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1、AbstractAbstractTheflowbehaviourofmicro-injectionmouldingproductswereinfluencedbywallslipeffects,viscousdissipation,surfacetensioninthemicro-cavitycomparedwiththeconventionalinjectionmolding.Andthemicroinjectionmoldingprocessinducedthecomplexmulti-layeredstructureintheinternalofthemi
2、cro-injectionproductsaswellasvirousmechanicalperformanceofthemicroproducts.Manyresearchswerefocusedontherelationshipbetweenmicrostructureandmacroscopicmechanics,whilehardlynoresearchonthemicro-mechanicalpropertiesofthemicro-injectionproducts.Thus,themainworkofthisthesisistheresearcho
3、fmulti-levelinternalmicroscopicmorphology,aswellastherelationshipbetweenmicro-mechanicalpropertiesandmicrostructure.Theworksareshownasfollows:1.Theeffectofmoldtemperatureonthehardness,modulus,crystallinity,morphology,grainsize,orientation,thecrystalgraindensityofmicrogearproductswere
4、investigatedbyPLM,nanoindentation,WAXDandothertestingmethods.Theresultshowthat,withthemoldtemperatureincreases,thethicknessofthecorelayerincreased,thethicknessoftheskinlayerandshearlayerdecreased,βcrystalcontentdecreased,thedegreeofcrystallinityincreased;Themodulusofshearlayerandtheh
5、ardnessofcoreisincreasedasthemoldtemperatureincreases;andthewallslipoeffectsappearedatthemoldtemperatureof50C.2.Withtheincreasingofflowrate,thethicknessofcorelayerandtheshearlayerdecreased,thethicknessofthecorelayerincreased,andthedistributionareaofβcrystalsbecameswider;higherflowrat
6、eresultinlowerdegreeoforientation;thehardnessandmodulusofshearlayernearthegatelocationreachthemaximumattheflowrateof28mm/s,thehardnessandmodulusofthecorelayerdecreaseswithincreasingflowrate.3.Differentprocessingparameterswereperformedtoinvestigateditseffectonthemicroscopicmorphologys
7、tructureandmicromechanicalproperties.Withthecontentofβnucleatingagentincreased,thedistributionofβcrystals’inlargedatcore,thethicknessofthecorelayerbecomessmaller,thethicknessoftheshearlayerbecomeslarge;thecrystallinityraisedwhentheβnucleatingagentwasaddedtothemicrogear,andreachesmaxi
8、mumwhentheco