常圧焼結Si_3N_4の繰返し荷重下におけるき裂進展特性(<特集>疲労特集)

概要

論文の詳細を見る
In order to make it clear whether the cycle-dependent crack propagation would occur in ceramic marteials under a cyclic load, the crack propagation rate was measured using compact tension specimens made of sintered Si_3N_4 at room temperature under ambient condition. In this study, the crack propagation rate da/dt, which ranged from 10^<-10>m/sec to 5x10^<-4>m/sec, was measured under static loads and cyclic loads in the form of square weve. In the case of cyclic loads, the hold time at the maximum and minimum loads was equal. The crack propagation rate da/dt was equal to 2fxda/dN, where da/dN is given in m/cycle and f, in Hz. Crack propagation tests were carried out at 1.1 Hz and at various stress ratio R=1, 0.4, 0.2, 0.1, R being the ratio of the minimum load to the maximum load. The results showed that, as R decreased, da/dt increased consistently and K_<Imax> at da/dt=2x10^<-10>m/sec decreased. In other words, as the load amplitude became large, the effect of cycling of the load became more damaging. Further tests were carried out at constant R(0.1) and at three levels of f, f=0.01Hz, 0.1Hz, 1.1Hz. As f increased, da/dt increased. Even under the condition of f=0.01Hz, crack propagation was accelerated by cycling of the load, as compared with da/dt under a static load. The f-da/dt diagram was constructed from the above data in order to distinguish the cycle-dependent crack propagation from the time-dependent crack propagation. In the range where K<Imax> was small (<3.57MPa√<m>), only the cycle-dependent crack propagation occurred. It is important to recognize that 3.57MPa√<m> is smaller than the threshold K<Imax> under a static load. When K<Imax> became larger than 3.57MPa√<m>, the time-dependent crack propagation appeared. In this region, both of the cycle-dependent crack propagation and time-dependent crack propagation existed. In the range where K<Imax> was large (>4.34MPa√<m>), the time-dependent crack propagation was predominant.
社団法人日本材料学会の論文
1987-10-15

常圧焼結Si_3N_4の繰返し荷重下におけるき裂進展特性(<特集>疲労特集)

スポンサーリンク

概要

著者

関連論文

スポンサーリンク