N121-019 TITLE: In-Situ Crack Characterization

TECHNOLOGY AREAS: Air Platform, Ground/Sea Vehicles, Materials/Processes

ACQUISITION PROGRAM: PMA 265

OBJECTIVE: Develop a method and associated instruments for on-aircraft, on the ground failure analysis of cracks found in metallic aircraft structure.

DESCRIPTION: In traditional Engineering Investigations, cracks are cut out of the part and opened up so that failure analysts can look at the crack faces and determine whether the crack propagated as a result of cyclic (fatigue) loading or a one-time (static) overload. This determination is nearly essential to finding the source of the load, and thus the cause of the cracking. However, in many situations where cracks are detected in aircraft structure, the most desirable in-service structural repair does not allow for excising the crack for traditional failure analysis. In these cases, engineers are not able to determine the cause of the cracking which inhibits development of corrective actions to prevent similar cracks in the rest of the fleet.

The initial goal is to have the ability to determine if the crack propagated by fatigue or static loading. Beyond that, identification of crack initiation site, and the presence of corrosion products would be desirable

PHASE I: Conceptualize, design and determine the feasibility of an innovative method for on-aircraft, on the ground failure analysis of cracks found in aluminum, steel, and/or titanium materials commonly used in aircraft structures.

PHASE II: Mature, verify and demonstrate the method developed in Phase I using lab-generated cracks in test coupons and/or cracks of known origins in real flight hardware.

PHASE III: Finalize the process and instrumentation for transition to aircraft in limited access areas.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: All industries maintaining metallic structures could use this technology, e.g. airliners, heavy equipment, bridges, buildings, ships.

REFERENCES:
1. Brooks, C. & Choudhury, A. (2001). Failure Analysis of Engineering Materials. McGraw-Hill Professional.

2. Hull, D. (1999). Fractography: Observing, Measuring and Interpreting Fracture Surface Topography Cambridge University Press.

KEYWORDS: crack; load; failure; structure; Fatigue; Material

** TOPIC AUTHOR (TPOC) **

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