The nonlinear and ball pass effects of a ball bearing on rotor vibration

A ball bearing is generally assumed as a linear spring in rotor dynamic analysis. In real case, the force equilibrium of the bearing is changed as the relative position, of each ball with respect to the direction of radial force. So, the stiffness of the bearing is also changed and is a function of time and position. In this study, the nonlinear characteristics of a ball bearing are considered in analyzing the vibration response of a rotating shaft due to an unbalance force. A finite element method is used to analyze the vibration characteristics of a rotor-bearing system and a direct numerical integration is performed to calculate the transient response of the rotor system. The responses are converted to the frequency domain and the effects of the parametric excitation due to a ball bearing are examined. The test rig for the investigation of the effect of a ball bearing on the rotor vibration is set up and the results are compared with those of numerical calculation. The calculation results show that the amplitudes of the nonlinear model are larger than those of the linear one. The frequencies of the calculations can be matched to the measured frequencies.     

Improved ball crater micro-abrasion test based on a ball on three disk configuration

An improved ball crater micro-abrasion test method has been developed that differs from the conventional ball crater method. A ball-on-three-disk (BOTD) configuration provides mechanical stability and three simultaneous measurements of abrasion. An inclined BOTD geometry allows the specimens to be totally immersed in abrasive, which allows the use of dry abrasives as well as slurries and pastes. Use of a rubber ball gives effective three-body abrasion and provides results that are highly correlated with the ASTM G65 method. Use of dry abrasive with a rubber surface, rather than use of slurries and a metal ball, provides cutting action that is closer to actual field conditions, and allows high temperature test. Flooding the substrate with abrasive also avoids the problems encountered in conventional ball crater tests in that it provides spherical scars even for large particle abrasives, and spherical geometry allows direct computation of the volume of wear. Modeling of the BOTD scar geometry indicates that the BOTD contact pressure is similar to the contact pressures used in the ASTM G65 test. The BOTD microabrasion method provided excellent ranking of the abrasion rates of bare steel and two thicknesses of a TiAlN coating.     

Resistance to rolling of a ball on a plane

Rolling of a ball on a plane is considered in the case of loads causing plastic deformations. Resistance to rolling is considered to be a consequence of the work spent on deformations. Formulas for calculating the factor of resistance to rolling are proposed. Calculated results are confirmed by experimental data obtained for single and multiple rolling.     

钛球阀中球体的加工

介绍一种应用车床加工钛球体成形工艺及所用工装的使用方法。它具有加工效率高，质量好，劳动强度低等优点。     

球体镀铬对圆弧槽强度及其使用寿命的影响

分析了阀杆对低强度钢或铜合金球体圆弧槽剪切破坏的原因。提出了球体及其圆弧槽的镀铬工艺方法，并进行了球体镀铬后的耐磨性试验。     

球阀球体研磨机设计

介绍了球体研磨机的结构与工作原理，分析了研磨块的运动轨迹，确定了研磨块与导向杆的合理位置。     

Hydrogen embrittlement of a stainless ball bearing steel

Ball bearing steels are susceptible to hydrogen embrittlement caused by lubricant degradation. It has been shown that hydrogen embrittlement of 440C stainless steels is associated with the existence of M₇C₃ carbides. The behaviour of M₇C₃ carbides during hydrogen embrittlement was investigated by classical rotating beam fatigue and tensile tests of specimens into which hydrogen had been introduced by cathodic charging. The effects of the current density, the time and the stress of charging and the relaxation time between charging and mechanical testing were assessed. The hydrogen embrittlement was characterized by using tritiated water. High resolution autoradiography and scanning electron microscopy were used to determine the location of the hydrogen in the martensitic matrix relative to the M₇C₃ carbides and to the interfaces between the M₇C₃ carbides and small M₂₃C₆ carbides.     

某深沟球轴承失效分析

通过材料与热处理多项检测方法,对某深沟球轴承的失效原因进行分析和探讨,排除了材料和热处理对轴承失效的影响。显微组织观察发现,轴承在运转过程中产生高温,使轴承滚道产生二次（重新）淬火,是造成轴承碎裂失效的原因。     

Lubrication of a rubber ball rolling with spin

Relative spin is present between surfaces at each point of contact when a ball is rolled between two circular contra-rotating plates. This gives rise to tangential frictional tractions transmitted across the contact surfaces which may result in a creep of the ball perpendicular to its direction of rolling. This paper reports a study made of rubber and steel balls rolling between plates of perspex lubricated with various oils and water.In dry contact an unrestrained ball, whether of rubber or steel, was found to creep radially outwards between the contra-rotating plates in a manner anticipated by earlier work, but when surfaces were lubricated with a viscous oil steel balls showed a neutral behaviour and rubber balls actually crept inwards. The inward creep was quite unexpected. Such behaviour suggests a greater traction, due to spin, over the back half of the contact zone arising by tilt between the contact surfaces. Estimates and actual measurements of tilt generated by elastohydrodynamic action were used to predict inward creep which could then be compared directly with experiment. The comparison shows that tilt clearly contributes to inward creep though does not fully explain the observed results.     

某故障轴承钢球裂纹分析

对故障轴承钢球开裂后的断口进行宏观和微观观察,并对裂纹断口纵剖面以及沿直径方向的剖面进行了金相检查和微观组织分析。通过对比同类产品,综合分析了钢球开裂的性质和发生开裂的原因。     

Nonlinear impact model of a tennis racket and a ball

A nonlinear impact model of a ball impacting on a tennis racket was developed to investigate the impact characteristics of this collision. The impact model included a tennis ball, the tennis racket frame and string bed in a tennis racket. The governing equations for the impact model were derived and were solved by applying numerical analysis. Extensive parametric studies were conducted to study the effects of the system parameters including ball dynamic stiffness, ball damping ratio, racket head size, string tension, string axial rigidity, etc. The analysis results showed that although head size and string axial rigidity have negligible effects on the dwell time and velocity ratio of the ball, string tension can have a significant effect on the dwell time and velocity ratio of the ball.     

滚珠丝杠副滚动体自旋运动分析

滚珠丝杠副滚动体自转运动中包含自旋和纯滚动,滚动体的自旋运动造成滚动体滑动。利用角接触轴承旋滚比的概念和目前对滚珠丝杠副自旋运动的研究情况,采用运动分析的方法分析了丝杠公称直径、接触角和螺旋升角对滚珠丝杠副自旋运动的影响情况,为设计和选用滚珠丝杠副参数提供了参考。     

调心球轴承装球辅具设计

调心球轴承生产中的装球工序,因手工装球效率低一直是生产中的薄弱环节。通过使用装球辅具,生产效率大幅度提高,同时,改善了工人的劳动条件,并对保证产品质量起到了很好的作用。     

The expected volume of a random polytope in a ball*

For any convex body K in d-dimensional Euclidean space E^d(d≥2) and for integers n and i, n ≥ d + 1,1 ≤ i ≤ n, let V^(d)_n-ii(K) be the expected volume of the convex hull H_{n-i, i} of n independent random points, of which n-i are uniformly distributed in the interior, the other i on the boundary of K. We develop an integral formula for V^(d)_{n-i, i}(K) for the case that K is a d-dimensional unit ball by considering an adequate decomposition of V^(d)_n-i, i into d-dimensional simplices. To solve the important case i = 0, that is the case in which all points are chosen at random from the interior of B_d, we require in addition Crofton's theorem on mean values. We illustrate the usefulness of our results by treating some special cases and by giving numerical values for the planar and the three-dimensional cases.     

深沟球轴承失效故障分析

6020/P5轴承在使用过程中发生抱死故障。经对轴承的故障特征和理化分析,发现轴承在工作时承受了附加过大的轴向力,钢球的工作轨迹偏离正常位置使钢球的接触载荷增大,形成恶性循环,造成轴承卡死保持架断裂。     

Vibrations of a deformable ball rolling on a lubricated rigid half-space

The problem of vertical vibrations of a deformable ball rolling on a lubricated rigid half-space has been stated and numerically solved. It is assumed that the force, which causes the ball’s elastic deformation in the zone of lubricated concentrated contact, is applied to the ball. The problem’s mathematical model is reduced to the system of nonstationary integrodifferential equations and inequalities with initial and boundary conditions. The computational algorithm of the problem’s solution was based on Newton’s method and application of an implicit scheme to approximate nonstationary equations. Vibrational solutions, which describe the behavior of the system consisting of the ball and the lubrication layer both under excitation of the initial conditions and under the excitation force, have been obtained. It is shown that as opposed to the traditional elastohydrodynamic lubrication theory approach, in which contacting bodies are considered as massless ones, taking the ball’s mass and corresponding inertia into account makes it possible to extend the category of obtained solutions and investigate vibrational processes in the contact zone. The results may be used to analyze processes occurring in lubricated concentrated contacts of gears and rolling bearings.     

Fault detection in a ball bearing system using a moving window

A signal processing method to detect flaws in a ball bearing system is proposed. The method is formulated theoretically and the performance of the method is expressed in terms of signal to noise ratios. To verify the method, ball bearings with man-made defects and an actual production line were tested.     

球阀球体研磨装置改进

介绍了球阀的超硬喷涂球体研磨装置的改进及研磨原理和方法。     

推力球轴承保持架锁球模具结构改进

原来生产的推力球轴承的钢球数量为偶数且钢球直径较小。根据市场需要,开发设计了大量奇数钢球和钢球直径较大的轴承产品。为满足该类轴承的生产需要,对原铜保持架锁球模具结构进行了改进,保证了产品质量和生产效率。