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-006-0271 Firm: Global Engineering and Materials, Inc. 1 Airport Place, Suite 1 Princeton, New Jersey 08540 Contact: Jim Lua Phone: (860) 398-5620 Web Site: www.GEM-Innovation.com Abstract: Global Engineering and Materials, Inc. (GEM) along with its team members Northwestern University, Lockheed Martin, and Boeing Company, propose to develop an automatic software tool for 2D/3D fatigue crack growth prognosis of complicated structures under multi-axial loading. The XFAT toolkit will be developed by integrating a unified crack initiation and propagation model with an enhanced mesh independent extended finite element toolkit (XFA) for ABAQUS. A direct mesh independent crack path tracking will be used for a 2D crack while a fast and robust level set characterization and update will be implemented for an arbitrary 3D crack and its growth. To accurately determine the mixed mode fracture parameters, an interaction integral will be implemented for the direct computation of mixed-mode stress intensity factors. A unified crack initiation and propagation solution module will be developed for the total fatigue life assessment. The proposed technique permits crack initiation or arbitrary insertion of initial cracks, independent of a base 3D model, and allows non-self-similar crack growth pattern without conforming to the existing mesh or local remeshing. Verification and validation of both 2D/3D fatigue crack growth modules for Abaqus will be performed using test data collected from LM/Boeing and from GEM�_s existing Navy sponsored programs. Benefits: The results from this research will have significant benefits and commercial application in the NAVAIR, DoD labs, and aerospace industries. Our team members Lockheed Martin and Boeing have already indicated interest in applying the toolkit to perform the damage tolerance and durability assessment of metallic aircraft structure components and plan cost-effective maintenance of their existing structures. Once developed, the prediction toolkit for Abaqus can be used effectively and efficiently to assist a designer and rule-maker to answer the following questions: 1) Does a proposed design have an acceptable risk of fatigue failure? 2) How tolerant is a proposed design of a crack without the risk of catastrophic failure? 3) If a crack is found in service, how long is it safe to leave the crack before repair? 4) If the vessel�_s mission and operational profile have changed, what are the implications for fatigue risk? 5) How often should the vessel be inspected for fatigue cracks? and 6) How can measured loads from a structural health monitoring system be used to update the fatigue risks? Teaming with LM Aero and Boeing will considerably shorten our development cycle from developing a prototype tool to commercially available design software. Return