New interpretations of the Charpy V test

Presently most structural integrity assessment procedures still allow the use of Charpy-V notch impact tests as a measure of fracture toughness. The use is generally made through some more or less reliable correlations between standard Charpy-V notch energy and fracture toughness or tearing resistance. Common for the present correlations is that very few studies have been made with respect to their usability to Ultra High Strength Steels (UHSS) with yield strengths in the excess of 900 MPa. This is the topic of this work. Focussing on novel directly quenched high performance steels, the applicability of the Master Curve methodology with special emphasis on the temperature dependence is examined and the validity of the standard T0-TCV28J transition temperature correlation is checked. Improvements to the criteria are proposed for further considerations. Additionally, a new simple procedure for converting sub-sized Charpy V data to full size specimens, that is in line with BS 7910, is presented. The new interpretations of the Charpy V test presented here enable an extension of present design rules like the ones in EN 1993-1-12 (2007) to steel strengths well beyond 1000 MPa. Providing a sufficient toughness for the steel is up to the steel manufacturer, but there is no basic reason why UHSS cannot be used based on an identical assessment procedure as for presently accepted steel strengths. Only 2 equations in EN 1993-1-12 (2007) needs to be changed, and the sub-size specimen conversion procedure needs to be adopted.