Digital Repository, ECF14, Cracow 2002

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Implementation of Damage Tolerance in High Cycle Fatigue Systems

Last modified: 2013-02-10


Damage tolerance is positioned to replace safe-life methodologies fordesigning aerospace structures. The argument for implementing a fracture mechanicsbased damage tolerance approach is established in the fundamental fact that aerospacestructures typically fail from cracks. Therefore, if the scientific means for predictingfatigue crack growth in a structure is feasible, this approach should deliver the mostaccurate representation of component life. Implementing damage tolerance (DT) into highcycle fatigue (HCF) components will require a shift from traditional DT methods that relyon an initial nondestructive inspection (NDI) flaw. The accumulation of cycles in a HCFcomponent will produce a classic DT design that is either unmanageable because offrequent inspectio, or unrealistic because the design will be too heavy to operate for areasonable life. Furthermore, once a crack in an HCF component begins propagating, thepredicted time to failure is sometimes less than one flight hour, which does not leave ampletime for NDI. Therefore, designing an HCF component will require basing the lifinganalysis on an initial flaw that is “undetectable” by NDI. In this paper the author willformulate a methodolgy for implementing damage tolerant design in a high cycle fatiguesystem.

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