DIGITAL PHOTOELASTICITY ANALYSIS OF STRESS SINGULARITY OF BIMATERIAL JOINTS

Based on singularity stress field equations of bimaterial joint at the interface corner, a phase-shifting digital photoelasticity method is applied to calculate stress intensity factors at the interface corner for the case with a unique positive stress singularity order. Aluminum alloy/ epoxy bimaterial joints having notch angle 90o and 135o have been respectively selected to perform four-point bending tests. The full-field isochromatic fringe orders near the joints obtained by the digital phase-shifting photoelasticity are regarded as raw data. Expressing the two principal stresses in terms of the equations of singularity stress field and substituting them into the stress-optics law, a linear logarithm relationship for 135o interfacial joint and a power function relationship for 90o interfacial joint are respectively deduced and are further fitted to the experimental data of fringe orders vs. distance to the joints. The experimental results reveal that the stress intensity factors increase gradually with the applied loads and have similar trend with the numerical calculation.