Plate-like wear particle formation in a lubricated ball-on-plate friction pair

The mechanism of formation of plate-like wear particles in a ball-on-plate lubricated friction pair has been examined for wear constants of K < 10⁻¹⁰ (mm³ mm⁻¹ N⁻¹). The plate Vicker's hardness was 2.80–3.00 kN/mm², the sliding speed 1.74 m s⁻¹ and the load 50 N. The following mechanism is suggested: scratching of the surface and formation of ridges at the scratch border, lateral deformation of ridges and formation of thin sheets, and cracking and separation of plate-like particles from these sheets.     

Decision of lubricated friction conditions for materials of automobile transmission gear using neural network

It is hard to inspect the state of lubrication of an automobile transmission visually. Thus, it is necessary to develop a new inspection method. Wear debris can be collected from the lubricants of an operating transmission of an automobile, and its morphology will be directly related to the friction condition of the interacting materials from which the wear debris originated in the lubricated transmission. In this study, wear debris in lubricating oil are extracted by membrane filter (0.45 μm), and the quantitative values of shape parameters of wear debris are calculated by digital image processing. These shape parameters are studied and identified by an artificial neural network algorithm. The results of the study may be applicable to the prediction and diagnosis of the operating condition of transmission gear.     

Friction in starved hydrodynamically lubricated line contacts

The hydrodynamic friction coefficient, which determines the friction coefficient at high Sommerfeld numbers (viscosity⁎velocity/load) has a unique solution for the fully flooded case. As such the friction coefficient can be predicted as a function of the above number. As shown by Cameron (1976) [1] the friction coefficient in the fully flooded regime increases as the square root of the Sommerfeld number. For very low Sommerfeld numbers, the asperity interaction causes the friction coefficient to increase when entering the mixed lubrication regime.Even though a unique (and low) friction coefficient exists in the fully flooded regime, the situation is more complex in the starved regime. First of all the friction coefficient is higher in the starved regime, and secondly the coefficient depends on the degree of starvation.This paper analyses the load carrying capacity, the Poiseuille flow based friction and the Couette flow based friction, as a function of the degree of starvation. It is shown that the Poiseuille friction force diminishes fastest with starvation, followed by the load carrying capacity, and finally the Couette term diminishes slowest of all three terms.As a consequence the friction coefficient for sliding starved conditions is dominated by the Couette term.The current paper analyses the friction coefficient evolution as a function of starvation for line contact conditions, using analytical and numerical tools. Finally, curve fitted equations are given for the friction as a function of the starvation level.     

变速箱直齿轮副表面故障机理分析与试验

某闭式变速箱研发测试过程中,变挡直齿轮副产生表面接触疲劳剥落现象.分析实际工况,通过解析解方法和有限元模拟方法理论计算轮齿齿面接触应力;在金相显微镜下观看主轴失效齿轮表面浅层疲劳剥落特征,用洛氏硬度计测量主副轴齿轮硬度.结果表明:理论设计强度满足正常载荷工作性能要求;根据齿轮表面疲劳失效原因提出改善措施,重制后的齿轮在台架上重复上一次工况试验,未见任何疲劳失效现象,验证机理分析结果及改进措施合理,相关分析方法可为其他齿轮失效现象机理分析及措施改进提供参考.     

变速箱直齿轮副表面故障机理分析与试验

某闭式变速箱研发测试过程中,变挡直齿轮副产生表面接触疲劳剥落现象.分析实际工况,通过解析解方法和有限元模拟方法理论计算轮齿齿面接触应力;在金相显微镜下观看主轴失效齿轮表面浅层疲劳剥落特征,用洛氏硬度计测量主副轴齿轮硬度.结果表明:理论设计强度满足正常载荷工作性能要求;根据齿轮表面疲劳失效原因提出改善措施,重制后的齿轮在台架上重复上一次工况试验,未见任何疲劳失效现象,验证机理分析结果及改进措施合理,相关分析方法可为其他齿轮失效现象机理分析及措施改进提供参考.     

Nonlinear dynamics of a spur gear pair with time-varying stiffness and backlash based on incremental harmonic balance method

In this paper the incremental harmonic balance method (IHBM) is extended to analyze the nonlinear dynamics of a spur gear pair and some new results are obtained. At first the dynamical model of a spur gear pair is established, where the backlash, time-varying stiffness and static transmission error are all included. Here the time-varying stiffness and static transmission error are represented by the multi-order harmonic series through Fourier expansion. Based on the IHBM, the general forms of the periodic solutions for this system are founded, which is useful to obtain the solutions with arbitrary precision. And the difference between the frequency-response to the multi-order and single-order harmonic is analyzed. Then the effects of the multi-order harmonic on the kinds of the periodic solutions are also investigated by IHBM, and the comparison with the numerical solutions shows the validity of the proposed method. At last the influence of the damping ratio and the excitation amplitude on frequency-response curves is researched, which presents some useful information to analyze and/or control the dynamics of gear system.     

Hysteresis and lubricated rubber friction

The effect on the hysteresis coefficient of a scaling down of surface texture is examined theoretically. It is shown that a uniform reduction in scale, where in particular the number of asperities per unit area increases as the square of the scale factor, has no effect on the magnitude of the hysteresis peak although the velocity at which the peak occurs decreases. Temperature is assumed to be unaltered by the scale change. This result indicates a method of deciding whether or not the so-called adhesion component of wet rubber friction is substantially hysteretic in character. The result may also be of use more generally in experimental work since macroscopic surfaces are easier to simulate than microscopic surfaces.Some interesting general formulae are presented for the hysteretic friction coefficient. In particular it is shown that, for rubber on a rigid rough surface at very high pressures, this quantity is given by an integral of the product of the loss modulus of the rubber, the spectral density function for the rigid surface and other trivial factors, or alternatively as an integral over the autocorrelation function for the surface and other factors.     

Wear investigation of spur gear teeth

An FZG back‐to‐back gear test machine has been used to investigate the initial wear of spur gears. By making plastic replicas of the tooth surfaces, and measurements of the same using a 3D stylus instrument, the wear pattern has been analysed. The wear tests were run on the machine according to a predefined schedule. During planned stops, negative surface replicas were made. The replicas were measured, and the amount and distribution of wear analysed. SEM pictures were also taken of the tooth surfaces, and several different types of damage were identified. The results were compared with simulated results using identical loading and geometry. It was found that the wear was quite severe at the root of the wheels and also significant at the tip. The wear was also found to form an overloaded wave pattern on the original involute form of the tooth.     

滚齿直齿圆锥齿轮齿形的研究

对滚齿直齿圆锥齿轮提出了在其范成齿条的法面内,将一对滚齿直齿圆锥齿轮的啮合关系,与齿轮和范成齿条的加工啮合关系相结合的研究方法.在此基础上,利用包络法分析建立了滚齿直齿圆锥齿轮轮齿的齿面方程、滚齿直齿圆锥齿轮和范成齿条啮合的接触线方程.研制了可调倾角式滚切圆锥形齿轮加工装置.进行了直齿圆锥形齿轮滚切加工试验.结果表明加工的齿轮齿面形状与建立的齿面方程一致.     

Thermal activation in boundary lubricated friction

The friction coefficients for copper pairs lubricated with fatty acids and fluorinated fatty acids have been measured over a wide range of sliding speeds and temperatures. Sliding speeds in the range 10⁻⁷−10⁻² m s⁻¹ and temperatures in the range 4.2–300 K were used. The friction coefficients near 300 K are generally low and increase with sliding speed, while the friction coefficients at low temperatures are markedly higher and relatively independent of velocity. Each lubricant's friction vs. velocity behavior over the temperature range 150–300 K can be described by a friction-velocity master curve derived from a thermal activation model for the lubricant's shear strength. The activation energies deduced from this friction model are identical to those obtained in the same temperature range for a vibrational mode associated with low temperature mechanical relaxations in similarly structured polymers. These results suggest that thermally activated interfacial shear is responsible for the fatty acids' positive-sloped friction vs. velocity characteristics at low sliding speeds near room temperature.     

Computation of helical or spur gear fillets

This paper presents an algorithm for computing the form of helical or spur gear fillets on a digital computer. These types of tools are considered to generate the fillet: rack-type tool (hob, rack cutter, or grinding wheel) with or without a protruberance, shaper cutter, and shaving tool. Formulae for the coordinates of the fillet are derived and the boundary points of the fillet are determined both for non-undercut and undercut gearing. Flow diagrams for the solution of some difficult problems are given.     

直齿锥齿轮齿廓修形

根据啮合刚度和噪声之间的关系,以修形减振降噪为目的,用旋转渐开线曲线对直齿锥齿轮进行齿廓修形.以减小齿轮传动误差和啮合刚度的波动大小为衡量标准,同时确保载荷变化呈平稳过渡.静态计算结果表明,直齿锥齿轮齿廓长修形具有较好的减振效果.直齿锥齿轮采用冷精锻进行齿廓修形,显著地降低了成本,这为齿轮传动系统的修形、减振、降噪和设计提供了一种新的研究方法.     

Study of a spur gear dynamic behavior in transient regime

In this paper the dynamic behavior of a single stage spur gear reducer in transient regime is studied. Dynamic response of the single stage spur gear reducer is investigated at different rotating velocities.First, gear excitation is induced by the motor torque and load variation in addition to the fluctuation of meshing stiffness due to the variation of input rotational speed. Then, the dynamic response is computed using the Newmark method. After that, a parameter study is made on spur gear powered in the first place by an electric motor and in the second place by four strokes four cylinders diesel engine. Dynamic responses come to confirm a significant influence of the transient regime on the dynamic behavior of a gear set, particularly in the case of engine acyclism condition.     

An efficient numerical analysis of starved thermohydrodynamically lubricated rolling line contacts

Effect of starvation in thermohydrodynamically lubricated high rolling speed line contacts has been investigated numerically by using an efficient numerical method in which temperature variations across the lubricant film is approximated by the second-order of Legendre polynomial. Mechanism of starvation at the contact has been set by creating gradual reduction in the length of the computational domain from the inlet side. In the solution, the lubricant has been assumed to be a Newtonian fluid. Minimum film thickness and rolling traction coefficient under fully flooded and starved conditions have been computed in this work. The rolling traction coefficient, minimum film thickness, and maximum mid film temperature rise in the starved line contact are found to be lesser than the fully flooded contact condition.     

直齿圆柱齿轮的计算机辅助设计

以参数化设计思想为依据,以开发专业化的计算机辅助设计系统为目的,利用AutoCAD2000软件所支持的AutoLISP语言和Dialogcontrollanguage(DCL)对话框设计语言,开发了用对话框形式进行设计参数输入,并对整个直齿圆柱齿轮的设计计算、参数校核直至设计图的绘制输出实现完全自动化的计算机辅助设计系统。     

直齿圆柱齿轮的虚拟设计与分析

利用Pro/E程序本身的参数化功能实现了渐开线直齿圆柱齿轮的三维造型,同时应用其内在的Mechanica模块对建立的参数化模型进行仿真和有限元分析,从而生成应力、应变条纹图,运行结果验证了应用Pro/E软件进行虚拟设计的可行性和分析研究的正确性,并提高了设计研究的效率。     

斜齿锥齿轮产型轮的数控加工

介绍了利用UG生成斜齿锥齿轮产型轮的刀具轨迹进而获得数控代码,并在此基础上由4轴联动加工中心完成其齿廓加工的基本思想和具体步骤。为该类齿轮的数字化加工提供了有益的参考。     

Modelling lubricated friction for dynamic contact systems

Multi-valued friction is often observed in lubricated contact systems operating under unsteady sliding conditions. In the past, this behaviour has been modelled using a measured time delay between changes in sliding velocity and resulting changes in friction. More recent work has revealed that fluctuations in normal separation are the principal cause of this deviation from steady friction behaviour. This paper demonstrates that tangential contact dynamics can result in apparent deviations from steady friction that can resemble true deviations found from fluctuations in normal separation. Two different dynamic models are considered. One model accommodates the tangential rider dynamics of a friction test apparatus. The other model considers the possibility of tangential dynamics associated with asperity contacts.     

Torque loss in a gearbox lubricated with wind turbine gear oils

In this study, four different fully formulated ISO VG 320 wind turbine gear oils were select: a mineral oil‐based, a polyalphaolefin‐based, an ester‐based and a polyalkyleneglycol‐based fluids. Their physical properties (viscosity, thermoviscosity, piezoviscosity etc.) were characterised for a wide range of operating temperatures. A two‐stage multiplying gearbox, with helical gears, was selected to evaluate the influence of the wind turbine gear oil formulation on torque loss with the gearbox operating at low speed (130–230 rpm) and high torque (500–1000 Nm). The results obtained showed that each wind turbine gear oil formulation generated very different torque losses, evacuated heat flows and operating temperatures, with differences above 20 °C under the most severe operating conditions. A numerical model was developed, simulating all power loss mechanisms inside the gearbox, in particular the churning and friction losses. The coefficients of friction, between gear teeth and between rolling elements and bearing raceways, were calculated for all the tested oils. Copyright © 2013 John Wiley & Sons, Ltd.     

Transient EHL analysis on spur gear teeth with consideration of gear kinematics

Transient 3-dimensional elasto-hydrodynamic lubrication (EHL) analysis is performed on the contacting teeth surfaces of involute spur gears. Kinematics of the gear and the pinion are taken into account to get accurate geometric clearance around the EHL region of the contacting teeth. The surface pressure and film thickness distribution for the whole contact faces in a lubricated condition at several time steps are obtained through the analysis. Besides the pressure spike at the outlet region, a representative phenomenon in EHL regime, the pressure at the inlet region is slightly higher than that of the center region. The film thickness of transient condition is thicker than that of steady condition.