TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: H-1, H-53, H-60

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop a reliable predictive capability for the evaluation of flaw tolerance in expected life of metal and composite airframe components, given part specifications, material properties, initial flaws, such as voids, inclusions, heterogeneous grain structure and design load spectra.

DESCRIPTION: During the early 70’s the Air Force moved to adopt the concept of damage tolerance based on the concepts and methods of linear elastic fracture mechanics (LEFM) for airframe design and fleet management. While this methodology has not been adopted by other services, methods based on fracture mechanics are routinely used as secondary design criteria and fleet management in the case of aged aircraft where cracks are known to be present. The disadvantage of damage tolerance methods based on LEFM is that unrealistic assumptions regarding initial cracks have to be made. Methodology for life prediction that relies on realistic representations of the nature and distribution of initial flaws in as manufactured airframe components would be of great benefit. Recent developments in numerical simulation technology, that support verification and validation procedures and multi-scale modeling, provide the necessary means for evaluating alternative failure initiation models capable of accounting for initial flaws. Over the last four years NAVAIR has been engaged in a program to develop analytical tools to characterize the corrosion fatigue process. This program has made substantial progress and has developed a number of features that would be required to support a flaw tolerance analytical tool. The goal is to extend the results of the corrosion fatigue program and develop an analytical tool that can be incorporated in a stress analysis program which has the capability to verify the accuracy of the numerical solution and the quality of the mathematical model.

PHASE I: Determine the feasibility of developing an algorithmic structure designed to meet the objectives enumerated above and development of an implementation plan. Existing software tools and processes will be utilized to the maximum extent possible. The implementation plan will include a detailed justification of the choice of software tools and the technical requirements for modifications and enhancements.

PHASE II: Design, develop, implement and test the algorithms developed. A parametric family of models that address the specific technological features of airframe components in detail and include crack nucleation analysis may be implemented. The implementation should include provisions for the integration with Product Lifecycle Management (PLM) systems employed by aerospace OEMS. At least three model problems that demonstrate the key features of the implementation will be solved and documented.

PHASE III: Transition the technology to the Program Offices and the airframe manufacturers.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The private-sector market for the software tool developed under this project will be the commercial divisions of aerospace OEMs and their suppliers. Substantial market opportunities exist in the automotive and shipbuilding sectors as well.

REFERENCES:
1. ASME V&V 10-2006. Guide for Verification and Validation in Computational Solid Mechanics. An American National Standard. The American Society of Mechanical Engineers, 2006.

2. P. J. Roach. Verification and Validation in Computational Science and Engineering. Hermosa Publishing, Albuquerque, 1998.

3. C. R. Cook and J. C. Glaser. Military Airframe Acquisition Costs: The Effects of Lean Manufacturing. Rand Report MR-1325-AF 2001 (ISBN: 0-8330-3023-X).

4. R. Martin and D. Evans, Reducing Costs in Aircraft: The Metals Affordability Initiative Consortium, JOM, 52 (3) (2000), pp. 24-28.

KEYWORDS: Certification; Flaw Tolerance; Corrosion; Fatigue; Analysis; Lifecycle Management.

** TOPIC AUTHOR (TPOC) **

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