砂轮英语.docx

砂轮英语.docx

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砂轮英语

Literaturereview

Inprecisiongrinding,conditioningofgrindingwheelshasalwaysbeenamajortopicofresearchasqualityandeconomyofthegrindingoperationaredirectlyrelatedtogrindingwheelconditioning.Underconditioningtheoperationsprofiling（indicatedbytruingforstraightprofiles）,sharpeningandcleaningareconsidered.Forsuper-abrasivegrindingwheels（CBNanddiamond）profilingismostchallengingbecausethelifetimeandaccuracyoftheprofilingtoolsarestronglylimitedbytheinherentwear-resistanceandabrasivenessoftheconsideredgrindingwheel.Below,availablemethodsarediscussedfollowedbythedevelopmentofaprofilingdeviceandformdiscdrivesystem.Eventuallytheprofilabilityofdifferentgrindingwheelsisinvestigatedanddemonstratedwithtwocases.

Theresin-bondeddiamondwheelshavebeenusuallyusedforgrindingvariouscementedtungstencarbides.Basedontheenvironmentalconsideration,thedryconditionwillbesometimesemployedtogrindthesematerials.However,thepoormachinabilityoftungstencarbidescausesdifficultiesindrygrinding.Especiallyinadrymachiningprocess,allthegrindingpowerisdissipatedasheatinthegrindingzone,attheinterfacebetweenthewheelandtheworkpiece.Thisheatcausesthewheelandworkpiecetemperaturestorise,whichmaycausethermaldamage.Undersuchacondition,increasingmaterialremovalratesandobtaininghigh-qualitysurfaceswouldbelimited.

Inordertoimprovethemachinabilityoftungstencarbidesinadrygrindingprocess,manystudieshavebeenconducted.TorranceandMetzgerstatedthatindrygrindingofcarbide,theresultingpredominantmodeofwheelwearisheatrelated.Furthermore,thewheellossinwetgrindingismainlymechanicalwear,andthegrindingratioincreaseswithincreaseofthewheelspeed.Inaddition,Metzgerindicatedthatfrequencyofthewheel/workpieceentryimpactsduringgrindingofcementedtungstencarbidewouldacceleratediamondwheelwear.Thedropingrindingratiocanreachvaluesashighas70%inreciprocatingfacegrindingwithresinbondwheels.

Forbestresultsindrygrindingcementedcarbides,thefollowingguidelinesareadopted:

（1）alowwheelspeedofaround18m/s;

（2）alowtablespeedof2–3m/min;（3）alowdepthofcutinthe0.01–0.05mmrange;（4）reductionintheareaofcontact.

Furthermore,intheselectionanduseofwheelsoperatedunderadrycondition,metallicadditivesandlubricantswouldbeaddedintotheresinbond,whichfacilitatesthedispersionofheatandthereductionoffrictioninthecontactzone.Besides,theirregularmetalcladdiamondparticleswiththemoderatestrengtharealsorecommendedtoimproveheatdissipationandretentionintheresinbond.Inturnthesebenefitsresultinincreasedtoollifeandenhancedperformance.

Eventhoughseveralstudiesontheperformanceofthediamondwheelsinthegrindingofcarbideshadbeeninvestigated.However,studiesrelatingtheeffectsofthefilleroftheresinbondonthedrygrindingoftungstencarbidearelittlereported.Inthispaper,theeffectsofseveralfillersoftheresin-bondeddiamondwheelontheperformanceofdrygrindingoftungstencarbidearestudied.

AnewkinddiamondgrindingwheelwithAl-basedbondingagentwaspreparedinthispaper.Theinfluenceofsinteringtemperaturetotherelativedensity,hardnessandservicelifeofdiamondgrindingwheelswithAlSnTi,AlSnTiNiCo,AlSnTiNiandAlSnNiCobondingagentwasstudied.Themicrostructureofdifferentbondingagentsinteredatdifferenttemperaturewasobserved.TheservicelifeoftheAl-basedgrindingwheelswascomparedwithCu-basedorresin-basedones.TheresultsshowedthattheAlSnTiNiCoisthebestcompositionsysteminthisresearch.Thebestsinteringtemperatureis300?

C.Thesamplehasahighrelativedensityaftersinteredat300C.TheretentionofAl-basedbondingagenttodiamondgritisstrong.TheservicelifeofthisAlbaseddiamondgrindingwheelisaboutthreetimesaslongasthatofresin-bondedgrindingwheel.

AnewkindofgrindingwheelhasbeenfabricatedwithAlbasedbondingagent.TheoptimalsystemofAl-basedagentinthisresearchisAlSnTiNiCo.Relativedensity,hardnesshardnessandservicelifeofAl-baseddiamondtoolsareeffectivelyinfluencedbysinteringtemperature.FortheseAl-basedsystems,theoptimalsinteringtemperatureisabout300C.ThegrindingeffectofceramictilesquaredbyAl-basewheelisasgoodasthatbyresin-basedwheel.TheservicelifeofAl-basedgrindingwheelisthreetimesaslongasthatoftheresinbased.

Epoxyresinshavebeencommercializedfor50years.Therearethousandsofepoxiesavailableinthemarkets.Thebasicpropertiesofepoxyresinscanbemodifiedinmanyways:

byblendingofdifferentresins,byselectionofcuringagentsandbytheuseofmodifiersandfillers.Theepoxyresinshaveexhibitedgoodthermalproperties,chemicalresistanceandelectricinsulationthroughacross-linkingreactionwithacuringagentthatmakesthetwo-dimensionalepoxystructurechangetothethree-dimensionalnetworkstructure.Thesepropertiesofcuredepoxiesalldependonthestructuresofcuringagentsandepoxyresin.

Thermalpropertiesdifferencesbetweenrigidrodtetramethylbiphenyl（TMBP）andflexiblediglycidylethersofbisphenolA（DGEBA）epoxieswerestudiedusingmodifieddifferentialscanningcalorimeter（MDSC）,thermogravimetricanalyzer（TGA）anddynamicmechanicalanalyzer（DMA）techniques.Theseepoxieswerecuredwithphthalicanhydride（PA）andphenolicresin（PF5110）,respectively.ThePF5110-curedepoxyhasbetterthermalpropertiesthanthePA-curedepoxywithahigherglasstransitiontemperature（Tg）andahigherdecompositiontemperature.ThegoodthermalpropertiesofthePF5110-curedepoxyareduetotherigidPF5110structureonthecuredepoxy.DGEBAepoxyhasahigherdecompositiontemperaturethantherigidrodepoxywhentheyarecuredwithPF5110.But,inthePAcuringsystem,rigidrodepoxyhasabetterthermalstability.Thesetwodifferentresultsareduetothedifferentstructuresofcuringagents.

Phenolicthermosettingmaterialswerethefirstmajorplasticmaterialusedbyindustry.Theyarestillamongthemostwidelyusedthermosetsbecausetheyaresomeofthelowest-costengineeringmaterialonacost-per-volumebasis.Phenolicsareformedfromthecondensationofpolymerizationreactionbetweenphenolandformaldehyde.Thecondensationreactionforphenolicscanbecarriedoutundertwodifferentconditions,resultingintwodifferentintermediatematerials.Oneoftheintermediatesiscalledresolesandtheothernovolacs.

Intheearlierstudyaboutpolymernetworkofphenolicandepoxiesresinsmixedwithlinseedoil,onlyPhencat15wasusedasthecatalystforthephenolicresin.Inthisstudy,Phencat382andUH（aureahydrochloridesolutionbasedona1:

1moleratioofurea:

hydrochloricacid32%）willbeusedascatalyststostudytheireffectsonthepolymernetworkofphenolicandepoxyresinsmixedwithepoxidizedlinseedoil（ELO）（58%）.Theeffectofeachoneofthesecatalystsonthecuringandthepropertiesoftheformednetworkwereinvestigated.ItwasdiscoveredthatPhencat382wasthebestcatalystforthecomposites.ItwasalsodiscoveredthatELOcanplayitsroleasplasticiserintheblendsofepoxyandphenolicresinsanddoesimprovetheflexuralstrengthandothermechanicalpropertiesofthepreparedresins.

Thestoragemodulus,flexuralmodulus,stressatpeakandglasstransitiontemperaturedecreasedwithincreasingpercentagebyweightofELOaddedirrespectiveofthecatalystsused,whilethestrainyieldincreased.Thecross-linkdensitydecreasedwiththeincreasingamountofELOintheresins.Thebestpropertieswereobtainedforthe80/20epoxy/phenolicresinblendsafterpost-curingfor4h.

Imidazolewithvariousmolecularweightspoly（ethyleneglycol）s,includingPEG1000,PEG2000,andPEG5000,wasblendedandevaluatedasthermallatentcatalystsforthepolymerizationofdiglycidyletherofbisphenolA（DGEBA）underliquid–liquidorliquid–solidtwophasesystems.ThethermallatencyandstoragestabilitypropertiesofDGEBAresincuredby1–5wt%ofmolecularweightimidazole/PEGcomplexesweremeasuredbyviscometer,differentialscanningcalorimetry（DSC）,andTGA.

Basedontheviscosity–shearrateresults,wefoundthe1–3wt%amountofimidazole/PEGsshowedthebetterthermallatencyinthethermalpolymerizationsystem.Fromthecureactivationenergyandtheviscosity–storagetimeofthesecomplexcatalysts,theorderofthermallylatentactivitywasimidazole/PEG1000

（2）>imidazole/PEG5000（4）>imidazole/PEG2000（3）>imidazole.Concerningtheglasstransitiontemperature（Tg）,theuseofimidazole/PEGcomplexcatalystsprovidedcompleteornearcompletecuringsystemsinthetemperaturerangeabout150.8C.

Togetabetterunderstandingofthecuringprocessofmulti-componentthermosetsdifferentialscanningcalorimetric（DSC）andtemperaturemodulatedDSC（TMDSC）measurementswereperformedduringisothermalcuringofsemi-interpenetratingpolymernetworks（semi-IPNs）withamountsof10or20wt.%oflinearpolymerandofthecorrespondingpurenetworksattemperaturesbetween333and393K.ThenetworkcomponentconsistsofdiglycidyletherofbisphenolA（DGEBA）cross-linkedwithdiaminodiphenylmethane（DDM）andthelinearpolymercomponentispolysulfone（PSn）orpolyethersulfone（PES）.Thecuringtimedependenceofconversionwasestimatedfromtimedependentheatflowmeasurementsduringisothermalcuring.Thecuringkineticsisdiscussedintheframeworkofdifferentmodels

takingintoaccountthecatalyticeffectsandtheinfluenceofdif