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Non-Destructive Inspection Tool to Measure Sustained Stresses in Metallic Components to Assess Environmentally Assisted Cracking Susceptibility
Navy SBIR 2010.2 - Topic N102-136 NAVAIR - Mrs. Janet McGovern - [email protected] Opens: May 19, 2010 - Closes: June 23, 2010 N102-136 TITLE: Non-Destructive Inspection Tool to Measure Sustained Stresses in Metallic Components to Assess Environmentally Assisted Cracking Susceptibility TECHNOLOGY AREAS: Air Platform, Materials/Processes ACQUISITION PROGRAM: PMA-261; H-53 Heavy Lift Helicopter Program RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted." The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected. OBJECTIVE: Develop and demonstrate a nondestructive depot level inspection tool capable of quantitatively measuring the magnitude and state of a sustained stress present in the primary aircraft structure. DESCRIPTION: It is widely recognized that a sustained stress can significantly inhibit or accelerate environmentally assisted cracking (Hydrogen embrittlement and stress corrosion cracking) depending on the state and magnitude of the stress. There are various origins of this stress including: clamping forces from fasteners, fit-up and alignment forces, thermal gradients, service history, plastic deformation, and thermo-mechanical processing of the material. While the presence of a sustained stress is sometimes known, quantitative knowledge of the stress state and magnitude is not. The lack of a quantitative characterization technique to assess the stress state/magnitude prohibits informed decision making with regards to the susceptibility of the aircraft structure to premature failure resulting from environmentally assisted cracking. This lack of knowledge has resulted in the reactive stance of high frequency inspections based on flight hours to detect subcritical cracks after they have formed rather than a proactive stance of identifying areas of the aircraft structure with unfavorable stress states/magnitudes and taking the appropriate steps to ensure crack initiation does not occur in service. There is currently a need for a nondestructive inspection tool that can be used at the Fleet Readiness Centers (FRCs) to determine the state and magnitude of a sustained stress in a metallic airframe component. In addition to providing highly reliable/accurate data, the tool must also be practical for operation in a functional depot environment. Historically, portable X-Ray diffraction devices and technologies based on magneto-elasticity have proven unreliable and only semi-quantitative. A successful tool would be durable, adaptable to components of various size/shape, have an easy to use operator interface, non-labor intensive, and easily integrated into a process flow with minimal disruption. Near-term benefits of this tool would be the establishment of a currently nonexistent diagnostics capability, which will yield improved flight safety and a reduction in inspection cycles for aircraft during fleet operations. The long-term benefit of this tool would be the ability to detect the susceptibility to environmentally assisted cracking for structural components. PHASE I: Develop a nondestructive inspection tool concept capable of quantitatively measuring the state/magnitude of a sustained stress in a structural airframe component. Demonstrate the feasibility of the proposed tool/system by providing diagnostics to determine the potential for crack initiation resulting from Hydrogen Embrittlement. PHASE II: Develop and demonstrate a prototype of the tool/system that can be effectively implemented into an environment equivalent that of a FRC without significantly disrupting the work flow or degrading the reliability of the data. Verify and demonstrate successful function of all requirements. PHASE III: Transition the tool/system to platforms that experience environmentally assisted cracking. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Areas that would benefit from this newly developed tool/system include civil aviation, petroleum/chemical industry, nuclear industry, mining operations, heavy equipment manufactures, and industrial overhaul/repair centers. REFERENCES: 2. Committee on Aging of U.S. Air Force Aircraft, Commission on Engineering and Technical Systems, National Research Council (1997). Aging of U.S. Air Force Aircraft: Final Report. Washington D.C., The National Academies Press. 3. Gangloff, R. P. (2005). Critical Issues in Hydrogen Assisted Cracking of Structural KEYWORDS: residual; stress; inspection; environmental; hydrogen; fatigue
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