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1、第一页Machineelements机械零件Howeversimple,anymachineisacombinationofindividualcomponentsgenerallyreferredtoasmachineelementsorparts.(无论多么简单的机床,都是由通常称为机械零件的一些单个元件组成的。)thus,ifamachineiscompletelydismantled,acollectionofsimplepartsremainssuchasnuts,bolts,springs,gears,cams,andshafts---thebuildingbloc
2、kofallmachinery.,因此,如果把机床完全拆开,就得到像螺母、螺栓、弹簧、齿轮、凸轮及轴等简单零件------所有机器的标准元件。amachineelementis,thereforeasingleunitdesignedtoperformaspecificfunctionandcapableofcombiningwithotherelements.因此,机械零件就是用来设计可以执行某一特定功能,而且能与其他零件配合的简单零件。,Sometimescertainelementsareassociatedinpairs某些特定的元件必须成对地工作,suchasnuts
3、andboltsorkeysandshafts.Inotherinstance,agroupofElementsiscombinedtoformasubassembly,suchasbearings,coupling,andclutches.如:螺栓和螺母,键和轴。在其他情况下,一组零件组成一个装配件,例如:轴承、联轴器及离合器等。ThemostcommonexampleofamachineelementIsagear,which,fundamentally,isacombinationofthelevertoformatoothedwheel.机械零件中最常见的是齿轮,它实际
4、上由轮子和杆组成的有齿的轮子。Therotationofthisgearonahuborshaftdriverothergearthatmay第二页rotatefasterorslower,dependinguponthenumberofteethonthebasicwheel.在轴套或轴上旋转的齿轮驱动其他齿轮作加速或减速运动,这取决于主动齿轮的齿数。Otherfundamentalmachineelementshaveevolvedfromwheelandlever.其他基本机械零件包含轮子和杆。Awheelmusthaveashaftonwhichitmayrotate.
5、轮子必须装在轴上才可以运动。Thewheelisfastenedtotheshaftswithcouplings.theshaftmustrestinbearings。轮子用联轴器固定在轴上,轴必须安装在轴承里,,maybeturnedbyapulleywithabeltorachainconnectingittoapulleyonasecondshaft由传动带或链条与第二根轴相连,并带动第二根轴转动。.Thesupportingstructuremaybeassembledwithboltsorriversorbywelding.支承结构可由螺栓或铆钉或通过焊接固定在一起。
6、Properapplicationofthesemachineelementsdependsuponknowledgeoftheforceonstructureandthestrengthofthematerialsemployed.这些机械零件的正确使用,取决于是否了解作用于结构上的力及所用材料的强度等相关方面的知识。Theindividualreliabilityofmachineelementsbecomesthebasisforestimatingtheoveralllifeexpectancyofacompletemachine.单个机械零件的可靠性成为估计整台机器使
7、用寿命的因素。Manymachineelementsarethoroughlystandardized.许多机械零件是完全标准化的。Testingandpracticalexperiencehaveestablishedthemostsuitabledimensionsforcommonstructural第三页andmechanicalparts.普通结构和机械部件的最佳尺寸可以通过测试和实际经验来确定Thoughstandardization,采用标准化,uniformityofprac