応力勾配を考慮した応力集中部の疲労寿命評価

抄録

In general, a fatigue life is assessed on SN curves obtained from small-sized smooth specimens. However, it is known that a fatigue life prediction at a stress concentration region based on a peak stress is always too conservative due to the stress gradient. To eliminate the conservatism and rationalize a fatigue design, the authors applied the stress-gradient approach proposed by Siebel to a Nickel based superalloy. Fatigue tests of notched and smooth round bar specimens of Nickel based superalloy were performed at 550℃. The relation between the stress gradient and the fatigue reduction rate was determined from the round bar fatigue tests. In addition, plate specimens with a fillet were subjected to fatigue tests to verify the stress-gradient approach. The predicted life well agreed with the experimental fatigue life.