Extension of an energy-based life prediction method to low and combined cycle fatigue regimes:

TLDR: In this paper, an energy-based fatigue life prediction method was developed to accurately predict lifetimes of coupon specimens in excess of 105 cycles, based on empirically determined room temperature high-cycle fatigue data for both Al 6061-T6 and Ti-6Al-4V in uniaxial, bending, and shear at various stress ratios (R).

Abstract: An energy-based fatigue life prediction method has been developed to accurately predict lifetimes of coupon specimens in excess of 105 cycles. The method has been shown to agree with empirically determined room temperature high-cycle fatigue data for both Al 6061-T6 and Ti-6Al-4V in uniaxial, bending, and shear at various stress ratios (R). As with any life prediction method, using a testing scheme to accurately predict fatigue performance from a reduced data set greatly reduces test time and material costs. For gas turbine engine components, this can account for a large portion of development costs, making the use of reduced order models very attractive. The stress state of these components can be difficult to characterize and simulate, as they are subjected to both low-cycle fatigue and high-cycle fatigue from both mechanical and vibrational loading. Mechanical loading is generally within the low-cycle fatigue regime and attributed to throttle excursions of various flight maneuvers or engine start-up/sh...