WO1996033407A1

WO1996033407A1 - Ultrasonic coupling agent

Info

Publication number: WO1996033407A1
Application number: PCT/DE1996/000663
Authority: WO
Inventors: Manfred Gregor
Original assignee: Krautkrämer Gmbh & Co.
Priority date: 1995-04-21
Filing date: 1996-04-16
Publication date: 1996-10-24
Also published as: EP0821789A1; DE19514281A1

Abstract

An ultrasonic coupling agent is disclosed for filling out the gap between an object to be examined and an ultrasonic testing head that can be moved in relation to the surface of the object. The coupling agent has a gelatinous, pasty to liquid consistency. It contains small spheres made of a solid material.

Description

Name: Ultrasonic coupling agent

The invention relates to an ultrasonic coupling means for filling a gap between a to be examined object and an ultrasonic test head, which is movable relative to the surface of the object, wherein the coupling means comprises a gel to liquid Kon ^¬ consistency. Ultrasonic coupling agent should ensure that there are between the probe and the intended object to be examined not un ^¬ inclusions, in particular air bubbles. Air bubbles would significantly change the propagation of sound, air bubbles could simulate errors in the object that actually do not exist.

The applicant offers a coupling agent of the type mentioned at the outset, which is composed of water, glycol and active ingredients. Coupling agents of the type mentioned at the outset are also known from a brochure from Echo Ultrasound (USA). This offers, for example, the product Ultragel II under the registered trademark. After the sheet is a coupling means high impedance and high viscosity, it is set for critical ultrasound investigation procedure ^¬, such as aircraft and components of nuclear Anla¬ gen. The coupling agent can be easily removed with water, it dries very slowly out.

A variety of other Kop ^¬ be from the said US company still offered pelmitteln, mostly in several viscosity grades, the Vis ^¬ viscosities ranging from liquid to gel. Under gel ^¬ since understood in the consistency as they have gelatine products, beispielswei ^¬ se jelly. Pasty means non-flowable, but deformable. The consistency of the coupling agent is chosen so that a gap between the ultrasound probe and the surface of the object to be examined is completely and uninterruptedly filled in the respective application. The coupling agents should be easy to apply to a surface of the object to be examined, and they should be just as easy to remove. They should have the necessary consistency in pre ^¬ gebenem temperature range. A disadvantage of the coupling means of the type mentioned at the outset is that the test head can be moved relative to the surface of the object to be ^examined . Low Especially with coupling means viscosity, game as pasty at ^¬ coupling means is, impedes movement of the probe over the surface often characterized in that the test head from sucking on the surface or does not move with the same force kontinuier ^¬ Lich over a surface. However, such pasty coupling agents are often used because they do not distribute themselves over the surface of the object to be examined and are also suitable for use on inclined surfaces, etc.

With coupling agents according to the prior art, increased wear can occur on the test heads. It was found that in many cases the sound impulses to be measured fluctuate relatively strongly. Overall, a reliable test result is often achieved only with great care.

This is where the invention begins. It has set itself the task of developing the ultrasonic coupling means of the type mentioned at the outset such that its advantages are essentially retained, but the sliding properties of a test head over the coupling means and compared to the surface of an object are significantly improved.

This object is achieved in that the coupling agent contains small balls made from a solid.

By the addition of balls, the sliding properties of a test head with respect to a ^¬ be considerably improved to be tested object. It suffice relatively few balls between the test head and the currently investigated surface fibers to the sliding properties markedly verbes ^¬. The balls preferably have a diameter which is smaller than the layer thickness of an applied coupling agent. The USAGE ^¬ Deten balls are therefore relatively small. These preferably represent only a minor share of the total weight of the coupling means, their weight proportion is preferably below 20, in particular un ^¬ ter 10%.

The diameter of the balls is subject to several test conditions adapted, in particular the frequency of the probe used, the roughness of the surface of the object under examination, etc. In testing ^¬ head-frequencies in the range 1-4 megahertz have balls in a diameter distribution of 90 to 130 micrometers as low he reported ^¬. For higher frequencies are better balls with diam ^¬ fibers of 50 to 90 microns. For frequencies below 1 Mega ^¬ hertz and with increasing surface roughness to ball diameter upper ^¬, suitable semi-100 microns, for example, of 200 microns in diameter.

A higher addition of glass beads to the coupling means or balls made of materials with greater acoustic impedance, for example, tungsten, copper, nickel, steel, the sonic impedance of the Kop can ^¬ pelmittels increase and the reflection loss at the sound entry in materials with high acoustic impedance, such as steel, significantly ver ^¬ wrestlers. In this way, the permeability of audit ^¬ can be increased fine direction.

As a gel-like or liquid component of the coupling agent are those which are already known, game, as a coupling agent materials used in ^¬ glycol, glycerin, oils, fats, z. B. silicone greases, liquid-enriched gels.

The balls are well distributed in the coupling means. Pasty Koppelmit ^¬ stuffs and coupling means lower viscosity not separate spheres and actual coupling means noticeably. In the case of coupling agents with a higher viscosity, it may be necessary to restore the mixture of balls and the actual coupling agent before the coupling agent is used. Separation can be avoided by using actual coupling agents with specific weights that largely correspond to the specific weight of the balls used.

For problems of wetting of the balls through the actual coupling ^¬ agents may be added, ^¬ provide the sufficient wetting and thus a sufficient adhesion between the surface of the balls and the actual coupling means ensure suitable chemical reagents. This also the above-mentioned segregation entgegenge ^¬ is mixed. Actual coupling agents which are water-soluble or can be diluted with water are preferably used. The coupling agent according to the invention is disposed of by rinsing the coupling agent off the object under investigation, for example with water. By strong dilution of the coupling means is achieved that the Glasku ^¬ to rules at the bottom of the receiver can deduct, in another embodiment, they can be collected with a simple filter. Metal meshes, such as those used for oil filtering, are suitable as filters, but fabric filters, such as are known for example for coffee filters, can also be used.

Basically, there is no problem if glass balls get into the ground or into a landfill. When using lead-free glass, there are no toxic problems, rather glass balls behave like sand, i.e. they serve to loosen the soil.

Under eigentlichem coupling means of gel to liquid at ^¬ part of the coupling agent of the invention is understood. The coupling agent itself is the mixture of the balls and the actual Koppelmit ^¬ tel. The actual coupling means does not differ from the already known coupling means which are currently on the market or are known.

It is possible hen the balls with a fluorescent additive to be sent ^¬. In this way, simple proof is obtained that the coupling agent is present on a surface and how much of it has been applied.

Basically, all objects that can be tested with ultrasound come into consideration as the object to be tested. Specifically, the appli ^¬ is dung Field of the invention, the non-destructive testing of materials, in ^¬ testing of steel or light metal parts of play.

If ^¬ eingegan particular glass balls as balls in the foregoing was gen, it is because that glass balls in these dimen ^¬ solutions in sufficient quantities and also available are inexpensive. A favorable additions of 5% (weight percent) balls erwie ^¬ sen have. With smaller additions, advantages are also achieved because it In principle, it is sufficient if the test head is supported by three balls. The balls allow the test head to move on all sides with respect to the surface to be tested.

Claims

P ATE NTAN SP RÜ C HE

1. Ultrasonic coupling means for filling a gap between an object to be examined and an ultrasonic test head which is movable relative to the surface of the object, the coupling means having a gel-like, pasty to liquid consistency, characterized in that it contains small balls made from a solid.

2. ultrasonic coupling means according to claim 1, characterized in ^¬ net that the balls have a diameter of between 30 krometer Mi¬ and 1 millimeter, preferably between 50 Mikrome ^¬ ter and is 200 microns.

3. Ultrasonic coupling agent according to claim 1, characterized gekennzeich¬ net that the balls are made of glass, preferably made of a lead-free glass.

4. ultrasonic coupling means according to claim 1, characterized in ^¬ net that the balls limpedanz of a material with the highest possible ^¬ scarf, for example, tungsten, copper, nickel, steel, are made.

5. ultrasonic coupling means according to claim 1, characterized in ^¬ net that, preferably 3 to 10 weight percent and most preferably 5 percent by weight of Ku ^¬ rules contained in the coupling means 2 to 50 weight percent.

6. ultrasonic coupling means according to claim 1, characterized in ^¬ net that is a solid body to be examined object.

7. ultrasonic coupling means according to claim 1, characterized in ^¬ net that minus 20% of a given nominal diameter, contains balls in a predetermined diameter range, for example plus /.

8. Ultrasonic coupling means according to claim 1, characterized in net that the surface of the object to be examined has a roughness and the diameter of the balls is greater than the measure of the roughness.

9. ultrasonic coupling means according to claim 1, characterized in ^¬ net that it contains glycol gels, glycerol or mineral oil.

10. ultrasonic coupling means according to claim 1, characterized in ^¬ net, that the acoustic impedance of the pasty or liquid portion, corresponding to the coupling means of the acoustic impedance of the material from which the balls are made possible.