The influence of the out-of- and in-plane constraint on fracture toughness of high strength steel in the ductile to brittle transition temperature range

In the paper the analytical formulae to predict the fracture toughness are proposed. They take into account the influence of in- and out-of-plane constraints. The formula which takes into account the out-of-plane constraint contains the plane strain JIC and Guo's Tz parameter. Alternatively the ratio of the effective to yield stress can be used. The influence of the in-plane constraint can be assessed using JIC and O'Dowd's, and Shih's Q parameter. The theoretical predictions were verified by the results of the experimental program. A good agreement between the theoretical and experimental results is observed.