Prediction of Fatigue Lives of MAR‐M247 LC Based on the Crack Closure Concept

Abstract

Low cycle fatigue (LCF), high cycle fatigue (HCF), and combined LCF and HCF tests are carried out on MAR‐M247 LC at 650 °C in air environment. Under combined LCF and HCF loading, block striations form on the fracture surface which are used to complete an effective crack growth curve by using the linear summation model. Crack growth lives starting from equivalent initial flaw sizes are calculated by the crack closure code FASTRAN and compared with experimental fatigue lives. Under HCF loading, predicted and experimental fatigue lives agree well for lifetimes above 105 cycles. Lower lifetimes are overestimated indicating that the linear summation model is not valid for MAR‐M247 LC in this loading range. Interactions between the non‐crystallographic HCF crack growth and striated crack growth that is caused by the LCF loading are probably responsible for this behavior.

Influence of phase angle on lifetime, cyclic deformation and damage behavior of Mar-M247 LC under thermo-mechanical fatigue

“…Subsequently it was solution annealed (1185715°C, 2-4 h) and aged (875°C, 4 h 710 min). The secondary dendrite arm spacing is about 32 mm [15]. From the bars, solid round specimens with a cylindrical gauge length of 17 mm and a gauge length diameter of 7 mm were machined.…”