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Zusammenfassung
Für die kennzeichnenden Größen eines industriellen Röntgenfilmsystems sind in der Norm EN 584-1 Grenzwerte für die Zugehörigkeit zu einer Filmsystem-Klasse sowie Messvorschriften für die Bestimmung der Kennwerte angegeben. Diese Messvorschriften erwiesen sich in der Praxis als zu großzügig gefasst. Der Ringversuch, an dem Filmhersteller und die BAM im Rahmen einer Ad Hoc Group der WG1 des CEN TC 138 teilnahmen, bestätigte das mit seinen beträchtlich voneinander abweichenden Ergebniswerten. Aus seinen Ergebnissen können Hinweise für präzisierte Messvorschriften und Algorithmen entnommen werden. Zusammen mit unabhängig davon durchgeführten Stichproben-Messungen der BAM an Filmsystemen vom Markt geben die Ergebnisse des Ringversuchs Hilfe für die Korrektur von Klassengrenzen der Norm.
The existence of some 100 million active mines threatens human life and curtails substantially the economic base in over 70 countries. Humanitarian demining is tedious and it currently only employs metal detectors, prodders, dogs and armoured mechanical vehicles.
Achieving a world free of mines within a period of 10 years as stipulated in international treaties requires safer and more efficient technologies. In response to this challenge the Working Group 5 of the European Federation for Non-Destructive Testing (EFNDT WG5) was founded in Berlin in March 1999. The subject of this working group now consisting of 50 members from 17 countries is the detection of antipersonnel mines (APMD). The basic idea was to investigate existing NDT methods into their ability to aid mine detection. The scope of activities ranged from collecting available information, setting up links to related organisation, defining terminology and standards to selecting dedicated research projects. Since some of these tasks are already conducted by other organisations on an European and international level the attention of the working group has been focused mainly on two R&D areas and on reliability assessment studies. Otherwise, EFNDT WG5 APMD nevertheless remains open to novel approaches in mine detection. Aim of all activities is to provide deminers with safer and more efficient tools than merely with prodders and metal detectors currently used for their dangerous task.
The reliability investigations are dedicated to throw light on the performance of the NDE system with
respect to the required aim. This is especially of interest when digitized and processed signals are
involved where it becomes hard to assess whether the quality of the system has raised or not. Three
different ways to investigate reliability of NDE signals will be described. The first way of investigation,
the performance demonstration, is preferred e.g. in the US American nuclear power industry. This is an
integral consideration of the non destructive test as a system where the whole NDE system is packed in a
black box and only the input in terms of the real existing flaws in the component is considered and
compared to the output in terms of the indications of the human inspector or of the automated system.
The second the European tradition relies on a standardized description of physical/technical
parameters of the NDE system which are preconditions for successful system performance. An example
for such a standardized set of performance parameters is given in the recently released standard about Xray
film digitization CEN EN 14096. The third approach the modular conception is a marriage of
both: The signal chain is cut into main modules. Each module is assessed in a most appropriate
individual way e.g. via modeling calculations. The single results are joint together according to the
reliability of the subsystems. Separating criteria for the system were proposed through a reliability
formula developed during a series of European-American workshops on NDE reliability. Examples of
all three approaches will be given.