机械制造行业机械外文翻译中英文.docx

1、机械制造行业机械外文翻译中英文附录附录1英文原文Rolling Contact BearingsThe concern of a machine designer with ball and roller bearings is fivefold as follows:(a) life in relation to load; (b) stiffness,ie.deflections under load; (c) friction; (d) wear; (e) noise. For moderate loads and speeds the correct selection of a st

2、andard bearing on the basis of a load rating will become important where loads are high,although this is usually of less magnitude than that of the shafts or other components associated with the bearing. Where speeds are high special cooling arrangements become necessary which may increase fricition

3、al drag. Wear is primarily associated with the introduction of contaminants,and sealing arrangements must be chosen with regard to the hostility of the environment. Because the high quality and low price of ball and roller bearing depends on quantity production,the task of the machine designer becom

4、es one of selection rather than design. Rolling-contact bearings are generally made with steel which is through-hardened to about 900HV,although in many mechanisms special races are not provided and the interacting surfaces are hardened to about 600HV. It is not surprising that,owing to the high str

5、esses involved,a predominant form of failure should be metal fatigue, and a good deal of work is based on accept values of life and it is general practice in bearing industry to define the load capacity of the bearing as that value below which 90 percent of a batch will exceed life of one million re

6、volutions. Notwithstanding the fact that responsibility for basic design of ball and roller bearings rests with the bearing manufacturer, the machine designer must form a correct appreciation of the duty to be performed by the bearing and be concerned not only with bearing selection but with the con

7、ditions for correct installation. The fit of the bearing races onto the shaft or onto the housings is of critical importance because of their combined effect on the internal clearance of the bearing as well as preserving the desired degree of interference fit. Inadequate interference can induce seri

8、ous trouble from fretting corrosion. The inner race is frequently located axially by against a shoulder. A radius at this point is essential for the avoidance of stress concentration and ball races are provided with a radius or chamfer to follow space for this.Where life is not the determining facto

9、r in design, it is usual to determine maximum loading by the amount to which a bearing will deflect under load. Thus the concept of static load-carrying capacity is understood to mean the load that can be applied to a bearing, which is either stationary or subject to slight swiveling motions, withou

10、t impairing its running qualities for subsequent rotational motion. This has been determined by practical experience as the load which when applied to a bearing results in a total deformation of 0.0025mm for a ball 25mm in diameter. The successful functioning of many bearings depends upon providing

11、them with adequate protection against their environment, and in some circumstances the environment must be protected from lubricants or products of deterioration of the bearing design. Moreover, seals which are applied to moving parts for any purpose are of interest to tribologists because they are

12、components of bearing systems and can only be designed satisfactorily on basis of the appropriate bearing theory. Notwithstanding their importance, the amount of research effort that has been devoted to the understanding of the behavior of seals has been small when compared with that devoted to othe

13、r aspects of bearing technology.Lathes Lathes are widely used in industry to produce all kinds of machined parts. Some are general purpose machines, and others are used to perform highly specialized operations. Engine lathesEngine lathes, of course, are general-purpose machine used in production and

14、 maintenance shop all over the the world. Sized ranger from small bench models to huge heavy duty pieces of equipment. Many of the larger lathes come equipped with attachments not commonly found in the ordinary shop, such as automatic shop for the carriage.Tracer or Duplicating LathesThe tracer or d

15、uplicating lathe is designed o produce irregularly shaped parts automatically. The basic operation of this lathe is as fallows. A template of either a flat or three-dimensional shape is placed in a holder. A guide or pointer then moves along this shape and its movement controls that of the cutting t

16、ool. The duplication may include a square or tapered shoulder, grooves, tapers, and contours. Work such as motor shafts, spindles, pistons, rods, car axles, turbine shafts, and a variety of other objects can be turned using this type of lathe.Turret LathesWhen machining a complex workpiece on a gene

17、ral-purpose lathe, a great deal of time is spent changing and adjusting the several tools that are needed to complete the work. One of the first adaptations of the engine lathe which made it suitable to mass production was the addition of multi-tool in place of the tailstock. Although most turrets h

18、ave six stations, some have as many as eight. High-production turret lathes are very complicated machines with a wide variety of power accessories. The principal feature of all turret lathes, however, is that the tools can perform a consecutive serials of operations in proper sequence. Once the tool

19、s have been set and adjusted, little skill is require to run out duplicate parts.Automatic Screw MachineScrew machines are similar in construction to turret lathes, except that their heads are designed to hold and feed long bars of stock. Otherwise, their is little different between them. Both are d

20、esigned for multiple tooling, and both have adaptations for identical work. Originally, the turret lathe was designed as a chucking lathe for machining small casting, forgings, and irregularly shaped workpieces. The first screw machines were designed to feed bar stock and wire used in making small s

21、crew parts. Today, however, the turret lathe is frequently used with a collect attachment, and the automatic screw machine can be equipped with a chuck to hold castings. The single-spindle automatic screw machine, as its name implies, machines work on only one bar of stock at a time. A bar 16 to 20

22、feet long is feed through the headstock spindle and is held firmly by a collect. The machining operations are done by cutting tools mounted on the cross slide. When the machine is in operation, the spindle and the stock are rotated at selected speeds for different operations. If required, rapid reve

23、rsal of spindle direction is also possible. In the single-spindle automatic screw machine, a specific length of stock is automatically fed through the spindle to a machining area. At this point, the turret and cross slide move into position and automatically perform whatever operations are required.

24、 After the machined piece is cut off, stock is again fed into the machining area and the entire cycle is repeated. Multiple-spindle automatic screw machines have from four to eight spindles located around a spindle carrier. Long bars of stock, supported at the rear of the machine,pass though these h

25、ollow spindles and are gripped by collects. With the single spindle machines, the turret indexes around the spindle. When one tool on the turret is working, the others are not. With a multiple spindle machine, however, the spindle itself index. Thus the bars of stock are carried to the various end w

26、orking and side working tools. Each tool operates in only one position, but tolls operate simultaneously. Therefore, four to eight workpieces can be machined at the same time.Vertical Turret Lathes A vertical turret is basically a turret lathe that has been stood on its headstock end. It is designed

27、 to perform a variety of turning operations. It consists of a turret, a revolving table, and a side head with a square turret for holding additional tools. Operations performed by any of the tools mounted on the turret or side head can be controlled through the use of stops.Machining Centers Many of

28、 todays more sophisticated lathes are called machining centers since they are capable of performing, in addition to the normal turning operations, certain milling and drilling operations. Basically, a machining center can be thought of as being a combination turret lathe and milling machine. Additio

29、nal features are sometimes included by the versatility of their machines.Numerical ControlOne of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control(NC). Prior to the advent of NC, all machine tools were manually operated and controlled. Among the ma

30、ny limitations associated with manual control machine tools, perhaps none is more prominent than limitation of operator skills. With manual control, the quality of the product is directly related to and limited to the skills of the operator. Numerical control represents the first major step away fro

31、m human control of machine tools. Numerical control means the control of machine tools and other manufacturing systems through the use of prerecorded, written symbolic instructions. Rather than operating a machine tool, an NC technician tool to be numerically controlled, it must be interfaced with a

32、 device for accepting and decoding the programmed instructions, known as a reader. Numerical control was developed to overcome the limitation of human operators, and it has done so. Numerical control machines are more accurate than manually operated machines, they can produce parts more uniformly, t

33、hey are faster, and the long-run tooling costs are lower. The development of NC led to the development of several other innovations in manufacturing technology:1. Electrical discharge machining.2. Laser cutting.3. Electron beam welding.Numerical control has also made machines tools more versatile than their manually ope