S45C/Si_3N_4/S45C接合体の引張破断応力に及ぼす残留応力の影響  [in Japanese] The Influence of Residual Stress on Tensile Fracture Stress in S45C/Si_3N_4/S45C Bonded Joints  [in Japanese]

Tensile tests of S45C/Si_3N_4/S45C bar-type specimens, which were bonded in 1987 and 1988 by the metalizing method, were carried out t room temperature in laboratory air. Then, bonding-induced tensile residual stress was mesured at the surface of Si_3N_4, near the boundary by means of the X-ray diffraction method. Generally, the crack initiated at the boundary between S45C and Si_3N_4, and then propagated into Si_3N_4. In this case, the fracture stress decreased with increasing diameter of the specimen, but the tensile residual stress increased (with increasing diameter of the specimen). In spite of the same diameter, the fracture stress of the specimen bonded in 1988 was lower than that bonded in 1987 and the tensile residual stress was larger. A good correlation was recognized between the fracture stress and the bonded-induced tensile residual stress. Consequently, it is concluded bonding-induced tensile residual stress is one of the important factors for fracture stress in ceramic/metal joints.