Innovative Unified Damage Mechanisms-Based Model to Predict Remaining Useful Life for Rotorcraft Structures Navy STTR FY2014.A Sol No.: Navy STTR FY2014.A Topic No.: N14A-T002 Topic Title: Innovative Unified Damage Mechanisms-Based Model to Predict Remaining Useful Life for Rotorcraft Structures Proposal No.: N14A-002-0186 Firm: Technical Data Analysis, Inc. 3190 Fairview Park Drive Suite 650 Falls Church, Virginia 22042 Contact: Mehdi Amiri Phone: (703) 226-4079 Web Site: www.tda-i.com Abstract: Most of current available methods for prediction of fatigue failure -such as cumulative damage models, cyclic plastic energy hypothesis, crack propagation rate models, and empirically-derived relationships -are based on empirical relations and their application requires many unknown parameters that must be experimentally determined or calibrated for specific locations/critical areas. Also, the aforementioned methods concentrate on specific types of loading and single fatigue modes, i.e., bending, or torsion, or tension-compression. In practice, however, fatigue involves simultaneous interaction of multimode processes. Further, their use and execution requires consideration of large factors of safety, often leading to gross over designs that waste resources and cost more fleet maintenance. In this STTR effort, we therefore focus on applying fundamentals of physics and mechanical principles to predict fatigue damage and remaining useful life (RUL) of metals under a variety of loading and environmental conditions. The proposed RUL approach is mechanism-based with little or no reliance on phenomenological parameters. First we develop physics basis for fatigue damage initiation and accumulation via irreversible thermodynamic framework by a detailed study of damage accumulation at the micro-meso-macro scales with and without environmental elements, then use this basic modeling information for prediction of RUL via measured changes in the field. Benefits: The end product of this research effort will be a set of computational and analytical tools in a framework that assess fatigue damage and predict remaining useful life under a variety of loading and environmental conditions. This framework will help both materials scientists and mechanical engineers to better select materials; improve existing materials and manufacturing processes to design against fatigue, especially under cyclic varying mechanical loading situations. TDA plans to mature this framework into a nondestructive evaluation (NDE) toolkit that enables calculation of material performance degradation due to fatigue using different test signals in one integrated package. The immediate benefit of the NDE tool is to reduce total ownership cost by refining serviceably criteria, rework and overhaul limits, maintenance schedule while assuring safety of aircrafts. The customizable NDE tool as envisioned in this effort could be used in many industries such as aerospace, automotive or machinery to significantly improve the reliability of various systems. Return