Abstract
An actual joint structure of ceramics-metal in the airtight seal parts for a neutron detector was studied on the residual stress generated in the joint process due to the difference of the thermal expansion coefficient between ceramics and metal. The influences of shape and dimension of the joint structure on the residual stress were clarified analytically by finite element method (FEM) and verified experimentally by checking cracks generated in prototype samples. Based on fracture mechanics, equivalent stress intensity factor KIeq was calculated in consideration of a latent flaw in the residual stress fields, and optimal geometries of the joint structure were proposed for reducing the residual stress. The residual joint strength was discussed by using the difference ΔKIeq between fracture toughness KIC and KIeq. The main results obtained are summarized as follows : the residual joint stress increases with the thickness of a Cu-Ti eutectic reaction layer; the residual joint stress decreases with the reduction in taper angle of the end of Cu interlayer; the residual joint stress is hardly influenced by wall thickness in the end of SUS304 pipe. On the basis of these results, the optimization in the structural factors can decrease the residual stress because of reducing stress concentration field near the interface of ceramic and metal, and so the residual joint strength increase with decreasing of the residual stress depending in the structural factors as the thickness of a Cu-Ti eutectic reaction layer, taper angle of the end of Cu interlayer and wall thickness in the end of SUS304 pipe.
