Variation in contact load at the most loaded position of the outer raceway of a bearing in high-speed train gearbox

For the fatigue failure and tribological property of a rolling element bearing,the contact load variation plays a significant role while the most loaded position of the bearing outer raceway takes the greatest risk of failure.This paper focuses on the variation in contact load on the most loaded position of the outer raceway of a gearbox bearing in high-speed train.Under operation conditions of different input speeds and torques,the dynamic contact load distribution in a gearbox bearing of high-speed train was measured by instrumenting the bearing with strain gauges.The most loaded position was identified accordingly and the features and reasons of the variation in contact load on this position were suggested.Three factors were found to have varying degrees of impact on the contact load variation under different gear meshing conditions:modal vibration of the cage or shaft,radial geometrical differences among the rollers and vibration of the gearbox housing.

Loaded multi-tooth contact analysis and calculation for contact stress of face-gear drive with spur involute pinion

The analytical method based on "Hertz theory on normal contact of elastic solids" and the numerical method based on finite element method (FEM) calculating the contact stress of face-gear drive with spur involute pinion were introduced, and their relative errors are below 10%, except edge contact, which turns out that these two methods can compute contact stress of face-gear drive correctly and effectively. An agreement of the localized bearing contact stress is gotten for these two methods, making sure that the calculation results of FEM are reliable. The loaded meshing simulations of multi-tooth FEM model were developed, and the determination of the transmission error and the maximal load distribution factor of face-gear drive under torques were given. A formula for the maximal load distribution factor was proposed. By introducing the maximal load distribution factor in multi-tooth contact zone, a method for calculating the maximal contact stress in multi-tooth contact can be given. Compared to FEM, the results of these formulae are proved to be reliable, and the relative errors are below 10%.

Enhanced drug loading efficiency of contact lenses via salt-induced modulation

Low drug loading efficiency is one of the main obstacles hindering the application of contact lenses(CLs) as the carrier for extended ocular drug delivery. Here in this study, a simple and effective drug loading method based on salt induced modulation was proposed and demonstrated with mechanism elucidation. First of all, using poly(2-hydroxyethyl methacrylate)(p-HEMA) as the contact lens material, betaxolol hydrochloride, Diclofenac Sodium and Betaxolol Base as the model drugs with different solubility, influence of salt concentration,salt type(sodium salts of sulfate, chloride, and sulfocyanate) and drug properties in the loading solution on drug loading efficiency was investigated. Mechanism of enhanced drug loading in contact lens was further explored via studying the influence of salt on the absorption isotherm, drug solubility and water content of CLs. Applicability of this method to other CLs materials was also investigated. It was demonstrated that adjusting the ionic strength of loading solutions resulted in significant increase of drug loading in CLs. Type and concentration of the salts and solubility of the drug were the main factors influencing enhancement ratio of drug loading. The mechanism for improved drug loading was related to the reduced drug solubility in loading solutions and the reduced bound water content in contact lenses. Modulation of drug loading by adjusting ionic strength was also applicable to other CLs and the light transmittance was not affected. This method was more suitable for salt-form drugs with high solubility. In summary, adjusting ionic strength of loading solution is an economical and effective way to improve drug loading in CLs, and this simple method may also find application in other hydrogel based drug delivery systems.

Design of Non-contact On-load Automatic Regulating Voltage Transformer

At present, an automatic-mechanic contact tap-changer is widely used in power system, but it can not frequently operate. In addition, arc will occur when the switch changes. In order to solve these two problems, this paper presented an automatic on-load voltage-regulating distributing transformer which employed non-contact solid-state relay as tap-changer, and mainly introduced its structure, basic principal, design method of each key link and experimental results. Laboratory simulation experiments informed that the scheme was feasible. It was a smooth and effective experiment device, which was practical in application.

Load distribution of involute gears along time-varying contact line

Base on the theory of energy minimization, a numerical algorithm is established to calculate load distribution, and the relationship curve of spur gear load distribution is obtained, and the load distribution ratio changes from 033 to 067 in double contact zone. This theory is adopted to compute the load distribution of helical gear along time-varying contact line, and the load distribution varies with the instantaneous position of the meshing point and the length of contact line, and the maximum value of load appears at the pitch point. Compared with the load distribution results, the helical gear changes more smoothly than spur gear. The load distribution provides a basis for calculate tooth bending deformation and critical stress.

Contact analysis and load distribution of double-envelop hourglass worm gearing affected by errors and load

An approach for the contact analysis and load distribution of double-envelop hourglass worm gearing is presented, which is based on a 3-D elastic contact finite element method (FEM) model that accommodates the influence of errors and load. As compared with existing tooth contact analysis model that assumes rigidity for the contacting surfaces, the proposed model provides a more realistic analysis on the contact patterns, the distribution of contact load and transmission errors. It is also capable of exploring the influence of different errors on meshing performances, the contact deformation, the shift of the contact zone and load share among the meshing tooth-pairs under different load.

STUDY ON LOADS AND CONTACT STRESSES FOR TOROIDAL DRIVE

The load distribution and calculating formulae of the contact stresses in the rotor worm and stator helical surface for toroidal drive are given. The effecting factors on contact stresses and their effects are analyzed. The results is useful for reference purposes in manufacture and design of the drive.

Dynamics of a Dual Power-split Transmission Based on Loaded Tooth Contact Analysis

In order to implement the dynamic characteristic of a dual power-split transmission, a dynamic me- chanics model is built. Firstly, according to the method of theoretical analysis of the tooth contact analysis （TCA） and loaded tooth contact analysis （LTCA）, the actual meshing process of each gear pairs is simulated, and the time-varying mesh stiffness excitations are obtained, which can improve the numerical precision. Second- ly, by using the lumped mass method, the bending-torsional coupling three dimensional dynamic model of the dual power-split transmission is established, and the identical dimensionless equations are deduced by elimina- ting the effect of rigid displacement and the method of dimensional normalization. Finally, by the method of the fourth order Runge-Kutta algorithm with variable step lengths, the responses of this system in a frequency domain and time domain are obtained, and the dynamic load change characteristics of each gear pairs are analyzed. The results show that the establishment, solution and analysis of the system dynamics model could provide a basis for the dynamic design, and have an important significance for the dynamic efficiency analysis and dynamic perform- ance optimization design of the dual power-split transmission.

Contact Force Distribution and Static Load-carrying Capacity of Large Size Double Row Four-point Contact Ball Bearing

Clearance not only affects the startup torque,rotation precision and stiffness of bearing,but also affects the load distribution,load-carrying capacity and life of bearing.A computational model in which the clearance of bearing is first included is presented for determining the contact force distribution and static load-carrying capacity of a double row four-point contact ball bearing which is subjected to the combined radial,axial and overturning moment loadings.The relation between the negative axial clearance and the contact force distribution is analyzed.The static load-carrying capacity curves are established,and the effects of the changes in negative axial clearance,curvature radius coefficient of raceway groove and initial contact angle on the static load-carrying capacity are analyzed.The results show that,with the increase in the absolute value of negative clearance,the maximum contact load decreases first and then increases.The clearance values in the range of 0.2 mme0 mm have little effect on the static load-carrying capacity of bearing.With the increase in the curvature radius coefficient of raceway groove and the decrease in the initial contact angle,the static load capacity of bearing decreases.

浸渍石墨材料在不同法向载荷下的磨损性能研究

研究不同摩擦体系下法向载荷对浸渍石墨的摩擦磨损特性的影响,采用扫描电子显微镜和激光共聚焦显微镜分别表征摩擦表面磨痕形貌、磨痕轮廓,对浸渍石墨与对偶球(GCr15钢球和Si_(3)N_(4)陶瓷球)的摩擦磨损情况与机制进行评估分析。结果表明:磨损痕迹随着施加载荷的增加而加深加宽,磨损率与法向载荷呈负相关,而摩擦因数、磨损体积则与法向载荷呈正相关;小载荷作用下石墨的磨损机制为黏着磨损和磨粒磨损,大载荷下则主要表现为黏着磨损、氧化磨损以及疲劳磨损;GCr15/石墨摩擦副相比于Si_(3)N_(4)/石墨摩擦副磨损率较低,在摩擦过程中形成完整、连续性更好的“第三体”转移膜减轻了磨损,对石墨基体起到保护作用。

安装误差对双圆弧齿轮啮合特性影响分析

为深入研究安装误差对双圆弧齿轮副啮合特性的影响,基于有限元法建立齿轮加载分析模型,研究啮合过程中单齿凸、凹齿廓的接触性能,对比分析安装误差对接触性能以及传动误差的影响规律。结果表明:啮合周期内,双圆弧齿轮的凹齿廓先接触且承担较大的法向接触力,但凸齿廓的啮入端接触应力最大,凸、凹齿面接触压力差与转矩成正比;安装误差对齿面接触性能影响较大,其中中心距误差容易引起齿轮分阶处应力集中,轴线平面的安装误差会引起齿面接触偏载,且对安装误差影响最大。

LOAD SHARING AND CONTACT OF HOURGLASS WORM GEARING

Based on solid modeling, the geometry and the FE model of the hourglass worm gearing are established. By the hybrid method of FEM and penalty function, the load sharing among tooth paris and the stress of contact teeth are calculated, the contact zones and the distribution of the contact pressure are investigated. The variation of the contact states with the load is investigated by comparision of its contact patterns under different loads.

基于滚珠丝杠副滚珠载荷分布的摩擦力矩计算方法研究

为了研究丝杠转速、轴向载荷、螺旋升角和滚珠直径对摩擦力矩的影响规律,在综合考虑滚珠载荷分布、实际工况中接触角变化、法向力差异、润滑油黏性阻力、滚珠惯性力和惯性力矩等因素上,建立了一种计算滚珠丝杠副摩擦力矩的方法。结果表明:当丝杠转速或轴向载荷增大时,摩擦力矩越来越大;增大的轴向载荷或者减小的丝杠转速导致摩擦因数越来越小;随着螺旋升角变大时,摩擦因数和摩擦力矩均逐渐减小,且随着螺旋升角的增大,两者的变化率逐渐减小;滚珠直径的变大致使摩擦力矩变大。分析结果可为滚珠丝杠副的设计提供参考,有助于进一步提高滚珠丝杠副的传动性能。

变载荷作用下的角接触球轴承动力学分析

为研究球轴承在变载荷作用下的动力学行为,建立了角接触球轴承的动力学模型,并在不同的载荷谱下进行了角接触球轴承的动力学计算,对比了不同载荷谱作用下球与内外圈的接触角和接触载荷以及球的自转角速度和公转角速度随时间的变化。结果表明:载荷瞬时变化产生的冲击会导致球与内外圈的接触载荷和接触角发生突变,且变化幅度与冲击载荷大小相关;在受载荷冲击后,球的自转角速度和公转角速度也会发生突变,并且随轴承的转动,球的自转角速度和公转角速度会最终达到一个稳定值;载荷变化幅度越大,变化频率越快,轴承运动的变化幅度就越大。

新型内啮合S型齿轮啮合效率计算与分析

为了准确计算新型内啮合S型齿轮的啮合效率,引入了考虑轮齿表面滑差、润滑油状况及时变载荷等因素的弹流润滑时变摩擦模型;分析啮合齿面润滑机制,通过轮齿接触分析(Tooth ContactAnalysis,TCA)及轮齿承载接触分析,计算了啮合齿面滑动摩擦因数及摩擦损失功率;在此基础上,获得内啮合S型齿轮啮合周期内的瞬时啮合效率和平均啮合效率,并给出了计算实例。研究结果表明,在相同设计参数下,新型内啮合S型齿轮较渐开线齿轮有更高的啮合效率;经螺旋线修形后,新型内啮合S型齿轮的啮合效率有所提高且随修形量的增大而增大。

基于时变啮合刚度的修形齿轮承载接触分析

为了解决传统齿轮承载接触分析力学解析方法难以考虑齿廓修形的问题,以齿廓修形渐开线直齿轮为研究对象,基于时变啮合刚度,提出了一种齿轮承载情况下齿间载荷分配系数与齿面接触应力解析算法。通过对比齿轮承载接触时接触点在啮合线方向的变形量与修形量,提出修形齿轮单双齿啮合状态判定方法,并计算不同状态下的啮合刚度;推导修形齿轮的啮合力、刚度与变形的力学关系,建立各啮合齿对的齿间载荷分配系数计算模型,应用赫兹接触理论求解齿面接触应力;分别在不同修形高度、修形曲线与配对齿数情况下,计算分析多种齿廓修形算例的齿间载荷分配系数与齿面接触应力。结果表明,解析算法求解的齿间载荷分布系数、齿面接触应力及相应单双齿啮合区间与有限元结果相一致,相对误差较小,证明了该算法有较高的精度与稳定性,为齿廓修形齿轮承载接触分析提供一种高效便捷的新方法。

高接触比螺旋锥齿面修形方法及动态特性研究

为抑制高接触比螺旋锥齿轮传动的振动,提出一种新的高阶齿面修形方法。根据高接触比螺旋锥齿轮的啮合特点,提出一种新的修形曲线,采用辅助齿面修形方法生成高阶修形螺旋锥齿轮。在考虑齿变形的情况下,计算了高阶修正弧齿锥齿轮传动的载荷传递误差和啮合冲击,在此基础上建立了降低高接触比螺旋锥齿轮传动的载荷传递误差和啮合冲击的优化模型。仿真结果表明:与二阶修形弧齿锥齿轮相比,高阶齿面修形方法不仅可以有效降低高接触比螺旋锥齿的载荷传递误差、啮合冲击和动态负载系数,而且可以提高其在全速范围内的动态性能。

径向游隙对圆柱滚子轴承疲劳寿命的影响

应用经典的滚动轴承理论和“切片法”的基本思想,以某大兆瓦风电机组齿轮箱输出轴轴承为例,采用Romax Designer工程分析软件,计算了圆柱滚子轴承不同径向游隙时的轴承内部载荷分布、接触应力、套圈滚道当量动载荷和寿命,分析径向游隙对轴承ISO/TS 16281寿命的影响。研究结果表明:径向游隙不仅通过对轴承内部载荷分布、接触应力和套圈滚道当量动载荷的影响而对寿命产生影响,还通过对寿命修正系数等因素的影响而对寿命产生影响。研究结果可为滚子类轴承的优化设计提供参考。

二级齿轮减速器高速级轴承动态特性分析

为探究减速器轴承在动载荷作用下的动态特性变化规律,以高速级轴承为研究对象,采用广义有限元法建立了计入轴柔性、齿轮与轴承时变刚度的二级齿轮传动系统动力学模型,求解并获得轴承动载荷。基于显示动力学法建立了轴承有限元模型,计算在动载荷作用下轴承外圈的应变时域历程,并通过试验验证仿真结果的正确性。最后分析了轴承在动载荷和恒定载荷下接触特性以及打滑特性的变化规律,结果表明:在动载荷作用下,动应力波动幅值增加且内圈运动轨迹呈不稳定态势;外圈动态接触力呈余弦分布形式且波动周期与动载荷保持一致;保持架和滚子的打滑率增加,滚子运动轨迹椭圆率减小且出现“滞后承载,提前退出”的承载形式。