《可焊接的结构钢》ppt课件

《《可焊接的结构钢》ppt课件》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、Lesson3MachineToolFramesTheframeisamachine'sfundamentalelement.Mostframesaremadefromcastiron,weldedsteel,composite,orconcrete.Thefollowingfactorsgovernmaterialchoice.Thematerialmustresistdeformationandfracture.Hardnessmustbebalancedagainstelasticity.T

2、heframemustwithstandimpact,yetyieldunderloadwithoutcrackingorpermanentlydeforming.frame床身castiron铸铁weldedsteel可焊接的结构钢composite复合材料govern决定hardness硬度bebalancedagainst与…平衡elasticity弹性impact冲击cracking裂纹deforming永久性变形Theframematerialmusteliminateorblockvib

3、rationtransmissiontoreduceoscillationsthatdegradeaccuracyandtoollife.Itmustwithstandthehostileshop-floorenvironment,includingthenewercoolantsandlubricants.Materialexpansionmustbeunderstood(inorder)tominimizeforcesneededtomoveslides.Thematerialmustnotbu

4、ilduptoomuchheat,mustretainitsshapeforitslifetime,andmustbedenseenoughtodistributeforcesthroughoutthemachine.vibration震动oscillation震荡degrade降低等级toollife刀具寿命withstand耐受hostile恶劣的coolant冷却液lubricant润滑剂slide滑动部件(滑块)ProsandConsEithercastingsorweldedsection

5、scanbeusedinmostapplications.Thedecisiononwhichisbestdependsonthecostsinagivendesignsituation.Castiron.Almostallmachinetoolframesweretraditionallymadeofcastironbecausefeaturesdifficulttoobtainanyotherwaycanbecastin.Castingshaveagoodstiffness-to-weightr

6、atioandgooddampingqualities.Modifyingwallthicknessandputtingthemetalwhereit'sneededisfairlyeasy.Althoughcastironisafairlycheapmaterial,eachcastingrequiresapattern.Largersizesarealimitingfactorbecauseofpatterncost,problemswithboltedjoints,andtheneedtoan

7、nealcastings,whichisdifficultandcostlywithlargersections.prosandcons优缺点casting铸件stiffness-to-weightratio刚度重量比dampingquality减震性能pattern模型boltedjoint螺栓连接anneal将…退火section截面尺寸Smaller,high-volumemachinesusuallyhavecastironframesbecausetheymoreeasilyabsorbp

8、atterncost.Weldedframesmaybecheaperforlowervolumemachines.Weldedsteel.Machinebuildersfabricatesteelframesfromweldedsteelsectionswhencastingisimpractical.Becausesteelhasahighermodulus,itisusuallyribbedtoprovidestiffness.Thenumberofweldsi