Innovative Capability to Quantify Fatigue Damage and Assessment of Endurance Limit in Spectrum Load Histories

Analysis methods are not available to predict the life of structures exposed to spectral loads containing large cycles of low amplitude loads. The challenge is developing a computational technique to predict damage accumulation in the ultra high cycle fatigue (UHCF) regime and then integrate that into a spectral loading capability. By its very nature, all UHCF damage growth rates are small at 10E-10 m/cycle. This damage is on a size scale such that the local material microstructural features and the random nature of the size, strength and location of these features causes large scatter in the damage accumulation rates. The objective of Phase I is to demonstrate the feasibility of applying a probabilistic micromechanics approach to UHCF durability prediction. VEXTEC will extend its current HCF predictive capabilities into the UHCF regime. The approach will evaluate common aerospace materials: aluminum, titanium, and steel. The program will evaluate each material system in terms of the UHCF failure modes and mechanisms and apply that knowledge into a micromechanics based spectral fatigue durability simulation. VEXTEC will build on its vast experience in the field of damage micro-mechanics and reliability to develop a demonstrator Fatigue Simulator Tool.