机械制造技术基础课件-新第2章课件(3)

2.1.3Cuttingheatandtemperature2.1.3.1Generationandtransmissionofcuttingheat2.1.3.2Cuttingtemperature2.1.3.3Influencefactorsoncuttingtemperature2.1.3.1GenerationandtransmissionofcuttingheatCuttingheatcomesfromtheconversionofcuttingenergy.AsshowninFig.2.35,thegeneralcuttingheatQincludesQp—thehearfromsheardeformationenergy,Qγf—theheatfromthechip-toolfriction,andQαf—theheatfrommachinedsurface–toolfriction.ThegeneralcuttingheatQcanbedecomposedintochipheatQch,toolheatQc,workpieceheatQwandsurroundingmediumheatQf,.Thereistherelation:Qp+Qγf+Qαf＝Qch+Qw+Qc+Qf(2.20)2.1.3.2CuttingtemperatureThroughthebalanceofthedeformationenergy,frictionenergygeneratedinthecuttingregionandheattransmission,thecuttingtemperaturemaybecalculatedapproximately.Takingthecalculationofaveragetemperatureinthecuttingregionasanexample:InaunittimethegeneratedheatqisequaltothedissipatedcuttingpowerPm,thatisq=Fzvc/60W(2.21)HereFz—maincuttingforce(N);vc—cuttingspeed(m/min)(1)CalculationofcuttingtemperatureThetemperatureincrementΔθresultingfromqisrelatedtothematerial’sdensityρandspecificheatcapacityc:Herep—perunitcuttingforce(N/m2)c—specificheatcapacity(J/kg•K)ρ—density(kg/m3).....cpbhvCvFDDccZ℃(2.22)2.1.3.2Cuttingtemperature2.1.3.2Cuttingtemperature750℃刀具二维切削中的温度分布工件材料：低碳易切钢；刀具：o=30，o=7；切削用量：ap=0.6mm，vc=0.38m/s；切削条件：干切削，预热611CWhencuttingplasticmaterial,themaximumTempisnearthetooltipoftherakeface.Whencuttingbrittlematerial,themaximumTempisnearthetooltipoftheflank.2.1.3.2CuttingtemperatureThereareseveralmethodsofmeasuringcuttingtemperaturesuchasthermoelectriccouple,heatradiation,coloringandinfraredmethodetc.Amongthemthethermoelectriccouplefindswideapplication.①Naturalthermoelectriccouple②Syntheticthermoelectriccouple2.1.3.3factorsInfluencingcuttingtemperatureCuttingtemperatureprincipallydependsontheamountofheatgeneratedinthecuttingprocess,alsoontheamountofheatdissipation.ThereareseveralInfluencefactorsoncuttingtemperature:toolgeometricparameters、cuttingparameters、workmaterial.(2)Measurementofcuttingtemperature2.1.3.2Cuttingtemperature•ExperientialformulaZyxcpCvfa刀具材料加工方法ＣθＺθＹθＸθ高速钢车削140～1700.35～0.450.2～0.30.08～0.10铣削80钻削150硬质合金车削320f(mm/r)0.10.410.150.050.20.310.30.26切削温度的系数及指数2.1.3.3factorsInfluencingcuttingtemperaturevc（m/min）切削速度、工件材料对切削温度的影响1—GH1312—1Cr18Ni9Ti3—45钢(正火)4—HT200刀具材料：YT15；YG8刀具几何参数：o=15，o=6~8，r=75，1=-10，s=0，b=0.1mm，r=0.2mm切削用量：ap=3mm，f=0.1mm/rθ（℃）103050709011013040060080010001243Discussion:Thegeometryofthecuttingtool:TheworkpiecematerialThetoolwearThecuttingfluid