Original paper(Vol.47 No.12 pp.1221)
Properties of fracture strength and reliability estimation in ceramics/metal joints
Takahashi Manabu; Okabe Nagatoshi; Kobayashi Hideo
Abstract:Room and high temperature four point bend tests for Si3N 4/SUS304 joints were carried out at constant loading. Fracture surfaces of the interlayer of joints were observed using SEM to discuss the fracture mechanism at high temperature. Furthermore, the fracture strength distribution was estimated based on the unified estimation method considering the fracture mechanism.
(1)Failure of brazed Si3N 4/metal joints in high stress level occurred at a flaw in ceramics near bonding interface. On the other hand, failure of the interlayer in low stress level occurred due to creep rupture. Creep rupture of joint was dominated on steady-sate creep of the linearity. Then creep rupture life also could be predicted from minimum creep strain rate in interlayer using both equation of Monkman-Grant and Norton's law.
(2)The fracture strength of the joints could be evaluated considering the temperature of strength as follows; (equation is omitted)
Reliability structural design of joints had better determine the stress level and proof life considering failure of the interlayer with small scatter of rupture lives.
Key Words:ceramics/metal joint, creep rupture, minimum creep strain, activation energy, unified estimation method, reliability estimation