Full-Range Fatigue Life Prediction of Metallic Materials Using Tanaka-Mura-Wu Model

In this research, the recently developed Tanaka-Mura-Wu (TMW) model is applied to common engineering materials including Ni-base superalloys Haynes 282 and Inconel 617, aluminum alloys 7075-T6 and 2024-T3, alloy steels SAE 4340 and SAE 1020, and titanium alloy Ti-6Al-4V, as well as a high-entropy alloy (HEA) CoCrFeMnNi over the full fatigue range comprised of low-cycle fatigue (LCF) and high-cycle fatigue (HCF). Through the analysis, it is shown that the TMW model is able to provide class A prediction for LCF (forecast before the event occurs) without resorting to fatigue testing; and with calibration at one stress level, it can be extended to the HCF regime. A relationship of fatigue life versus the total strain is established with the use of the Ramberg-Osgood equation. The TMW model predictions agree well with the experimental data and/or the Coffin-Manson-Basquin relation for the above materials. The TMW model describes the full-range fatigue life in terms of material’s elastic modulus, Poisson’s ratio, surface energy, and the Burgers vector. Thus it establishes a physics-based baseline for characterizing the effects of other contributing factors such as microstructure and surface roughness, which contribute to the uncertainty in the fatigue scatter.