変動荷重下での内部応力・有効応力の過渡挙動と疲労損傷の評価

抄録

The purpose of this study was to estimate the influence of amplitude fluctuation on fatigue damage. For this purpose, a new method to measure internal and effective stresses only from the stress-strain hysteresis data was developed. By using this method, the transient behaviours of total strain, plastic strain width and effective stress were observed during two-step stress cycling tests.
Using a new cumulative damage criterion named ES-Miner's rule, fatigue damages under multiple repeated stresses in two levels were calculated and compared with those obtained by Miner's rule. The fatigue damage caused by stress amplitude fluctuations was evaluated on the viewpoint of internal stress and effective stress.
The results obtained are as follows:
1. The influences of stress amplitude fluctuation on plastic strain width and effective stress leasted up to 1000 cycles.
2. The stress amplitude fluctuation, regardless of its direction, gave a transient damage greater than that under a constant stress amplitude.