GB2143710A

GB2143710A - Process and appliance for testing moving strip material

Info

Publication number: GB2143710A
Application number: GB08416309A
Authority: GB
Inventors: Theodor Tenbusch
Original assignee: RHEIN WESTFAEL TECH UEBERWACH
Current assignee: RHEIN WESTFAEL TECH UEBERWACH
Priority date: 1983-07-13
Filing date: 1984-06-27
Publication date: 1985-02-13
Also published as: FR2549225A1; SE8403683L; NL8402200A; GB2143710B; CA1217882A; ES534325A0; GB8416309D0; AU3058284A; ES8503850A1; AU563295B2; FR2549225B1; DE3325281C2; BR8403496A; DE3325281A1; SE8403683D0; JPS6089738A

Abstract

Continuous, non-destructive materials testing of strip material (7), moving continuously at a velocity vB, particularly of continuously-running conveyor belts, is effected by directing a beam (8) of penetrating radiation from a source (1) of radiation at the moving strip material and the picture produced by the penetrating radiation material is made visible on a fluorescent screen (2), the beam of penetrating radiation forming a radiation cone possessing on the strip material a width b in the direction of movement of the strip material, the radiation source being operated by an impulse drive (6) with pulses of radiation of impulse duration tI with a period duration T and a thereby specified pulse frequency f, the impulse duration tI being so chosen that vBtI is small compared with a desired picture resolution, and vB/f being small compared with the width b of the cone of radiation on the strip material in its direction of movement and, in accordance with the pulse frequency of, a continuous succession of penetrating radiation pictures on the fluorescent screen being recorded by means of a video camera (4) and stored by recording equipment (5) the video camera also being impulse-driven synchronously with the impulse drive of the radiation source. <IMAGE>

Description

SPECIFICATION Process and appliance for testing moving strip material This invention relates to a process for the continuous, non-destructive materials testing of strip material moving continuously at a velocity V5 in which a beam of penetrating radiation from a source of radiation is directed at the moving strip material and a picture produced by the beam of penetrating radiation is made visible on a fluorescent screen, the beam of penetrating radiation forming a radiation cone in the direction of movement of the strip material, possessing a width b on the strip material.

The width b in the direction of movement of the strip amounts to e.g 60 cm. At right angles to the direction of movement it is expedient for it to correspond to the width of the strip. The strip material may particularly be conveyor belts which operate underground and which move at a speed of up to e.g. 7 metres per second.

The invention also relates to an appliance for performing such a process.

In known processes of this nature the fluorescent screen is watched by an operator. It is not possible to break down the observation, as it were, into single pictures, and evaluate these independently of the instantaneous observation by viewing the screen, or automatically.

It is therefore the object of the invention to modify the process in such a way that breakdown of the observation into single pictures, and corresponding assessment by means of examination of a screen or by automatic picture evaluation is possible.

According to the present invention, the radiation source is operated by an impulse drive with pulses of radiation of impulse duration t1 with a period duration T and a thereby specified pulse frequency f, the impulse duration tl being so chosen thatv5t is small compared with a desired picture resolution, vB/f being small compared with the width b of the cone of radiation on the material in its direction of movement and, in accordance with the pulse frequency, a continuous succession of penetrating radiation pictures is produced on the fluorescent screen, the penetrating radiation pictures being recorded from the fluorescent screen, and electronically stored by means of a video camera which is also impulse-driven, this being synchronously with the impulse drive of the radiation source.

Within the scope of the invention an X-ray tube can be used as the radiation source. Then the impulse drive of the radiation source can be produced by an appropriate blocking voltage being applied in the form of a pulsed high voltage. In this way operation is as it were with flashes of X-rays.

The possibility also exists however of using a gamma-ray specimen as radiation source. Then the impulse operation is expediently produced by means of a rotating shutterwhich posseses apertures for the passage of the radiation pulse, whilst screening takes place between the apertures according to the length of the cycle. In the process according to the invention the length of impulse t1 is usually short compared with the length of the cycle.

This can be utilized for the recording of the penetrating radiation pictures with the help of the video camera. To that end the individual penetrating radiation pictures on the fluorescent screen are preferably stored in accordance with the period duration Tfrom one picture to another. This can be done without difficulty by means of modern electronics. Usually a plurality of penetrating radiation pictures are taken of each area of the moving strip material corresponding to the width b of the radiation cone, so that the result is that the moving strip material whilst running in service is fully illuminated with penetrating radiation with the desired resolution and consequently can be examined for faults. It is within the scope of the invention to brighten the penetrating radiation pictures on the fluorescent screen electronically, with the assistance of an image intensifier.The impulse duration tl is basically determined by the desired resolution capacity of about 1 mm. in the direction of movement of the strip material. Accordingly it is desirable for the impulse duration t not to exceed 150 microseconds. The period duration T and therewith the pulse frequency f is determined by video camera picture speed of e.g.

25 frames per second. A picture is illuminated by one X-ray flash. Adequate overlapping is normally provided with a picture succession frequency of 25 per second (as for example with a strip speed of 7 metres/sec. a further picture is taken after a strip movement of 280mm.) The advantages achieved are to be seen in that in the process according to the invention the radiation penetrating the moving strip material during continuous non-destructive material testing is broken down into a succession of individual pictures which can be subjected to individual picture assessment by examination of a screen, orto automatic picture evaluation.In this respect the process according to the invention leads to a succession of individual pictures, and in so doing the process can nevertheless be performed without difficulty in such a way that the strip material can be fully adequately investigated for faults whilst running in service, according to the picture resolution.

It is a fact of particular advantage that well proved components and assemblies can be used to perform the process according to the invention. An appliance for performing the process comprises a radiation source, e.g. an X-ray tube, a fluorescent screen, an image intensifier if required, a video camera with recording equipment, and equipment for the impulse drive of the radiation source and the video camera synchronously with one another.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagramatic drawings, in which Figure 1 shows an appliance for performing the process according to the invention: and Figure 2 a diagram which explains the impulse drive of the appliance according to Figure 1.

The appliance shown in Figure 1 comprises a radiation source, which is an X-ray tube 1, a fluorescent screen 2, an image intensifier 3, a video camera 4 and recording equipment 5 for the pictures taken by the video camera 4. The video camera 4 and the X-ray apparatus 1 are coupled together via equipment 6 for the production of an impulse drive.

They are pulsed synchronously. The strip material 7 that is to be subjected in the moving condition to a continuous, non-destructive materials test moves continuously between the X-ray tube 1 and the fluorescent screen 2. It may be a continuouslymoving conveyor belt is underground operation.

The moving strip material 7 moves at a velocity vB, this velocity is indicated in Figure 1. It is to be seen that the penetrating rays from the radiation source 1 are directed at the moving strip material 7. The radiation source 1 is operated by an impulse drive with pulses of radiation of impulse duration t with a period duration T and a thereby specified pulse frequency f. The impulse duration t1 as well as the period T and the relationship between them have been represented in Figure 2 where time is represented as abcissa and the intensity of penetrating rays is represented as ordinate.The design is so arranged that the impulse duration t1 is such that the product vBtl is small in relation to the picture resolution (e.g. 1 mm.) and vBff is small in relation to the width b of the cone of radiation as measured on the strip material in its direction of movement. Thus in accordance with the pulse frequency a continuous succession of penetrating radiation pictures is produced on fluorescent screen 2. The penetrating radiation pictures are recorded from fluorescent screen 2 by means of a video camera 4 and are electronically stored. An image intensifier 3 is interposed. The video camera 4 is also pulse-driven, this being synchronously with the pulse drive of the radiation source 1. A plurality of penetrating radiation pictures is taken of each area of the moving strip material 7 corresponding to the breath b of the cone of radiation 8 and they consequently overlap one another The result is that the moving strip material 7 can be completely investigated for faults whilst running in service, with the accuracy of the picture resolution. Evaluation takes place by the assessment of individual frames of the pictures recorded by means of video camera 4, by means of examination of a screen or by automatic picture evaluation.

Claims

1. A process for the continuous non-destructive materials testing of strip material moving continuously at a velocity Vs, in which a beam of penetrating radiation from a source of radiation is directed at the moving strip material and a picture produced by the beam of penetrating radiation is made visible on a fluorescent screen, the beam of penetrating radiation forming a radiation cone in the direction of movement of the strip material and possessing a width b on the strip matrial, the radiation source being operated by an impulse drive with pulses of radiation of impulse duration tl with a period duration T and thereby specified pulse frequency f, the impulse duration t being so chosen that v5t1 is small compared with a desired picture resolution, v5/f being small compared with the width b of the cone of radiation on the strip material in its direction of movement and in accordance with the pulse frequency, a continuous succession of penetrating radiation pictures being produced on the fluorescent screen, the penetrating radiation pictures being recorded from the fluorescent screen and electronically stored by means of a video camera which is also impulse-driven, this being synchronously with the impulse drive of the radiation source.

2. A process according to Claim 1, wherein an X-ray tube is used as the radiation source.

3. A process according to Claim 1, wherein a gamma-ray speclmen is used as the radiation source.

4. A process as in Claim 3, wherein the impulse operation is produced by means of a rotating shutter which possesses apertures for the passage of the radiation pulse, whilst screening takes place between the apertures according to the length of the cycle.

5. A process according to any one of Claims 1 to 4, wherein the individual penetrating radiation pictures on the fluorescent screen are stored in accordance with the period duration from one picture to another.

6. A process according to any one of Claims 1 to 5, wherein a plurality of penetrating radiation pictures are stored of each area of the moving strip material corresponding to the width b of the radiation cone in the direction of movement.

7. An appliance for performing the process according to any one of Claims 1 to 6, comprising a radiation source (1), a fluorescent screen (2), a video camera (4) with recording equipment (5), and equipment (6) for impulse drive of the radiation source (1 ) and the video camera (4) in synchronism with one another.

8. An appliance according to Claim 7, wherein the radiation source (1) comprises an X-ray tube.

9. An appliance according to Claim 7 or Claim 8, wherein an image intensifier is provided.

10. A process for the continuous non-destructive materials testing of strip material substantially as hereinbefore described with reference to the accompanying drawings.

11. An appliance for performing the process for the continuous non-destructive materials testing of strip material substantially as hereinbefore described with reference to the accompanying drawings.