机械工程英语考试题.ppt

Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Your company slogan,Review,LOGO,A distinction may be made between open-die forging,usually in the form of,hammer forging,and closed-die forging.(),A.,自由锻；,B.,模锻；,C.,锤锻；,D.,手工锻,.,Powder metallurgy is a highly developed method of manufacturing reliable,ferrous,and nonferrous parts.(),A.,铁的；,B.,铜的；,C.,合金的；,D.,钢的,Injection molding is the predominant process for fabrication of,thermoplastics,into finished forms.(),A.,热塑性的；,B.,热固性的；,C.,塑料的；,D.,耐热的,An estimate showed that about 10 to 15%of all the metal produced in USA was converted into,chips,.(),A.,芯片；,B.,碎屑；,C.,成品；,D.,半成品,It is the angle between the face of the tool called the,rake face,and the normal to the machining direction.(),A.,前刀面；,B.,后刀面；,C.,低面；,D.,侧面,Grinding can be performed on flat,cylindrical,or even internal surfaces by employing specialized,machine tools,.(),A.,机器；,B.,机床；,C.,工具；,D.,夹具,Lapping has two main functions.Firstly,it produces a superior,surface finish,.(),A.,表面光洁度；,B.,表面波度；,C.,表面精度；,D.,表面切削量,lathetype,machine tools can be classified as follows:Engine lathes,toolroom,lathes,turret lathes,etc.(),A.,普通车床；,B.,工具车床；,C.,立车；,D.,专用车床,The,spindle,is driven through the gearbox,which is housed within the headstock.(),A.,心轴；,B.,轴线；,C.,转轴,D.,主轴,CIMS,is a term to describe the most modern philosophy to manufacturing.(),A.,计算机集成控制系统；,B.,计算机数控；,C.,计算机集成制造系统,D.,计算机辅助工程,To begin to understand these processes,consider a steel of the,eutectoid composition,.(),A.,共析成分；,B.,共晶成分；,C.,亚共析成分；,D.,亚共晶成分；,The opposite of elongation is,upsetting,which produces compressive shortening.(),A.,拔长；,B.,冲压；,C.,拉深；,D.,镦粗；,This compacted material is placed in an oven and,sintered,in a controlled atmosphere at high temperatures and the metal powders coalesce and form a solid.(),A.,熔化；,B.,压缩；,C.,烧结；,D.,成型；,Injection molding is increasingly being used for thermosetting plastics,fiber-filled composites,and,elastomers,.(),A.,陶瓷；,B.,塑料；,C.,弹簧；,D.,人造橡胶,A very large,clearance angle,reduces the strength of the tool tip,and hence normally an angle of the order of 50-60 is used.(),A.,刃倾角；,B.,前角；,C.,后角；,D.,夹角,Lapping is a,finishing operation,used on flat and cylindrical surfaces.(),A.,半成品加工；,B.,最终加工；,C.,粗加工；,D.,精加工,The inorganic coatings perform,electroplatings,conversion coatings,thermal sprayings,etc.(),A.,电镀；,B.,电解；,C.,电腐蚀；,D.,电加工,lathe type machine tools can be classified as follows:,Toolroom,lathes,engine lathes,turret lathes,etc.(),A.,工具车床；,B.,普通车床；,C.,六角车床；,D.,立式车床,The tailstock assembly consists basically of three parts,its lower base,an intermediate part,and the,quill,.(),A.,卡盘；,B.,顶尖；,C.,主轴；,D.,套筒,A,FMS,is a process under control to produce varieties of components or products within its stated capability and to a predetermined schedule.(),A.,柔性制造系统；,B.,集成制造系统；,C.,数字控制系统；,D.,微机电系统,Some metal alloys,such as those based on aluminum,have low densities and are used in aerospace,for fuel economy.,Fracture toughness,can be described as a materials ability to avoid fracture,especially when a flaw is introduced.,It is impossible to see through metals,since these,valence electrons,absorb any photons of light which reach the metal.,Adding other metals can affect the density,strength,fracture toughness,plastic deformation,electrical conductivity and,environmental degradation,.,However,many materials scientists add the,stipulation,that ceramics must also be crystalline.,Instead,“,sintering,”or“firing”is the process typically used for the production of crystalline ceramics.,The middle layer is glass with a lower refractive index known as the cladding which protects the core glass from scratches and other,surface imperfections,.,Alloy steels,owe,their properties,to,the presence of one or more elements other than carbon.,With this process the rate of cooling is the controlling factor,and rapid cooling from above the,critical range,results in hard structure.,This structure is composed of two distinct phases,but has its own set of characteristic properties and,goes by the name,pearlite,because of its resemblance to mother-of-pearl at low magnification.,With slow heating,these transitions occur,in the reverse manner,.,Material and process selection depends on the parts complexity and function,the products,quality specifications,and the projected cost level.,This is facilitated by designing a,draft,a slight angular offset from the vertical to the vertical surfaces of the pattern.,These shrinkage allowances are only approximate,because the exact,allowance,is determined by the shape and size of the casting.,One of the basic operations of hammer forging is the,elongation,of a piece of metal by stretching with hammer blows.The opposite of elongation is,upsetting,.,Closed die forging can produce components of greater complexity and accuracy,with a better,surface finish,than the more traditional methods not using closed dies.,Partially alloyed powders are a,compromise approach,.,This reduces the strength of the tool tip as well as the,heat dissipation,through the tool.,The metal in front of the tool rake face gets immediately compressed,first,elastically,and then,plastically,.,If the friction between the tool rake face and the underside of the chip(deformed material)is,considerable,then the chip gets further deformed,which is termed as secondary deformation.,Fig.8.1 indicates the two possible variations,either a,horizontal,or,vertical,machine spindle.,It is used as a method of obtaining very,close fit,s between mating parts such as pistons and cylinders.,Lapping minimizes the surface irregularities,thereby increasing the,available contact area,.,As a,replenishment,for these deposited ions,the metal from the anode is dissolved and goes into the solution and balances the ionic potential.,In spite of that diversity of lathe type machine tools,they all have common features,with respect to,construction and principle of operation.,The function of the gearbox is to provide a number of different spindle speeds(usually 6 up to 18 speeds).Some modern lathes have headstocks with,infinitely variable spindle speeds.,The hole in the open side of the quill is tapered to enable mounting of lathe centers or other tools like,twist drills,or boring bars.,These features can best be,illustrated,by considering the commonly used representative type,the engine lathe.,In practice,two,symmetrical,cutting edges that rotate about the same axis are employed.,When drilling copper or soft plastics,higher values for the helix angle are,recommended,.,Injection molding is the predominant process for fabrication of,thermoplastics,into finished forms.,An estimate showed that about 10 to 15%of all the metal produced in USA was converted into,chips,.,lathe-type machine tools can be classified as follows:,Engine lathes,toolroom,lathes,turret lathes,etc.,CIMS,is a term to describe the most modern philosophy to manufacturing.,Plastic deformation is the ability of a material to bend or deform before breaking.As engineers,we usually design materials so that they dont deform under normal conditions.You dont want your car to lean to the east after a strong west wind.However,sometimes we can take advantage of plastic deformation.The crumple zones in a car absorb energy by undergoing plastic deformation before they break.,A distinction may be made between open-die forging,usually in the form of hammer forging,and closed-die forging.In hammer forging,the component is shaped by hammer blows aided by relatively simple tools.These may include open dies i.e.,dies that do not completely enclose the metal to be shaped.One of the basic operations of hammer forging is the elongation of a piece of metal by stretching with hammer blows,causing it to become thinner and longer.In hand forging the work piece is usually turned 90 after each blow,in order to forge it thoroughly and prevent its lateral expansion.,Rake angle.It is the angle between the face of the tool called the rake face and the normal to the machining direction.Higher the rake angle,better is the cutting and less are the cutting forces,increasing the rake angle reduces the metal backup available at the tool rake face.This reduces the strength of the tool tip as well as the heat dissipation through the tool.Thus,there is a maximum limit to the rake angle and this is generally of the order of 15 for high speed steel tools cutting mild steel.It is possible to have rake angles at zero or negative.,Grinding can be performed on flat,cylindrical,or even internal surfaces by employing specialized machine tools,which are referred to as grinding machines.Obviously,grinding machines differ in construction as well as capabilities,and the type to be employed is determined mainly by the geometrical shape and mature of the surface to be ground,e.g.,cylindrical surfaces are ground on cylindrical grinding machines.,Why are metals and alloys used?Many metals and alloys have high densities and are used in applications which require a high mass-to-volume ratio.Some metal alloys,such as those based on aluminum,have low densities and ate used in aerospace for fuel economy.(1)Many alloys also have high fracture toughness,which means they can withstand impact and are durable.,For the,semimechanized,forging of small to medium sized components,forging hammers powered by various means are employed.The feature common to all of them is that,like the hand forging hammer,they utilize the energy of a falling weight to develop the pressure needed for shaping the metal.Larger components are forged by means of forging presses operated by steam or compressed air or by hydraulic or electric power.Largely automatic forging machined are used for the quantity production of engineering parts.,Clearance angle.This is the angle between the machined surface and the underside of the tool called the flank face.The clearance angle is provided such that the tool will not rub the machined surface thus spoiling the surface and increasing the cutting forces.A very large clearance angle reduces the strength of the tool tip,and hence normally an angle of the order of 50-60 is used.,Surface grinding.As the name surface grinding suggests,this operation involves grinding of flat or plane surfaces.Fig.8.1 indicates the two possible variations,either a horizontal or vertical machine spindle.In the first case(horizontal spindle),the machine usually has a planer-type reciprocating table on which the,workpiece,is held.However,grinding machines with vertical spindles can have either a planer-type table like that of the horizontal spindle machine or a rotating worktable.,数控程序包含一系列,指令,，使得数控机床执行一定的操作。数控编程可通过工厂现有的内部编程系统或购买编程器，也可通过手工或计算机辅助实现。,A program for,numerical control,consists of a sequence of,direction,s that causes an NC machine to carry out a certain operation,machining being the most commonly used process.Programming for NC may be done by an internal programming department,on the shop floor,or purchased from an outside source.Also,programming may be done manually or with computer assistance.,工业机器人,是最近发展的,机电一体化,产品，它正在改变现代工业。工业机器人并不像科幻小说所描述的具有类似人类的能力，并伴随人类进行太空旅行。二十多年来，科学家们致力研究，使机器人能够具有看、听、触的能力，现在已取得丰硕成果。,Industrial robots,are relatively new,electromechanical,devices that are beginning to change the appearance of modern industry.Industrial robots are not like the science fiction devices that,possess,human-like abilities and provide companionship with space travelers.Research to enable robots to“,see”,”hear”,”touch,”,and“listen”has been underway for two decades and is beginning to bear fruit.,计算机辅助编程包含专门的符号编程语言，它们决定零件的圆角、边和表面的一系列点的坐标。编程语言使用这些符号化代码与计算机进行通信。编程人员使用编程语言描述待加工的零件，然后计算机将其转换为数控机床命令。,Computer-aided part programming,involves special symbolic programming languages that determine the coordinate points of corners,edges,and surfaces of the part.,Programming language,is the means of communicating with the computer and involves the use of symbolic characters.The programmer describes the component to be processed in this language,and the computer converts it to commands for the NC machine.,美国机器协会将机器人定义为：一个可再编程、多功能的机械手，它通过各种可以改变程序的运动来完成不同的工作任务，用于搬运原料、零件、刀具以及专用装置。如果将各种加工种类解释为各种功能，那么数控加工中心也可看作是一种机器人。,The,Robotics Institute of America,defines a robot as“a,reprogrammable multifunction manipulator,designed to move materials,parts,tools,or other specialized devices through variable programmed motions for the performance of a variety of tasks.”A NC machining center would be qualified as robot if one can interpret different types of machining as different functions.,Lathe bed,support,carriage,Headstock,chuck,Tailstock,feed rod,lead screw,gearbox,center,S,elf-introduction,I,nformation includes:name,personality,favor,university,major,courses,skills,