3012 構造用木質パネルの面内せん断疲労に及ぼす二段二重変動荷重の影響(S40-3 生分解ポリマー,木質材料の強度評価,S40 バイオマス由来材料の成形加工と特性評価)

抄録

Two-stage fatigue test of structural plywood under panel shear load was conducted. Pulsating load with a triangular waveform and a loading frequency of 0.5Hz was applied along the length of specimens. Minimum stress applied was zero, and maximum stress was once changed during the fatigue test. Four patterns for changing the maximum stress were determined in High-Low and Low-High sequence, respectively. Stress-strain relationships were measured throughout the fatigue test. Fatigue life of plywood specimen obtained in two-stage fatigue did not follow the Palmgren-Miner rule. On the analyses of strain energy, the change of applied maximum stress induced the corresponding change of strain energy in a loading cycle. Relationships between cumulative strain energy at failure and fatigue life in both High-Low and Low-High sequences were almost equivalent to that obtained under constant fatigue loading. These results indicate that the plywood specimen fractures irrespective of loading history when its cumulative strain energy reaches the failure criterion obtained under constant fatigue loading.