JPH02184756A - Probe for water-dip surface wave - Google Patents

Abstract

PURPOSE:To detect a defect present in the surface layer part of a body to be inspected without reference to the holding direction of the probe and to shorten the inspection time by providing a vibrator and an acoustic lens in a case. CONSTITUTION:When a pulse signal is applied to the vibrator 5 in the case 4, the vibrator 5 oscillates an ultrasonic wave by piezoelectric vibration and the oscillated ultrasonic wave is emitted underwater through the acoustic lens 6 and converged on a focus F through the lens operation of a curved surface 6a. At this time, a water-dip surface wave 3 is excited around the focus F on the surface 1a of the body to be inspected and propagated having isotropy from the focus F to the surface 1a at an angle of incidence from the curved surface 6a. Consequently, the probe P is scanned on the surface 1a at constant pitch and then if there is the defect in the surface layer part of the body 4 to be inspected, a vertical surface wave is made incident once in the direction of the defect, so the defective echo of a reflected wave which is reflected vertically from the defect can be detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a probe that generates water immersion surface waves in water on the surface of ceramics, metals, etc. The present invention relates to a water immersion surface wave probe suitable for exciting a water immersion surface wave having a water immersion surface wave.

[Conventional technology]

Water immersion surface waves are waves suitable for detecting defects existing in the surface layer, including the surface of a specimen immersed in water.
Conventionally, the probes that generate water immersion surface waves have been normal water immersion vertical probes or oblique probes that emit parallel plane waves underwater. The ultrasonic beam is incident on the probe with the probe tilted at a certain angle with respect to the surface so that immersion surface waves are generated. An example is shown in FIG. In the figure, 1 is a test object immersed in water, La is the surface of test object 1, and 2 is the normal water immersion probe, which is also immersed in water and is tilted by an angle θ from the perpendicular line χ to the surface 1a. and is held in such a way that it emits ultrasonic waves. 3 is the object surface 1a from the water immersion probe 2
This is a water immersion surface wave excited in the surface layer including the surface 1a by the ultrasonic beam incident on the surface 1a. In this case, the angle θ is the sound velocity of water VW, and the water immersion surface wave 3 excited in the object 1.
Letting the speed of sound be V, it is determined by the following formula.

＼Flaw detection of the object 1 is carried out at the angle θ with respect to the surface 1a so that the water immersion surface waves 3 are incident as perpendicularly as possible to minute defects (for example, hair cracks, etc.) that exist randomly on the surface layer. This is done by scanning the held water immersion probe 2 from various directions.

[Problem to be solved by the invention]

In the conventional water immersion probe, the water immersion surface waves excited in the surface layer of the subject 1 propagate in only one direction, which is the same as the direction of the ultrasonic beam emitted from the angle θ. During flaw detection, only scanning in this direction will only mainly detect defects that exist in the propagation direction of the water immersion surface wave and have a defect surface in a direction perpendicular to the propagation direction. Therefore, in order to detect defects that are randomly present on a test object, it is necessary to detect them with the highest sensitivity possible by entering the surface of each defect from the perpendicular direction. Need to scan. As the defects become smaller, the detection sensitivity also decreases, so in order to prevent this, it is necessary to scan in different scanning directions so that the light is incident not only in the X and Y directions but also in the direction perpendicular to each defect as much as possible. had to increase. Therefore, not only does the inspection take a long time, but it is also difficult to detect all minute defects.

In view of the above-mentioned problems, the present invention makes it possible to detect defects that are randomly present on the surface of a test object, regardless of the direction in which the probe is held, and extremely shortens the inspection time compared to the conventional method. The purpose of the present invention is to provide a water immersion surface wave probe that can be used for water immersion.

[Means to solve the problem]

In order to achieve the above object, the water immersion surface wave probe according to the present invention includes a transducer that oscillates piezoelectrically to oscillate ultrasonic waves by applying a pulse signal in a cylindrical case; A curved surface of curvature that focuses the ultrasonic waves emitted from the transducer that is integrally attached to a certain distance in the water, and excites water immersion surface waves that propagate isotropically on the surface. It has an acoustic lens formed inside.

Of the ultrasonic beams emitted from the transducer into the water through the acoustic lens, the probe does not allow the ultrasonic beams within the range that are incident almost perpendicularly to the surface of the object to be incident on the surface of the object. It is effective to provide a mask that protects the

Furthermore, it is preferable that the mask be attached to the center of the curved surface of the acoustic lens.

[Effect]

When a pulse signal is applied to the water immersion surface wave probe with the above configuration, the transducer piezoelectrically vibrates and oscillates an ultrasonic wave.
The ultrasonic waves are radiated into the water via an acoustic lens that is integrally attached to the transducer. In this case, the curved surface of the acoustic lens that emits ultrasound into the water focuses the ultrasound beam to a certain distance in the water, and when the ultrasound beam reaches the surface of the object, it Since the surface wave is formed with a curvature that excites water immersion surface waves, by holding the ultrasonic wave so that it is perpendicular to the surface, the water immersion surface waves excited on the surface of the object are The beam is propagated isotropically from the focal point to the surface of the object with the center at .

The propagated water immersion surface waves will be reflected from the defect if there is a defect in the surface layer of the object, and the reflected wave will be received by the probe as a defect echo, and if there is no defect, it will be reflected. No waves are generated and no echoes are received. By holding the probe in the above state and scanning the surface of the object at a constant pitch in χ and one direction, even if defects exist in random directions, they will be detected somewhere during scanning. Since the probe sometimes directly faces the surface of the defect, it is possible to detect defects without leaking.

In addition, water immersion surface waves can be excited on the surface of the object by providing the probe with a mask that prevents ultrasonic beams from entering the surface of the object almost perpendicularly to the surface of the object. It blocks the incidence of the ultrasonic beam within the incident angle range that is directly reflected from the surface and received by the probe.
The ratio can be improved. By setting the mask to a size corresponding to the curved lens surface and attaching it to the center of the curved lens surface, the incident ultrasonic beam within the range that is directly reflected from the surface of the object and received by the probe is reduced. Blocking is performed more effectively.

〔Example〕

An embodiment will be described with reference to FIG. In the figure, the same reference numerals as in FIG. 2 indicate the same things. In the figure, 4 is a cylindrical case made of a cylinder or a rectangular tube, and 5 is a vibrator installed inside the case 4. In the case of this embodiment, a disk-shaped electrostrictive vibrator is used. . A plano-concave acoustic lens 6 is integrally attached to the transducer 5, and focuses the ultrasonic beam emitted from the transducer 5 to a focal point F that is a certain distance away underwater. The curved surface 6a acting as a lens is formed to have a curvature that excites an isotropic water immersion surface wave 3 around the focal point F on the surface 1a when the focal point F is focused on the surface 1a of the subject. 7 is a damper attached to the back of the vibrator 5 and also serves as a holder for the vibrator 5; 8 is a cable that electrically connects the vibrator 5 to a flaw detector (not shown); 9 is a curved surface 6a of the acoustic lens 6; The mask attached to the center of the (
Among the ultrasonic beams radiated into the water from the transducer 5 via the acoustic lens 6, the ultrasonic beams in the range that are incident almost perpendicularly to the surface 1a of the subject are blocked from being incident on the surface 1a. It is something to do. P is case 4 above. Vibrator 5. Acoustic lens 6° damper 7, cable 8
A water immersion surface wave probe consisting of a mask 9 and a mask 9 is held perpendicularly opposite the surface 1a of the object to be inspected during flaw detection, and is immersed together with the object 1 in water.

When a pulse signal is applied to the vibrator 5, the vibrator 5 vibrates piezoelectrically and oscillates an ultrasonic wave, and the emitted ultrasonic wave is radiated into the water via the acoustic lens 6 and brought to a focal point F by the lens action of the curved surface 6a. Focus. At that time, a water immersion surface wave 3 is excited on the surface 1a around the focal point F, and the excited water immersion surface wave 3 is isotropically directed from the focal point F to the surface 1a due to the incident angle from the curved surface 6a having the above-mentioned curvature. It is propagated with a characteristic.

For this reason, the probe P is moved over the surface la at a constant pitch, χ,
By scanning once in the y direction, if there is a defect in the surface layer of the object 1, a surface wave perpendicular to the direction of the defect will be incident once, so a defect echo of the reflected wave vertically reflected from the defect will be generated. can be detected. The characteristic of the water immersion surface wave 3 being propagated isotropically is that the water immersion surface wave 3 is always incident from the perpendicular direction to randomly existing defects,
Since the defect echo of the reflected wave is reliably detected, even if the existing defect is minute, it can be detected without omission with the highest sensitivity that can be received from the defect. Since scanning on the specimen surface 1a can be completed by scanning from χ and one direction at a constant pitch, the inspection time is reduced by 172 or more times compared to conventional flaw detection which scans from multiple incident angle directions in χ and y directions. It becomes possible to shorten the time by a factor of 1.

By the way, during flaw detection, the ultrasonic beam emitted from the probe P is focused on a focal point F on the surface 1a of the object to be inspected, but there is a range in which it is emitted at an angle close to perpendicular to the surface 1a of the object to be inspected. Since the ultrasonic beam in this range is reflected by the surface 1a and is received by the probe P with almost no attenuation, it does not interfere with the detection of echoes of the weak water immersion surface waves 3 from minute defects. There is. The mask 9 is provided to suppress the occurrence of this interference, but as described above, the probe P
Among the ultrasonic beams emitted from the surface, the ultrasonic beams emitted at angles close to perpendicular to the surface 1a are blocked so as not to be emitted, and the surface 1a is immersed in water with the focal point F as the center. The dimensions are such that a range of ultrasound beams is emitted that is incident at an angle that excites the waves 3.

By providing the mask 9, the S/N ratio of detected defect echoes can be greatly improved, and minute defects can be reliably detected. In addition, mask 9
The position may be placed anywhere as long as it can block the ultrasonic beam in the range that is incident at an angle close to perpendicular to the surface 1a, but as shown in the figure, it may be placed at the center of the curved surface 6a of the acoustic lens 6. By attaching the mask 9 to the mask 9, the above-mentioned blocking can be ensured with a simple structure, and the dimensions of the mask 9 can also be easily adjusted.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

When the acoustic lens focuses the ultrasound beam on the surface of the object using the curved surface of the acoustic lens, water immersion surface waves propagate isotropically around the focal point on the surface of the object. Since it is formed to be excited, it can detect defects that exist randomly on the surface of the test object, even if they are minute defects.
Since flaws can be detected with only one scan in the ν and ν directions, the inspection time can be significantly shortened compared to the conventional method.

By providing a mask on the probe and blocking the ultrasonic beam in the range that is incident almost perpendicularly to the surface of the specimen, the S/N ratio of the defect echoes to be detected can be improved, allowing the detection of minute defects. can be done reliably and easily.

In addition, by attaching the mask to the curved surface of the acoustic lens, it is possible to reliably perform cutting with a simple configuration, and the mask dimensions can be easily adjusted.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an overall sectional view of a water immersion surface wave probe according to the present invention and an example of its usage state. FIG. 2 is an explanatory diagram of the conventional method for generating water immersion surface waves.

Claims (3)

[Claims] 1. Inside the cylindrical case, there is a vibrator that oscillates piezoelectrically to oscillate ultrasonic waves when a pulse signal is applied, and a vibrator that is integrally attached to the vibrator and focuses the ultrasonic waves emitted from the vibrator at a certain distance underwater. The surface is formed into a curved surface with a curvature that excites water immersion surface waves that are focused to connect and when the focal point coincides with the surface of the subject, propagating isotropically on the surface with the focal point as the center. A water immersion surface wave probe equipped with an acoustic lens. 2. Among the ultrasonic beams emitted from the transducer into the water through the acoustic lens, the probe disables the ultrasonic beams within a range that are incident almost perpendicularly to the surface of the object to be incident on the surface of the object. 2. The water immersion surface wave probe according to claim 1, further comprising a mask. 3. 3. The water immersion surface wave probe according to claim 2, wherein the mask is attached to the center of the curved surface of the acoustic lens.