滚动轴承英文54翻译

1、rolling contact bearingsthe concern of machine designer with ball and roller bearings is fivefold as follows: (a) life in rlation to load; (b) stiffness, i.e. deflection under load; (c) friction; (d) wear; (e) noise. for moderat loads and speeds the correct selection of a standard bearing on the bas

2、is of load rating will usually secure satisfactory performance. the deflection of the bearing elements will become important where loads are high, although this is uaually od less magnitude than that of the shafts or other componentsassociated with the bearing. where speeds are high special cooling

3、arrangements become necessary which may increase frictional drag. wear is primarily associated with the introduction of contaminants, and sealing arrangements must be chosen with regard to the hostility of the environment.became the high quality and low price of ball and roller bearings dependson qu

4、antity production, the task of the machine designer becomes one of selection rather than design. rolling-contact bearings are generally made with steel which is through-hardened to about 900 hv, although in many mechanisms special races are not provided and the interacting surfaces are hardened to a

5、bout 600 hv. it is not surprising that, owing to the high stresses involved, a predominant form of failure should be metal fatigue, and a good deal of work is currently in progress intended to improve the reliability of this type of bearing. design can be based on accepted values of life and it is g

6、eneral practice in the bearing industry to define the load capacity of the bearing as that value below which 90 per cent of a batch will exceed a life of one million revolutions. notwithstanding the fact that responsibility for the basic design of ball and roller bearings rests with the bearing manu

7、facturer, 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 conditions for correct installation.the fit of the bearing races onto the shaft or onto the housings is of critical importance beca

8、use 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 serious trouble from fretting corrosion. the inner race is frequently located axially by abutting against a shoulder. a radius at thi

9、s point is essential for the avoidance of stress concentration and ball races are provided with a radius or chamfer to allow space for this.where life is not the determining factor in design, it is usual to determine maximum loading by the amount to which a bearing will deflect under load. thus the

10、concept of "static load-carrying capacity" is understood to mean the load that can be applied to a beating, which is either stationary or subject to slight swiveling motions, without impairing its running qualities for subsequent rotational motion. this has been determined by practical exp

11、erience as the load which when applied to a bearing results in a total deformation of the rolling element and raceway at any point of contact not exceeding 0.01 per cent of the rolling-element diameter. this would correspond to a permanent deformation of 0.0025 mm for a ball 25 mm in diameter.the su

12、ccessful functioning of many beatings depends upon providing 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 surfaces. achievement of the correct functioning of seals

13、 is at essential part of bearing design. moreover, seals which are applied to moving parts for any purpose are of interest to tribelogists because they are components of bearing systems and can only be designed satisfactorily on the basis of appropriate bearing theory. notwithstanding their importan

14、ce, the amount research effort that has been devoted to the understanding of the behavior seals has been small when compared with that devoted to other aapects of bearing technology.virtually all machines contain shafts. the most common shape for shafts is circular result in and the cross section ca

15、n be either solid or hollow (hollow shafts can weight savings).rectangular shafts，are sometimes used as in screwdriver blades，socket wrenches and control knob stems.a shaft must have adequate tensional strength to transmit torque and not be overstressed. it must also be torsionally stiff enough so t

16、hat one mounted component does not deviate excessively from its original angular position relative to a second component mounted on the same shaft. generally speaking, the angle of twist should not exceed one degree in a shaft length equal to 20 diameters.shafts are mounted in bearings and transmit

17、power gears, pulleys，cams and clutches. these devices introduce forces which attempt to bend the shaft; hence，the shaft must be rigid enough to prevent overloading of the supporting bearings. in general，the bending deflection of a shaft should not exceed 0.01 in. perft of length between bearing supp

18、orts.in addition，the shaft must he able to sustain a combination of bending and torsional loads. thus an equivalent load must he considered which takes into account both torsion and bending. also, the allowable stress must contain a factor of safety which includes fatigue; since torsional and bendin

19、g stress reversals occurfor diameters less than 3 in，the usual shaft material is cold-rolled steel containing abort 0.4 percent carbon. shafts are either cold-rolled or forged in sizes form 3 in. to 5 in. for sizes above 5 in .，shafts are forged and machined to size. plastic shafts are widely used f

20、or light load applications. one advantage of using plastic is safety in electrical applications，since plastic is a poor conductor of electricity.components such as gears and pulleys are mounted，on shafts by means of key. the design of the key and the corresponding keyway in the shaft must be properl

21、y evaluated. for example，stress concentrations in shafts due to keyways, and the material removed to form the keyway further weakens the shaft.if shafts are run at critical speeds，severe vibrations can occur which can seriously damage a machine. it is important to know the magnitude of these critica

22、l speeds so that they can be avoided. as a general rule of thumb，the difference between the operating speed and the critical speed should be at least 20 percent.another important aspect of shaft design is the method of directly connecting one shaft to another. this is accomplished by devices such as

23、 rigid and flexible couplings.a coupling is a device for connecting the ends of adjacent shafts. in machine construction，couplings are used to effect a semipermanent connection between adjacent rotating shafts. the connection is permanent in the sense that it is not meant to be broken during the use

24、ful life of the machine, but it can be broken and restored. in an emergency or when worn parts are replaced.there are several types of shaft couplings，their characteristics depend on the purpose for which they are used. if an exceptionally long shaft is required in a manufacturing plant or a propell

25、er shaft on a ship, it is made in sections that are coupled together with rigid couplings. a common type of rigid coupling consists of two mating radial flanges (disks) that are attached by key-driven hubs to the ends of adjacent shaft sections and bolted together through the flanges to form a rigid

26、 connection. alignment of the connected shafts is usually effected by means of a rabbet joint on the face of the flanges.in connecting shafts belonging to separate devices(such，an electric motor and a gearbox)，precise aligning of the shafts is difficult and，flexible coupling is used. this coupling c

27、onnects the shafts in such a way as to minimize the harmful effects of shaft misalignment. flexible couplings also permit the shafts to deflect under their separate systems, of loads and to move freely (float) in the axial direction without interfering with one another. flexible couplings can also s

28、erve to reduce the intensity of shock loads and vibrations transmitted from one shaft to another.滚动轴承对于球轴承和滚子子轴承，一个机器设计人员应该考虑下面五个方面：（a）寿命与在和的关系；（b）刚度，也是在载荷作用下的变形；（c）摩擦，（d）磨损；（e）噪音。对于中等载荷和转速，根据额定伏在选择一个标准轴承，通常都可以保证其具有令人满意的工资性能。当载荷较大时，轴承零件的变形，尽管他通常小于轴和其他与轴承一起工作的零部件的变形，将会变的重要起来。在较高转速的场合需要有专门的冷却装置，而这可能会增

29、加摩擦阻力。摩擦主要是由于污染物的进入引起的，必须选用密封装置以防止周围环境的不良影响。因为大批量生产这种方式决定了球轴承和滚子轴承不但质量高，而且价格低，因而机器设计人员的任务是选择而不是设计轴承。滚动接触轴承通常是采用硬度约为900hv，整体淬火的钢来制造的。但在许多机构上不使用专门的套圈，而将相互作用的表面淬火硬到大约600hv。滚动轴承由于在工作中会产生高的应力，其主要失效形式是金属疲劳，这一点并不奇怪，目前正在进行大量的工作以求改进这种轴承的可靠性。轴承设计可以基于能够被人们所接受的寿命值来进行。在轴承行业中，通常将轴承的承载能力定义为这样的值，即所承担的载荷小于这个值时，一批轴承终

30、将会有90%的轴承具有超过一百万转的寿命。尽管球轴承和滚子轴承的基本设计责任在轴承制造厂家，机器设计人员必须对所要完成的任务做出正确的评价，不仅要考虑轴承的选择，而且还要考虑轴承的正确安装条件。轴承套圈与轴或轴承座的配合非常重要，因为它们之间的配合不仅应该保证所需要的过盈量，而且也应该保证轴承的内部间隙。不正确的过盈量会产生微振腐蚀磨损从而导致严重的故障。内圈同行藏时通过近靠在轴肩上进行轴向定位的。轴肩处的圆弧半径主要时为了避免应力集中。在轴承内圈上加工出一个圆弧或者倒角，用来提供容纳轴肩处圆弧半径的空间。在使用寿命不是设计中的决定因素的场合，通常根据轴承载荷时产生的变形量来确定其最大载荷。因

31、此，“静态承载能力”这个概念可以理解为对处于静止状态的进行缓慢转动的轴承所能够是假的载荷。这个载荷对轴承在随后进行旋转运动的质量没有不利影响。按照实践经验确定，静态承载能力时这样一个载荷，当它作用轴承上时，滚动体与滚道在任何一个接触点处的总变形量不超过体直径的0.01%。这相当于直径为25mm的球产生0.0025mm的永久变形。只有将轴承与周围环境适当地隔离开时，许多轴承才能成功地实现它们的功用。在某些情况下，必须保护环境，使其不受润滑剂和轴承表面磨损生成物的污染。轴承设计的一个重要组成部分是使密封装置起到应有作用。此外，对摩擦学研究人员来说，为了任何目的而应用与运动零部件上的密封装置都是他们感兴趣的。因此密封装置是轴承系统的一部分，只有根据适当的轴承理论才能设计出令人满意的密封装置。虽然它们很重要，与轴承其他方面的研究工作相比，到目前为止在密封装置的研究方面所做的工作还是比较少的。 实际上，几乎所有的机器中都装有轴。轴最常见的形状是圆形，其截面可以是实心的，也可以是空心的(空心轴可以减轻重量)。有时也采用矩形轴，例如，螺丝起子的头、套筒扳手和控制旋扭的杆。为了在传递扭矩时不发生过载，轴应该具有适当的抗扭强度。轴还应该具有足够的抗扭刚度，以使同一个轴上的两个传动零件之间的相对转角不会过大。一般说来，在轴的长度等于其直径的20倍时，