Ein hochlagenorientiertes und duktilitätsgesteuertes Stahlgütewahlkonzept

An upper shelf oriented and ductility-controlled steel selection concept.

The European steel work codes contain a simplified steel selection method for the avoidance of brittle fracture (DIN EN 1993-1-10) that is based on a fracture mechanical consideration of toughness properties in the lower shelf of the toughness transition curve. For the unambiguous characterisation of the material behaviour of ferrite structural steels the development of the toughness properties for the full temperature range and therewith the upper shelf behaviour is crucial. The latter affects the material's ductile capacity and thereby its ability for plastic redistribution that is presumed as an integral element for the strength functions in case of the ultimate limit state design. In this respect only inadequate ductility criteria exist to date in DIN EN 1993-1-1 which cannot clearly be justified by mechanical means nor derived from upper shelf aspects. Something similar applies to the so-called Aufschweißbiegeversuch acc. to SEP 1390 that in Germany still in some cases is obligatory for thicker elements of several steel grades. In this light a toughness-oriented model for the choice of steel material for the plastic design taking inelastic redistributions into account was developed which allows to quantify upper shelf demands for adjusting a required ductility level by combining the upper shelf and the transition region with the lower shelf.