机械工程专业英语课件--L09

EnglishechanicalEngineering 机械工程专业英语 Slottedconepointedsetscrew Hexnut Slottednut Brightwasher Springwasher Tabwasher锥端紧定螺钉六角螺母六角槽形螺母平垫圈弹簧垫圈外舌止动垫圈 Hexagonheadbolt Stud Slottedcheeseheadscrew Slottedpanheadscrew Slottedcountersunkscrew Hexagonsocketcap六角头螺钉双头螺柱头圆柱头螺钉盘头螺钉沉头螺钉圆柱头内六角螺钉 Typesofscrewfasteners螺纹紧固件的种类 Partswiththreadsusedforjoiningandfasteningarecalledscrewfasteners Themostwidelyusedcomponentsasscrewfastenersarebolts doublescrewbolts stud screws nutsandwashers 用螺纹联接并起紧固作用的零件称为螺纹紧固件 常用的螺纹紧固件有螺栓 双头螺柱 螺钉 螺母 垫圈等 Lesson19Screws fastenersandjoints 机械工程专业英语 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints Boltedjointsareoneofthemostcommonelementsinconstructionandmachinedesign Theyconsistofcapscrewsorstudsthatcaptureandjoinotherparts andaresecuredwiththematingofscrewthreads Therearetwomaintypesofboltedjointdesigns Inonetheboltistightenedtoacalculatedclampload usuallybyapplyingameasuredtorqueload Thejointwillbedesignedsuchthattheclamploadisneverovercomebytheforcesactingonthejoint andthereforethejoinedpartsseenorelativemotion Theothertypeofboltedjointdoesnothaveadesignedclamploadbutreliesontheshearstrengthoftheboltshaft Thismayincludeclevislinkages jointsthatcanmove andjointsthatrelyonlockingmechanism likelockwashers threadadhesives andlocknuts 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints Boltedjoint Screwjoint Studjoint Bolt螺栓 Theboltassemblyisusedwhenjointpartsarenottoothicktodrillthroughholes 螺栓用于联接二通孔薄件 Stud双头螺柱 Studareusedinsituationswhereapartwithathroughholeandapartwithblindtappedhole 双头螺柱用于联接一通孔薄件和一盲孔厚件 Screw螺钉 Screwsaremostlyusedforthecaseswithsmallbearingforces suchasinspectioncoverswhichhavetoberemovedfrequently 螺钉多用于用于受力不大需要经常拆卸的情况 Nut螺母 Nutareusedtomatchtheotherscrewfasteners 螺母与其他螺纹件配合使用 Washer垫圈 弹簧垫圈平垫圈 Washerareusedtomatchtheotherscrewfasteners 垫圈与其他螺纹件配合使用 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints TheoryTheclampload alsocalledpreload ofacapscrewiscreatedwhenatorqueisapplied andisgenerallyapercentageofthecapscrew sproofstrength Capscrewsaremanufacturedtovariousstandardsthatdefine amongotherthings theirstrengthandclampload Torquechartsareavailablethatidentifytherequiredtorqueforcapscrewsbasedontheirpropertyclassorgrade Whenacapscrewistighteneditisstretched andthepartsthatarecapturedarecompressed Theresultisaspring likeassembly Externalforcesaredesignedtoactonthepartsthathavebeencompressed andnotonthecapscrew 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints TheoryTheresultisanon intuitivedistributionofstrain inthisengineeringmodel aslongastheforcesactingonthecompressedpartsdonotexceedtheclampload thecapscrewdonotseeanyincreasedload Thismodelisonlyvalidwhenthemembersundercompressionaremuchstifferthanthecapscrew Thisisasimplifiedmodel Inrealitytheboltwillseeasmallfractionoftheexternalloadpriortoitexceedingtheclampload dependingonthecompressedparts stiffnesswithrespecttothehardware sstiffness 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints TheoryTheresultsofthistypeofjointdesignare Greaterpreloadsinboltedjointsreducethefatigueloadingofthehardware Forcyclicloads theboltdoesnotseethefullamplitudeoftheload Asaresult fatiguelifecanbeincreasedor ifthematerialexhibitsanendurancelimit extendedindefinitely Aslongastheexternalloadsonajointdon texceedtheclampload thehardwaredoesn tseeanymotionandwillnotcomeloose nolockingmechanismsarerequired Inthecaseofthecompressedmemberbeinglessstiffthanthehardware soft compressedgasketsforexample thisanalogydoesn tholdtrue Theloadseenbythehardwareisthepreloadplustheexternalload 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints TheoryTheresultsofthistypeofjointdesignare Greaterpreloadsinboltedjointsreducethefatigueloadingofthehardware Forcyclicloads theboltdoesnotseethefullamplitudeoftheload Asaresult fatiguelifecanbeincreasedor ifthematerialexhibitsanendurancelimit extendedindefinitely Aslongastheexternalloadsonajointdon texceedtheclampload thehardwaredoesn tseeanymotionandwillnotcomeloose nolockingmechanismsarerequired Inthecaseofthecompressedmemberbeinglessstiffthanthehardware soft compressedgasketsforexample thisanalogydoesn tholdtrue Theloadseenbythehardwareisthepreloadplustheexternalload 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints ThreadstrengthNutthreadsaredesignedtosupporttheratedclamploadoftheirrespectivebolts Iftappedthreadsareusedinsteadofanut thentheirstrengthneedstobecalculated Steelhardwareintotappedsteelthreadsrequiresadepthof1 5 threaddiametertosupportthefullclampload Ifanappropriatedepthofthreadsisnotavailable orthethreadsareinaweakermaterialthanthecapscrew thentheclampload andtorque needstobederatedappropriately 机械工程专业英语 预备知识 一 Backgroundination Lesson19Screws fastenersandjoints FailuremodesThemostcommonmodeoffailureisoverloading Operatingforcesoftheapplicationproduceloadsthatexceedtheclampload