机械专业毕业设计（论文）外文翻译-滚动轴承

机械专业毕业设计（论文）外文翻译-滚动轴承 附录 附录1 英文原文 Rolling Contact Bearings The concern of a machine designer with ball and roller bearings is fivefold as follows:(a) life in relation to load; (b) stiffness,i.e.deflections under load; (c) friction; (d) wear; (e) noise. For moderate loads and speeds the correct selection of a standard 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 fricitional 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 becomes 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 stresses 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 revolutions. Notwithstanding the fact that responsibility for basic design of ball and roller bearings rests with he 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 conditions 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 serious 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 factor 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, without 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 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 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 other 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 lathes Engine lathes, of course, are general-purpose machine used in production and 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 Lathes The tracer or duplicating 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 tool. 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 Lathes When machining a complex workpiece on a general-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 have 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 tools have been set and adjusted, little skill is require to run out duplicate parts. Automatic Screw Machine Screw 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 designed 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 screw 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 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 reversal 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. 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 hollow 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 working 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 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 today's 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. Additional features are sometimes included by the versatility of their machines. Numerical Control One 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 many 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 from 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 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, they 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 operated predecessors. An NC machine tool can automatically produce a wide variety of parts, each involving an assortment of widely varied and complex machining processes. Numerical control has allowed manufacturers to undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tools and processes. Like so many advanced technologies, NC was born in the laboratories of the Masschusetts Institute of Technology. The concept of NC was developed in early 1950s with funding provided by the U.S.Air force. In its earliest stages, NC machines were able to make straight cuts efficiently and effectively. However,curved paths were a problem because the machine tool had to be programmed to undertake a series of horizontal and vertical steps to produce a curve. The shorter is straight lines making up the steps, the smoother is the curve. Each line segment in the steps had to be calculated. This problem led to the development in 1959 of the Automatically Programmed Tools(APT) language. This is a special programming language for NC that uses statements similar to English language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. The development of the APT language was a major step forward in the further development of NC technology. The original NC systems were vastly different from those used today. The machines had hardwired logic circuits. This instructional programs were written on punched paper, which was later to be replaced by magnetic plastic tape. A tape reader was used to interpret the instructions written on the tape for the machine. Together, all of this represented a giant step forward in the control of machine tools. However, there were a number of problems with NC at this point in its development. A major problem wad the fragility of the punched paper tape medium. It was common for the paper tape containing the programmed instructions to break or tear during a machining process. This problem was exacerbated by the fact that each programmed instructions had to be return through the reader. If it was necessary to produce 100 copies of a given part,it was also necessary to run the paper tape through the reader 100 separate times. Fragile paper tapes simply could not withstand the rigors of a shop floor environment and this kind of repeated use. This led to the development of a special magnetic plastic tape. Whereas the paper tape carried the programmed instructions as a series of holes punched in the tape, the plastic tape carried the instructions as a series of magnetic dots. The plastic tape was much stronger than the paper taps, which solved the problem of frequent tearing and breakage. However, it still left two other problems. The most important of these was that it was difficult or impossible to change the instructions entered on the tape. To make even the most minor adjustments in a program of instructions, it necessary to interrupt machining operations and make a new tape. It was also still necessary to run the tape through the reader as many times as there were parts to be produced. Fortunately, computer technology became a reality and soon solved the problem of NC associated with punched paper and plastic tape. The development of a concept known as direct numerical control(DNC)solved the paper and plastic tape problems associated with numerical control by simply eliminating tape as the medium for carrying the programmed instructions. In direct numerical control machine tools are tied, via a data transmission link, to a host computer. Programs for operating the machine tools are stored in the host computer and fed to the machine tool as needed via the data transmission linkage. Direct numerical control represented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend o a host computer. When the lost computer goes down, the machine tools also experience downtime. This problem led to the development of computer numerical control. The development of the microprocessor allowed for the development of programmable logic controllers(PNC)and microcomputer. These two technologies allowed for the development of computer numerical control(CNC). With CNC, each machine tool has a PLC or a microcomputer that serves the same purpose. This allows programs to be input and stored at each individual machine tool. It also allows programs to be developed off-line and download at the individual machine tool. CNC solved the problems associated with downtime of the host computer, but it introduced another known as data management. The same program might be loaded on ten different being solved by local area networks that connect microcomputer for better data management. CNC machine tool feed motion systems CNC machine tool feed motion systems, especially to the outline of the control of movement into the system, must be addressed to the movement into the position and velocity at the same time the realization of two aspects of automatic control, as compared with the general machine tools, require more feed system high positioning accuracy and good dynamic response. A typical closed-loop control of CNC machine tool feed system, usually by comparing the location of amplification unit, drive unit, mechanical transmission components, such as feedback and testing of several parts. Here as mechanical gear-driven source refers to the movement of the rotary table into a linear motion of the entire mechanical transmission chain, including the deceleration device, turning the lead screw nut become mobile and vice-oriented components and so on. To ensure that the CNC machine tool feed drive system, precision, sensitivity and stability, the design of the mechanical parts of the general requirement is to eliminate the gap, reducing friction, reducing the movement of inertia to improve the transmission accuracy and stiffness. In addition, the feeding system load changes in the larger, demanding response characteristics, so for the stiffness, inertia matching the requirements are very high. Linear Roller Guides In order to meet these requirements, the use of CNC machine tools in general low-friction transmission vice, such as anti-friction sliding rail, rail rolling and hydrostatic guideways, ball screws, etc.; transmission components to ensure accuracy, the use of pre-rational, the form of a reasonable support to enhance the stiffness of transmission; deceleration than the best choice to improve the resolution of machine tools and systems converted to the driveshaft on the reduction of inertia; as far as possible the elimination of drive space and reduce dead-zone inverse error and improve displacement precision. Linear Roller Guides outstanding advantage is seamless, and can impose pre-compression. By the rail body, the slider, ball, cage, end caps and so on. Also known as linear rolling guide unit. Use a fixed guide body without moving parts, the slider fixed on the moving parts. When the slider moves along the rail body, ball and slider in the guide of the arc between the straight and through the rolling bed cover of Rolling Road, from the work load to non-work load, and then rolling back work load, constant circulation, so as to guide and move the slider between the rolling into a ball. Bridge Crane Bridge crane is having an elevated track running in a bridge-type crane, also known as the crane. Bridge Crane in the laying of the bridge on both sides along the elevated track on the vertical run, lifting trolley along the bridge laying on the track in the horizontal operation, a scope of work of a rectangle, it can take full advantage of having the space below lifting materials from the ground equipment hindered. Bridge Crane widely used in indoor warehouses, factories, wharves and open storage yard and other places. Able to carry items, stood up, lifting status, and adjust operations, mainly for the workshop, sections and steel production lines yard, etc.. Lifting capacity usually in the 10 to 100 t. Bridge crane itself for horizontal movement, the winch frame for the vertical movement of the winch suspended from the hook for vertical movement, the direction of movement of three of the crane can work. In order to prevent bridge crane driver not clear in the specific hook campaign, on the ground are equipped with lifting the general command or folder, put hook. If hanging overhead crane hoisted electromagnetic lifting plate, often operated by the drivers themselves. Bridge cranes can be divided into general overhead crane, simple girder bridge crane for bridge crane and metallurgical three. Ordinary general overhead crane from lifting trolley, having run institutions, having composed of a metal structure. Lifting up from the car and from institutions, agencies and the car running small frame consists of three parts. Lifting bodies, including the motor, brakes, reducer, and the pulley drum group. Motor through the reducer, driven rotating drum so that the wire rope around 42.50 or 42.50 down to lifting weights. Small frame is from the brackets and install or run agencies and institutions, such as car parts rack, usually welded structure. Crane running the driving mode can be divided into two categories: one category is the concentrated drive, which uses a motor-driven initiatives on both sides of the drive shaft driven wheel; were driven to another, that is, on both sides of the initiative the wheels with a motor drive. Small, medium and larger overhead crane with brake, and motor reducer combination into one of the "triple play" drive, the weight of the ordinary from the overhead crane for easy installation and adjustment, often drive the use of universal - axis. Crane normally used only four active and driven wheels, if a great weight, increase common approach to reduce wheel round pressure. When more than four wheels, must adopt a balanced hinged frame device so that the crane load evenly distributed in the wheels. Bridge metal structure from the main sorghum and sorghum-composed of the main beam is divided into single-and double-girder bridge having two categories. Single-beam bridge from the main beam and a single on both sides of the span at the end of sorghum, dual-beam bridge by the two main sorghum and sorghum-component. Liang Liang Gang and the end of the link-beam ends with wheels, for supporting an elevated bridge in the running. A main beam welding on track for the lifting trolley running. Having the structure of the main beam type is more a typical box structure, the four truss structure and fasting truss structure. Box structure can be divided into two-track box girder, partial double-track box-beam, single-bias-rail box and several main sorghum. Dual-track box girder is the extensive use of a basic form, the main beam from the upper and lower flange on both sides of the plate and vertical web composition, layout rail car in the center of the flange plates online, and its simple structure , manufacturing convenient, suitable for mass production, but larger forces. Partial tracks box-girder and partial double-track box-section of the main beam are from the upper and lower ranges flange plates and thick web of the main components, rail car in the main web layout above, the short Xiangbenna omit the stiffening plate, which tracks box-side main beam from a wide flange box instead of the main sorghum two main sorghum, respect smaller, but more complex manufacturing. 4 truss-type structure from four plane truss structure into a closed space, in the general level of the surface Truss shops follow plate, light weight, rigidity, but compared with other structures, and its dimensions, creating more complex, fatigue lower intensity, has been less productive. Partial fasting truss structure similar to the main tracks box-girder from the four components of a closed steel structure, in addition to the main web for the Solid shaped beam, the other three plate in accordance with the design requirements cut into many windows, forming a no-ramps Fasting Truss, in the lower level of the surface occupied by taking truss plate, cranes and the operation of electrical equipment installed in the bridge house, lighter forces, the overall stiffness, and that in China is a more widely used type. General overhead crane used mainly driven power, the general is in the driver indoor manipulation, but also remote control. From the weight of up to 500 tons, up to 60 m span. Simple beam bridge crane known as sorghum cranes, and the structure and composition of ordinary bridge crane similar to a weight, span and speed are smaller. Bridge is the main sorghum or other steel I-beam and plate steel girder section composed of simple, hand-pull or electric hoist accompanied by gourd simple as lifting trolley car, the car usually in the word sorghum run on the next flange . Bridge can be elevated along the orbit, but also along the elevated suspension in the following orbit, such as a crane hoisted sorghum crane. Metallurgical dedicated bridge crane in the steel production process can be involved in a specific process operation, and its basic structure and general overhead crane similar, but in small vehicles are equipped with lifting the work of special agencies or devices. This feature is the work of a crane used frequently, poor, working-level higher. Dual-beam bridge crane factories on the track along the vertical direction of movement, the lateral movement and trolley movements campaign to hook work. Applied to machining and assembly shop, a metal structure workshop, mechanical workshops, metallurgy and casting workshop and warehouse type lifting work. With scores from the weight of the form, molecular weight mainly Gouqi, the denominator as vice Gouqi weight. There are five main types. Casting Crane: for the lifting of hot metal into Mixer, furnaces and molten steel into lifting equipment or continuous ingot steel ingot mould used. Sheng barrels lifting the car, a flip-sheng, deputy trolley barrels, and other auxiliary work. Tongs crane: Using tongs high temperature steel ingot will be vertically being lifted onto a deep soaking pits, or put it out the car shipped spindles. Stripper Crane: an ingot from the mandatory extrusion ingot mold. There are special small car Stripper devices, spindles Stripper under way and the shape of the model: Some Stripper crane-is attributable to suppress billets, ingots filed with the clamp module; Some of the clamp punctured ingot mould, with Ingot filed small pair of pliers. Feeding Crane: Charge will be added to the open hearth furnace. Trolley bottom of the column with the pick-and inciting material to me and it into the furnace. The main column to bypass the vertical axis rotation, pick-and rotary can swing from top to bottom. Deputy car repair furnace for such auxiliary operations. Forging Crane: to meet with hydraulic forging large workpieces. Trolley displayed on the main hook up special feeder to support and flip the workpiece; Vice car used to lift the workpiece. Dual-beam bridge crane, the biggest weight from 100 tons, the hook-and-grab, electromagnetic, metallurgical cranes, quenching crane, manual double girder bridge crane, electric hoist double girder overhead crane with the crane unit JB / T14405 "generic bridge crane" standard, the quality of products to JB/T53442 "universal overhead crane product quality grade" first-class requirements. Its structural features of starting up and running with the car running on the bridge, a metal structure for the double-girder box form. From the characteristics of the device in accordance with the classification for the hook, grab, electromagnetic and multipurpose bridge crane, mainly for the mines, factories, wharves and warehouses, and other material handling operations frequent stops, as a crane quenching equipment, a high-speed heat treatment process of decline . Metallurgical casting molten steel crane to transport packet is indispensable than smelting industrial equipment. The use of modern means of science and technology, will enable any crane structure with a jump-speed performance. Can be used with high-level rotating hook for stacking operations. Single-girder bridge crane, the largest weight of 10 tons from, hook-and-grab, electromagnetic, flying single-girder bridge crane, manual single-girder bridge crane with the crane unit JB/T1306 "electric single-girder bridge Crane "and JB/T2603" electric single-girder overhead crane hoisted the "standard requirements. Its structure is characterized manual or electric hoist monorail car along the main beam under the flange I-beam operation, material handling operations, normally used for workshops, warehouses and other material handling operations, which manual does not allow for single-girder crane No electricity or power occasions. Grab motor with the monorail or bulk materials can also be used to grab operations, the unit crane compact structure, operational flexibility, can be used to ground, can also be used to operate the cab. Special circumstances can also be used for remote operation. Industrial production or storage is indispensable equipment. Crane normal working hours to allow a lifting of the greatest quality as rated starting weight. Rated crane hook from the hook and the weight does not include the fixed pulley group themselves. Grab sucker and electromagnetic devices, such as the quality of admission included in the ratings from the weight. In accordance with the standard provisions of the bridge crane from the weight of a series of priority number system is R10, from 3.2 t, beginning with the increment of 1.25 Gongpi 4,5,6.3,8,10,12.5,16,20,25,32, 40,50 t……. But domestic products only under the bridge crane years of production practices, from the above series of elected part of the actual composition of a series of weight. Is the most commonly used Series 5 t, 10t, 16t, 20t, 32t and 50 t. Normally, when a weight of more than 10 t, or from the establishment of two bodies, namely the lifting of lifting bodies and institutions, both from the weight of a ratio of about 1:4. Main body from the weight or, for lifting heavy cargo lifting of the weight from the small, but faster, lighter for the lifting of the goods or for supporting efforts to enhance work efficiency. Generally experienced the largest crane lifting weights to determine the starting weight,taking into account the conditions of work reproduced or process requirements. Crane does not allow the use of overloading, in the lifting of the frequent changes of the occasion, crane should consider certain margin. In some cases, the occasional object to the lifting of overweight available when two cranes coordinated operations. In the process fixed, the lifting of the weight will remain basically unchanged, the use of cranes loaded with the basic circumstances, can be lifted up from vice, to simplify the structure of a crane and lower costs. Foreign large-tonnage it is not all bridge crane with a lifting body vice, but necessary option. The use of overhead crane safety matters: (1) Each crane must be obvious from the weight rated local hang the signs. (2) Work, it was not allowed on the bridge or hook couriers. (3) No Operator's Certificate and is not allowed to drink driving cranes. (4) Operating must focus on the spirit, not talk, smoking or do not do. (5) To clean the car; while Luanfang equipment, tools, flammable materials, explosive materials and dangerous goods. (6) The cranes could be allowed to use super. (7) The following situations while lifting: bundling is not solid; mechanical overload; signal unknown; Cable; buried in the ground or frozen items; suspended on some items; no security protection measures for the flammable and explosive - and dangerous goods; drive liquid items do not meet the safe use of wire rope; fault movements institutions. (8) The cranes in the absence of obstructions on the lines running, as well as hanging hook or spreader of the base must be more than 2 m from the ground. If the crossing barriers, obstacles to be more than 0.5 m high. (9) From the weight lifting rated less than 50 per cent of the objects, allowing the two bodies at the same time movements hanging from the weight rating greater than 50% of the objects, only a body can move. (10) Has the main, the Vice hook overhead crane, not to increase or decrease the same time, Vice hook (exceptional). (11) While in the objects on a cause or hammering and welding in the work of the following items (can support). (12) It must be a power outage, and hung in a gated power operation signs, before the examination or maintenance work. If it is necessary to live, work, there must be security protection, and a personal care. (13) While casually throw things down from the board. (14) Limit switches and interlock devices, it is necessary to carry out regular checks. (15) Not used as a parking collision limit switch approach. (16) Movements brake problems, not lifting weights. (17)Were not allowed in the hanging objects or equipment over the operation. (18) Crane unit welding, it is necessary to set up specialized ground, do not use fuselage ground. (19) Hook in a position under the limit, must remain on the roll more than two laps with the safety of Min Quan. (20) Crane allowed mutual collisions, but also does not allow use of a crane to promote another crane to work. (21) Lifting heavy objects, liquid metal and explosive and dangerous goods, must be slowly lifting from the ground 100 to 200 mm, the reliability of brake test. (22) Repair and inspection of the lights by its voltage must be below 36 V. (23) Bridge crane cover all electrical equipment should be grounded. If trolley track is not in the main beam welding, the welding earth measures to be taken. Earthing available cross-sectional area greater than 75 mm2 galvanized flat iron or 10 mm2 of bare copper or galvanized more than 30 mm2 bar. Cab of the crane or grounding location should be more than two. Crane power to any point in the neutral grounding resistors, should be less than 4 . (24) Security technology to regular inspection, good pre-preparatory work. 附录2 中文翻译 滚动轴承 对于球轴承和滚子轴承，一个机械设计人员应该考虑下面五个方面:(a)寿命与载荷关系;(b)刚度，也就是在载荷作用下的变形;(c)摩擦;(d)磨损;(e)噪声。对于中等载荷和转速，根据额定负荷选择一个 标准 excel标准偏差excel标准偏差函数exl标准差函数国标检验抽样标准表免费下载红头文件格式标准下载 轴承，通常都可以保证其具有令人满意的工作性能。当载荷较大时，轴承零件的变形，尽管它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。在转速高的场合需要专门的冷却装置，而这可能会增大摩擦阻力。磨损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。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硬到大约600HV。滚动轴承由于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，一批轴承中将会有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 须对轴承所完成的任务做出正确的评价，不仅要考虑轴承的选择，而且换药考虑轴承的正确安装条件。轴承圈套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余要的过盈量，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动腐蚀从而导致严重的故障。内圈通常是通过靠紧在轴肩上进行轴向定位的。轴肩处的圆弧半径主要是为了避免应力集中。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，通常根据轴承受载荷时产生的变形量来确定其最大载荷。因而，“静态承受能力”这个概念可以理解为对处于静止状态的或进行缓慢转动的轴承所能够施加的载荷。这个载荷对轴承的随后进行旋转运动时的质量没有不利影响。按照时间经验确定，静态载荷能力是这这样一个载荷，当它作用在轴承上时，滚动体与滚到在任何一个接触点处的总变形量不超过滚动体直径的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开，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，使其不受到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的作用，此外，对摩擦学研究人员来说，为了任何目的而应用于运动零部件上的密封装置都是他们感兴趣的。因为密封装置是轴承的一部分，只有根据适当的轴承理论才能设计出令人满意的密封系统。虽然它们很重要，与轴承其他方面的研究工作相比，在密封装置的研究方面所做的工作还是比较少的。 车床 车床是工业生产生活中被广泛用来加工各种类型的机械零件。一些车床是通用机床，而另一些车床则被用来完成某些专门工序的加工任务。 普通车床 普通车床是全世界的生产车间和维修车间里广泛使用的通用机床。它的尺寸范围很广，从小型的台式车床到巨大的重型车床。许多大型的车床装配在普通车间中通常看不到得附件，例如，滑板的自动挡块。 靠模车床或仿形车床 靠模车床或仿形车床被设计用来对形状不规则的零件进行自动加工。这种车床的基本操作如下:在夹持装置上安装平面或立体形状的样板，然后，导向触头或指针沿着它的外形移动。从而控制切削刀具的运动。仿形加工可以包括方形或锥形轴承肩、各种槽、锥体和轮廓。像电动机的轴、主轴、活塞、杆件、汽车轴、汽轮机轴和其他很多种类的工件都可以采用这种车床来进行切削加工。 转塔车床 在通用车床上加工一个复杂的工件时，在更换和调整加工时所用的一些刀具上要花费很多时间。对普通车床的早期改装工作之一是增加一个可以安装多把刀具的转塔来代替尾架，使它能够更好地适应大批量生产的需要。虽然大多数转塔有六个工位，但有些转塔有八个工位。 高生产率的转塔车床是装有许多动力附件的非常复杂的机器。然而，所有转塔车床的主要特点是刀具能按适当顺序完成一系列的加工工序。一旦这些刀具被安装调整好后，只需要很低的技术就可车削加工很多相同的零件。 自动螺丝车床 螺丝车床在结构上与转塔车床类似，不同之处是螺丝车床的主轴头部能被设计用来夹持和送进长棒料。除此之外，它们之间几乎没有什么差别。这两种车床都用于多刀具切削，都适合加工同样的工件。最初，为转塔车床设计的用途和卡盘车床的用途一样，也是用来加工小型铸件、锻件和形状不规则的零件。早期的螺丝车床通过棒料和线材的选送，制造小的螺丝零件。时至今日，转塔车床上经常使用夹头附件，而自动螺丝车床上则可通过安装卡盘来夹持铸件。 单轴自动螺丝车床，顾名思义，一次仅能加工一根棒料。一根16至20英尺长的棒料可以通过主轴箱中的主轴孔送进，并用夹头将其夹紧。机械加工工序是由装在转塔和横刀架上的刀具完成的。当机床工作时，主轴和棒料按照每道工序所选择的转速旋转。如果需要时也可以使主轴快速反转。 在单轴自动螺丝车床上，棒料的一段规定好的长度穿过主轴自动送到加工区。在这里，转塔和横刀架进入加工位置并自动完成所需的任何加工工作。当加工好的零件被切断后，棒料再次被送入加工区，并重复整个循环。 多轴自动螺丝床在主轴鼓周围装有4到8根主轴。在机床尾部支撑着的长棒料穿过这些空心主轴，通过夹头进行夹紧。在单轴车床上，转塔围绕主轴转位。当转塔丝杠的一个刀具工作时，其他的刀具不工作。然而，在多轴自动车床上，主轴自己转位。因此，几根棒料被传送到各个不同的端面加工和侧面加工的刀具位置处。每把刀具仅在一个位置工作，但是所有的刀具都能同时工作。因此，在同一时间内加工4到8个工件。 立式转塔车床 立式转塔车床基本上就是将其从床头箱一端向下面立起来的一台转塔车床。它被设计用来完成各种各样的切削工作。它由一个转塔，一个旋转工作台和一个侧面溜板组成的。 在侧面溜板上装有可以安装几把刀具的正方形刀架。由安装在转塔或侧面 溜板上的任何刀具完成的加工工序都可通过使用挡块来加以控制。 加工中心 当前，许多技术更为先进的车床叫做加工中心。因为，它们除了完成常规的车削工作之外，还可以完成某些铣削、钻削工作。加工中心基本上可以认为是转塔车床和铣床的组合体。有时，制造厂商为了增加机床的多用性，还会增加一些其他的性能。 数字控制 先进制造技术中的一个最基本的概念是数字控制(NC)。在数控技术出现之前，所有的机床都是人工操纵和控制的。在与人工控制的机床有关的很多局限性中，操作者的技能大概是最突出的问题。在采用人工控制时，产品的质量直接与操作者的技能有关。数字控制代表了从人工控制机床走出来的第一步。 数字控制以为着采用预先录制的，存储的符号指令，控制机床和其他制造系统。一个数控技师的工作部是去操纵机床，而是编写能够发出机床操作指令的程序。对于一台数控机床，其上必须装有一个被称为阅读机的界面装置，用来接受和解释编程指令。 发展数控技术是为了克服人类操作者的局限性。而且她确实完成了这项工作。数字控制的机器比人工控制的机器的精度更高、生产的零件的一致性更好、生产的速度更快、而且长期的工艺设备成本更低。数控技术的发展导致制造工艺中的其他几项新发明的产生: 1、 电火花加工技术 2、 激光切削 3、 电子束焊接 数字控制还使得机床比它们采用人工操纵的前辈们的用途更为广泛。一台数控机床可以自动生产很多种类的零件，每个零件都可以有不同的和复杂的加工过程。数控可使生产厂家承担那些对于采用人工控制的机床和工艺来说，在经济上时不划算的产品的生产任务。 与许多先进技术一样，数控诞生于麻省理工学院的实验室中。数控这个概念是20世纪50年代初在美国空军的资助下提出来的。在其最初的阶段，数控机床可以经济和有效的进行直线切割。 然而，曲线轨迹成为机床加工的一个问题，在编程时应采用一系列的水平与竖直的台阶来生成曲线。构成台阶的每个线段越短，曲线就越光滑。台阶中的每个线段都必须经过计算。 在这个问题的促使下，于1959年诞生了自动编程工具(APT)语言。这是一个专门适用于数控的编程语言，使用类似于 英语 关于好奇心的名言警句英语高中英语词汇下载高中英语词汇 下载英语衡水体下载小学英语关于形容词和副词的题 的语句来定义零件的几何形 状，描述切削刀具的形状和规定必要的运动。APT语言的研究和发展是数控技术进一步发展过程中的一大进步。最初的数控系统与今天应用的数控系统是有很大的差别的。在那时的机床中，只有硬线逻辑线路。指令程序写在穿孔纸带上(它后来被塑料磁带取代)，采用带阅读机将写在纸带或磁带上的指令给机器翻译出来。所有这些共同构成了机床数字控制方面的巨大进步。然而，在数控发展的这个阶段中还存在着许多问题。 一个主要问题是穿孔纸带的易损坏性。在机械加工过程中，载有编程指令信息的纸带断裂和被撕坏事常见的事情。在机床上每加工一个零件，都需要将载有编程指令的纸带放入阅读机中重新运行一次。因此，这个问题变的很严重。如果需要制造100个某种零件，则应该将纸带分别通过阅读机100次。易损坏的纸带显然不能承受严酷的车间环境和这种重复使用。 这就导致了一种专门的塑料磁带的研制。在纸带上通过采用一系列的小孔来载有编程指令，而在塑料带上通过采用一系列的磁点来载有编程指令。塑料带的强度比纸带要高的多，这就可以解决常见的撕坏和断裂问题。然而，它依然存在着两个问题。 其中最重要的一个问题是，对输入带中的指令进行修改时非常困难的，或者是根本不可能。即使对指令程序进行微小的调整。也必须中断加工，制造一条新带。而且带通过阅读机的次数还必须与需要加工的零件的个数相同。幸运的是，计算机技术的实际应用很快解决了数控个技术中与穿孔纸带和塑料纸带有关的问题。 在形成直接数字控制(DNC)这个概念后，可以不再采用纸带或塑料带作为编程指令的载体，这样就解决了与之有关的问题。在直接数字控制中，几台机床通过数据传输线路连接到一台主计算机上。操纵这些机床所需要的程序都存储在这台主计算机中。当需要时，通过数据传输线路提供给每台机床。直接数字控制是在穿孔纸带和塑料带基础上的一大进步。然而，它也有着与其他依赖于主计算机的技术一样的局限性。当主计算机出现故障时，由其控制的所有机床都将停止工作。这个问题促使了计算机数字控制技术的产生。 微处理器的发展为可编程逻辑控制器和微型计算机的发展做好了准备。这两种技术为计算机数控(CNC)的发展打下了基础。采用了CNC技术后，每台机床上都有一个可编程逻辑控制器或微机对其进行数字控制。这可以使得程序被输入和存储在每台机器内部。它还可以在机床以外编制程序，并且将其下载到每台机床中。计算机数控主要解决了主计算机发生故障所带来的问题，但是它产生了另一个被称为数据管理的问题。同一个程序可能要分别装入十个相互之间没有通信联系的微机中。这个问题正在解决之中，它是通过采用局部区域网 络将各个微机连接起来，以利于更好的进行数据管理。 数控机床的进给运动系统 数控机床进给运动系统，尤其是轮廓控制的进给运动系统，必须对进给运动的位置和运动的速度两个方面同时实现自动控制，与普通机床相比，要求其进给系统有较高的定位精度和良好的动态响应特性。一个典型数控机床闭环控制的进给系统，通常由位置比较放大单元、驱动单元、机械传动装置及检测反馈元件等几部分组成。这里所说的机械传动装置是指将驱动源的旋转运动变为工作台直线运动的整个机械传动链，包括减速装置、转动变移动的丝杠螺母副及导向元件等等。为确保数控机床进给系统的传动精度、灵敏度和工作的稳定性，对机械部分设计总的要求是消除间隙，减少摩擦，减少运动惯量，提高传动精度和刚度。另外，进给系统的负载变化较大，响应特性要求很高，故对刚度、惯量匹配都有很高的要求。 为了满足上述要求，数控机床一般采用低摩擦的传动副，如减摩滑动导轨、滚动导轨及静压导轨、滚珠丝杠等;保证传动元件的加工精度，采用合理的预紧、合理的支承形式以提高传动系统的刚度;选用最佳降速比，以提高机床的分辨率，并使系统折算到驱动轴上的惯量减少;尽量消除传动间隙，减少反向死区误差，提高位移精度等。 直线滚动导轨 直线滚动导轨的突出优点是无间隙，并且能够施加预紧力。由导轨体，滑块，滚珠，保持器，端盖等组成。又称单元式直线滚动导轨。使用时，导轨体固定在不运动件上，滑块固定在运动部件上。当滑块沿导轨体移动时，滚珠在导轨体和滑块之间的圆弧直槽内滚动 并通过端盖内的滚道，从工作负荷区到非工作负荷区，然后再滚动回工作负荷区，不断循环，从而把导轨体和滑块之间的移动变成滚珠的滚动。 桥式起重机 桥式起重机是桥架在高架轨道上运行的一种桥架型起重机，又称天车。桥式起重机的桥架沿铺设在两侧高架上的轨道纵向运行，起重小车沿铺设在桥架上的轨道横向运行，构成一矩形的工作范围，就可以充分利用桥架下面的空间吊运物料，不受地面设备的阻碍。 桥式起重机广泛地应用在室内外仓库、厂房、码头和露天贮料场等处。能对物品进行搬运、翻身、调整吊运状态等作业，主要用于各车间、分段生产线和钢材堆场等处。起重能力一般在10,100 t。桥式起重机本身作横向移动，车架上的绞车作纵向移动，吊在绞车上的吊钩作垂向移动，三个方向的运动的合成才能使起重机起作用。为了防止桥式起重机在驾驶员看不清楚具体的吊钩运动方式， 地面上一般配备有起重工进行指挥或夹、放吊钩。如果桥式起重机悬挂电磁吊吊运钢板，则往往由驾驶员自己操作。桥式起重机可分为普通桥式起重机、简易粱桥式起重机和冶金专用桥式起重机三种。 普通桥式起重机一般由起重小车、桥架运行机构、桥架金属结构组成。起重小车又由起升机构、小车运行机构和小车架三部分组成。 起升机构包括电动机、制动器、减速器、卷筒和滑轮组。电动机通过减速器，带动卷筒转动，使钢丝绳绕上卷筒或从卷筒放下，以升降重物。小车架是支托和安装起升机构和小车运行机构等部件的机架，通常为焊接结构。 起重机运行机构的驱动方式可分为两大类:一类为集中驱动，即用一台电动机带动长传动轴驱动两边的主动车轮;另一类为分别驱动、即两边的主动车轮各用一台电动机驱动。中、小型桥式起重机较多采用制动器、减速器和电动机组合成一体的“三合一”驱动方式，大起重量的普通桥式起重机为便于安装和调整，驱动装置常采用万向联轴器。 起重机运行机构一般只用四个主动和从动车轮，如果起重量很大，常用增加车轮的办法来降低轮压。当车轮超过四个时，必须采用铰接均衡车架装置，使起重机的载荷均匀地分布在各车轮上。 桥架的金属结构由主粱和端粱组成，分为单主粱桥架和双粱桥架两类。单主粱桥架由单根主粱和位于跨度两边的端粱组成，双粱桥架由两根主粱和端粱组成。 主粱与端粱刚性连接，端粱两端装有车轮，用以支承桥架在高架上运行。主粱上焊有轨道，供起重小车运行。桥架主粱的结构类型较多比较典型的有箱形结构、四桁架结构和空腹桁架结构。 箱形结构又可分为正轨箱形双粱、偏轨箱形双粱、偏轨箱形单主粱等几种。正轨箱形双粱是广泛采用的一种基本形式，主粱由上、下翼缘板和两侧的垂直腹板组成，小车钢轨布置在上翼缘板的中心线上，它的结构简单，制造方便，适于成批生产，但自重较大。 偏轨箱形双粱和偏轨箱形单主粱的截面都是由上、下翼缘板和不等厚的主副腹板组成，小车钢轨布置在主腹板上方，箱体内的短加劲板可以省去，其中偏轨箱形单主粱是由一根宽翼缘箱形主粱代替两根主粱，自重较小，但制造较复杂。 四桁架式结构由四片平面桁架组合成封闭型空间结构，在上水平桁架表面一般铺有走台板，自重轻，刚度大，但与其他结构相比，外形尺寸大，制造较复杂，疲劳强度较低，已较少生产。 空腹桁架结构类似偏轨箱形主粱，由四片钢板组成一封闭结构，除主腹板为实腹工字形粱外，其余三片钢板上按照设计要求切割成许多窗口，形成一个无斜 杆的空腹桁架，在上、下水平桁架表面铺有走台板，起重机运行机构及电气设备装在桥架内部，自重较轻，整体刚度大，这在中国是较为广泛采用的一种型式。 普通桥式起重机主要采用电力驱动，一般是在司机室内操纵，也有远距离控制的。起重量可达五百吨，跨度可达60米。 简易梁桥式起重机又称粱式起重机，其结构组成与普通桥式起重机类似，起重量、跨度和工作速度均较小。桥架主粱是由工字钢或其他型钢和板钢组成的简单截面粱，用手拉葫芦或电动葫芦配上简易小车作为起重小车，小车一般在工字粱的下翼缘上运行。桥架可以沿高架上的轨道运行，也可沿悬吊在高架下面的轨道运行，这种起重机称为悬挂粱式起重机。 冶金专用桥式起重机在钢铁生产过程中可参与特定的工艺操作，其基本结构与普通桥式起重机相似，但在起重小车上还装有特殊的工作机构或装置。这种起重机的工作特点是使用频繁、条件恶劣，工作级别较高。 双梁桥式起重机依靠沿厂房轨道方向的纵向移动，小车的横向移动和吊钩的升降运动来进行工作。适用于机械加工与装配车间、金属结构车间、机械维修车间、冶金与铸造车间以及种类仓库的吊运工作等。起重量用分数形式表示，分子为主钩起重量，分母为副钩起重量。主要有五种类型。 铸造起重机:供吊运铁水注入混铁炉、炼钢炉和吊运钢水注入连续铸锭设备或钢锭模等用。主小车吊运盛桶，副小车进行翻转盛桶等辅助工作。 夹钳起重机:利用夹钳将高温钢锭垂直地吊运到深坑均热炉中，或把它取出放到运锭车上。 脱锭起重机:用以把钢锭从钢锭模中强制脱出。小车上有专门的脱锭装置，脱锭方式根据锭模的形状而定:有的脱锭起重机用项杆压住钢锭，用大钳提起锭模;有的用大钳压住锭模，用小钳提起钢锭。 加料起重机:用以将炉料加到平炉中。主小车的立柱下端装有挑杆，用以挑动料箱并将它送入炉内。主柱可绕垂直轴回转，挑杆可上下摆动和回转。副小车用于修炉等辅助作业。 锻造起重机:用以与水压机配合锻造大型工件。主小车吊钩上悬挂特殊翻料器，用以支持和翻转工件;副小车用来抬起工件。 双梁桥式起重机，最大起重量100吨，吊钩式，抓斗式，电磁式，冶金起重机，淬火起重机，手动双梁桥式起重机，电动葫芦双梁桥式起重机 本单元起重机符合JB/T14405《通用桥式起重机》标准的规定，产品质量达到JB/T53442《通用桥式起重机产品质量分等》一等品要求。 其结构特点式具有起升及运行机构的小车位于桥架上运行，金属结构为箱形双主梁形式。按照取物装置特点分类为吊钩，抓斗，电磁以及多用途桥式起重机，主要用于矿山，工厂，码头及仓库等 作业频繁的物料搬运站，淬火起重机作为热处理工艺装备具有高速下降特性。冶金铸造起重机适用于运钢水包，是冶炼工业比不可少的设备。采用现代科技手段，可使起重机的任何一个结构具备跳速性能。还可配用旋转吊钩用于高层堆放作业。 单梁桥式起重机，最大起重量10吨，吊钩式，抓斗式，电磁式，悬挂单梁桥式起重机，手动单梁桥式起重机 本单元起重机符合JB/T1306《电动单梁桥式起重机》及JB/T2603《电动单梁悬挂桥式起重机》标准规定。其结构特点是电动葫芦或手动单轨小车沿主梁工字钢下翼缘运行，进行物料搬运作业，通常用于车间，仓库等物料搬运作业，其中手动单梁起重机用于不允许用电或者无电源场合。配合马达抓斗或单轨抓斗还可用于散装物料作业，本单元起重机结构紧凑，操作灵活，既可用于地面操作，也可用于司机室操作。特殊要求情况下，还可以进行遥控操作。是工业生产或贮运不可缺少的装备。 起重机正常工作时允许一次起吊的最大质量称为额定起重量。吊钩起重机的额定起重量不包括吊钩和动滑轮组的自重。抓斗和电磁吸盘等取物装置的质量计入额定起重量内。按标准规定，桥式起重机的起重量系列采用的是R10优先数系，从3.2 t开始，按1.25公比递增为4，5，6.3，8，10，12.5，16，20，25，32，40，50t„„。但目前国内的桥式起重机产品只是根据多年的生产惯例，从上述数列中选出一部分组成实际的起重量系列。最为常用的系列是5t，10t，16t，20t，32t和50t。通常，当起重量超过10t时设两个起升机构，即主起升机构和副起升机构，二者起重量之比约为1:4。主起升机构的起重量大，用以起吊重的货物;副起升机构的起重量小，但速度较快，用以起吊较轻的货物或作辅助性工作，以提高工作效率。 一般以起重机遇到的最大起吊重物来确定起重量，同时考虑转载工作的条件或工艺过程的要求。起重机不允许超载使用，因此在起吊物经常发生变化的场合，起重机应考虑一定的裕量。在某些情况下，偶尔需吊运超重物件时，可用两台起重机协同作业。在工艺流程固定，起吊物重量基本不变，起重机基本满载使用的情况下，可以取消副起升机构，以简化起重机的结构，降低成本。国外的大吨位桥式起重机也并不是都带有副起升机构的，而是按需要选装。 桥式起重机的使用安全事项: (1)每台起重机必须在明显的地方挂上额定起重量的标牌。 (2)工作中，桥架上不许有人或用吊钩运送人。 (3)无操作证和酒后都不许驾驶起重机。 (4)操作中必须精神集中、不许谈话、吸烟或做无关的事情。 (5)车上要清洁干净;不许乱放设备、工具、易燃品、易爆品和危险品。 (6)起重机不允许超荷使用。 (7)下列情况不许起吊:捆绑不牢;机件超负荷;信号不明;斜拉;埋或冻在地里的物件;被吊物件上有人;没有安全保护措施的易燃品、易爆器和危险品;过满的液体物品;钢丝绳不符合安全使用要求;升降机构有故障。 (8)起重机在没有障碍物的线路上运行时，吊钩或吊具以及吊物底面，必须离地面2m以上。如果越过障碍物时，须超过障碍物0.5m高。 (9)对吊运小于额定起重量50%的物件，允许两个机构同时动作;吊大于额定起重量50%的物件，则只可以一个机构动作。 (10)具有主、副钩的桥式起重机，不要同时上升或下降主、副钩(特殊例外)。 (11)不许在被吊起的物件上施焊或锤击及在物件下面工作(有支撑时可以)。 (12)必须在停电后，并在电门上挂有停电作业的标志时，方可做检查或进行维修工作。如必须带电作业时，须有安全措施保护，并设有专人照管。 (13)不许随便从车上往下乱扔东西。 (14)限位开关和联锁保护装置，要经常检查。 (15)不允许用碰限位开关作为停车的办法。 (16)升降制动器存在问题时，不允许升降重物。 (17)被吊物件不许在人或设备上空运行。 (18)对起重机某部进行焊接时，要专门设置地线，不准利用机身做地线。 (19)吊钩处于下极限位置时，卷筒上必须保留有两圈以上的安全绳圈。 (20)起重机不允许互相碰撞，更不允许利用一台起重机去推动另一台起重机进行工作。 (21)吊运较重的物件、液态金属、易爆及危险品时，必须先缓慢地起吊离地面100~200mm，试验制动器的可靠性。 (22)修理和检查用的照明灯，其电压必须在36V以下。 (23)桥式起重机所有的电气设备外壳均应接地。如小车轨道不是焊接在主梁上时，应采取焊接地线措施。接地线可用截面积大于75mm2的镀锌扁铁或10mm2的裸铜线或大于30mm2的镀锌圆钢。司机室或起重机体的接地位置应多于两处。起重机上任何一点到电源中性点间的接地电阻，均应小于4Ω。 (24)要定期做安全技术检查，做好预检预修工作。