b of the metal tube 6.
(B) FIG. 1 (a) is an explanatory view showing the longitudinal cross-sectional shape of the tip 8c of the improved type vibrator 8 invented by the present inventor in comparison with the longitudinal cross-sectional shape of the tip 7c of the vibrator 7 described above. to be. In addition, FIG.1 (b) shows the situation which inclines angle flaw detection of the high t / D metal pipe 6 (outer diameter 40mm, thickness 10mm) using this vibrator 8, and uses the vibrator 7 at high t /. It is explanatory drawing shown in contrast with the situation which inclination angle flaw detection of the D metal pipe 6 is performed. In addition, in FIG.1 (a), the position whose horizontal axis is 0 mm shows the center position of the high t / D metal pipe 6 which is a flaw detection object.
(i) As illustrated in Fig. 1 (a), the radius of curvature of the vibrator 8 constituting the inclination angle transducer is continuously increased from one end 8b side to the other end 8a side. A shape having at least a portion of a non-target curve shape, and
(ii) From the center position of the metal tube 6, the one end 8b side of the front end portion 8c of the vibrator 8 is the non-wave wave direction side of the refraction wave in the metal tube 6 (Fig. 1 (a). ), And the other end 8a side of the tip 8c of the vibrator 8 is located on the propagation direction side of the refracted wave (left side of the paper in Fig. 1 (a)). By arranging the vibrator 8 at a specific position with respect to the high t / D metal tube 6 and satisfying the two conditions of performing the tilt angle flaw detection, as shown by the solid arrow in FIG. 1 (b), the other end 8a side The incident angle of the incident wave 1 transmitted from and the refractive angle of the refractory longitudinal wave 2 can be largely secured. Thereby, the refractive longitudinal wave 2 does not reach the inner surface 6a of the metal tube 6, but reaches the outer surface 6b of the metal tube 6 directly. Therefore, generation of multiple reflection echoes by the refractive longitudinal wave 2 can be eliminated.
As described above, the longitudinal cross-sectional shape of the tip 8c of the vibrator 8 is a shape having at least a portion of an asymmetrical curved shape in which the radius of curvature continuously increases from one end 8b side to the other end 8a side. The magnitude of the radius of curvature, the degree of increase, and the ratio of forming the asymmetric curved portion, etc., together with the refractive shear wave 3 reaching the inner surface 6a of the metal tube 6, the inner surface 6a. What is necessary is just to determine suitably individually, considering the kind of metal pipe 6, etc. so that it may collect | focus on at the specific position of () vicinity.
The present invention provides an ultrasonic probe that detects a tubular specimen by injecting ultrasonic waves obliquely from a built-in vibrator into a metallic tubular specimen and generating a refractive longitudinal wave and a transverse transverse wave propagating inside the tubular specimen. The front end portion of is an ultrasonic probe, characterized in that it has at least a portion of an asymmetrically curved shape in which the radius of curvature continuously increases from one end side to the other end side.
Moreover, this invention is equipped with the built-in vibrator and the acoustic lens arrange | positioned in the front of the ultrasonic transmission direction of this vibrator, An ultrasonic wave is obliquely injected into a metallic tubular subject through this acoustic lens, and the An ultrasonic probe for scanning a coronal subject by generating a refractive longitudinal wave and a refractive transverse wave propagating therein, wherein the tip of the acoustic lens has at least a portion of an asymmetrical curved shape in which the radius of curvature continuously increases from one end to the other. Ultrasonic transducer characterized by having.
Moreover, this invention is an ultrasonic probe which detects a tubular test object by making an ultrasonic wave obliquely enter into a metal tubular test object from a built-in vibrator, and generating the refractive longitudinal wave and the refractive transverse wave which propagate the inside of this tubular test object, While the vibrator is constituted by a plurality of vibration generating elements arranged side by side, by the interference of the ultrasonic wave oscillated from each of the plurality of vibration generating elements, a portion of an asymmetric curve shape in which the radius of curvature continuously increases from one side to the other end side is removed. An ultrasonic probe having at least an incident wave having a wavefront is oscillated.
In the ultrasonic probe according to the present invention, it is exemplified to include a delay time adjusting device for oscillating the incident wave by adjusting the delay time of the ultrasonic transmission and reception of each of the plurality of vibration generating elements. In this case, it is preferable to have an acoustic lens disposed in front of the ultrasonic transmission direction of the vibrator.
In these ultrasonic probes according to the present invention, it is exemplified that the tubular subject is a metal tube with a ratio of the thickness to the outer diameter of more than 15%.
In another aspect, the present invention is, from the center position of the metal tubular object, the end side of the end of the vibrator or acoustic lens constituting the ultrasonic probe according to the present invention described above is small to the tubular object The refraction longitudinal wave and the tubular blood which are located on the non-wave direction direction side of the refraction wave, and whose end side with a large radius of curvature are located on the propagation direction side of the refraction wave, and which do not reach the inner surface of the coronal subject. The ultrasonic flaw detection method is characterized by arranging an ultrasonic probe with respect to a metal tube so as to transmit an incident wave that generates a refractive shear wave focused on the inner surface of the specimen.
In addition, the present invention relates to a metal tube having an end side with a small radius of curvature at the wave front of the tip of the incident wave oscillated from the oscillator constituting the ultrasonic probe according to the present invention as viewed from the center position of the metallic tubular subject. The inner side of the refraction longitudinal wave and the metal tube which are located on the non-wave direction direction side of the refraction wave and the end side of which the radius of curvature in the wave surface is large are located on the propagation direction side of the refraction wave, and do not reach the inner surface of the metal tube. An ultrasonic probe is disposed on a metal tube to perform an inclination angle inspection so as to transmit an incident wave that generates a refractive shear wave that is focused at.
Moreover, this invention is the ultrasonic flaw detection method characterized by the oblique-angle flaw detection of the metal tubular test object which is a specific value of more than 15% of thickness ratio with respect to the outer diameter using the ultrasonic flaw detection method which concerns on this invention mentioned above.
Moreover, from another viewpoint, this invention is the ultrasonic flaw detector provided with the ultrasonic probe which concerns on this invention mentioned above.
[Effects of the Invention]
According to the present invention, the inside of the tubular specimen is also arranged by placing the ultrasonic probe according to the present invention in a proper position even for a metallic tubular specimen, particularly a high t / D metallic tube having a ratio (t / D) of 15% or more. Among the refraction waves that propagate, the refraction transverse wave focuses and the refraction longitudinal wave can be prevented from reaching the inner surface of the coronal subject. For this reason, the concentration of the refraction cross waves increases the reflection echo intensity from the minute defects, and the refraction longitudinal wave follows a propagation path that does not reach the inner surface of the coronal subject, thereby eliminating the occurrence of multiple reflection echoes due to the refraction longitudinal wave. can do. This makes it possible to reliably perform highly accurate tilt angle flaw detection, especially for high t / D metal pipes.
In this way, according to the present invention, even in the case of a tubular specimen, especially a high t / D metal tube having a ratio (t / D) of 15% or more, the microscopic defects existing therein can be reduced in inspection efficiency and increase in inspection cost. It is possible to reliably detect with high precision by inclination angle flaw detection.
Fig.1 (a) is explanatory drawing which showed the longitudinal cross-sectional shape of the improved vibrator tip part which the inventor devised, compared with the conventional longitudinal cross-sectional shape of the vibrator tip part, and FIG. It is explanatory drawing which showed the situation of inclination angle flaw detection of a / D metal tube, compared with the situation of inclination angle flaw detection of a high (t / D) metal tube using a conventional vibrator.
It is a block diagram which shows schematic structure of the ultrasonic flaw detector of embodiment.
3 is a flow chart schematically showing the procedure for designing the shape of the vibrator tip.
4A is an explanatory diagram for illustrating the design procedure of the shape of the tip of the vibrator when a high t / D metal tube having an outer diameter of 40 mm and a thickness of 10 mm is the inspection target.
4B is an explanatory diagram for illustrating a design procedure of the shape of the tip of the vibrator when a high t / D metal tube having an outer diameter of 40 mm and a thickness of 10 mm is the inspection target.
4C is an explanatory diagram for illustrating a design procedure of the shape of the vibrator tip when a high t / D metal tube having an outer diameter of 40 mm and a thickness of 10 mm is the inspection target.
4D is an explanatory diagram for illustrating the design procedure of the shape of the vibrator tip when a high t / D metal tube having an outer diameter of 40 mm and a thickness of 10 mm is subjected to inspection.
FIG. 5 shows the vibrator tip portion based on the procedures S1 to 8 shown in FIG. 3 for a high t / D metal tube having three kinds of dimensions (outer diameter 40 mm and thickness 10 mm, outer diameter 26 mm and thickness 6.5 mm, outer diameter 60 mm and thickness 15 mm). It is explanatory drawing which showed an example of the result which designed the shape of.
Fig. 6 is a graph showing the relationship between the defect incident angle θ and the reflectance (%) of the slit defects extending in the axial direction of the high t / D metal tube and present in the slit shape.
FIG. 7 shows an example of a flaw detection waveform which is an output signal waveform of a main amplifier obtained when flaw detection of a 0.1 mm deep defect present on the inner surface of a mechanical tube made of a high t / D metal tube is performed by the ultrasonic flaw detector according to the first embodiment. FIG. Is a graph.
8 is an explanatory diagram showing a schematic configuration of an ultrasonic flaw detector according to the second embodiment.
9 is a block diagram showing a schematic configuration of an ultrasonic flaw detector according to the third embodiment.
10 is an explanatory diagram for explaining a method of setting a transmission delay time and a reception delay time.
It is explanatory drawing which shows the relationship between the incident wave and the refraction wave in the oblique angle flaw detection method.
It is explanatory drawing which shows the situation where a refraction wave propagates the inside of a metal pipe.
It is explanatory drawing of the situation of flaw detection of the high t / D metal pipe by the inclination angle flaw detection method.
FIG. 14 is an explanatory diagram showing the propagation behaviors of the refractive longitudinal wave and the refractive shear wave propagating inside the metal tube in the case of focusing the refractive shear wave on the inner surface of the metal tube according to the invention disclosed in Non-Patent Document 1; FIG. 14 (a) shows the refractive transverse wave when the metal tube with ratio (t / D) is about 15% or more, FIG. 14 (b) shows the refractive longitudinal wave when this metal tube is used, and FIG. 14 (c) shows the ratio ( The refractive transverse wave when the metal tube whose t / D) is less than about 15% (about 10%) is used, and FIG. 14 (d) shows the case where this metal tube is used.
15 is a graph showing an example of the reflected echo observed when a high t / D metal tube is inspected.
[Description of Symbols for Main Parts of Drawing]
0: flaw surface 1: incident wave
2: refraction longitudinal wave 3: refraction shear wave
4: vibrator 5: metal tube
5a: inner surface 5b: outer surface
5c: inside 6: high t / D metal tube
6a: inner surface 6b: outer surface
6c: inside 7: vibrator
9: metal tube 10: ultrasonic flaw detector
11: ultrasonic probe 12: ultrasonic flaw detector
13: alarm 14: marking device
15: vibrator 15a: the other end
15b: First 15c: Tip
16: high t / D metal tube 16a: inner surface
16b: outer surface 16c: inner
17: focusing point 18: initial point
19: Pulsar 20: Preamplifier
21 filter 22 main amplifier
23: defect determination unit 30: ultrasonic flaw detector
31: vibrator 32: ultrasonic transducer
33: transducer holder 34: lower horizontal arm
35: vertical moving arm 36: horizontal moving arm
37: upper horizontal arm 38: tube following mechanism
39: air cylinder 40: ultrasonic flaw detector
41: vibrator 41a: piezoelectric element
42: ultrasonic transducer 43: transmission circuit
44: receiving circuit 45: alarm
46: marking device 47: metal tube
47a: face 48: pulsar
49: delay circuit (transmission delay circuit) 50: preamplifier
51: delay circuit (receive delay circuit) 52: adder
53: main amplifier 54: defect determination unit
(Embodiment 1)
EMBODIMENT OF THE INVENTION Hereinafter, the best form for implementing an ultrasonic probe, an ultrasonic flaw detection method, and an ultrasonic flaw detection apparatus concerning this invention is demonstrated in detail, referring an accompanying drawing. In addition, in the following description, the case where a metal tubular test object is the high t / D metal pipe 16 whose ratio (t / D) of the thickness t with respect to the outer diameter D is 15% or more is taken as an example.
2 is a block diagram showing a schematic configuration of the ultrasonic flaw detector 10 according to the present embodiment.
As shown in this figure, the ultrasonic flaw detector 10 of the present embodiment includes the ultrasonic probe 11, the ultrasonic flaw detector 12, the alarm 13, and the marking device 14. It demonstrates sequentially.
[Ultrasound transducer 11]
The ultrasonic probe 11 has a casing for accommodating a sound absorbing material, a vibrator 15 and the like arranged so as to transmit the ultrasonic wave at an angle to the flaw face, similarly to this type of ultrasonic probe commonly used. Since the casing, the sound absorbing material, and the like may all be well known, the illustration in FIG. 2 and the description thereof will be omitted. Moreover, in this embodiment, water was used as a contact medium, and the casing which can fill the flaw surface of the high t / D metal pipe 16 was used.
In the present embodiment, the oscillator 15 receives and transmits a transmission signal for every predetermined period from the pulser 19 constituting the ultrasonic flaw detector 12 described later. Thereby, the incident wave U of the ultrasonic wave is obliquely incident on the outer surface 16b of the high t / D metal tube 16 through water W as the contact medium. The incident wave U is a refracted wave consisting of the refracted longitudinal wave U1 and the refracted transverse wave U2, and propagates the interior 16c of the high t / D metal tube 16. The reflection echoes (defect echoes, etc.) of the refractive shear wave U2 due to defects or the like present in the outer surface 16b, the inner surface 16a, or the inside 16c of the high t / D metal tube 16 are vibrators 15. Is received by. The received signal is transmitted to the ultrasonic flaw detector 12. In this way, inclination angle flaw detection of the high t / D metal pipe 16 is performed.
At least a part of the tip portion 15c of the vibrator 15 has a radius of curvature from at least one end 15b side to the other end 15a side as described with reference to FIGS. 1A and 1B. From ρ 1 to the radius of curvature ρ 2 , it is molded to have a portion of an asymmetrical curved shape in which the radius of curvature continuously increases. In order to precisely mold the tip portion 15c to have at least this asymmetrically curved portion, the vibrator 15 is a ceramic piezoelectric represented by PZT (PbZrO 3 -PbTiO 3 ), which is commonly used as a vibrator but is hard to be hardened. Not a device but a PZT-epoxy composite piezoelectric device having good workability.
The asymmetrically curved portion of the tip portion 15c is determined based on, for example, the following steps (hereinafter, abbreviated as "S") 1 to S8.
The determination procedure of the asymmetrically curved portion of the tip portion 15c will be described. 3 is a flowchart schematically showing a procedure for designing the shape of the tip portion 15c of the vibrator 15. 4A-4D are explanatory drawing for showing the design procedure of the shape of the front end part 15c of the vibrator 15 when the high t / D metal pipe 16 of 40 mm in outer diameter and 10 mm in thickness is made into a test object. .
As shown in Fig. 3, in Step 1, (1) the shape (outer diameter (D) and thickness (t)) of the high t / D metal tube 16, (2) the high t / D metal tube 16 To the sound velocity Vs of the refractive shear wave U2 of (3), (3) the sound velocity VL of the refractive longitudinal wave U1 of the high t / D metal tube 16, and (4) the contact medium (water in this embodiment). The sound velocity Vi of the incident wave U and (5) the length along the circumferential direction of the distal end of the high t / D metal tube 16 of the vibrator 15 is conditionally set.
In addition, the sound velocity Vi of the incident wave in the contact medium, the sound velocity Vs of the refractive transverse wave U2 in the high t / D metal tube 16, and the sound velocity VL of the refraction longitudinal wave U1, Conventionally known numerical data may be used according to the type of contact medium, the material of the high t / D metal tube 16, or the like, or the previously collected experimental data may be used as the set value.
Moreover, what is necessary is just to set the length along the circumferential direction of the front-end | tip part of the high t / D metal pipe 16 of the vibrator 15 to the length which can be manufactured while being sufficient transmission / reception sensitivity. In general, although the shape of the high t / D metal tube 16, the size of the defect to be detected, the material, and the like depend on the material, the length of the vibrator 15 along the circumferential direction of the high t / D metal tube 16 is 6 to 6, inclusive. It is about 20mm. Then, the process proceeds to S2.
In S2, as shown in FIG. 4A, the focal point 17 of the refractive shear wave U2 on the inner surface 16a of the (6) high t / D metal tube 16 is appropriately set.
In the provisional setting of the focusing point 17, it is preferable to consider the reflectance of the defect. That is, as shown in Fig. 6 illustrating the relationship between the defect incident angle θ and the reflectance (%) of the slit defects extending in the axial direction of the high t / D metal tube 16 and present in the slit shape, The reflectance of the refractive shear wave U2 depends on the incident angle θ of the shear wave ultrasound. Considering in the range of the incident angle which can be set realistically, reflectance becomes large when the defect incidence angle (theta) is about 40-50 degrees. Therefore, in order to increase flaw detection accuracy and increase the intensity of the defect echo, it is preferable to temporarily set the focal point 17 at which the incident angle θ can be about 40 to 50 degrees as an initial value. Then, the process proceeds to S3.
In S3, based on the conditions (1), (2), (4), and (6) described above, the propagation path of the refracted transverse wave U2 propagated to the preset focal point S is calculated. That is, as shown in FIG. 4A, initially from the focusing point 17 set on the inner surface 16a of the high t / D metal tube 16 toward the outer surface 16b of the high t / D metal tube 16. , A plurality of propagation paths of the refractive shear wave U2 radially (actually, the refractive shear wave U2 propagates from the outer surface 16b toward the focusing point 17), and then a high t / D metal tube Based on Snell's law that holds at the interface between the outer surface 16b of (16) and the contact medium W, the incident angle of the incident wave is calculated based on the conditions of (2) and (4) described above. Each propagation path of the longitudinal wave ultrasonic wave U in the contact medium W respectively connected to each propagation path of the refractive shear wave U2 is calculated. The vibrator 15 assuming the initial point of each propagation path of the refractive longitudinal wave U1 and the refractive transverse wave U2 propagating to the focusing point 17, that is, the end point 18 opposite to the focusing point 17. ) So that the initial point 18 is separated from the high t / D metal tube 16 by a distance approximately equal to the offset distance of the high t / D metal tube 16, and the propagation time of the ultrasonic wave along each propagation path (the Determined by the length and the speed of sound).
In this way, the shape (outer diameter (D), thickness (t), etc.) of the high t / D metal tube 16 to be inspected by S1 to S3, and the refractive shear wave U2 in the metal tube 16. Based on Sonic's speed Vs, the velocity V of the incident wave in the contact medium, and the focal point 17 of the refracted transverse wave U2 in the metal tube 16, according to Snell's law, The propagation path of the refractive shear wave U2 propagating to the point 17 is calculated. Then, the process proceeds to S4.
In S4, the tip end of the vibrator 15 is based on the propagation path calculated in S3 and the above-mentioned condition (the length along the circumferential direction of the high t / D metal tube 16 of the vibrator 15). The shape of (15c) is calculated. That is, the length of the curve which sequentially connected each initial point 18 of each propagation path | route, or the curve approximated by the least square approximation method etc. from each initial point 18 is computed. Comparing this with the condition of (5) described above, a curve D obtained by each initial point 18 of the remaining propagation path is devised by dedicating unnecessary propagation paths from the end so that both are approximately the same length. It is set as the longitudinal section shape of the front-end | tip part 15c of 15). In addition, the example shown to FIG. 4A has shown the state which delimited the unnecessary propagation path so that it might become the shape of the front-end | tip part of substantially the same length to the left and right with respect to the central axis of the high t / D metal pipe 16. As shown in FIG.
As described above, in S4, the radius of curvature is once defined as described above based on the propagation path calculated in S3 and the length along the circumferential direction of the high t / D metal tube 16 of the preset vibrator 15. The shape of the tip portion 15c of the vibrator 15 is determined by calculating the shape of the tip 15c of the vibrator 15 so as to form an asymmetric curve continuously increasing from the radius of curvature ρ 1 to the radius of curvature ρ 2 from the side of the other end 15a to the side of the other end 15a. do. Then, the process proceeds to S5.
In S5, based on the shape of the tip portion 15c of the vibrator 15 determined in S4, and the refractive longitudinal wave U1 propagating into the high t / D metal tube 16, based on the conditions of the above (3). Compute the propagation path. That is, as shown in FIG. 4A, from each initial point 18 constituting the determined shape of the tip portion 15c of the vibrator 15 to the incident wave U along each propagation path in the contact medium W; In accordance with Snell's law established on the interface 16b of the high t / D metal tube 16 and the contact medium W, the high t / D metal tube 16 is based on the condition of (3). The angle of refraction of the longitudinal wave ultrasonic wave U1 propagating through the inner portion 16c is calculated, and the respective propagation paths of the refraction longitudinal wave U1 connected to the respective propagation paths of the incident wave U are calculated.
Thus, in S5, Snell's law is based on the shape of the tip portion 15c of the vibrator 15 calculated in S2 and the sound velocity VL of the refractive longitudinal wave U1 in the metal tube 16 set in advance. By this, the propagation path of the refractive longitudinal wave U1 propagating inside the metal tube 16 is calculated. Then, the process proceeds to S6.
In S6, it is determined whether or not a propagation path reaching the inner surface 16a of the high t / D metal tube 16 exists among the propagation paths of the refractive longitudinal wave U1 calculated in S5. The example shown in FIG. 4A is a case where a propagation path reaching the inner surface 16a exists.
If there is a propagation path reaching the inner surface 16a, the flow advances to S7, for example, to move the focal point 17 of the determined refractive shear wave U2 to a position apart from the predetermined circumference along the inner circumferential surface 16a, for example. In other words, the above operations of S1 to 6 are repeatedly performed.
4B-4D are explanatory drawing which showed the form of this iteration operation. As shown in FIGS. 4B to 4D, the set position of the focusing point 17 is gradually moved from the central axis of the high t / D metal tube 16 along the inner surface 16a of the high t / D metal tube 16. Change it so that it is spaced apart. As a result, in the state shown in FIG. 4D, all the propagation paths of the refractive longitudinal wave U1 do not reach the inner surface 16a of the high t / D metal tube 16.
On the other hand, when the propagation path which reaches the inner surface P2 does not exist, it transfers to S8, and computes the shape of the front-end | tip part 15c of the vibrator 15 which was computed immediately before and decided finally, of the vibrator 15 It determines as a shape of the front-end | tip part 15c. In the example shown in FIG. 4A, the shape of the tip part 15c of the vibrator 15 when it is in the state shown in FIG. 4D is determined as the shape of the tip part 15c.
Thus, in S6-8, when the propagation path which reaches the inner surface 16a of the high t / D metal pipe 16 exists among the propagation paths of the refractive longitudinal wave U1 computed in S5, it is high t. The focal point 17 of the refractive shear wave U2 is changed until the propagation path reaching the inner surface 16a of the / D metal tube 16 is not present, and the calculation from S1 to S3 is repeated. When the propagation path reaching the inner surface 16a of the high t / D metal tube 16 does not exist, the shape calculated in S2 at that time is used as the shape of the tip portion 15c of the vibrator 15. Decide
According to the procedures S1 to 8 described above, the radius of curvature ρ 2 is the radius of curvature ρ 1 from the radius of curvature ρ 1 from one end 15b side to the other end 15a side of the front end portion 15c of the vibrator 15. It is determined as an asymmetric curve shape that increases continuously.
In addition, although the whole description of the front-end | tip part 15c of the vibrator 15 showed this asymmetric curve shape, it is not limited to this, For example, the area | region of one part of the front-end part 15c is this asymmetric curve. In addition to the shape, the remaining area of the tip portion 15c may have a shape other than the asymmetric curve shape (for example, a linear shape or an arc shape). For example, an asymmetric curved portion exists inside the circumferential direction of the tip portion 15c of the vibrator 15, and a portion other than an asymmetric curved portion exists at one or both ends of the asymmetric curved portion. The case is also included in the present invention.
In order to perform the inclination angle flaw detection of the high t / D metal tube 16, as the ratio t / D of the high t / D metal tube 16 increases, an asymmetric curve formed on the tip portion 15c of the vibrator 15 is obtained. The proportion of the shape occupies the whole area in the circumferential direction of the tip portion 15c. However, when the ratio (t / D) is about 15%, this ratio is 70%. For this reason, the ratio which the asymmetrically curved part formed in the front-end | tip part 15c of the vibrator 15 occupies with respect to the whole area | region in the circumferential direction of the front-end | tip part 15c is high that a test | inspection object is 15% or more (t / D). About the t / D metal tube 16, it is preferable that it is 70% or more, and it is more preferable that it is 80% or more.
In addition, the relationship between the radius of curvature ρ 1 and the radius of curvature ρ 2 may be ρ 1 <ρ 2 . What is necessary is just to define this radius of curvature suitably in relationship with the outer diameter and thickness of the pipe | tube to be measured, and, thereby, the diameter of the solid (t / D) pipe of a specific ratio (t / D) without generating the multiple reflection of a refractory longitudinal wave. Square flaw detection can be performed.
The above-described steps S1 to 8 may be executed by the designer by drawing each time, but it is also possible to program and execute the program automatically. The latter is preferable in terms of design efficiency.
4A to 4D, in order to facilitate the explanation, by analyzing the propagation path of the ultrasonic wave in two dimensions, the vibrator in the axial direction of the high t / D metal tube 16 is similar to the conventional cylindrical curved shape. The design procedure of the shape of the front-end | tip part 15c by which the edge part of each cross section of 15) becomes a uniform curve was demonstrated as an example. However, by analyzing the propagation path of the ultrasonic wave in three dimensions, the shape of the tip portion 15c such that the end portions of the respective cross sections of the axial vibrator 15 in the axial direction of the high t / D metal tube 16 become a curved surface may be designed. do.
FIG. 5 shows the high t / D metal pipe 16 having three kinds of dimensions (outer diameter 40mm and thickness 10mm, outer diameter 26mm and thickness 6.5mm, outer diameter 60mm and thickness 15mm) based on the above-described procedures S1 to 8, It is explanatory drawing which showed an example of the result of having designed the shape of the vibrator 15 tip part 15c. In Fig. 5, the shape of the tip 15c designed in order to clarify the difference in the shape of the tip 15c of the vibrator 15 designed according to the various dimensions of the high t / D metal tube 16 is horizontal and vertical. The positions are shown aligned by moving in parallel to each other.
As shown in FIG. 5, the shapes of these tip portions 15c continuously increase from the radius of curvature ρ 1 to the radius of curvature ρ 2 from the one end 15b side to the other end 15a side. It is an asymmetric curve shape.
As shown in Fig. 5, the present embodiment is not limited to the high t / D metal tube 16 having an outer diameter of 40 mm and a thickness of 10 mm described with reference to Figs. 4A to 4D, but the normal ratio (t / D The same can be applied to metal tubes of) and high t / D metal tubes of various dimensions.
Although the ultrasonic probe 11 demonstrated above is comprised so that an incident wave U may be transmitted directly from the vibrator 15, unlike this, the front side of the ultrasonic transmission direction of the vibrator 15 is, for example, acrylic resin etc. The acoustic lens (not shown) produced by this is arrange | positioned, and the incident wave U is obliquely incident on the high t / D metal tube 16 via this acoustic lens, and the inside of the high t / D metal tube 16 is opened. The propagated longitudinal wave U1 and the refracted transverse wave U2 may be generated. In this case, the vibrator 15 has a normal arc-shaped tip, and the tip of the acoustic lens has a radius of curvature from the radius of curvature ρ 1 to the radius of curvature ρ 2 from one side to the other end. What is necessary is just to make it the asymmetric curve shape which increases continuously. By doing in this way, since the ceramic-type piezoelectric element which has low workability represented by PZT but a favorable piezoelectric effect can be used as the vibrator 15, the performance of the vibrator 15 can be aimed at.
The ultrasonic probe 11 of this embodiment is comprised as mentioned above.
[Ultrasonic flaw detector 12]
As shown in FIG. 2, the ultrasonic flaw detector 2 according to the present embodiment includes a pulser 19, a preamplifier 20, a filter 21, a main amplifier 22, and a defect determining unit 23. ).
Both the pulser 19 and the preamplifier 20 are connected to the vibrator 15 by the coaxial cable C via the coupling stopper (all not shown) provided in the casing rear part of the ultrasonic transducer 11. Transmitter signals are transmitted from the pulser 19 to the vibrator 15 at predetermined intervals, whereby the vibrator 15 is excited, and the incident wave enters the high t / D metal tube 16 through water W as a contact medium. (U) is incident. The incident wave U propagates inside the high t / D metal tube 16 as a refracted wave consisting of the refracted longitudinal wave U1 and the refracted transverse wave U2. The reflected echo (defect echo, etc.) is received by the vibrator 15, and the received signal is transmitted to the preamplifier 20 via the coaxial cable C. The received signal is amplified by the preamplifier 20, filtered by the filter 21 in a predetermined frequency band, and then further amplified by the main amplifier 22. The output signal from the main amplifier 22 is compared with a predetermined threshold predetermined in the defect determination unit 23. And the defect determination part 23 judges that there exists a defect, if it is an output signal of this threshold value or more, and when it determines that there is a defect, it outputs the operation command to the alarm 3 or the marking apparatus 4.
Since the ultrasonic flaw detector 12 of this embodiment is a well-known common thing comprised as mentioned above, further description regarding the ultrasonic flaw detector 12 is abbreviate | omitted.
[Alarm (13)]
The alarm device 13 outputs an alarm sound based on the operation command from the ultrasonic flaw detector 12.
Since the alarm 13 of this embodiment is a well-known common thing comprised as mentioned above, further description regarding the alarm 13 is abbreviate | omitted.
[Marking Device 14]
The marking device 14 performs a predetermined marking on the surface of the high t / D metal pipe 16 based on the operation command from the ultrasonic flaw detector 12.
Since the marking apparatus 14 of this embodiment is a well-known conventional thing comprised as mentioned above, further description regarding the marking apparatus 14 is abbreviate | omitted.
The situation where the high t / D metal tube 16 is examined using the ultrasonic flaw detector 10 of this embodiment comprised in this way is demonstrated.
In this embodiment, as shown in FIG. 2, the vibrator of the ultrasonic probe 11 which comprises the ultrasonic flaw detector 10 of this embodiment from the center position of the high t / D metal tube 16 which is the object of ultrasonic flaw detection. One end 15b side of the tip portion 15c of (15) is the non-wavelength direction side of the refracted wave in the high t / D metal tube 16 (the right side of the high t / D metal tube 16 in FIG. 2). The vibrator 15 is positioned so that the other end 15a side of the tip portion 15c of the vibrator 15 is located on the propagation direction side of the refraction wave (left side of the page in Fig. 1 (a)). It arrange | positions with respect to the high t / D metal pipe 16, and performs an inclination angle flaw detection.
In other words, the ultrasonic transducer 11 has a refractive wave in the high t / D metal tube 16 with respect to the high t / D metal tube 16 at one end 15b of the tip portion 15c of the vibrator 15. While located on the non-wave wave direction side (right side of the high t / D metal tube 16 in FIG. 2), the other end 15a side of the tip portion 15c of the vibrator 15 is the propagation direction side of the refracted wave (FIG. 2). It is good to arrange | position so that it may be located in the left side of the high t / D metal pipe | tube 16 of the.
In other words, when the ultrasonic transducer 11 is disposed with respect to the high t / D metal tube 16 in this manner, as shown in FIG. 2, the incident angle of the incident wave U transmitted from the other end 15a of the large radius of curvature and The refraction angle of the refraction longitudinal wave U1 can be secured large.
Therefore, according to the present embodiment, among the refraction waves 2 and 3 propagating inside the high t / D metal tube 16 having a ratio t / D of 15% or more, the deflection transverse wave U2 converges while refracting. Since the longitudinal wave U1 does not reach the inner surface 16a of the metal tube 16, the refractive shear wave U2 is focused to increase the reflected echo intensity from the minute defects, and the refractive longitudinal wave U1 Since the propagation path which does not reach the inner surface 16a of the metal tube 16 is followed, generation | occurrence | production of the multiple reflection echo by a refractive longitudinal wave can be eliminated. This makes it possible to reliably perform highly accurate inclined flaw detection even on the high t / D metal tube 16.
For this reason, according to this embodiment, the micro-defect which exists in the inside of the high t / D metal pipe 16 whose ratio (t / D) is 15% or more, for example, reduces the inspection efficiency and raises the inspection cost. It is possible to reliably detect with high precision by inclination angle flaw detection.
When the high t / D metal tube 16 is inspected by the ultrasonic flaw detector 10 having the above-described configuration, the high t / D metal tube 16 is conveyed in the axial direction while rotating in the circumferential direction, whereby In this way, the flaw detection over the entire surface of the high t / D metal tube 16 is enabled. However, the present invention is not limited thereto, and the ultrasonic probe 10 may be rotated in the circumferential direction of the high t / D metal tube 16 while conveying the high t / D metal tube 16 in the axial direction.
In addition, the ultrasonic flaw detection apparatus 10 which concerns on this embodiment is a steel pipe whose ratio (t / D) is 15% or more, such as mechanical tubes used for automobile parts, etc., stainless steel pipes used under high temperature environment, etc., for example. It is particularly suitable for inspecting the interior.
Fig. 7 shows the main amplifier 24 obtained when the ultrasonic flaw detector 10 according to the present embodiment detects a small defect of 0.1 mm in depth present on the inner surface of a mechanical tube made of a high t / D metal tube. It is a graph which shows an example of the flaw detection waveform which is an output signal waveform.
As shown in the graph of FIG. 7, according to the ultrasonic flaw detector 10 according to the present embodiment, the refractive transverse wave U2 of the refraction waves U1 and U2 is focused inside the high t / D metal tube 16. As the reflected echo intensity from the microscopic defects increases, the refractive longitudinal wave U1 simultaneously occurs along the propagation path which does not reach the inner surface 16a of the high t / D metal tube 16, and thus the refractive longitudinal wave U1 Multiple reflection echoes can be suppressed, and only defect echoes can be detected with a good SN ratio.
(Embodiment 2)
FIG. 8: is explanatory drawing which showed schematic structure of the ultrasonic flaw detector 30 of this embodiment.
As illustrated in FIG. 8, the ultrasonic flaw detector 30 according to the present embodiment includes two ultrasonic probes 32 each having vibrators 31 and 31, an ultrasonic flaw detector (not shown), and an alarm (not shown). ) And a marking device (not shown). In addition, since the ultrasonic flaw detector, alarm, and marking apparatus which are not shown are the same structure as Embodiment 1 mentioned above, the description is abbreviate | omitted.
The ultrasonic flaw detector 30 further includes transducer holders 33 and 33 holding the vibrators 31 and 31, and lower horizontal arms 34 and 34 holding the holders 33 and 33, respectively. The upper and lower movable arms 35 and 35 connected to the upper horizontal arm 37 and the upper and lower directions, and the upper and lower movable arms 35 and 35 fixed to the upper and lower movable arms 35 and 35. Horizontal movable arms 36 and 36 arranged to be able to move the upper surface of the upper horizontal arm 37 in the extension installation direction (left and right direction in FIG. 8) of the upper horizontal arm 37, and the horizontal movable arms 36, 36 and the upper and lower movable arms 35 and 35 so as to be movable in the horizontal direction, the upper and lower horizontal arms 37 supported by the air cylinder 39 to be lifted and lowered by the air cylinder 39. A pipe following mechanism 38 and an air cylinder 39 are supported.
The transducer holders 33 and 33 are provided via the lower horizontal arm 34 and 34, the upper and lower movable arms 35 and 35, the horizontal movable arms 36 and 36, and the upper horizontal arm 37. ) The pipe follower 38 is connected to the air cylinder 37 and moves up and down. When the tube follower 38 moves up and down, the lower horizontal arms 34 and 34, the up and down moving arms 35 and 35, the horizontal moving arms 36 and 36 and the upper horizontal arm 37 also move up and down, Thus, the transducer holders 33 and 33 are also integrated to move up and down.
The vibrators 31 and 31 constituting the ultrasonic transducers 32 and 32 may be formed according to the material (the refraction longitudinal wave of the ultrasonic wave, the sound velocity of the refraction transverse wave), the outer diameter D, the thickness t, or the like of the metal tube 9 to be measured. As shown in FIG. 1, the tip portion has an asymmetric curve shape in which the radius of curvature continuously increases from the radius of curvature ρ 1 to the radius of curvature ρ 2 from one end 15b side to the other end 15a side. It is molded and is loaded manually or automatically into the transducer holders 33 and 33.
The vibrators 31 and 31 drive the vertical movement arm 35 and the horizontal movement arm 36, and one end 15b side of the vibrators 31 and 31 is connected to the metal tube 9 with respect to the metal tube 9. In the non-wave direction direction side of the refraction wave (in FIG. 8, the right side part of the metal tube 9 in the left vibrator 31, and the left part in the right vibrator 31), the other end 15a side It is arrange | positioned so that it may be located in the propagation direction side of a refraction wave (the left part of the metal tube 9 in the left vibrator 31 in FIG. 8, and the right part in the right vibrator 31).
When the relative positional relationship between the vibrators 31 and 31 and the metal tube 9 is shifted, the transverse wave ultrasonic wave in the metal tube 9 assumed when determining the asymmetrical curve shape of the tip portions 31c and 31c of the vibrators 31 and 31. Since the position of the focal point (17 in FIG. 2) is shifted, the defect detection capability decreases. Therefore, in order to accurately set the relative positional relationship between the vibrators 31 and 31 and the metal pipe 9, it is preferable to use a linear guide as the up-and-down movement arms 35 and 35 and the horizontal movement arms 36 and 36. As shown in FIG.
When the metal tube 9 is inspected by the ultrasonic flaw detector 30 having the above configuration, the metal tube 9 is closed in a state where the tip of the metal tube 9 is blocked by a stopper (not shown) for preventing water from entering the inside. ) While passing in the axial direction while rotating in the circumferential direction, passes through a flaw detection tank (not shown).
At this time, the air cylinder 37 is started at the timing when the front end portion of the metal tube 9 is detected by a predetermined material detecting sensor, whereby the tube following mechanism 38, the vertical movement arms 35, 35, and the horizontal movement are performed. The arm 37 and the transducer holders 36 and 36 are united and lowered, so that the tube follower 38 is pressed onto the outer surface of the metal tube 38 at an appropriate pressure.
The pipe follower 38 crimped at an appropriate pressure is configured to move only in a predetermined range up, down, left, and right, and at the time of conveyance of the metal pipe 9 while maintaining a state in which the bottom thereof contacts the outer surface of the metal pipe 9. Follow the rattling of and move up and down and left and right. At this time, the vertical movement arms 35 and 35, the horizontal movement arms 36 and 36, and the transducer holder 38, which are connected to the tube follower 38, also follow the vertical movement. As a result, the relative positional relationship between the vibrators 31 and 32 loaded on the transducer holders 33 and 33 and the metal tube 9 is kept constant.
In this manner, also by the ultrasonic flaw detector 30 according to the present embodiment, the refraction longitudinal wave is focused to increase the reflection echo intensity from the microscopic defects, and at the same time, the refraction longitudinal waves generated at the same time do not reach the inner surface of the metal tube 9. Since a propagation path that does not follow, the generation of multiple reflection echoes due to the refraction longitudinal wave can be eliminated, and only defect echoes can be detected with a good SN ratio.
In addition, in the ultrasonic flaw detector 30 shown in FIG. 8, the form which arrange | positions two vibrators 31 and 31 so that the propagation direction of the refraction wave in the metal pipe 9 may become two directions of clockwise rotation and counterclockwise rotation is provided. As an example, in order to further improve flaw detection efficiency, it is also possible to arrange a plurality of vibrators 31 along the axial direction of the metal tube 9, for example, in which the propagation direction of the refraction wave is clockwise and counterclockwise. It is possible.
(Embodiment 3)
In Embodiment 3, unlike Embodiments 1 and 2 described above, a case in which the vibrators are configured in a flat form by a plurality of vibration generating elements provided side by side will be described.
9 is a block diagram showing a schematic configuration of the ultrasonic flaw detector 40 according to the present embodiment. As shown in this figure, the ultrasonic flaw detector 40 according to the present embodiment includes an ultrasonic probe 42 having a vibrator 41, a transmission circuit 43, a reception circuit 44, and an alarm ( 45 and a marking device 46. In addition, since the alarm 45 and the marking apparatus 46 are the same structures as Embodiment 1 mentioned above, the description is abbreviate | omitted.
The vibrator 41 which comprises the ultrasonic probe 42 which concerns on this embodiment is arrange | positioned facing the outer surface 47a of the metal pipe 47, and plurality (for example, 32) minute pieces are small pieces. Piezoelectric elements 41a are arranged (arranged) side by side in a straight line at an interval of, for example, 0.5 mm in a direction orthogonal to the axial direction of the metal tube 47. That is, this ultrasonic transducer 42 is what is called an array transducer.
The transmission circuit 43 includes a pulser 48 and a delay circuit (transmission delay circuit) 49 equal to the number of piezoelectric elements 41a included in the vibrator 41. Each pulser 48 is connected to each piezoelectric element 41a of the vibrator 41 and to each delay circuit 49. Each piezoelectric element 41a is excited with a transmission signal for each predetermined period from each pulser 48 connected to each piezoelectric element 41a, and ultrasonic wave is applied to the metal tube 47 through water W as a contact medium. Incident wave U is incident.
Here, the timing of transmitting the transmission signal from each pulser 48 can be different for each pulser 48 according to the transmission delay time set by each delay circuit 49, and each pulser will be described later. By appropriately setting the transmission delay time of (48), the same aspect as the aspect which transmits the incident wave U of an ultrasonic wave from the vibrator whose tip part is asymmetrical arc shape shown in Embodiment 1, 2 is implement | achieved.
The incident wave U incident on the metal tube 47 propagates through the inside 47c of the metal tube 47 as a refracted wave consisting of the refractory longitudinal wave U1 and the refracted transverse wave U2, and the reflected echo is an oscillator 41. Is received by the piezoelectric element 41a, and the received signal is transmitted to the receiving circuit 44.
The receiving circuit 44 includes a preamplifier 50 and a delay circuit (receive delay circuit) 51 equal to the number of piezoelectric elements 41a of the vibrator 41. In addition, the receiving circuit 44 includes an adder 52, a main amplifier 53, and a defect determining unit 54. Each preamplifier 50 is connected to each piezoelectric element 41a of the vibrator 41 and to each delay circuit 51. The received signal from each piezoelectric element 41a is amplified by each preamplifier 50 connected to each piezoelectric element 41a and then by each delay circuit 51 connected to each preamplifier 50. The delay of the reception delay time equal to the transmission delay time of each piezoelectric element 41a (the transmission delay time of each pulser 48 connected to each piezoelectric element 41a) is performed. The output signal of each delay circuit 51 is added by the adder 52 included in the receiver circuit 44 and then amplified by the main amplifier 53. The output signal from the main amplifier 53 is input to the defect determination unit 54 having the same configuration as the defect determination unit 23 of the first embodiment, and the presence or absence of a defect is determined.
Hereinafter, the above-described method of setting the transmission delay time and the reception delay time will be described.
10 is an explanatory diagram for explaining a method of setting a transmission delay time and a reception delay time. As shown in this figure, when setting the transmission delay time and the reception delay time, first, in the horizontal direction of the asymmetric curve shape D designed in the same order as the procedures S1 to 8 shown in FIG. 10 and the length of the vibrator 11 are compared, and the piezoelectric element 41a to be used is selected so that both may become substantially the same length. The set of the selected piezoelectric elements 41a is called a selection element group.
Next, the center coordinates of the piezoelectric elements 41a constituting this selection element group and the relative distance between the asymmetric curves D are set to 0, and the relative distances of the piezoelectric elements 41a and the asymmetric arcs are 0. , Respectively. In FIG. 10, the relative distance between the right-side piezoelectric element 41a and the non-arc shape D was zero. And the value which divided each relative distance by the sound velocity of the incident wave U in the contact medium W is set as the transmission delay time and reception delay time corresponding to each piezoelectric element 41a.
By setting the transmission delay time and the reception delay time by the method described above, the same behavior as in the case of transmitting / receiving ultrasonic waves using the vibrator 41 whose cross-sectional end shape becomes an asymmetric curve shape D is exhibited. That is, as shown in FIG. 9, in the refraction wave composed of the refraction longitudinal wave U1 and the refraction cross wave U2 propagating in the interior 47c of the metal tube 47, the refraction cross wave U2 is focused and refracted. The longitudinal wave U1 does not reach the inner surface 47a of the metal tube 47. Therefore, the convergent transverse wave U2 is focused to increase the reflection echo intensity from the micro defects and to eliminate the occurrence of multiple reflection echoes due to the simultaneous refraction longitudinal wave U1, so that only the defect echoes are detected at a good SN ratio. It is possible to do
As for the ultrasonic flaw detector 40 which concerns on this embodiment, the ultrasonic transducer 42 is comprised by the many piezoelectric element 41a, the vibrator 41 is comprised, it is comprised as an array probe, and each piezoelectric element 41a has By appropriately setting the delay time of ultrasonic transmission / reception, the ultrasonic transducer having the tip portion described by Embodiments 1 and 2 having a vibrator having an asymmetrical curved shape is simulated.
That is, due to the interference of the ultrasonic wave oscillated from each of the plurality of vibration generating elements, the incident wave having the wavefront having at least a wavefront portion having an asymmetric curved shape whose curvature radius continuously increases from one side to the other side can be oscillated. It is composed. As a result, the arrangement of the piezoelectric elements 41a is arranged in a straight line as in the present embodiment, and the delay time of ultrasonic transmission and reception is appropriately changed only by using the vibrator 41 fixed. It is possible to provide a vibrator that has an effect equivalent to that of a vibrator having a tip.
Therefore, it is not necessary to prepare a large number of asymmetrically curved vibrators depending on the material, outer diameter D, thickness t, and the like of the metal tube 47, and it is possible to suppress the rise of the running cost. In addition, since it is not necessary to replace the asymmetrically curved vibrator according to the material, outer diameter D, and thickness t of the metal tube 47, the time required for replacement and the like can be shortened, thereby improving inspection efficiency. have.
In addition, in this embodiment, although the case where the array probe which arrange | positioned each piezoelectric element 41a in linear form as the vibrator 41 was demonstrated, this invention is not limited to this, The ultrasonic wave according to each arrangement was demonstrated. It is also possible to apply an array transducer arranged in an arc or polygonal shape by simply setting a delay time for transmission and reception of the antenna.
