SINGLE SPECIMEN METHODS TO EVALUATE J-R-CURVES FROM INSTRUMENTED CHARPY TESTS: RESULTS OF A ROUND ROBIN

摘要

Based on a previous round robin exercise of the German DVM-group on instrumented impact testing another exercise was performed to explore the possibilities of extended evaluations like single specimen methods. The previously determined multi-specimen cleavage J_R-curve serves as a reference. Different methods like, e.g. the key curve method were applied. Overall, the results are encouraging and the agreement of the calculated J_R-curve with the reference curve is quite good especially for large amounts of crack extension. However, there is some uncertainty left in the first part of the J_R-curve, where notch blunting and initiation of crack growth take place: In this region, the calculated curves tend to overestimate the crack resistance. Thus, the possibilities to determine initiation toughness values from such curves and their physical meaning need to be further clarified.