A continuum surface layer effect in polycrystalline aggregates

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dc.contributor.authorLaurent, Michel P.en
dc.contributor.departmentEngineering Mechanicsen
dc.date.accessioned2014-03-14T21:37:05Zen
dc.date.adate2009-06-08en
dc.date.available2014-03-14T21:37:05Zen
dc.date.issued1994-08-05en
dc.date.rdate2009-06-08en
dc.date.sdate2009-06-08en
dc.description.abstractUniaxial tension tests on uniform cross section specimens of Ti-6Al-4V and aluminum 7475-T651 show that the stress in the direction of load application determined by x-ray diffraction and the nominal applied stress display the expected linear correspondence up to a maximum stress somewhat below the bulk yield paint. Above this stress, the xray stress is noticeably less than expected. Upon unloading, there is a substantial acquired compressive residual stress. Because the x-ray diffraction measurements provided average stress values in a surface layer of only a few grain diameters, these results suggest that the surface layer of the metal is yielding at a lower stress than the bulk. This anomalous behavior is duplicated qualitatively with a continuum model of an aggregate of soft and hard square grains obeying the Von Mises yield criterion. The effect is purely mechanical. No material effects, such as lower yield point or dislocation density for the surface grains, are invoked. The continuum effect decreases rapidly with depth, becoming negligible for depths exceeding 2-3 grain or domain diameters. Further work is required to refine the model for real systems and to assess the importance of material effects acting in conjunction with the continuum effect.en
dc.description.degreeMaster of Scienceen
dc.format.extentxxvii, 361 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-06082009-170819en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06082009-170819/en
dc.identifier.urihttp://hdl.handle.net/10919/42890en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1994.L387.pdfen
dc.relation.isformatofOCLC# 32290166en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1994.L387en
dc.subject.lcshAluminum alloysen
dc.subject.lcshStrains and stressesen
dc.subject.lcshTitanium-aluminum-vanadium alloysen
dc.titleA continuum surface layer effect in polycrystalline aggregatesen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineEngineering Mechanicsen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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