Pressure-sensitivity Effects on Toughness Measurements of Compact Tension Specimens for Strain-hardening Solids

The path-independent J-integral is used as a fracture prediction criterion for loading beyond the elastic limit as Linear Elastic Fracture Mechanics (LEFM) cannot be applied. While J was originally defined from an energy perspective, it was demonstrated that it could be inferred from load-displacement diagrams. Therefore, the Compact Tension (CT) specimen testing is used to compute J for materials. In this work, the η-factor, an important parameter in the computation of the J-integral, is investigated for compact tension specimen for materials with pressure sensitive yielding. This is achieved by using a lower bound approach to derive the appropriate expression from η from the test geometry and material properties. The specimen is considered at fully plastic loading where it is in the state of collapse. The effect of pressure sensitivity is accounted for by using a Drucker-Prager yield criterion for solid materials. Since CT testing is usually conducted on metallic materials, strain-hardening behavior of the material is incorporated in this analysis. This is done by assuming a simple linear hardening curve of the material. Numerical results computed for different cases show that as the material strain hardening increases.