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Abstract The fixture design should meet the following basic requirements(1) the appropriate accuracy and dimensional stabilityFolder of the concrete on the important surfaces, such as the installation of the surface of the positioning components, install the surface of the knife and oriented components, as well as the specific folder to install the base surface (connected to the machine surface) should be the appropriate size and shape accuracy, they between should be the appropriate location accuracy.The folder of the stability of the specific dimensions, casting folder specific to the aging treatment, welding and forging folder specific annealing.(2) have sufficient strength and stiffness.Process, the specific folder you want to bear a greater cutting force and clamping force. To ensure that the folder does not produce does not allow deformation and vibration folder should have sufficient specific strength and stiffness, so the folder the specific needs of a certain wall thickness.(3) the structure of technology is good.Specific folder should be easy to manufacture, assembly and test. Casting folder the surface of the concrete on the installation of various components should be cast out of 3 5mm convex in order to reduce the processing area. Casting folder concrete wall thickness should be uniform, corner outside the due R3 R5mm, rounded corners. Specific folder structure should facilitate the loading and unloading of the workpiece.(4) to have the appropriate chip space and good chip evacuation.Cutting little jig for cutting can increase the distance between the work surface and fixture positioning components or addition of Chip grooves in order to increase the chip space; for processing a large number of chip fixture, you can set the BTA gap or bevel, bevel desirable.(5) installed on the machine stable and reliable.The installation of the fixture on the machine through the folder of the specifics of the installation of the base surface and the corresponding surface on the machine contact or in combination to achieve. When the fixture is installed in the machine table, the center of gravity of the fixture should be as low as possible, the center of gravity the higher the bearing surface shall be the greater; fixture underside of the four sides should be protruding, so that good contact folder of the installation of the base surface and the machine table. Contact edge or the width of the foot should be greater than the width of the machine table, trapezoidal slot, should be a processing and to guarantee a certain plane accuracy; When the fixture is installed on the machine spindle, fixture installation base surface with the corresponding spindle surface should be higher with precision, and to ensure stable and reliable specific folder to install.(6) have a good look.Specific folder appearance novel, steel folder to the specific needs of blueing or demagnetization, raw casting parts must be clean and paint.(7) Stamps play the fixture number to the appropriate location in the fixture tooling management.fixture manufacturing and process(1) fixture manufacturing precisionFixture is usually a single piece production, and manufacturing cycle is very short. In order to ensure that the workpiece processing requirements, many fixtures have a high manufacturing precision. The tool shop has a variety of processing equipment, such as the processing of the holes in the jig borer, processing of complex-shaped surface of the universal milling machines, precision lathes and a variety of grinders, have good processing properties and processing accuracy. Fixture manufacturing, in addition to the different production methods and products in general, in the application of the interchangeability principle under certain restrictions to ensure that the manufacturing precision of the fixture.(2) guarantee the accuracy of the method of fixture manufacturingDirectly related to the workpiece size and high precision parts, repair method commonly used in the fixture manufacture and adjustment to ensure that the fixture accuracy.1) Application of the Method of RepairParts need to use the repair method, in its pattern, marked assembly finishing assembly or worthy words. Assembly of the bearing plate and the supporting nail positioning surface, with the specific folder merge processing to ensure that positioning the face of the folder concrete base surface parallelism.Lathe fixture errors, and requires greater processing can be used in machine tools, processing positioning surface for concentricity. Such as the measurement process lathe fixture hole round of processing and correction, by excessive disk and use the lathe to connect directly processed, so that these two processing side of the centerline of the lathe spindle center overlap, to obtain more accurate positional accuracy .Boring jig is often used repair method. For example, boring sets of holes and the use of the actual size of the boring bar with a single gap in between 0.008 0.01mm can be boring mold high guiding accuracy.Fixture repair methods are related to a specific folder of the base surface, which does not result in a variety of error accumulation, and to achieve the desired accuracy requirements.2) Adjustment Act applicationsAdjustment Act and the Method of Repair, usually in the fixture can be set to adjust the washer, adjust the plate, adjust the set of components to control the assembly size. This method is relatively easy to adjust the right choices to other components of the compensation error, in order to improve the manufacturing precision of the fixture.(3) structural technicalStructural technical performance of the fixture for fixture parts manufacturing, assembly, commissioning, measurement, and use the performance. Structural elements of the general standard of the fixture parts and castings, and so on, can access to the manual design. Fixture components of the processing, maintenance, assembly and measurement process.1) Note that the processing and maintenance processFixture connection of the main components of positioning screws and pins. In Figure 1.2 (a) of the pin hole is made through-hole, so that maintenance can pin press out; shown in Figure 1.2 (b) pin, the pin hole at the bottom of the horizontal hole demolition; Figure 1.2 (c) is commonly used with threaded taper pins (GB118-2000).(A) The pin hole is made through-hole (b) A transverse hole (c) with threadedFigure 1.2 pin hole connection processFig. 1.2 pin hole connection technology2) Note that the measurement process of assemblyThe fixture assembly measurement is an important part of the fixture manufacturing. Assembly of the repair method or the method of adjustment assembly, or submit a test fixture accuracy, should deal with the problem of a good benchmark.In order to fixture assembly, measurement process, we should follow the benchmark uniform principles, to clip the specific surface is uniform benchmarks, in order to facilitate the assembly measurement fixture manufacturing to ensure accuracy. When the basal plane of the fixture can not meet the above requirements, you can set the process holes or craft Boss.BEARING LIFE ANALYSIS1 .WHY BEARINGS FAILAn individual bearing may fail for several reasons; however, the results of an endurance test series are only meaningful when the test bearings fail by fatigue-related mechanisms. The experimenter must control the test process to ensure that this occurs. The following paragraphs deal with a few specific failure types that can affect the conduct of a life test sequence.The influence of lubrication on contact fatigue life is discussed from the standpoint of EHL film generation. There are also other lubrication-related effects that can affect the outcome of the test series. The first is particulate contaminants in the lubricant. Depending on bearing size, operating speed, and lubricant rheology, the overall thickness of the lubricant film developed at the rolling element-raceway contacts may fall between 0.05 and 0.5 m . Solid particles and damage the raceway and rolling element surfaces, leading to substantially shortened endurances. This has been amply demonstrated by Sayles and MacPherson 19.6 and others.Therefore, filtration of the lubricant to the desired level is necessary to ensure meaningful test result. The desired level is determined by the application which the testing purports to approximate. If this degree of filtration is not provided, effects of contamination must be considered when evaluating test results. Chapter 23 discusses the effect of various degrees of particulate contamination, and hence filtration, on bearing fatigue life. The moisture content in the lubricant is another important consideration. It has long been apparent that quantities of free water in the oil cause corrosion of the rolling contact surfaces and thus have a detrimental effect on bearing life. It has been further shown by Fitch 19.7 and others, however, that water levels as low as 50-100 parts per million(ppm) may also have a detrimental effect, even with no evidence of corrosion. This is due to hydrogen embrittlement of the rolling element and raceway material. See also Chapter 23. Moisture control in test lubrication systems is thus a major concern, and the effect of moisture needs to be considered during the evaluation of life test results. A maximum of 40 ppm is considered necessary to minimize life reduction effects.The chemical composition of the test lubricant also requires consideration. Most commercial lubricants contain a number of proprietary additives developed for specific purposes; for example, to provide antiwear properties, to achieve extreme pressure and/or thermal stability, and to provide boundary lubrication in case of marginal lubricant films. These additives can also affect the endurance of rolling bearings, either immediately or after experiencing time-related degradation. Care must be taken to ensure that the additives included in the test lubricant will not suffer excessive deterioration as a result of accelerated life test conditions. Also for consistency of results and comparing life test groups, it is good practice to utilize one standard test lubricant from a particular producer for the conduct of all general life tests.The statistical nature of rolling contact fatigue requires many test samples to obtain a reasonable estimate of life. A bearing life test sequence thus needs a long time. A major job of the experimentalist is to ensure the consistency of the applied test conditions throughout the entire test period. This process is not simple because subtle changes can occur during the test period. Such changes might be overlooked until their effects become major. At that time it is often too late to salvage the collected data, and the test must be redone under better controls.For example, the stability of the additive packages in a test lubricant can be a source of changing test conditions. Some lubricants have been known to suffer additive depletion after an extended period of operation. The degradation of the additive package can alter the EHL conditions in the rolling content, altering bearing life. Generally, the normal chemical tests used to evaluate lubricants do not determine the conditions of the additive content. Therefore if a lubricant is used for endurance testing over a long time, a sample of the fluid should be returned to the producer at regular intervals, say annually, for a detailed evaluation of its condition.Adequate temperature controls must also be employed during the test. The thickness of the EHL film is sensitive to the contact temperature. Most test machines are located in standard industrial environments where rather wide fluctuations in ambient temperature are experienced over a period of a year. In addition, the heat generation rates of individual bearings can vary as a result of the combined effects of normal manufacturing tolerances. Both of these conditions produce variations in operating temperature levels in a lot of bearings and affect the validity of the life data. A means must be provided to monitor and control the operating temperature level of each bearing to achieve a degree of consistency. A tolerance level of3C is normally considered adequate for the endurance test process.The deterioration of the condition of the mounting hardware used with the bearings is another area requiring constant monitoring. The heavy loads used for life testing require heavy interference fits between the bearing inner rings and shafts. Repeated mounting and dismounting of bearings can produce damage to the shaft surface, which in turn can alter the geometry of a mounted ring. The shaft surface and the bore of the housing are also subject to deterioration from fretting corrosion. Fretting corrosion results from the oxidation of the fine wear particles generated by the vibratory abrasion of the surface, which is accelerated by the heavy endurance test loading. This mechanism can also produce significant variations in the geometry of the mounting surfaces, which can alter the internal bearing geometry. Such changes can have a major effect in reducing bearing test life.The detection of bearing failure is also a major consideration in a life test series. The fatigue theory considers failure as the initiation of the first crack in the bulk material. Obviously there is no way to detect this occurrence in practice. To be detectable the crack must propagate to the surface and produce a spall of sufficient magnitude to produce a marked effect on an operating parameter of the bearing: for example, noise, vibration, and/or temperature. Techniques exit for detecting failures in application systems. The ability of these systems to detect early signs of failure varies with the complexity of the test system, the type of bearing under evaluation, and other test conditions. Currently no single system exists that can consistently provide the failure discrimination necessary for all types of bearing life tests. It is then necessary to select a system that will repeatedly terminate machine operation with a consistent minimal degree of damage.The rate of failure propagation is therefore important. If the degree of damage at test termination is consistent among test elements, the only variation between the experimental and theoretical lives is the lag in failure detection. In standard through-hardened bearing steels the failure propagation rate is quite rapid under endurance test conditions, and this is not a major factor, considering the typical dispersion of endurance test data and the degree of confidence obtained from statistical analysis. This may not, however, be the case with other experimental materials or with surface-hardened steels or steels produced by experimental techniques. Care must be used when evaluating these latter results and particularly when comparing the experimental lives with those obtained from standard steel lots.The ultimate means of ensuring that an endurance test series was adequately controlled is the conduct of a post-test analysis. This detailed examination of all the tested bearings uses high-magnification optical inspection, higher-magnification scanning electron microscopy, metallurgical and dimensional examinations, and chemical evaluations as required. The characteristics of the failures are examined to establish their origins and the residual surface conditions are evaluated for indications of extraneous effects that may have influenced the bearing life. This technique allows the experimenter to ensure that the data are indeed valid. The “Damage Atlas” compiled by Tallian et al. 19.8 containing numerous black and white photographs of the various bearing failure modes can provide guidance for these types of determinations. This work was subsequently updated by Tallian 19.9, now including color photographs as well. The post-test analysis is, by definition, after the fact. To provide control throughout the test series and to eliminate all questionable areas, the experimenter should conduct a preliminary study whenever a bearing is removed from the test machine. In this portion of the investigation each bearing is examined optically at magnifications up to 30 for indications of improper or out-of-control test parameters. Examples of the types of indications that can be observed are given in Figs. 19.2-19.6.Figure 19.2 illustrates the appearance of a typical fatigue-originated spall on a ball bearing raceway. Figure 19.3 contains a spalling failure on the raceway of a roller bearing that resulted from bearing misalignment, and Fig. 19.4 contains a spalling failure on the outer ring of a ball bearing produced by fretting corrosion on the outer diameter. Figure 19.5 illustrates a more subtle form of test alteration, where the spalling failure originated from the presence of a debris dent on the surface. Figure 19.6 gives an example of a totally different failure mode produced by the loss of internal bearing clearance due to thermal unbalance of the system.The last four failures are not valid fatigue spalls and indicate the need to correct the test methods. Furthermore, these data points would need to be eliminated from the failure data to obtain a valid estimate of the experimental bearing life.2 .AVOIDING FAILURESThe best way to handle bearing failures is to avoid themThis can be done in the selection process by recognizing critical performance characteristicsThese include noise，starting and running torque，stiffness，non-repetitive run out，and radial and axial playIn some applications, these items are so critical that specifying an ABEC level alone is not sufficientTorque requirements are determined by the lubricant，retainer，raceway quality(roundness cross curvature and surface finish)，and whether seals or shields are usedLubricant viscosity must be selected carefully because inappropriate lubricant，especially in miniature bearings，causes excessive torqueAlso，different lubricants have varying noise characteristics that should be matched to the application. For example，greases produce more noise than oilNon-repetitive run out(NRR)occurs during rotation as a random eccentricity between the inner and outer races，much like a cam actionNRR can be caused by retainer tolerance or eccentricities of the raceways and ballsUnlike repetitive run out, no compensation can be made for NRR.NRR is reflected in the cost of the bearingIt is common in the industry to provide different bearing types and grades for specific applicationsFor example，a bearing with an NRR of less than 0.3um is used when minimal run out is needed，such as in diskdrive spindle motorsSimilarly，machinetool spindles tolerate only minimal deflections to maintain precision cutsConsequently, bearings are manufactured with low NRR just for machine-tool applicationsContamination is unavoidable in many industrial products，and shields and seals are commonly used to protect bearings from dust and dirtHowever，a perfect bearing seal is not possible because of the movement between inner and outer racesConsequently，lubrication migration and contamination are always problemsOnce a bearing is contaminated, its lubricant deteriorates and operation becomes noisierIf it overheats，the bearing can seizeAt the very least，contamination causes wear as it works between balls and the raceway，becoming imbedded in the races and acting as an abrasive between metal surfacesFending off dirt with seals and shields illustrates some methods for controlling contaminationNoise is as an indicator of bearing qualityVarious noise grades have been developed to classify bearing performance capabilitiesNoise analysis is done with an Ander-on-meter, which is used for quality control in bearing production and also when failed bearings are returned for analysis. A transducer is attached to the outer ring and the inner race is turned at 1,800rpm on an air spindle. Noise is measured in andirons, which represent ball displacement in m/rad.With experience, inspectors can identify the smallest flaw from their sound. Dust, for example, makes an irregular crackling. Ball scratches make a consistent popping and are the most difficult to identify. Inner-race damage is normally a constant high-pitched noise, while a damaged outer race makes an intermittent sound as it rotates.Bearing defects are further identified by their frequencies. Generally, defects are separated into low, medium, and high wavelengths. Defects are also referenced to the number of irregularities per revolution.Low-band noise is the effect of long-wavelength irregularities that occur about 1.6 to 10 times per revolution. These are caused by a variety of inconsistencies, such as pockets in the race. Detectable pockets are manufacturing flaws and result when the race is mounted too tightly in multiple jaw chucks.Medium-hand noise is characterized by irregularities that occur 10 to 60 times per revolution. It is caused by vibration in the grinding operation that produces balls and raceways. High-hand irregularities occur at 60 to 300 times per revolution and indicate closely spaced chatter marks or widely spaced, rough irregularities.Classifying bearings by their noise characteristics allows users to specify a noise grade in addition to the ABEC standards used by most manufacturers. ABEC defines physical tolerances such as bore, outer diameter, and run out. As the ABEC class number increase (from 3 to 9), tolerances are tightened. ABEC class, however, does not specify other bearing characteristics such as raceway quality, finish, or noise. Hence, a noise classification helps improve on the industry standard.Key words: bearing shell processing technology fixture design 摘要夹具设计应符合以下基本要求（1）有适当的精度和尺寸稳定性夹具体上的重要表面，如安装定位元件的表面、安装对刀和导向元件的表面以及夹具体的安装基面（与机床相连接的表面）等，应有适当的尺寸和形状精度，它们之间应有适当的位置精度。为使夹具体尺寸稳定，铸造夹具体要进行时效处理，焊接和锻造夹具体要进行退火处理。（2）有足够的强度和刚度。加工过程中，夹具体要承受较大的切削力和夹紧力。为保证夹具体不产生不允许的变形和振动，夹具体应有足够的强度和刚度，因此夹具体需要有一定的壁厚。（3）结构工艺性好。夹具体应便于制造、装配和检验。铸造夹具体上安装各种元件的表面应铸出35mm高的凸面，以减少加工面积。铸造夹具体壁厚要均匀，转角外应有R3R5mm的圆角。夹具体结构形式应便于工件的装卸。（4）要有适当的容屑空间和良好的排屑性能。对于切削时产生切削不多的夹具，可加大定位元件工作表面与夹具之间的距离或增设容屑沟槽，以增加容屑空间；对于加工时产生大量切屑的夹具，可设置排屑缺口或斜面，斜角可取。（5）在机床上安装稳定可靠。夹具在机床上的安装都是通过夹具体上的安装基面和机床上相应表面的接触或配合实现的。当夹具在机床工作台上安装时，夹具的重心应尽量低，重心越高则支承面应越大；夹具底面四边应凸出，使夹具体安装基面与机床的工作台面接触良好。接触边或支脚的宽度应大于机床工作台梯形槽的宽度，应一次加工出来，并保证一定的平面精度；当夹具在机床主轴上安装时，夹具安装基面与主轴相应表面应有较高的配合精度，并保证夹具体安装稳定可靠。（6）有较好的外观。夹具体外观造型要新颖，钢质夹具体需要发蓝处理或退磁，铸件未加工部位必须清理，并涂油漆。（7） 在夹具适当位置用钢印打出夹具编号，以便于工装的管理。夹具的制造及工艺性（1）夹具的制造精度夹具通常是单件生产，且制造周期很短。为了保证工件的加工要求，很多夹具要有较高的制造精度。企业的工具车间有多种加工设备，例如加工孔系的坐标镗床、加工复杂形面的万能铣床、精密车床和各种磨床等，都有具有良好的加工性能和加工精度。夹具制造中，除了生产方式与一般产品不同外，在应用互换性原则方面也有一定的限制，以保证夹具的制造精度。（2）保证夹具制造精度的方法对于与工件加工尺寸直接有关的且精度较高的部位，在夹具制造时常用修配法和调整法来保证夹具精度。 1）修配法的应用对于需要采用修配法的零件，可在其图样上注明“装配时精加工”或“装配时件配作”字样等。支承板和支承钉装配后，与夹具体合并加工定位面，以保证定位面对夹具体基面的平行度。车床夹具的误差较大，对于同轴度要求较大的加工，即可在所使用的机床中加工出定位面来。如车床夹具的测量工艺孔和校正圆的加工，可通过过度盘和所使用的车床连接后直接加工出来，从而使这两个加工面的中心线和车床主轴中心重合，获得较精确的位置精度。镗床夹具也常采用修配法。例如，将镗套的内孔与使用的镗杆的实际尺寸单配间隙在0.0080.01mm之间，即可是镗模具有较高的导向精度。夹具的修配方法都涉及到夹具体的基面，从而不致使各种误差累积，能够达到预期的精度要求。 2）调整法的应用调整法与修配法相似，在夹具上通常可设置调整垫圈、调整垫板、调整套等元件来控制装配尺寸。这种方法较简易，调整件选择得当即可补偿其他元件的误差，以提高夹具的制造精度。（3）结构工艺性夹具的结构工艺性主要表现为夹具零件制造、装配、调试、测量、使用等方面的综合性能。夹具零件的一般标准和铸件的结构要素等，均可查阅有关手册进行设计。以下就夹具部件的加工、维修、装配、测量等工艺性进行分析。 1）注意加工和维修的工艺性夹具主要元件的连接定位采用螺钉和销钉。 2）注意装配的测量工艺性夹具的装配测量是夹具制造的重要环节。无论是修配法装配或调整法装配，还是用检具检测夹具精度时，都应处理好基准问题。为了使夹具的装配、测量具有良好的工艺性，我们应遵循基准统一原则，以夹具体的基面为统一的基准，以便于装配、测量时保证夹具的制造精度。当夹具的基面不能满足上述要求时，可设置工艺孔或工艺凸台。 轴承寿命分析1 .轴承失效的原因轴承失效有以下多种原因，然而轴承的寿命实验却是所有机械实验中最有意义的。实验者必须控制实验过程以确保结果。下边几段就详细论述了可以影响寿命试验结果的几种失效模式。从EHL的观点讨论了润滑条件对寿命试验结果的影响，同时还有其他的润滑条件会影响实验的结论，首先是润滑剂的接触面积，受到轴承的尺寸，转速，润滑剂的流动性等因素的影响，润滑剂在轴承表面形成的润滑层的厚度一般小于0.050.5um，大于这个薄层厚度的固体微粒会残留在接触面上，从而划伤润滑沟道和轴承的滚动面。从而大大缩短轴承的耐用性。关于这点Sayles和MacPherson以及其他人都有详细的论证。因此，为了确保实验结果我们必须选用合适等级的润滑剂。润滑剂的选择由工况决定，实验时也如此。如果工况选择的范围不确定，就必须考虑到接触面积对实验结果的影响。不同的接触面积对轴承失效寿命实验结果的影响。潮气是影响润滑结果的另一个重要因素，长时间在水中和油中被腐蚀不但对外观质量有影响，还会影响到滚动表面的轴承寿命。关于这点Fitch等人19.7有过论证。而且，即使是仅有50100PPM（百万分之一）的水汽含量也会产生有害影响，甚至产生表面看不出痕迹的腐蚀。这是由于轴承的沟道和滚动面之间会产生氢脆现象，从23章中也可以看出在润滑实验中湿气是如此重要的一个因素。因此在轴承寿命的试验结果中必须考虑到潮气的影响。为了降低对寿命减少的影响，潮气的含量最多不能超过40PPM。润滑剂的化学成分也是需要考虑的。大多数商业润滑油包含许多为特定目的而开发的专有添加剂。例如，为了提高抗磨损性能，为了能达到极限压力，或者耐热性，还可以在边际润滑油膜的情况下提供边界润滑还能为边界润滑提供一个边界润滑层。这些添加剂同时也能即时的或者逐渐地影响滚动轴承的耐用性。为了避免添加剂成为加速寿命试验的条件，我们必须小心以确保测试润滑剂的添加剂不会受到恶化。为了保证同组产品寿命试验的结果有连贯性，最好在整个寿命试验中都用同一供应商的标准润滑剂。为了得到一个合理的结果，统计学要求做很多组寿命试验。因此一个轴承的寿命试验需很长的时间。实验人员必须保证整个实验过程的连续性，由于任何微小的变化都会影响实验结果，因此这个过程是很复杂的。甚至这些微小的变化在造成重大变化之前都不会被注意到。一旦发生这样的情况，就没机会补救了。只能在更好的控制条件下重新做实验。比如说：添加剂的稳定性会影响到整个实验的条件。现在已经知道了一些添加剂在长期使用时会造成大量的额外损耗。这些易退化的添加剂会影响轴承表面的润滑条件，从而影响轴承的寿命。一般的对润滑剂做化学检测时是不会检测添加剂的成分的。因此，如果一种润滑剂用于长时间的轴承寿命实验的话，生产者应该定期更换实验的样品，比如一年一次。用来详细