Estimation of strength reliability for ceramic/metal jointing structure - the basic study of thermal stress and residual stress behavior during ceramic/metal joint process
Okabe Nagatoshi; Zhu Xia; Hirobe Kouta; Nakahashi Masako
Abstract:A simple analysis method was developed by making well use of finite element method (FEM) program for general purposes. The temperature dependence of mechanical properties for every material consisting of ceramic/metal jointing was considered in this method. Using this method, the residual stresses producing during the jointing process were analyzed for Si3N4/SUS304 joints with the insert layer of Cu made by an active metal brazing (Ti-Ag-Cu) method so as to clarify the residual stress behavior due to the creep of Cu. The equivalent normal stress calculated from the multi-axial stresses was used to evaluate the strength of fracture which resulted from initial flaws existing in the ceramic side. From the analytical results, it is found that the temperature at which the residual stress begins to generate is about 550 degree C, and it is clarified that the creep of Cu layer during cooling process may relax the residual stress in ceramics side and can not be neglected for the estimation of ceramic fracture due to residual stress. Key Words:Residual stress, Equivalent normal stress, Ceramics/metal joint, Elastic-plastic analysis, Creep analysis, Finite-element method, Stress relaxation