NDLI: Nondestructive evaluation of metal fatigue using nonlinear acoustics

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Nondestructive evaluation of metal fatigue using nonlinear acoustics

Content Provider	NASA Technical Reports Server (NTRS)
Author	Cantrell Jr., John H.
Copyright Year	2008
Description	Safe-life and damage-tolerant design philosophies of high performance structures have driven the development of various methods to evaluate nondestructively the accumulation of damage in such structures resulting from cyclic loading. Although many techniques have proven useful, none has been able to provide an unambiguous, quantitative assessment of damage accumulation at each stage of fatigue from the virgin state to fracture. A method based on nonlinear acoustics is shown to provide such a means to assess the state of metal fatigue. The salient features of an analytical model are presented of the microelastic-plastic nonlinearities resulting from the interaction of an acoustic wave with fatigue-generated dislocation substructures and cracks that predictably evolve during the metal fatigue process. The interaction is quantified by the material (acoustic) nonlinearity parameter extracted from acoustic harmonic generation measurements. The parameters typically increase monotonically by several hundred percent over the fatigue life of the metal, thus providing a unique measure of the state of fatigue. Application of the model to aluminum alloy 2024-T4, 410Cb stainless steel, and IN100 nickel-base superalloy specimens fatigued using different loading conditions yields good agreement between theory and experiment. Application of the model and measurement technique to the on-site inspection of steam turbine blades is discussed.
File Size	3589954
Page Count	15
File Format	PDF
Alternate Webpage(s)	http://archive.org/details/NASA_NTRS_Archive_20100032049
Archival Resource Key	ark:/13960/t8bg7nt1p
Language	English
Publisher Date	2008-07-20
Access Restriction	Open
Subject Keyword	Solid-state Physics Micromechanics Metal Fatigue Harmonic Generations Nondestructive Tests Sound Waves Turbine Blades Acoustic Properties Dislocations Materials Nonlinearity Aluminum Alloys Steam Turbines Crack Propagation Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science
Content Type	Text
Resource Type	Article

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