JPS60198454A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To detect accurately by the crack of an objective body by fitting a delay material to the ultrasonic probe, dividing the delay material into an upper and a lower part and rotating and adjusting turnably the upper delay material about the lower delay material, and making an ultrasonic wave incident on the crack at right angles. CONSTITUTION:The upper delay material 23 and lower delay material 25 are fitted to an ultrasonic probe case 29. The lower part of the upper delay material 23 is formed into a semicylindrical surface 27 and the lower delay material 25 is fitted therein while the upper delay material 23 is made slidable as shown by an arrow A. Then when a flaw of the tenon 41 of a turbine blade 39 is detected by this probe 20, the lower delay material 25 is set abutting on the surface of the tenon 41 and the upper delay material 23 is rotated to make an adjustment so that the ultrasonic wave is incident to cracks A and B at right angles. Even when the cracks A and B run in different angle directions, the upper delay material 23 is rotated to make an adjustment. Thus, the ultrasonic wave is made incident on the cracks at right angles and its reflected wave is received, so cracks in the objective body are detected accurately.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an ultrasonic probe used in an ultrasonic flaw detection device, and particularly to an ultrasonic probe suitable for use in ultrasonic flaw detection of the tenon portion of a turbine blade of a steam turbine. Regarding ultrasonic probes.

[Technical background of the invention and its problems]

In general, ultrasonic flaw detection equipment uses an ultrasonic probe that is brought into contact with the object to be inspected, and the ultrasonic probe injects ultrasonic waves into the object. Defects inside the object are detected by receiving sound waves (reflected waves) with the same or different ultrasonic probes. However, such an ultrasonic flaw detection device cannot detect shallow parts of the object due to the energy propagation of the incident ultrasonic waves. Therefore, a delay material is used to enable shallow flaw detection.

For example, as shown in FIG.
In this case, the delay material 5 is fixed to the lower part of the probe case 3 containing a transducer that generates ultrasonic waves. Due to this delay material 5, all the ultrasonic waves incident on the tenon 7 of the turbine blade 6, which is the object to be inspected, become far-field sound waves 9, and the flaw detection surface 9 of the tenon 7
It is also possible to detect cracks A that occur directly below (approximately 3 to 4 cm). Note that the reference numeral 11 in the figure is a shroud.

However, even with the probe 1 using such a delay material 5, cracks occurring in the Tenon 7 may not be able to be detected. The testing surface 9 of the claw 9 and tenon 7 is inclined with respect to the shroud 11 surface, and the cracks A and B that occur in the tenon 7 are almost parallel to the shroud 11 surface, so the vertical probe is installed perpendicular to the testing surface 9. This is because the child 1 cannot receive the ultrasonic waves reflected by the cracks A and B as shown by the arrow in FIG.

Therefore, as shown in FIG. 2, an oblique probe 15 in which the lower end of the delay material 13 is inclined is used. In FIG. 2, the same parts as in FIG. 1 are given the same reference numerals. According to this angle probe 15, the ultrasonic waves generated by the vibrator in the probe case 3 are bent at the flaw detection surface 9 and are transmitted through the crack A in the tenon 7.
, is incident perpendicularly to B. Then, the reflected waves from cracks A and B travel in the same direction as the incident wave and reach the angle probe 1.
Reach 5.

Therefore, with this angle probe 15, Shrou +-
Cracks A and B that occur almost parallel to the n-plane can be detected.

However, the cracks A and B are not always parallel to the shroud 11 surface, and empirically, they are often inclined within a range of about 100 degrees. On the other hand, the angle of inclination of the lower end surface of the delay material 15 in the angle probe 15 is constant, and therefore the ultrasonic waves incident into the Tenon 7 are always perpendicular to the shroud 11 surface. Therefore, it is not possible to detect all cracks with various inclinations with one angle probe 15, and in order to do so, it is necessary to use multiple types of angle probes with different ultrasonic incident angles. There must be. As a result, the flaw detection work becomes complicated and the flaw detection accuracy may decrease.

[Purpose of the invention]

The present invention has been made in view of the above facts, and it is an object of the present invention to provide an ultrasonic probe that can accurately and easily detect cracks occurring within a subject.

[Summary of the invention]

In order to achieve the above object, the ultrasonic probe according to the present invention has a probe case containing a transducer for generating ultrasonic waves, which is rotated around a delay material, so that flaws can be detected even in shallow parts of the object. In the ultrasonic probe, the delay material is divided, and the movable divided delay material that fixes the probe case is slidable relative to the fixed divided delay material that can be installed on the flaw detection surface of the object. In this configuration, the angle of incidence of the ultrasonic waves that enter the subject from the transducer through the delay members on both sides is continuously changed.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIGS. 3 and 4 are explanatory diagrams showing one embodiment of the ultrasonic probe according to the present invention.

The delay material 21 to which the ultrasonic probe is attached is divided into upper and lower halves in the height direction, and consists of an upper delay material 5 as a movable divided delay material and a lower delay material 5 as a fixed divided delay material. This dividing surface is formed into a semi-cylindrical curved surface M, and this semi-cylindrical curved surface n is curved and protrudes toward the lower delay member 5 side. Therefore, while the upper delay material part is sliding against the lower delay material 5,
It is provided so as to be swingable about the axis 0 of the semi-cylindrical curved surface 27 in the curving direction of the semi-cylindrical curved surface n.

Further, a metal case 29 as a probe case is implanted on the upper surface of the upper delay material. This metal case 4 contains a vibrator that converts electrical vibrations into ultrasonic waves.

A high frequency cable 31 is connected to this vibrator, and electric vibrations are sent to the vibrator. The longitudinal ultrasonic wave generated from the vibrator passes through the upper delay material section and the lower delay material 25 and becomes a far-field sound field wave, as shown by the two-dot chain line in FIG. 4. Far-field sound field waves refer to ultrasonic waves that can detect flaws even in shallow parts of the object because the distance from the transducer to the object is long.

Further, a cylindrical casing 33 is fitted and fixed to the upper outer periphery of the lower delay member 5. The upper delay member n is housed inside the casing 33 with a certain gap therebetween, and the swing of the upper delay member n is not hindered by this gap.

Further, movable adjustment screws 35A and 3.5B are screwed onto the opposite side walls of the casing. These pair of movable adjustment screws 35A and 35B are provided so that their tip surfaces can abut on both side surfaces 37A and 37B of the upper delay material section located in the swinging direction, respectively. Due to this contact of the movable adjustment screws 35A and 35B, the upper delay member B is held at a position inclined at an arbitrary angle with respect to the lower delay member 6. By continuously changing the inclination angle of the upper delay material section, the incident angle of the ultrasonic wave can be continuously changed within a range of, for example, 35 degrees.

On the other hand, the lower end surface of the lower delay member 5 is formed to be inclined at a certain angle. This angle of inclination is, for example, as shown in FIG.
Ultrasonic probe 20; steam turbine blade 3 as a test object
When the ultrasonic probe + 9's upper delay member 23 is not inclined with respect to the lower delay member (angle of inclination θ°), the ultrasonic waves incident from the flaw detection surface 43 into the tenon 41 , is set to be incident perpendicularly to the shroud 45 surface as shown by the arrow in the figure. For example, the tilt angle is set to about 5°.

Next, a method of detecting flaws in the tenon portion of a turbine blade of a steam turbine using this ultrasonic probe +9 will be explained.

First, we will discuss the structure of the tenon part of the turbine blade and the cracks that occur in the tenon part. In a steam turbine, as shown in FIG. 5, a plurality of rows of turbine rotor blades 49 are formed on a turbine rotor 47. The turbine rotor blades 49 are formed by a large number of turbine blades [39] arranged in an annular shape, and the tips of these turbine blades 39 are connected to the shroud 45 in several pieces, as shown in FIG. .

That is, a tenon 41 is provided protruding from the tip of the turbine blade 39, and this tenon 41 is fitted into the through hole 51 of the shroud 45 as shown in FIG. The tip of this fitted tenon is caulked and fixed to the shroud 45 as shown in FIG. As a result of connecting several turbine blades 39 to the shroud 49 in this way, the strength of the turbine blade 490 against steam force, centrifugal force, etc. is ensured.

By the way, while the turbine is rotating, the caulked Tenon 4
1, shear and bending stresses occur. Among them, the bending stress causes stress concentration in the 0 part and the D part in FIG. 9, and this stress concentration causes cracks to occur in the 0 part and the D part. This crack A.

As shown in FIG. 10, B extends from each of the 0 section and the D section approximately parallel to the shroud 45 surface toward the central axis of the tenon 41. These cracks A.

Bft, flaws are detected using an ultrasonic probe.

With the inclination angle of the upper delay material phantom relative to the lower delay material 5 set to 00, the ultrasonic probe +9 is placed on the flaw detection surface 43 of the Tenon 41.
to be installed. At this time, the ultrasonic waves entering the tenon 41 from the flaw detection surface 43 are perpendicular to the shroud 45 surface as shown by the arrow in FIG.

Now, in this case, since the ultrasonic waves generated from the vibrator in the metal case 9 pass through the upper and lower delay members O, 25 and become far-field sound field waves, a crack A occurs at the close position C.
k can also be detected.

In addition, when the cracks A and B that occur in the 0 and D parts are within ±3 degrees with respect to the shroud 45 surface, the ultrasonic waves will be able to penetrate the cracks A and BK without adjusting the inclination angle of the upper delay material part. incident almost perpendicularly. As a result, the ultrasonic waves reflected from the cracks A and B travel backward in the direction of the ultrasonic probe +9. In addition, if the cracks A and B are inclined by ±3° or more with respect to the shroud surface 45, continuously adjust the inclination angle of the upper delay material section with the movable adjustment screws 35A and B, and 4
The angle of incidence of the ultrasonic waves incident into the cracks A and B is varied, for example, up to 35 degrees, and the ultrasonic waves are made perpendicular to each of the variously inclined cracks A and B. As a result, in this case as well, the ultrasonic waves reflected from the ridge-sloping cracks A and B can be made to travel backwards in the direction of the ultrasonic probe +9.

In this way, since the ultrasonic waves reflected from the cracks A and B travel backwards in the direction of the ultrasonic probe +9, the projected cross-sectional area of the Tenon 41 in the direction of the central axis in the cracks A and B is small, and the Even when the energy of the ultrasound reflected from B is small,
Ultrasonic probe +9 catches almost all of this reflected energy.

According to experiments, when a crack A with a circular cross section of 1 m+ in diameter is detected using an ultrasonic frequency of 20 MHz and an incident sound pressure of 80 dB, as shown by arrow E in Fig. The reflected ultrasonic wave is approximately 10% of the incident sound pressure.
The wave height appears on the CRT screen. Note that an arrow F in the figure indicates a reflected wave between the tenon 41 and the delay material 21. In this way, as shown in Figure 12, if the crack A that occurs at part 0 has a diameter of approximately 0.8 rIrM or more, the ultrasonic probe will catch the energy of the reflected wave from this crack A. can. In addition, the crack B that occurs in the D part
Then, as shown in Figure 13, the diameter is about 0.411111
If it is one or more, the energy of the ultrasonic wave reflected from this crack B can be similarly caught. In addition,
12 and 13 above, the incident ultrasonic frequency is 20 MH2.

Therefore, even if the projected cross-sectional area of cracks A and H is small, and even if cracks A and B are inclined at various angles, the incident angle of the ultrasonic waves can be continuously adjusted using the movable adjustment screws 35A and 35Bi. By changing this, it is possible to make the ultrasonic waves perpendicularly enter the cracks A and H.

B can be reliably detected. This improves the accuracy of detecting cracks that occur in the Tenon, and increases the reliability of the turbine blade. At the same time, flaw detection work can be simplified.

In the above embodiment, the semi-cylindrical curved surface 27 serving as the dividing surface protrudes toward the lower delay material portion, but it may protrude toward the upper delay material portion and curve.

Further, in the above embodiment, the dividing surface of the delay material 210 is a semi-cylindrical curved surface, but the dividing surface may have a spherical shape. In this case, since the upper delay member n is provided so as to be tiltable in all directions with respect to the lower delay member 5, the accuracy of detecting cracks occurring in the tenon 41 can be further improved.

Further, in the above embodiment, the delay material 21 is divided into two parts, but the delay material 21'f is divided into three parts by dividing the dividing surface into a semi-cylindrical curved surface or a spherical surface in the height direction. Good too.

〔Effect of the invention〕

As described above, according to the ultrasonic probe according to the present invention,
The delay material to which the probe case containing the transducer is fixed is divided, and the movable split delay material that fixes the probe case slides against the fixed split delay material that can be installed on the test surface of the test object. Because of its flexible structure, it is possible to continuously change the angle of incidence of the ultrasonic waves that enter the inside of the test object from the flaw detector and make the ultrasonic waves perpendicular to the cracks inside the test object. This has the effect that cracks that occur inside can be detected accurately and easily.

[Brief explanation of drawings]

Fig. 1 is a side view showing a situation where a vertical probe is used to perform full Tenon flaw detection, Fig. 2 is a side view showing a situation where a full Tenon flaw is detected using an angled probe, and Fig. 3 is a side view showing a situation where a full Tenon flaw is detected using a vertical probe. FIG. 4 is a longitudinal sectional view of this embodiment; FIG. 5 is a perspective view of a turbine rotor blade of a steam turbine; and FIG. 6 is a plan view of a shroud. , FIG. 7 is a perspective view showing the shroud and turbine blade before the tenon is crimped, FIG. 8 is a perspective view showing the turbine blade and shroud after the tenon is crimped, and FIG. 9 is IX-IX in FIG. 8.
10 is a side view showing the situation in which Tenon is detected using this embodiment, and FIG. 11 is a cross-sectional view taken along the line.
A schematic diagram of a cathode ray tube screen obtained when a crack A having a circular projected cross-sectional area of
The figure is a diagram showing the relationship between the diameter of crack A and the wave height of the ultrasonic wave reflected from this crack A when this embodiment is used.
FIG. 3 is a diagram showing the relationship between the diameter of the crack B and the wave height of the ultrasonic wave reflected from the crack B when this embodiment is used. Add: Ultrasonic probe, 21: Delay material, Phantom: Upper delay material, 5: Lower delay material, 27: Semi-cylindrical curved surface, 4: Metallic case, 35A , 35B... Movable adjustment screw, 39... Turbine blade, 41... Tenon,
43...Flaw detection surface, A, B...Crack, 0...Axis of semi-cylindrical curved surface. B Fig. 111 Fig. 12 Fig. 13 υ, Lo -, υ 1.5

Claims (1)

[Scope of Claims] 1. An ultrasonic probe in which a probe case containing a transducer for generating ultrasonic waves is fixed to a delay material so that flaws can be detected even in shallow parts of the object, The ultrasonic detector is characterized in that the material is divided and the movable divided delay material that fixes the probe case is configured to be slidable relative to the fixed divided delay material that can be installed on the flaw detection surface of the test object. Tentacles. 2. The ultrasonic probe according to claim 1, wherein the movable segmented delay material is provided so as to be swingable around a straight line parallel to the flaw detection surface of the object. 3. The ultrasonic probe according to claim 1 or 2, wherein the delay material is vertically divided into two parts in the height direction.