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Recent development of NDT-systems - applications to on-line process control, to railway safety and in-line pipeline inspection

 
: Dobmann, G.

Centro Atomico Constituyentes:
CORENDE 2005 ,Congreso Regional de Ensayos No Destructivos y Estructurales
Buenos Aires: Centro Atomico Constitutyentes CNEA, 2005
pp.13-33
Congreso Regional de Ensayos No Destructivos y Estructurales (CORENDE) <2005 , Ciodad de Neuquén, Argentina>
English
Conference Paper
Fraunhofer IZFP ()
non-destructive characterization of material; inhomogeneity; thermal aging; corrosion

Abstract
Non-destructive testing (NDT) is mainly discussed as inspection task to detect materials non-regularities and/or inhomogeneities after certain production process steps (casting, forging, rolling, joining, welding, etc.) of the material and components. The task is to detect and to classify non-conformities which very often also are named 'defects' of which the size is a lifetime limiting factor under static as well as cyclic loads. Concerning the number of NDT-applications in practice this task is still at the top of the list if we discuss safety relevant components which during lifetime are under mechanical loads superimposed by other ageing effects like thermal ageing, creep and corrosion.
However, in the last decades NDT has more and more developed also microstructure- and stress-sensitive technology which nowadays has a breakthrough in on-line process monitoring and control. These NDT-technologies with their measuring quantities show potential to early detect materials ageing and degradation or to find correlation to mechanical properties like the yield strength, tensile strength or the hardness. Systems were recently developed to on-line characterize these properties, for instance, in a hot-dip-galvanizing line in the steel sheet production for car bodies or in the rolling mill for heavy steel plates.
Railway traffic has to be safely performed the more high speed trains are in use which suffer under fatigue and wear - mainly restricted of the near-surface regions in wheels as well in the rail. IZFP has developed automated systems which are in application for a daily quick check of the surface state, i.e. in order to detect surface-breaking nonconformities. In that case the train rolls at low speed (4-6 km/h) on a track with EMAT-transducers build-in the rails. Other systems check the wheel after 150000 km running distance or after 25o000 km if the wheels are removed from the cars in order to re-profiling the surface.
Pipelines are the most safe transportation facility of oil and gas, compared with for instance tankers, however, the lines are under influence of the medium, the load and corrosion effects. Therefore pipelines are periodically inspected by so-called 'intelligent pigs', i.e. inspection tools based on magnetic flux leakage or ultrasonic inspection which are pumped with the medium through the pipe detecting corrosion wall thinning or even stress corrosion cracking.
The contribution introduces into the different inspection tasks, the NDT systems developed and their potential to contribute to an economical and safe technical world.

: http://publica.fraunhofer.de/documents/N-34396.html