Measurement of fatigue-induced surface plasticity

A method is presented for measuring at a surface the localized plastic strains induced by fatigue within individual grains. The technique uses mica flakes distributed on a sample surface as reference gauges, relative to which strains in the surface can accurately be determined. An application of the...

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Bibliographic Details
Published in:Journal of materials science 1982-05, Vol.17 (5), p.1413-1419
Main Authors: MORRIS, W.L, INMAN, R.V, JAMES, M.R
Format: Article
Language:English
Subjects:
aluminum
Applied sciences
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Elasticity. Plasticity
Exact sciences and technology
Fatigue
granular materials
Materials science
Mechanical and acoustical properties of condensed matter
Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology
Metals, semimetals and alloys
Metals. Metallurgy
Physics
plasticity
Specific materials
strain
surface properties
tensile strength
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Summary:A method is presented for measuring at a surface the localized plastic strains induced by fatigue within individual grains. The technique uses mica flakes distributed on a sample surface as reference gauges, relative to which strains in the surface can accurately be determined. An application of the method to the study of fatigue induced microplasticity in an Al 2219-T851 alloy is discussed. On an unfatigued specimen, subjected to applied stresses less than the yield strength, deformation is elastic over gauge lengths comparable with the grain size. After fully-reversed cyclic loading at a peak tensile stress of 75% of the yield strength for 20 x 10 super(3) cycles, the larger grains in the alloy exhibit a residual tensile strain after a tensile loading cycle. Neighboring smaller grains are driven into elastic compression to accommodate this tensile plastic deformation. Peak localized tensile plastic strains may exceed 0.5% at the surface. This technique will be useful in evaluating models of fatigue crack initiation and surface damage accumulation.
ISSN:0022-2461
1573-4803
DOI:10.1007/BF00752254