Static fatigue strength of sintered silicon nitride disks with shoulder fillet at 1000 degree
Baba Hidenari; Suzuki Akihiko; Hayashi Seijiro
Abstract:Static fatigue strength of sintered silicon nitride in multi axial stress field is studied using shoulder fillet disks at 1000 degree. Strength under step up loading is also studied using specimens that survived static fatigue test over 106 seconds. In case of static fatigue test, the strength can be evaluated by slow crack growth (SCG) theory. Under step up loading, the strength increases with total exposing time at high temperature. Fracture origin observation reveals that the percentage of fracture originated from surface defects decreases from 55% to 10%. These results imply that increase in strength under step up loading is associated with the crack healing in surface defects. Key Words:static fatigue strength, shoulder fillet disks, multi-axial stress, step up loading, crack heating, fracture origin, silicon nitride