Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 27, 2023 - September 29, 2023
The effect of tension hold on high temperature fatigue crack propagation in Inconel 718 was investigated. Fatigue crack propagation tests were conducted at 650 °C in air, and single tension hold at maximum load was applied during cyclic loading with various conditions of stress intensity factor K and hold time. When the K value at the tension hold was high, fatigue crack acceleration occurred after the tension hold. When the K value was low, fatigue crack retardation occurred after the tension hold. Based on results of fracture surface analyses using scanning electron microscopy and energy dispersive X-ray spectroscopy, the acceleration was attributed to grain boundary embrittlement due to oxygen diffusion from the crack tip. On the other hand, the retardation was attributed to stress relaxation induced by creep deformation. The transition from the retardation to the acceleration depending on the K value was discussed based on a size comparison between the stress relaxation field calculated by finite element analysis and the grain boundary embrittlement area around of the crack tip.
