Innovative Capability to Quantify Fatigue Damage and Assessment of Endurance Limit in Spectrum Load Histories Navy SBIR FY2010.2 Sol No.: Navy SBIR FY2010.2 Topic No.: N102-113 Topic Title: Innovative Capability to Quantify Fatigue Damage and Assessment of Endurance Limit in Spectrum Load Histories Proposal No.: N102-113-0638 Firm: VEXTEC Corporation 750 Old Hickory Blvd Bldg. 2, Suite 270 Brentwood, Tennessee 37027 Contact: Richard Holmes Phone: (615) 372-0299 Web Site: www.vextec.com Abstract: 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. Benefits: Innovative methods are needed to quantify fatigue damage and assess the endurance limit are needed in order to extend the life of the CH-53 fleet. On average, every hour a CH-53E flies costs the Marine Corps approximately $20,000 and requires 44.1 maintenance man-hours. A Service Life Assessment Program conducted on the CH-53E determined that the current fleet will start reaching this fatigue life limit in FY11 at a rate of up to 15 aircraft per year. Return