Strength Evaluation of Ceramic-Metal Joints Based on Interfacial Fracture Mechanics

Strength evaluation of ceramic-metal joints, which had thin copper layers between ceramic materials and joint metals, and had interface cracks between ceramic materials and copper layers, was conducted based on interfacial fracture mechanics, considering plasticity of metals. A four point bending test of the ceramic-metal joints was also conducted. Estimated fracture load was compared with the experimental value. As a result, it was shown that linear interfacial fracture mechanics was applicable in strength evaluation of ceramic-metal joints with interface cracks, if thermal elastic plastic residual stress analysis was conducted to evaluate stress intensity factors corresponding to residual thermal stress. Fracture load estimated by thermal elastic-plastic analysis agreed fairly well with experimental value. Effectiveness of the σθmax criterion in strength evaluation of ceramic-metal joints considering plasticity of metals was confirmed. A good linearity of stress intensity factors extrapolation was obtained. Even in thermal elastic-plastic analysis, a good linearity was obtained in the range of r≥0.1a.