Abstract
Crack tip opening angle CTOA is a fracture parameter for crack propagation resistance. Three
high strength steel sheet materials (DP780, DP980 and martensitic B-steel) and a magnesium
sheet alloy (AZ31) were tested to measure the CTOA according to the recent ASTM E 2472-06
standard. Optical imaging as recommended in the standard was used in this work for the
determination of CTOA. For steel sheets, critical CTOA decreased with increasing yield strength
and decreasing elongation. Crack flanks of the tested steel and Mg materials were relatively
straight and the CTOA measurement method described in the standard was found suitable.
