Evaluation of environment-assisted cracking using wedge-loaded compact tension specimens

The constant displacement method has frequently been used for determining the cracking resistance of materials in aggressive environments. For this purpose, bolt-loaded compact specimens or wedge-loaded double cantilever beam (DCB) specimens are usually stored under specified environmental conditions over a certain period of time inside a chamber. However, compact tension (CT) specimens are smaller and easier to be manufactured than these standard specimens. Because of these advantages, the present study investigates the feasibility of employing wedge-loaded CT specimens for evaluating environment-assisted cracking. Finite element (FE) analysis was used for calculating the stress intensity factor (SIF), the equivalent contact force between the CT specimen and the inserted wedge, and the position of the equivalent contact force. Purely elastic behavior as well as elastoplastic behavior of the specimens were modeled. Linear relationships between the SIF and the applied displacement and the equivalent contact force, respectively, were identified for elastic wedge-loaded CT specimens. This also applies to wedge-loaded DCB specimens. For CT specimens the offset of the equivalent contact force from the nominal loading line was larger than for DCB specimens. Because of plastic deformation around the inserted wedge, both types of elastoplastic specimens show non-linear relationships between the SIF and the applied displacement and the equivalent contact force, respectively. As the plastic deformation is more remarkable in CT specimens, the relationship between the applied displacement and the offset of the equivalent contact force is non-monotonic.