Abstract: A probabilistic model is derived based on the weakest link theory to evaluate the specimen thickness effect and the size effect of coarse-grained heat-affected zone (CGHAZ) on CTOD toughness values in heat-affected zones (HAZ) of high strength steels. The scatter of CTOD fracture toughness values in heterogeneous weldments is predicted using this model. The specimen thickness has influence on the CTOD toughness values of HAZ. With increase in the specimen thickness the estimated and experimental mean CTOD values decrease while the lower boundary CTOD values remain almost unchanged. The size of CGHAZ has strong negative effect on the mean CTOD values of HAZ. The estimated mean CTOD values and lower boundary CTOD values agree with experimental CTOD testing results of HAZ notched specimens. The facture toughness scatter is dependent on the Weibull shape parameter a and specimen thickness.

Key words: probabilistic model, CTOD toughness, the size effect, heataffected zone