1、TheVibrationAnalysisHandbook第五章滚动轴承的诊断中英对照感谢红星的审阅和指导,文章某些部分还是有翻的不对的地方,如有发现请通知我CHAPTER FIVE:Accurate Diagnosis of Antifriction Bearings章节5滚动轴承的精确诊断INTRODUCTION 简介This chapter describes procedures for identifying defects in antifriction bearings by analyzing frequencies generated by the moving parts.
2、Defects on bearing raceways, rolling elements, and the cage generate different frequencies. The spectrum shape, amplitude, frequency, sum and difference frequencies, and the time domain signal are useful in identifying the nature, location, combination, and size of defects.本章节描述了如何通过分析运动部件产生的频率来识别滚动
3、轴承的缺陷。轴承滚道，滚动元件和保持架上的缺陷会产生不同的频率。频谱形状，振幅，频率，和差频率，以及时域信号都有助于辨认缺陷的性质，位置，组合和大小。Methods are presented to calculate the bearing frequencies; identify if the bearing is in a thrust or radial load; calculate the length of inner race defects with the time domain signal; and measure the length of a defect on
4、the outer race in the frequency domain spectra. The nature of the defect, such as shallow flaking, deep fatigue spalls, corrosion, acid etching, fluting, and inadequate lubrication can be determined by analyzing the frequency and time domain data. These techniques can also identify bearings with exc
5、essive clearance and bearings that are not properly installed, such as those turning on the shaft or loose in the housing. Techniques used to predict the life span of a defective bearing are discussed.提出计算轴承频率的方法；确定轴承是否承受轴向或径向负荷；通过时域信号计算内圈缺陷长度；通过频域谱估算外圈上某个缺陷的长度。缺陷的性质，如浅层剥落，深层疲劳碎裂，腐蚀，酸蚀，电蚀和润滑不足等都可以通过
6、分析频域和时域数据确定。这些技术也可以用于识别轴承游隙过量以及轴承安装不当，例如跑内圈或跑外圈。对预测有缺陷轴承寿命的技术进行了讨论。DATA COLLECTION 数据采集Data collection is the most important step in evaluation of bearing condition. Data should be collected by placing the transducer in the bearing load zone with due respect to flexibility. If this is not done, the
7、best signal definition may not be obtained. For example, with a radial bearing in a radial load, the best signal is obtained in the radial position. For an angular contact bearing or a radial bearing in a thrust load, the best signal definition is obtained in the axial direction. The machine interna
8、l geometry, as well as which problems generate radial or thrust loads, must be determined in order to properly place the transducer. Data should be taken where the transfer function is best; for example, put the transducer on a bolt head, not the cover. For pillow-block, tending side dryer, and simi
9、lar bearings, the transducer should be placed near the top of the bearing. For bearings in gear housings, the transducer should be placed on a bolt head in the load zone.数据采集是评估轴承状况最重要的一步。采集数据时应该把传感器布置在轴承的承载区同时兼并灵活性。不这样做就无法获得最好的清晰信号。举例，在一个承受径向载荷的径向轴承，径向承载区可以采集到最好的信号。对于角接触轴承和径向轴承承受轴向载荷时，最佳的信号的采集位置是在轴
10、向。为了合理安装传感器，必须确认设备内部构造，以及哪些故障会产生径向或轴向载荷。数据应当在信号传递路径最好的位置采集；例如，把传感器放在螺栓头上，而不是轴承座端盖上。针对枕式轴承,操作侧吹风机，和类似的轴承，传感器应当被放在接近轴承顶部的位置。齿轮箱里的轴承，传感器应该放在承载区的螺栓头部上。TRANSDUCER SELECTION 传感器的选择Success or failure in diagnosing bearing defects often depends on the selection of the proper transducer. The discussions of t
11、ransducer selection in other chapters apply. However, a few words should be added here. Spherical roller bearings rotating at 1200 RPM can generate harmonics of BPFO in the 3,000 Hz range when fluting occurs. An accelerometer must be used in such cases.诊断轴承缺陷成功或失败通常取决于是否选择了适当的传感器。关于传感器的选择其他章节已经讨论过。但
12、是，这里需要做一些简单说明。转速1200RPM的球面滚子轴承，当出现电蚀的时候能在3000HZ范围内产生外圈缺陷频率的谐波。其他类似情况必须使用加速度传感器Low speed machines rotating as low as 2 or 3 RPM, other machines when bearing frequencies are below 10 Hz, and lightweight shafts installed in heavy housings all require either contacting or non-contacting displacement tra
13、nsducers for accurate diagnostics.低速设备的转速可能只有2或3RPM，其他设备如当轴承频率低于10HZ时以及重量轻的轴安装在较重的轴承座中时都需要接触式或非接触位移传感器才可以准确诊断The velocity transducer is still the best choice for frequencies between 10 and 2,000 Hz.针对频率处在10-2000Hz内的设备，速度传感器依然是最好的选择。GENERATED FREQUENCIES 产生的频率In order to understand the relationships
14、between the different rotating elements of a bearing, the equations describing the relative speeds must first be developed. These equations define the frequencies generated by antifriction bearings. A machine with a defective bearing can generate at least five frequencies. These frequencies are:为了理解
15、一个轴承不同旋转部件之间的关系，必须先建立一个描述其相对速度关系的公式。这些公式定义滚动轴承产生的频率。这些频率分别为：1. Rotating unit frequency or speed (S)2. Fundamental train frequency (FTF)3. Ball pass frequency of the outer race (BPFO)4. Ball pass frequency of the inner race (BPFI)5. Two times ball spin frequency (2 X BSF)1 旋转部件的频率或速度(S)2 轴承保持架故障频率 (F
16、TF)3 外圈通过频率(BPFO)4 内圈通过频率(BPFI)5 2倍的滚珠滚动频率 (2 X BSF)Figs. 5-1 and 5-2 show the axial and cross-sectional views of the geometry for a ball bearing, where vo, vc and vi are the linear velocities of the outer race, ball center, and inner race, respectively. Bd is the ball diameter, Pd is the pitch diam
17、eter of the bearing and is measured from ball center to ball center, andis the contact angle. If a vertical line is drawn through the bearing and another line is drawn where the ball contacts the inner and outer races, the angle between the two lines is the contact angle. See Fig. 5-2.图5-1和5-2显示了一个普
18、通深沟球轴承的侧面及轴向剖视图，其中vo,vc和vi分别是外圈，滚珠和内圈的线性速度。Bd是滚珠直径，Pd是轴承的节圆直径（滚动体中心圆直径），即对称位置的滚珠的中心距。是接触角。如果垂直画线垂直通过轴承中心，在画一条线连接滚珠和内外圈的接触点，那么这两条线之间的夹角就是接触角。请参见图 5-2。Fundamental Train Frequency轴承保持架故障频率The train or cage frequency is equivalent to the angular velocity of the individual ball centers. From Fig. 5-1, th
19、e linear velocity of each ball center can be described as,轴承保持架故障频率可被描述为单个滚珠中心的角速度。图5-1所示，每个滚珠中心线速度可被描述为，Angular velocity () is defined as the linear velocity (v) about a radius (r) or, 角速度（）可被定义为线速度（v）除以半径（r）,即：Therefore 因此可得到保持架的角速度公式3where c, is the angular velocity of the ball center or cage. Si
20、nce v =/r from Equation 2, c can be expressed as Equation 4, where i and o are the angular velocities of the inner and outer bearing races. The quantity c is also known as the fundamental train frequency.公式3中c是滚珠中心或保持架的角速度。利用公式2中的v=/r，c可用公式4来表述，i和o分别为轴承内外圈滚道的角速度。c的数值也被认为是保持架故障频率。Ball Pass Frequency
21、of Outer Race滚珠外圈通过频率The ball pass frequency of the outer race is defined as the frequency of the balls passing over a single point on the outer race. The BPFO can be described as the number of balls multiplied by the difference frequency between the cage and the outer race or,滚珠外圈通过频率被定义为滚珠通过外圈滚道面上
22、某一点的频率。BPFO可被说成是滚珠数乘以保持架和外圈的频率差，即：which can be rewritten, using Equation 4, as Equation 6 where Nb is the number of balls.公式5可通过公式4变化，得到公式6，其中Nb为滚珠的数量。Ball Pass Frequency of Inner Race 内圈通过频率The ball pass frequency of the inner race is defined as the frequency of the balls passing over a single poin
23、t on the inner race. The BPFI can be described as the number of balls multiplied by the difference frequency between the inner race and the cage or,滚珠内圈通过频率被定义为滚珠通过内圈滚道面上某一点的频率。BPFI可被描述为滚珠数乘以内圈和保持架的频率差，即：which can be rewritten, again using Equation 4, as Equation 8.公式7可通过公式4变换，即公式8.Ball Spin Frequen
24、cy滚珠自转频率The angular velocity of a ball about its center can be expressed in two different ways. First, considering the linear velocity of a point on the inner race in contact with the ball surface, the linear velocity (Vb) of a point on the ball surface is given as滚珠相对其自身中心的角速度可通过两种不同方式表达。首先，通过到滚珠表面
25、与内圈接触的某一点的线速度来说明，滚珠表面的某一点线速度Vb为：where ri, is the radius of the inner race. The ball angular velocity or ball spin frequency is thenri为内圈半径。滚珠角速度或滚珠自转频率为：or, from Fig. 5-2,由图5-2可得到公式11where rb, is the radius of the ball. Equation 11 can also be rewritten, using Equation 4, as Equation 12.rb为滚珠半径。公式11
26、同样可使用公式4变换，其结果为公式12。Second, considering the linear velocity of a point on the outer race in contact with the ball surface, the linear velocity of a point on the ball surface is given as其次，从滚珠表面与外圈接触的某一点的线速度来说明，此时滚珠表面某一点线的速度可表示为：Therefore,因此where ro, is the radius of the outer race. The ball spin fre
27、quency can then be expressed as Equation 15, which is exactly the same as Equation 12.ro为外圈滚道半径。滚珠自转频率可通过公式15表示，其公式变化过程参考公式12。Application of the Bearing Formulas 轴承公式的运用Equations 4, 6, 8, and 12 are general formulas where either bearing race, or both, could be rotating. Also, the bearing can have ei
28、ther balls or rollers and the contact angle may be equal to zero as in deep groove ball bearings.公式4，6，8和公式12是常用公式，可在轴承任一滚道或两个滚道一起旋转的情况下使用。另外，轴承可能是滚珠或滚子并且接触角可能像深沟球轴承那样为0。For the case where the outer race is stationary and the inner race is rotating,针对内圈转动外圈固定的情况，where S is the angular velocity or sp
29、eed of the rotating system. Equations 4,6,8, and 12 can then be reduced to:S为系统角速度或旋转速度。公式4,6,8和公式12可缩写为：For the case where the inner race is stationary and the outer race is rotating针对内圈固定外圈转动的情况，Equations 4,6,8 and 12 can then be reduced, in this case, to在这种情况下，公式4,6,8和12也可缩写为：The formula for BSF
30、calculates the speed of the ball or roller. However, the frequency generated by roller speed is seldom measured. This is true because the balls or rollers are incased in the cage and between the inner and outer races. If one of the rolling elements has a defect of any kind, the defect can strike the
31、 inner and outer races and/or the front and back side of the cage alternately. This generates two times BSF because the timing for each event is exact and occurs when the roller rotates half a revolution.BSF的公式计算了滚珠或滚子的自转速度。然而，很少测量到由滚子自转产生的频率。的确，这是因为滚珠或滚子都装在保持架中并且处在内外圈滚道之间。如果某一个滚动部件有某种缺陷，则缺陷会击打在内外圈面
32、上或交替击打在保持架的前后两侧上。这产生了2xBSF，因为当滚子旋转每半个周期时该事件都以非常精确的时间发生。All of these ideal bearing frequency formulas are based on the assumption of pure rolling contact between the rollers and races. The small error resulting from any slipping of these surfaces would produce somewhat lower values in the above equations. Also, if the bearing is turning on the shaft or in the housing, the bearing frequencies can be lower. When looseness is involved, the spectral lines at the bearing fr
