納米金屬材料宏觀力學(xué)性能的數(shù)值模擬研究.pdf

1、天津大學(xué)碩士學(xué)位論文納米金屬材料宏觀力學(xué)性能的數(shù)值模擬研究姓名：楊文芳申請學(xué)位級別：碩士專業(yè)：固體力學(xué)指導(dǎo)教師：李林安20030101ABSTRACTAllkindspr@ertieshavebeenstudiedsincenanostructuredmaterialswerefound。MuchprogresshasbeenacquiredinstudyingofmechanicalpropertiesNumericalsimulat

2、ionisanimportantmethodtostudymechanicalpropertiesofnanostructuredmaterials。BasedoilfiniteelementmethodandMorsepotentialfunction，constitutiverelationsofgrainboundarywerederivedbyincorporatingmoleculardynamicssimulationmet

3、hodwithfiniteelementmethod，thecompositeconstitutivemodelconsistingofincludecrystalline，grainboundaryandporositywasbuiltupFiniteelementmodelwasbuiltaccordingtoconstitutiverelation，andfiniteelementprogramsweregeneratedbyme

4、allSoffiniteelementprogramantomaticgeneratesystemFEPGsomeprogramsweremodifiedinordertocalculateelasticmodulusofnanocrystatlinewhichisonbalance，crystallinesizewasadjusted，elasticmodulusofnanocrystallinewithdifferentcrysta

5、llinesizewerecalculatedWiththedecreaseofcrystallinesize，itwasfoundthat，volumepercentofgrainboundaryandporosityincreased，andthemacroelasticmodulusdeclinedstepbystep，itsinitialthllingwasslowelasticmodulusdecreasedrapidlyaf

6、tercrystallinesizereducedto20nmWhilecrystallinesizereducedto2nm，columnpercentofgrainboundaryandporositywasabout70percents，elasticmodulusofthe3typesmetaldecreasedtoabout70percentsofgeneralcrystalElementstiffnessmatrixeswe

7、remodified，linearincrementiterativealgorithmwasdesigned，elasticmodulusofthesemetalswithdifferentcrystallinesizesineachloadingstepwascalculatedbeforegrainboundarysoftensItwasfoundthat，withthedecreaseofcrystallinesize，nonl

8、inearconstitutivecharacteristicsofiron，al【uminumandcopperbecamemoreandmoreobvious，andtheextensionofmaterialswasintensified。Elongationofnanocrystallinewith2nmisabout2～3timesofcommoncrystallineComparedthenumericalanalysisr

9、esultswiththeexperimentationresultsofotherscholars，itisshownthatthetheoryandmodelinthisarticlewerefeasibleDatesfromdifferentscholarsexisteddifferencethroughexperimentationsduetotherestrictionofpreparationmethodsandtestme