材料压缩时的力学性能Mechanicalpropertie

材料压缩时的力学性能Mechanicalpropertiesofmaterialsduringcompression主讲人：王雅君12目录CONTENTS低碳钢压缩实验铸铁压缩实验LowcarbonsteelcompressionexperimentCastIronCompressionExperiment机械设计基础MechanicalDesign测定低碳钢(Q235钢)的强度性能指标:服强度。Measurethestrengthperformanceindexoflow-carbonsteel(Q235steel):clothingstrength.测定铸铁的强度性能指标:抗拉强Measurethestrengthperformanceindexoflow-carbonsteel(Q235steel):clothingstrength.。观察、比较低碳钢(Q235钢)和铸铁两种材料的力学性能、压缩过程及破坏现象。Observeandcomparethemechanicalproperties,compressionprocess,andfailurephenomenaoflow-carbonsteel(Q235steel)andcastiron.1低碳钢压缩实验LowcarbonsteelcompressionexperimentONE一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment1.设备和仪器Equipmentandinstruments微机控制电液伺服万能材料试验机Mainresearchobject:Straightrods-rodswithstraightaxes.一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment2.实验条件experimentalcondition常温(20℃)、静载(缓慢地加载）Normaltemperature(20℃),staticload(slowlyloaded)3.压缩标准试件CompressionstandardL0=10d0或L0=5d0一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment4.实验步骤Procedure(1)测量试样尺寸Measuresamplesize(2)开机。打开电源开关;启动计算机，打开试验机控制软件;按复位按扭使控制系统上电。Poweron.Turnonthepowerswitch;Startthecomputerandopenthecontrolsoftwareofthetestingmachine;Presstheresetbuttontopoweronthecontrolsystem.(3)试验参数设置Experimentalparametersettings(4)装夹试样。试样应置于球形承垫中心籍球形承垫自动调节实现轴向受载。Clampthesample.Thespecimenshouldbeplacedatthecenterofthesphericalbearingpadtoachieveaxialloadingthroughautomaticadjustmentofthesphericalbearingpad.球形承垫Sphericalbearingpad一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment4.实验步骤Procedure(5)开始压缩实验测试。实验过程中观察图形和数据显示窗口以及试样破坏情况Startcompressionexperimenttesting.Observationofgraphicsanddatadisplaywindowsduringtheexperiment,aswellassampledamage(6)打印输出实验曲线Printoutexperimentalcurves(7)卸载并取出试样。Unloadandremovethesample.(8)关机。退出试验程序，关闭主机油源电源，关闭测控系统电源关闭计算机。Shutdown.Exitthetestprogram,turnoffthemainengineoilsourcepower,turnoffthemeasurementandcontrolsystempower,andturnoffthecomputer.一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment(1)弹性阶段obElasticstageob①弹性变形:Elasticdeformation:比例极限σₚ:材料在不偏离应力与应变正比关系(胡克定律)条件下所能承受的最大应力Proportionallimitσₚ:Themaximumstressthatamaterialcanwithstandwithoutdeviatingfromtheproportionalrelationshipbetweenstressandstrain(Hooke'slaw)弹性极限σₚ:材料产生纯弹性变形时的最大应力值Elasticlimitσₚ:Themaximumstressvalueatwhichthematerialundergoespureelasticdeformation②斜直线oa:Obliquelineoa:σ=EεE—弹性模量Obliquelineoa:低碳钢压缩应力-应变图Lowcarbonsteelcompressionstress-straindiagram一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment(2)屈服阶段bcYieldstagebc应力不增加，应变不断增加。Thestressdoesnotincrease,butthestraincontinuestoincrease.屈服极限σs:试样还继续发生明显变形的最小应力Yieldlimitσs:Theminimumstressatwhichthespecimencontinuestoundergosignificantdeformation低碳钢压缩应力-应变图Lowcarbonsteelcompressionstress-straindiagram一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment(3)cd一一试件压扁CD-flatteningoftestpieces比例极限σp、弹性极限σe、屈服极限σs弹性模量E与拉伸时相同，而强度极限σb,测不出Proportionallimitσp.Elasticlimitσe.YieldlimitσsTheelasticmodulusEisthesameasintension,whilethestrengthlimitσb.Unabletomeasure低碳钢压缩应力-应变图Lowcarbonsteelcompressionstress-straindiagram一、低碳钢压缩实验Lowcarbonsteelcompressionexperiment经过屈服阶段后，低碳钢试样被压成鼓形Aftertheyieldstage,thelow-carbonsteelsampleispressedintoadrumshape继续不断加压试样将愈压愈扁，压成薄饼形状而不破裂Continuetoapplypressurecontinuously,andthesamplewillbecomeflatterandflattened,formingathincakeshapewithoutbreaking低碳钢压缩的变形DeformationofLowCarbonSteelunderCompression2铸铁压缩实验CastIronCompressionExperimentTWO二、铸铁压缩实验CastIronCompressionExperiment

铸铁压缩应力-应变图Compressionstress-straindiagramofcastiron应力割线Stresssecant二、铸铁压缩实验CastIronCompressionExperiment剪切破坏，铸铁试样破裂后呈鼓形，破裂面与轴线大约成45°Shearfailure,thecastironsampleshowsadrumshapeafterfracture,andthefracturesurfaceisapproximately45°fromtheaxis.铸铁压缩的变形Compressiondeformationofcastiron1自测题一单选题SelfTestQuestion1-MultipleChoiceQuestion1.脆性材料的失效形式为_________。Thefailureformofbrittlematerialsis_________.

A.屈服失效Yieldfailure

B.断裂失效YieldfailureC.扭转失效Torsionalfailure

D.点蚀失效TorsionalfailureBB自测题SELF-TEST2完成实验报告，包括实验目的，设备名称及型号，实验原始数据记录(列表表示)与实验数据处理，试样破坏形状示意图，分析讨论。Completetheexperimentalreport,