MULTI-SCALE DUAL-PHASE CYCLIC PLASTICITY WITH QUANTITATIVE TRANSITIONS AND SIZE EFFECTS OF LAYERED STRUCTURES

(整期优先)网络出版时间:2002-01-11
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Amethodisdevelopedforcyclicelastoplasticanalysisacrossmicro/meso/macroscaleswhichiseffectiveforthequantitativetransitionofphysicalvariablesandforevaluatingthesizeeffectsofmicrostruc-tures.Byusingtheimprovedself-consistentsehemeproposedbyFanandcarryingoutadelicatemesoscop-icanalysisbasedonashear-lagmodel,thesizeeffectsincludingthethicknessofhardandsoftlayersrelativetotheinclusiondimensionareobtainedontheoverallelastoplasticresponsesofmaterialsupto50cycles.Thedominantcharacteristicsoftheanalysisrarethatthecharacteristicdimensionsofamicrostructuresuchasthethicknessofthelayersandtheinclusiondimensioncanbeexplicitlyincorporatedintotheformulation.Resultsofnumericalanalysisusingonly4plasticconstantsshowthatthethickerthelayerrelativetothein-clusionsize,thesofterthematerialinproducingmoreplasticstrainvaluesforagivenappliedstressampli-tude.Thisisinagreementwiththewell-knownexperimentalrulethattheyieldstrengthoflayeredstructuresisinverselyproportionultothesquarerootofthespacingbetweenlayers.Itisfoundthatratchetingdependsverymuchonthesizeofthelayered-structureandthatthethinnertherelativethicknessofthelayerthelesstheratchetiugdisplacement.Thisfindingmaybeusedtoexplainwhyphenomenologicalmodelsonratchetingarenotquitesuccessfulsofar,indicatingthesignificanceofaerossscaleanalysisinunderstandingissueswhichhaveexistedforalongtime.