Total Fatigue Life Assessment of Complicated Structures Navy STTR FY2012.A Sol No.: Navy STTR FY2012.A Topic No.: N12A-T006 Topic Title: Total Fatigue Life Assessment of Complicated Structures Proposal No.: N12A-006-0040 Firm: Technical Data Analysis, Inc. 3190 Fairview Park Drive Suite 650 Falls Church, Virginia 22042 Contact: Subhasis Sarkar Phone: (703) 237-1300 Web Site: www.tda-i.com Abstract: SIF and non-SIF based approaches are used to study the damage/crack growth involving complex crack shapes under complicated loading conditions. In the SIF based approach, we use alternating, non-hypersingular Symmetric Galerkin Boundary Element Method (SGBEM)-Finite Element Method (FEM) formulation to study both 3D and 2D crack growth situations. This technique enables study of surface or embedded 3D cracks growing in non-coplanar mode, 2D through crack growing in non-collinear way, and transitioning of 3D into 2D cracks. A large number of benchmark problems will be solved to validate the methodology and case studies will be conducted to demonstrate proposed method's superiority. In the non-SIF based approach, we explore the use of Peridynamics to study fracture processes and application to fatigue problems. Peridynamics is a non-local approach , where material particles exert influence within a neighborhood distance as opposed to the classical local approach. The most important part in Peridynamics is in the formulation of constitutive laws to express the bond forces between material points. Owing to its formulation expressed in integral forms, it is well suited to discontinuities such as cracks. In this study, we explore linking continuum damage mechanics models with Peridynamics for applications involving HCF and composites. Benefits: The software implementation of the alternating SGBEM-FEM will lead to a well validated, state-of-the-art, accurate and computationally efficient crack growth analysis tool which is anticipated to be used widely in aerospace industry and academia. It will replace many of the current cumbersome techniques employed to analyze the growing crack problem and estimation of fatigue life. The field of Peridynamics is an exciting and new field with a great potential to study discontinuities in structures such as cracks or cavities and the present study will explore many of the possibilities in this new research area to answer some of the most fundamental questions in fatigue research such as crack initiation, crack growth, short crack problem, retardation and acceleration effects in variable amplitude loading, damage evolution, etc. Return