A holistic approach to Thermo-Mechanical Fatigue phase angle effects for an aerospace nickel superalloy

Abstract Thermo-Mechanical Fatigue (TMF) is one of the most complex mechanical phenomena that couples creep, fatigue and oxidation. So far, developing simple empirical relationships like those that exist in isothermal equivalents have proven elusive. This work presents a study on the TMF behaviour of the aerospace nickel based superalloy RR1000 using TMF fatigue crack growth rates, strain controlled TMF results, studies of the fracture morphologies and empirical lifing models. This paper takes a holistic approach to TMF lifing, specifically focusing on the impact of phase angle. As a result, this work develops an elastic modulus normalisation technique that when a Coffin-Manson type relationship is applied, predicts life of material under interim TMF phase angles.