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1、Unit5Designofmachineandmachineelements机器和机器零件的设计Machinedesign机器设计Machinedesignistheartofplanningordevisingneworimprovedmachinestoaccomplishspec讦icpurposes.Ingeneral,amachinewillconsistofacombinationofseveraldifferentmechanicalelementsproperlydesignedandarrangedtoworktogether,asawhol
2、e・Duringtheinitialplanningofamachine,fundamentaldecisionsmustbemadeconcerningloading,typeofkinematicelementstobeused,andcorrectutilizationofthepropertiesofengineeringmaterials.Economicconsiderationsareusuallyofprimeimportaneewhenthedesignofnewmachineryisundertaken.Ingeneral,thelowes
3、tover-allcostsaredesigned・Considerationshouldbegivennotonlytothecostofdesign,manufacturethenecessarysafetyfeaturesandbeofpleasingexterrialappearance・Theobjectiveistoproduceamachinewhichisnotonlysufficientlyruggedtofunctionproperlyforareasonablelife,butisatthesametimecheapenoughtobee
4、conomicallyfeasible.机器设计为了特定的bl的而发明或改进机器的一，种艺术。一般來讲，机器时有多种不同的合理设计并有序装配在一起的部件构成的，在最初的机器设计阶段，必须基木明确负载、元件的运动情况、：T穆材料的合理使用性能。负责新机器的设计最初的最重要的是经济性考虑。一般来说，选择总成木最低的设计方案，不仅要考虑设计、制造、销传、安装的成木。还要考虑服务的费用，机械要保证必要的安全性能和美观的外形。制造机器的日标不仅要追求保证貝用功能的合理寿命，还要保证足够便宜以同时保证其经济的叫行性。Theengineerinchargeofthedesi
5、gnofamachineshouldnotonlyhaveadequatetechnicaltraining,butmustbeamanofsoundjudgmentandwideexperienee,qualitieswhichareusuallyacquiredonlyafterconsiderabletimehasbeenspentinactualprofessionalwork.负责设计机器的工程师，不仅要经过专业的培训，而且必须是一个准确判断而又有丰富经验的人，具有一种有足够时间从事专门的实际工作的素质。Designofmachineelements
6、机器零件的设计Theprinciplesofdesignare,ofcourse,universal.Thesametheoryorequationsmaybeappliedtoaverysmallpart,asinaninstrument,or,toalargerbutsimilarpartusedinapieceofheavyequipment・Innoease,however,shouldmathematicalcalculationsbelookeduponasabsoluteandfinal.Theyareallsubjecttotheaccurac
7、yofthevariousassumptions,whichmustnecessarilybemadeinengineeringwork・Sometimesonlyaportionofthetotalnumberofpartsinamachinearedesignedonthebasisofanalyticcalculations.Theformandsizeoftheremainingpartsaredesignedonthebasisofanalyticcalculations.Ontheotherhand,ifthemachineisveryexpens
8、iv巳orifweightisafac
