The new brittle fracture concept for EN13445, Pt. 2, Annex B

A model in the European pressure vessel standard EN 13 445 for prevention of brittle failure has been analysed using recent fracture mechanical results from ECOPRESS, SINTAP, and other recent European research project. Although it is recommended that some basic parts of the model are exchanged, practically all of the output of the model is consistent with more recent findings. The main concern involves the crack detection. A maximum allowed crack depth of 25% of the thickness is assumed in EN 13 445, which is now believed to be too optimistic for thin gauges. This fraction is proposed to decrease with the thickness. To characterise the crack detection performance, a parameter (t50) is introduced for the thickness where a crack with a depth of half the specimen thickness can readily be detected. Analysis of literature on non-destructive testing techniques indicates that t50 = 15 mm gives a sufficiently safe design model. (orig.)