JPS63295959A - Ultrasonic probe - Google Patents

Abstract

PURPOSE:To keep an angle of refraction almost the same in a material to be inspected regardless of change in temperature, by arranging the surface of a wedge abutting a contact medium to be inclined longitudinally in the direction of propagating ultrasonic waves to include a polystyrene film on the wedge surface. CONSTITUTION:An ultrasonic probe 1 is provided with a wedge 5 made of organic glass o the like and a polystyrene film 6 is included on the surface A to reduce multiple reflected waves. The surface A of the wedge 5 abutting a contact medium 3 is inclined at an angle theta5 f 1-10 deg.C. An ultrasonic wave from a transmitting/receiving vibrator 2 is made incident into material 4 to be inspected through the contact medium 3 from the center point P of the surface of the wedge 5. Here, in the design temperature (for example, 20 deg.C), an angle of incidence into the material 4 being inspected is theta1 while an angle of refraction thereinto 4 is theta2. But when a temperature is higher or lower than the design temperature, angles theta1a and theta1b of incidence and angles theta2a and alpha2b of refraction vary larger or smaller. So, the variations in the angles are brought very close to the angle theta2 of refraction as designed. This minimizes changes in the angle of refraction of the material being inspected owing to temperature changes, thereby improving the S/N ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an ultrasonic probe for detecting defects occurring on the inner and outer surfaces of steel pipes and the surface layer of round bars.

[Conventional technology]

FIG. 3 is a diagram showing a conventional ultrasonic probe and flaw detection method, for example, shown in Ultrasonic Flaw Detection Method (published by Nikkan Kogyo Shimbun, 1972).

FIG. 3(a) is a diagram showing a conventional method of detecting flaws by moving an ultrasonic probe parallel to the central axis of the test subject side to obtain a predetermined refraction angle. FIG. 3 (kl) is a diagram showing a method of flaw detection by tilting a conventional ultrasonic probe with respect to the central axis of the test subject side to obtain a predetermined refraction angle.

In Figures 3(a) and (t)), ``11'' is an ultrasonic probe, (2) is a transmitting/receiving transducer, (31Fi is a contact medium such as water or oil, 14) is a steel pipe, round bar, etc. Phase detection, ■ is the incident point where the ultrasonic wave enters the phase to be tested 14), θ1 is the incident angle, θ2
is the refraction angle at the design temperature (for example, 20°C), θ3 is the refraction angle when the temperature is higher than the design temperature, θa Fi is the refraction angle when the temperature is lower than the design temperature, ll is the central axis Y of the tested phase 14) -Y' to the center beam of the ultrasound probe fil.

By the way, in the ultrasonic flaw detection of steel pipes, it goes without saying that the selection of the refraction angle θ2 in the phase to be tested14) is very important. It's not true.

There may be cases where defect detection becomes impossible. Especially when performing flaw detection at high speed using automatic ultrasonic flaw detection equipment.

It is extremely difficult to always maintain a constant positional relationship between the specimen 14) and the ultrasonic probe fil, and this positional deviation also causes a change in the refraction angle θ2. Therefore, in order to reduce the change in the refraction angle θ2, it is important for K to reduce the amount of change in the refraction angles 03 to θ4 due to temperature changes.

[Problem that the invention seeks to solve]

In the conventional water immersion ultrasonic probe Ill as shown in Fig. 3(a) and (b), a thin matching layer (epoxy resin, etc.) is placed on the surface of the transducer (2). Because it is only coated parallel to 1. The ultrasonic waves emitted from the vibrator (2) propagate through the contact medium (3), and the conditions until they reach the incident point on the surface of the specimen 14) remain unchanged at any temperature.

However, the relationship between the temperature of the contact medium (3), water, and the solid material to be tested (4), such as iron, and the sound speed has changed (the opposite characteristics exist. In other words, the temperature of the contact medium (3) increases Then, the speed of sound becomes faster (and conversely, as the temperature of the iron f'i of the material to be tested (4) increases, the speed of sound becomes slower, so according to Snell's law, when the temperature is low, the angle of refraction θ4 increases, When the temperature is high, the refraction angle θ3 becomes smaller.For example, in the case of an ultrasonic probe f1) that was designed with a refraction angle θ2 of 38° at a temperature of 20°C, when the temperature changes from 10°C to 35°C, Respective refraction angle θ4.

θ5 is 39.4° to 36.7°, which is different from the actual design value and causes variations in the refraction angle during ultrasonic flaw detection.

The cause of this angle variation is mostly due to the temperature characteristics of the liquid contact medium (3).

This invention greatly improves these conventional drawbacks.

An object of the present invention is to provide an ultrasonic probe that can obtain substantially the same refraction angle even if the ambient temperature changes.

[Means for solving problems]

The ultrasonic probe according to the present invention has an angle of 1° to 10° on the surface of the wedge that comes into contact with the contact medium in the front-rear direction of the ultrasound propagation direction.
A thin film made of polystyrene resin is provided on the wedge surface.

[Effect]

In this invention, since a gap is provided between the vibrator and the contact medium, as the sound velocity value of the contact medium increases, the angle of incidence in the contact medium also increases.

Conversely, if the sound velocity value of the contact medium decreases, the angle of incidence in the contact medium also decreases, thereby making it possible to reduce changes in the refraction angle during the test.

In addition, a thin film of polystyrene resin, which has a lower acoustic impedance than organic glass, is attached to the surface of the wedge that comes into contact with the contact medium, which reduces surface echoes generated between the wedge and the surface of the test material. It is possible to reduce the level of multiple reflected waves.

[Example] Fig. 1 is a cross-sectional view of the ultrasonic probe according to the present invention and a diagram showing the path of the ultrasonic beam.
ll-1t ultrasonic probe, (2) is a transceiver transducer, (
3) is a contact medium such as water or oil, (4) is a specimen 1 such as a twisted pipe or round bar, and 151 is an organic material having a predetermined angle θ5 on the surface A facing the specimen 14) according to the present invention. Glass wedge, 16
1 is a thin film emitted from polystyrene resin, P is the incident point of the central beam of ultrasonic waves on the A plane of cutout (5), θ
6 The angle of incidence with respect to the normal line X-ga made with the A plane of V′i,
θ1 is the test material 14 at the design temperature (e.g. 20°C)
), θ1a is the angle of incidence at a temperature higher than the design temperature, θ1bH is the angle of incidence at a temperature lower than the design temperature, engineering υ
is the incident point at the design temperature.

F1 is the point of incidence at a temperature higher than the design temperature, T2 is the point of incidence at a temperature lower than the design temperature, θ2 is the refraction angle in the test material (4) at the design temperature, and θ2a is the point of incidence at a temperature lower than the design temperature. The refraction angle when the temperature is high, θ2b is the refraction angle when the temperature is lower than the design temperature.In the ultrasonic probe fi+ according to this invention, the transducer (
Since a wedge (5) is provided between 2) and the contact medium (3), the normal X-X'I with respect to the incident point P of F+51
F against C! 15) Under the condition that the direction of incidence of the ultrasonic wave in the wedge is from the rear in the direction of propagation of the ultrasonic wave,
) to the coupling medium (3) and the angle of incidence θ1 in the coupling medium (3) to the specimen (4) are expressed by equations (1) and (2), respectively.

β= sin' (: X sinθ6)
....-(1) θ1=β+05 vl: Speed of sound v2: Speed of sound of the contact medium θ5: Angle θ6 of the A surface of the wedge: Incident angle of Koshin, and the angle of refraction θ2 in the test subject 41141 is the (3rd ).

v3: The sound velocity of the test phase, that is, as is clear from Equation (3), the angle of incidence θ1 on the test phase (4) is the sound velocity of the test phase. Taking advantage of this fact, when the value of the sound velocity v2 of the contact medium increases, the value of the incident angle θ1 in the contact medium (3) increases, and conversely, when the value of the sound speed v2 of the contact medium decreases, the value of the incidence angle θ1 in the contact medium (3) increases.
By making the value of the incident angle θ1 in phase 3) small, it is possible to extremely reduce variations in the refraction angle θ2 in the phase to be tested 14) due to temperature changes. Wedge (5
) is an organic glass, the optimum value of the angle θ5 of the A-plane of the cutout (5) is around 2° to 4°. Further, the specific propagation path of the ultrasonic wave is as follows.

When the humidity is lower than room temperature, the ultrasonic wave is incident at the point of incidence P at the pipe (5).
The value of the angle of incidence θ1b on the tested phase 14) becomes small because the path is from there to the incident spot 2 on the tested phase 14).

Also, when the temperature is higher than room temperature, the ultrasonic sound tfLiltfR(
5), the value of the angle of incidence 01a on the tested phase 14) is large (becomes large) because the path is from the incident point P of 5) to the entrance point 1 on the tested phase 14).

FIG. 2 shows actual measured values of the relationship between the temperature of the ultrasonic probe according to the present invention and the refraction angle in the test phase, as well as some calculation examples.

In Fig. 2, A is the ultrasonic probe fl) according to the present invention.
Actual value when the angle θ5 of the A side of the wedge (5) is 4°C.

The opening is the calculated value when the angle θ5 of the A side of the pipe 5 is 6°.

C is the calculated value when the angle θ5 of plane A of cutout (5) is 10°.

The second is the calculated value when the angle θ5 of the A side of the cutout (5) is 13°.

E is the actual measurement value of the conventional ultrasonic probe, θ2! ri test phase 1
4) The angle of refraction in T (di degrees).

As is clear from Fig. 2, the ultrasonic probe according to the present invention is capable of changing the ambient temperature from 10°C to 35°C even when the temperature T is 20°C and the refraction angle θ2 is 38°. The refraction angle θ2a to θ2b in the test phase is the designed value refraction angle θ2 if the angle of the A side of the wedge (5) is in the range of 1° to 10°.
It is possible to achieve an accuracy of within +0.5° relative to the distance, greatly improving the reliability of the reed and flaw detection performance.

Also, the above f12! +5) The angle of the A side is 1° to 10°
Therefore, if the cutout (5) is an organic glass, there will be a large difference in acoustic impedance from the 1w catalyst (3), and the difference between the A side of the cutout (5) and the surface of the Shinken phase 14) will be large. Multiple reflected waves of surface echoes occur between the two, leading to an increase in noise. Therefore, for the reduction of the above noise.

On the entrance surface of the cutter (5), organic glass and a contact medium (
By providing polystyrene I (thin film) with acoustic impedance close to 3), noise echoes due to multiple reflected waves of one surface echo can be reduced, and the S/N ratio can be improved by 4 to 5 dB.

〔Effect of the invention〕

As explained above, in this invention, 10 to 1
By providing an inclination of 0° and further providing a thin film made of polystyrene resin on the above-mentioned replacement surface,
This has the effect of providing an ultrasonic flaw detection device with a good S/N ratio that reduces the change in the refraction angle during the test phase due to temperature changes and at the same time reduces the level of multiple reflected waves of two surface echoes.

[Brief explanation of the drawing]

Figures 3+a) and (t)) are diagrams showing conventional ultrasonic probes and flaw detection methods, Figure 1 is a sectional view of the ultrasonic probe according to the present invention, and Figure 2 is a diagram showing each ultrasonic probe. In the figure, (1) is an ultrasonic probe, (2) is a transducer, (
3) is a contact medium, (4) is a test phase, (5) is a wedge, 161
The film is made of tristyrene resin, and θ5 is the angle set on the A side of the cutter. Note that the same or corresponding parts in the three figures are designated by the same reference numerals.

Claims (1)

[Claims] In a water immersion type ultrasonic angle probe having a wedge made of organic glass, the surface of the wedge that comes into contact with the contact medium is sloped by 1° to 10° in the front-rear direction of the ultrasound propagation direction, and An ultrasonic probe characterized in that a thin film made of polystyrene resin is provided on the wedge surface.