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1、mechanicalengineeringAnintroductionto1Lecturer:LiuJu-rongCHAPTER5MaterialsandStressOVERVIEW1TENSIONANDCOMPRESSION23RESPONSEOFENGINEERINGMATERIALS2SHEAR4FACTOROFSAFETY5Vocabulary3shearstress剪应力stress-strain应力-应变aluminum铝elasticmodulus弹性模数plasticbehaviorn.塑性roundrod圆钢shrink收缩Poissoncontraction(
2、泊松收缩gauge测量rubberband橡皮筋springbackvi.弹回hypothetical假想的chassis底盘low-carbonsteel低碳钢stiffness刚度ductility延展性;塑性brittlematerials脆性材料castiron铸铁;生铁concrete混凝土Vocabulary4ceramics陶器glass玻璃low-strain小应变permanentset永久变形;残余变形proportionallimit比例极限pipefittings管接头bushings衬套annealed退火tempered回火heattreatmentn
3、.热处理quenchingn.淬火artificialagingn.人工时效;人工老化hingepinn.铰销1OVERVIEW5Aspartoftheirresponsibilities,mechanicalengineersmustdesignhardwaresothatitdoesn'tbreak.Knowingthoseforcesalone,however,isnotsufficientforanengineertopredictwhetheracertainmechanicalcomponentwillbestrongenoughandnotfailinthetask
4、athand.By"fail"or"failure"wemeanthatthehardwarewillnotbreak,stretch,orbendsomuchastobecomenonusable.Inshort,engineersareabletocombinetheirknowledgeofforces,materials,shapes,anddimensionsinordertolearnfrompastfailuresandtobetterdesignnewhardware.1OVERVIEW6Inthischapter,wewilldiscusstheproperti
5、esofengineeringmaterialsandexaminethevarioustypesofstressesthatcandevelopwithinthem.Tension,compression,andshearstressarequantifiesthatengineerscalculatewhentheyrelatethedimensionsofamechanicalcomponenttotheforcesactingonit.Thosestressesarethencomparedwiththematerial'sphysicalpropertiesinorde
6、rtodeterminewhetherornotfailureisexpectedtooccur.Engineersgenerallyconductthistypeofforce,stress,andfailanalysisearlyinaproduct'sdesigncycleaschoicesaremadefordimensions,materials,andoperatingconditions.1OVERVIEW7FINGURE5.1Abrokencrankshaftfromasingle-cylinderinternalcombustionengine.1OVERVIE
7、W---Theabilitytobeavailableinthischapter8Afterstudy,whatshouldyoubeabletohave?Identifycircumstanceswhereamachinecomponentisloadedintension,compression,orshear,andcalculatethestressthatispresent.Drawstress-straincurvesforandsteel,anddeterminet
