NDTnet 1998 Aug, Vol.3 No.8

Abstract

General
A new architectural concept of a multichannel automatic ultrasonic system for the inspection of steel plate is presented and discussed. It has been designed and built and is currently in operation in a rolling mill. High productivity, high sensitivity/reliability and low cost (also maintenance costs are optimized) are the central parameters considered for the specifications of the system.

System description
Up to 3.5 meters width plate are scanned in one pass with 100% surface coverage at a speed of up to 1 m/s. 176 water coupled twin crystal T-R probes are kept to a 0. 1 mm distance from the upper plate surface achieving a reliable and reproducible acoustic coupling. Each groupe of 4 probes is mounted in a cardan joint to follow possible lack of planitude. 22 electronic modules working in paralell, driving 8 T-R probes each, are connected via bus VME to a pair of computers. Data are captured at a rate of up to 2,000 per second per transducer. Data processing is carried out in three main steps:

- a local processing is performed by the data acquisition card. At this level two gates allow the detection of defect and backwall echoes. Signals in the echo gate higher than a predefined threshold are detected and its amplitude and time of flight recorded. The same data are recorded for the backwall echo. Each local processor is able to drive 8 channels.
- data collected by 22 local processors are feed into the 2 preprocessing computers, connected via bus VME. At this stage data from different probes are segmented so that coherent defect data are produced. This allows to determine the geometry of the reflector (its area and its position with reference to the plate edges) and its ultrasonic parameters (echo amplitude, time of flight, residual backwal echo amplitude).
- Data from preprocessing computers are finally processed and displayed by the main computer. This is the interface that allows the operator to select the specification or standard to filter the data, to show B, C or D scans and to enter into the data base with the plates already scanned. At the same time, this computer makes the interface with the production computer.
Other interesting tools such as automatic callibration facility, automatic evaluation or optimized cutting routine are also available at the operator's keyboard.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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