BiBeam Specimen Design for investigating Stress Corrosion Cracking in Brittle Materials

The existing method for testing and collecting Stress Corrosion data requires application of externally applied load on the specimen in the corrosive media. We propose a new type of specimen consisting of a bi-beam where two materials having slightly different coefficient of thermal expansions are bonded together and cooled to room temperature such that a self-loaded specimen is produced because of the presence of residual stress. This creates a very stable stress field that is ideal for long-term toughness experiments. A finite element model was developed to design such specimens while ensuring that the crack propagates at a steady state across the specimen. The model was first verified against analytical results for a thin film on a substrate. Then, since non-constant stress intensity factor are desirable for recording a spectrum of response, specimen geometries were investigated to determine the best geometry suitable for such experiments. The results obtained were validated by performing a stress corrosion cracking experiment using Schott B/Soda-lime glass bi-beam in water and the numerical data compares well with the experimental data.