Q NET Engineering GmbH

WS 98 Array
Surface flaw testing of aluminium sheet coils

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Situation

Aluminium is used in almost all areas of daily life and technology like for example in the aviation-, automotive-, engineering-, building- and packaging industries as well as in electrical engineering. 25 million tons of aluminium are used worldwide every year, 2.61 million of which in Germany. This renders aluminium a versatile and widely spread material.
Due to increasing quality requirements for material quality documentation has become an important competitive factor. Therefore, the demand for inexpensive, easy-to-operate, manual and automated testing systems for continuous product quality control and quality documentation is rising. Particularly in case of rolling processes, overlapping or inclusions that cause rejections in further processing steps have to be avoided.

Band from aluminium sheet coil
Figure 1: Band from aluminium sheet coil

Solution

In cooperation with Fraunhofer IZFP, Q NET Engineering has developed an eddy current testing method for detecting surface flaws in aluminium raw and end products. The state-of-the-art testing device is based on the WS98 system. It is easy to handle and has a modular build-up. The instrument enables fast testing even of large surfaces at low mechanical effort because the conventional rotation probes have been replaced by coil arrays. During the testing process, the collected data is displayed as a C scan. For evaluation and documentation purposes, the complete test data and flaw information is visualised and can be examined in detail offline.

Eddy current testing device WS98
Figure 2: Eddy current testing device WS98

System

The eddy current testing device consists of three components:

Eddy current basic module
Figure 3: Eddy current basic module

Advantages

Example

For testing aluminium sheet coil within the production line, about 90 probes are used. The same amount of probes is placed above and below the aluminium band. The flaw types and sizes are represented by calibration plates. The aluminium band is tested during the rolling process. The testing instrument is installed behind the cold rolling machine. Maximum speed of the conveyor is 1m/s. The temperature of the aluminium band lies between 60-90°C. Cooling ducts are integrated into the mounting of the sensors through which a cooling agent will be sent in case of overheating.

The eddy current sensors are distributed among 4 array probes. The distance between the scanned points is 1mm max. A 1mm drill hole is scanned at least 9 times.

Results / Evaluation

Visual illustration of crack testing with colour code offline

Bilddarstellung
Figure 4: Image

Different colours are used for the classifications of by how far the recording limit is exceeded. The recording limit can be adjusted freely. The scale between the recording limit and the signal level of the calibration notch is divided into three categories ranging from yellow at the lower end over orange to red at the top end. Violet indicates a signal level higher than the calibration notch.

Hardware

The testing device comprises of the modules of the plug-in WS98 technology:

Software

The WS98 software controls the operating functions of a single WS98 board. In case of a network of an unlimited number of WS98 boards and a computer, the software controls the communication between the single elements of the network.

Each WS98 board contains its own SHARC processor which communicates with the computer. There is data transfer in both directions, to and from the computer. For the in- and output of slave data at the computer an Ethernet interface is used.

Contact

Paul Kröning
Phone: +49 (0) 6 81/9 76 71 53
Fax: +49 (0) 6 81/9 76 71 58