DE7625312U - Test head for continuous ultrasonic testing of rolled strip using the pulse echo method with Lamb waves - Google Patents

Description

76 25 ZfZ .

Andrejewski, Honlce, Gesthuysen & Masch patent attorneys Physicist Dr. Walter Andrejewski Graduate engineer Dr.-lng. Manfred Honlce Graduate engineer Hans Dieter Gesthuysen Physicist Dr. Karl Gerhard Masch

Lawyer files: 43 Essen 1, Theaterplatz 3, Postf. 789

46 676 / B + August 11, 1976

Utility model registration
Thyssen Niederrhein AG
Metallurgical works and rolling mills
Essener Strasse 66
42oo Oberhausen

Test head for continuous ultrasonic testing of rolled strip using the pulse echo method Lamb waves

The invention relates to a test head for a continuous Ultrasonic testing of rolled strip according to the pulse-echo! Method with Lamb waves, with two juxtaposed j th, water-filled chambers for transmitters and receivers, each formed from two parallel plates and connected by means of a housing part covering the open sides of the chambers with the exception of a coupling window are, and with an air gap between the adjacent plates, which is bridged by a web on the strip side

7625312 23.1176

Andrejewski, Honke, Gestiiuysen & Masch, patent attorneys in Essen

As is well known, for the generation of Lamb waves usually the The so-called wedge method is used in which individual latin wave modes are used stimulated in a defined manner by changing the angle of incidence of longitudinal waves in the strip surface be, wherein the longitudinal wave wedge z. B. is formed from water. To avoid a dead zone in front of the probe As a result of reflections of the transmission pulse within the test head, the SE method is often used the transmitter and receiver chamber η arranged side by side are. The intensity of Lamb wave reflections at defects occurring in the rolled strip is relative to the transmitted intensity tiny. In order to achieve a sufficiently low detection limit, an exceptionally lower limit is therefore required Interference signal level as well as the lowest possible useful signal attenuation to strive for; the ratio of useful and interfering signals must therefore be as large as possible. The useful signals here are edge and false echoes and, as interference signals, the so-called echo grass, d. i. the electromagnetic and acoustic background, as well as the over-coupling of transmission energy on the receiver, which occurs predominantly in the coupling area.

In a known test head of the type mentioned (DT-PS 2 253 530), the web is to avoid overcoupling designed with a small thickness in relation to the panel thickness. The disadvantage is that dirt particles, which from the water are washed off by the rolled strip, more and more pass through the open coupling window into the brackets, where they pollute the transmitter and the receiver in the shortest possible time so that the ratio of useful to interfering signal, i.e. i. that Ratio of false echo amplitude or edge echo amplitude to overcoupling amplitude, due to strong attenuation

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Andrejewslci, Honlce, Gesthuysen & Masch, Pcrtentan in Essen

of the useful signal is too small - possibly 41 - and thus a further testing without prior cleaning is no longer possible is.

The invention is based on the object of specifying an ultrasonic reverberation probe which has both a large overcoupling attenuation as well as the lowest error echo attenuation over time constant sensitivity of transmitter and receiver guaranteed.

The invention consists in that the coupling window of Plastic sheets with an ultrasound attenuation of less than 4 dB and a speed of sound less than 24oo m / sec | are covered and the plastic plates opposite the web, j the plates and the housing part with oewebegumni acoustically j are isolated. Preferably, the plastic plates j

and receiver and thus an attenuation of the useful signals UFiter- | surprisingly, a high i over-coupling attenuation remains as a result of the second, although due to theoretical j Considerations to consider the covering of the coupling window with the plastic plates mentioned above due to impairment of the energy of the longitudinal wave impulses as unfavorable is. The overcoupling attenuation is further intensified by the fact that the web consists of a multi-connector structure on the basis of Pheaeplast / paper. the Overcoupling attenuation that can be achieved by a web constructed in this way is also fiber-optic because it is more layered Plastic for Longitecüjaalwellen does not have a large Däapfuog. In any case, the coupling attenuation is so great.

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Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen -r ~

that the last-described measures in connection with the generic ultrasound head also have an independent meaning comes to. The coupling between plastic sheets and rolled strip takes place via a 2 mm thick flowing water gap.

The advantages achieved are to be seen in the fact that an ultrasonic probe for rolled strip, which has the operational reliability essential for rough operation and required for a sufficiently low defect detection limit has high coupling attenuation and low useful signal attenuation.

In the following, the invention is based on an embodiment at spie ± aarste ± xenaen Aeichmuig near * · e

The single figure shows a test head for continuous ultrasonic testing of rolled strip 1 in cross section the pulse-echo method with Lamb waves. In its basic structure, the test head initially consists of two side by side, filled with water chambers 2, 3, one for a transmitter 4 and the other for j a receiver 5 is determined. The chambers 2, 3 are each; formed from two parallel plates 6 and by means of an i the open sides of the chambers 2, 3 with the exception of one each Coupling window covering housing part 7 connected. Between the adjacent plates 6 of the two chambers 2, 3 there is an air gap 8, which passes through the belt side a web 9 is bridged.

7625312 12/23/76

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen

According to the invention, the coupling windows are now approximately Io mm thick plastic, in particular polystyrene plates with an ultrasonic attenuation of less than 4 dB, as well as one Speed of sound less than 24oo m / sec covered, which compared to the web 9, the plates 6 and the housing part 7 are acoustically isolated with fabric rubber 11. The intermediate web 9 consists of a multilayer plastic based on phenoplast / paper and is also available under circuit of fabric rubber od. Like. Fixed on the adjacent plates 6, for example by means of screws. the The test head has a flat surface on the strip side. The coupling of the ultrasound from the plastic plate to the belt takes place via a flowing water gap 12, which is connected by a slot-shaped DÜ56 13 ·· - «- - ·· a connected to a water network

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Claims (1)

Andrejewski, Honke, Gesthuysen & Masch, patent attorneys in Essen Protection claims 1. Probe for continuous ultrasonic testing of Rolled strip using the pulse-echo method with Lamb waves, with two water-filled ones arranged next to one another Chambers for transmitters or receivers, which are each formed from two parallel plates and by means of one the open sides of the chambers, with the exception of a coupling window, are connected with a covering housing, and with a Air gap between the adjacent plates, which is bridged by a web on the strip side, as a result marked without t that the docking window of Plastic plates (lo) with an ultrasonic damping smaller 4 dB and a speed of sound less than 24oo m / sec are covered, and the plastic plates (lo) opposite the web (9), the plates (o) and the housing part (7) are acoustically insulated with fabric rubber (11). 2. Test head according to claim 1, characterized in that the plastic plates (lo) are made of polystyrene. 5. Test head according to claim 1 or 2, characterized in that that the web (9) consists of a multilayer plastic based on phenoplast / paper. 7625312 12/23/76