Proposal on the Method of Fixing Proof Strength for Ceramic Components

The method of determining proof strength of ceramic components based on the fracture behavior is proposed. Our experimental results about the fracture behavior of ceramics show that the strength for short time fracture, static fatigue and cyclic fatigue mainly depend on the sizes of initial defects detected in the ceramics. Fracture strength for short time fracture has a nonlinear relation to defect size, and the critical stress intensity factor for a small crack is lower than that for a large crack. Under the condition of a constant load is applied, there exists a static-fatigue limit below which cracks are arrested. The static-fatigue limit also shows a nonlinear relationship to defect size similar to that for short time fracture. Moreover, cyclic fatigue life seems to be equivalent to the life of static-fatigue with certain modification. By considering these dependence of the strength of ceramics for defects, the method of giving proof strength of ceramic components is shown. The method proposed in this paper is very effective because the allowable design stress and safety factor in ceramic structural design can be fixed determinately.