Using wedge-loaded compact tension specimens for investigating hydrogen-induced cracking

Constant displacement loading under gaseous charging at elevated pressure over a long time is a convenient method for determining the resistance of materials against hydrogen-induced cracking (HIC). This work investigates the feasibility of using compact tension (CT) specimens loaded by double-tapered wedges, as the combination of CT specimens and wedge loading benefits not only from small specimens that can be easily manufactured, but also from a straightforward loading method. As recalculating the applied stress intensity factor (SIF) after HIC testing is challenging for a wedge-loaded CT specimen, an experimental-numerical method is proposed for determining the SIF. Firstly, the separation load between the wedge and the specimen was experimentally obtained from a lift-off curve and, secondly, a correction factor calculated using finite element analysis (FEA) was applied to predict the equivalent contact load between the wedge and the specimen. To verify the proposed approach, the threshold SIF ([Formula: see text]) of high-strength steel (HSS) DIN 55NiCrMoV7 in gaseous hydrogen was determined using wedge-loaded CT specimens as well as standard bolt-loaded compact specimens. The comparison of [Formula: see text] obtained with both types of specimens revealed a good agreement, which confirmed the feasibility of the proposed method.