Advancing high-speed train gearbox durability:enhanced bearing load and contact stress through transition from helical to herringbone gears

High-speed trains typically utilize helical gear transmissions,which significantly impact the bearing load capacity and fatigue service performance of the gearbox bearings.This paper focuses on the gearbox bearings,establishing dynamic models for both helical gear and herringbone gear transmissions in high-speed trains.The modeling particularly emphasizes the precision of the bearings at the gearbox's pinion and gear wheels.Using this model,a comparative analysis is conducted on the bearing loads and contact stresses of the gearbox bearings under uniform-speed operation between the two gear transmissions.The findings reveal that the helical gear transmission generates axial forces leading to severe load imbalance on the bearings at both sides of the large gear,and this imbalance intensifies with the increase in train speed.Consequently,this results in a significant increase in contact stress on the bearings on one side.The adoption of herringbone gear transmission effectively suppresses axial forces,resolving the load imbalance issue and substantially reducing the contact stress on the originally biased side of the bearings.The study demonstrates that employing herringbone gear transmission can significantly enhance the service performance of high-speed train gearbox bearings,thereby extending their service life.

Measured load spectra of the bearing in high-speed train gearbox under different gear meshing conditions

The load spectrum is a crucial factor for assess-ing the fatigue reliability of in-service rolling element bear-ings in transmission systems.For a bearing in a high-speed train gearbox,a measurement technique based on strain detection of bearing outer ring was used to instrument the bearing and determine the time histories of the distributed load in the bearing under different gear meshing conditions.Accordingly,the load spectrum of the total radial load car-ried by the bearing was compiled.The mean value and class interval of the obtained load spectrum were found to vary non-monotonously with the speed and torque of gear mesh-ing,which was considered to be caused by the vibration of the shaft and the bearing cage.As the realistic service load input of bearing life assessment,the measured load spectrum under different gear meshing conditions can be used to pre-dict gearbox bearing life realistically based on the damage-equivalent principle and actual operating conditions.

Generalized Demodulation Transform for Bearing Fault Diagnosis Under Nonstationary Conditions and Gear Noise Interferences

It is a challenging issue to detect bearing fault under nonstationary conditions and gear noise interferences. Meanwhile, the application of the traditional methods is limited by their deficiencies in the aspect of computational accuracy and e ciency, or dependence on the tachometer. Hence, a new fault diagnosis strategy is proposed to remove gear interferences and spectrum smearing phenomenon without the tachometer and angular resampling technique. In this method, the instantaneous dominant meshing multiple(IDMM) is firstly extracted from the time-frequency representation(TFR) of the raw signal, which can be used to calculate the phase functions(PF) and the frequency points(FP). Next, the resonance frequency band excited by the faulty bearing is obtained by the band-pass filter. Furthermore, based on the PFs, the generalized demodulation transform(GDT) is applied to the envelope of the filtered signal. Finally, the target bearing is diagnosed by matching the peaks in the spectra of demodulated signals with the theoretical FPs. The analysis results of simulated and experimental signal demonstrate that the proposed method is an e ective and reliable tool for bearing fault diagnosis without the tachometer and the angular resampling.

Coupled lateral-torsional-axial vibrations of a helical gear-rotor-bearing system

Considering the axial and radial loads, a math- ematical model of angular contact ball bearing is deduced with Hertz contact theory. With the coupling effects of lateral, torsional and axial vibrations taken into account, a lumped-parameter nonlinear dynamic model of helical gearrotor-bearing system （HGRBS） is established to obtain the transmission system dynamic response to the changes of dif- ferent parameters. The vibration differential equations of the drive system are derived through the Lagrange equation, which considers the kinetic and potential energies, the dis- sipative function and the internal/external excitation. Based on the Runge-Kutta numerical method, the dynamics of the HGRBS is investigated, which describes vibration properties of HGRBS more comprehensively. The results show that the vibration amplitudes have obvious fluctuation, and the frequency multiplication and random frequency components become increasingly obvious with changing rotational speed and eccentricity at gear and bearing positions. Axial vibration of the HGRBS also has some fluctuations. The bearing has self-variable stiffness frequency, which should be avoided in engineering design. In addition, the bearing clearance needs little attention due to its slightly discernible effect on vibration response. It is suggested that a careful examination should be made in modelling the nonlinear dynamic behavior of a helical gear-rotor-bearing system.

Nonlinear Dynamic Analysis of Coupled Gear-Rotor-Bearing System with the Effect of Internal and External Excitations

Extensive studies on nonlinear dynamics of gear systems with internal excitation or external excitation respectively have been carried out. However, the nonlinear characteristics of gear systems under combined internal and external excitations are scarcely investigated. An eight-degree-of-freedom（8-DOF） nonlinear spur gear-rotor-bearing model, which contains backlash, transmission error, eccentricity, gravity and input/output torque, is established, and the coupled lateral-torsional vibration characteristics are studied. Based on the equations of motion, the coupled spur gear-rotor-bearing system（SGRBS） is investigated using the Runge-Kutta numerical method, and the effects of rotational speed, error fluctuation and load fluctuation on the dynamic responses are explored. The results show that a diverse range of nonlinear dynamic characteristics such as periodic motion, quasi-periodic motion, chaotic behaviors and impacts exhibited in the system are strongly attributed to the interaction between internal and external excitations. Significantly, the changing rotational speed could effectively control the vibration of the system. Vibration level increases with the increasing error fluctuation. Whereas the load fluctuation has an influence on the nonlinear dynamic characteristics and the increasing excitation force amplitude makes the vibration amplitude increase, the chaotic motion may be restricted. The proposed model and numerical results can be used for diagnosis of faults and vibration control of practical SGRBS.

Bifurcation and Chaos of Gear Pair System Supported by Long Journal Bearings Based on Turbulent Flow Effect and Nonlinear Suspension Effect

A systematic analysis of the dynamic behavior of a gear-bearing system with nonlinear suspension, turbulent flow effect, long journal bearing approximation, nonlinear oil-film force and nonlinear gear mesh force is performed in the present study. The dynamic orbits of the system are observed by bifurcation diagrams plotted using the dimensionless unbalance coefficient and the dimensionless rotational speed ratio as control parameters. The onset of chaotic motion is identified from the phase diagrams, power spectra, Poincaré maps, Lyapunov exponents and fractal dimension of the gearbearing system. The numerical results reveal that the system exhibits a diverse range of periodic, sub-harmonic, quasiperiodic and chaotic behaviors. The results presented in this study provide some useful insights into the design and development of a gear-bearing system for rotating machinery that operates in highly rotational speed and highly nonlinear regimes.

Effect of Supported Bearing Clearance on Load-Sharing Characteristics of a Double-Row Planetary Gear System

Few studies were focused on the load-sharing characteristics of double-row planetary gear(DRPG)systems with bearings.Meanwhile,the supported bearing has an important influence on the transmission characteristics of the entire system.To overcome this problem,a multi-body dynamic(MBD)model of the DRPG system fully considering the influences of bearing parameters is established.Dynamic loads among contacting gear pairs have been obtained to calculate the load-sharing coefficient(LSC)of the system.The LSC of each gear tooth pair has been compared to study the effect of the supported bearing clearance on the load-sharing characteristics.These methods are based on Hertz contact theory.The liner stiffness and damping are used in the model.The results show that the supported bearing clearance has a greatly effect on the LSC of the DRPG system.Choosing appropriate clearance parameters of supported bearing can help suppress the uneven load distribution of the DRPG system.The results can provide some guidance to find new method to study the LSC and increase the service life of planetary gear systems.

CVRgram for Demodulation Band Determination in Bearing Fault Diagnosis under Strong Gear Interference

Fault-related resonance frequency band extraction-based demodulation methods are widely used for bearing diagnostics.However,due to the high peaks of strong gear meshing interference,the classical band selection methods have poor performance and cannot work well for bearing fault type detection.As such,the CVRgram-based bearing fault diagnosis method is proposed in this paper.In the proposed method,inspired by the conditional variance(CV)index and root mean square(RMS),a novel index,named the CV/root mean square(CVR),is first proposed.The CVR index has high robustness for the interference of non-Gaussian or Gaussian noise and has the ability to determine the center frequency of the weak bearing fault-related resonance frequency band under strong interference.Secondly,motived by the Kurtogram,the CVRgram algorithm is developed for adaptively determining the optimal filtering parameters.Finally,the CVRgram-based bearing fault diagnosis method under strong gear meshing interference is proposed.The performance of the CVRgram-based method is verified by both the simulation signal and the experiment signal.The comparison analysis with the Kurtogram,Protrugram,and CVgram-based method shows that the proposed technique has a much better ability for bearing fault detection under strong noise interference.

Improved Dynamics Model of Locomotive Traction Motor with Elasticity of Rotor Shaft and Supporting Bearings

The locomotive traction motor is described as a rotor-bearing system coupling the kinetic equations of the traction shaft and its support bearings with the determination of their elastic deformations in this study.Under the effect of excitations induced by the dynamic rotor eccentric distance and time-varying mesh stiffness,the elastic structure deformations of the shaft and support bearings are formulated in the vibration environment of the locomotive.In addition,the nonlinear contact forces between the components of the rolling bearing,the lubricating oil film,and radial clearance are comprehensively considered in this study.The results indicate that the elastic deformations of the shaft and bearings can change the dynamic responses of the traction motor and its support bearings.There are large differences between the ranges of the rotor motion calculated by the rigid and the flexible traction motor models when the intensified wheel-rail interaction is considered.With the increase of the rotor eccentricity,the results underscore the role of the elasticity of traction shaft and support bearings in dynamic researches of the traction motor.The critical value of the initial eccentric distance for the rub-impact phenomenon decreases from 1.23 mm to 1.15 mm considering the flexible effect of the shaft and bearings.This dynamics model of the traction motor can provide more accurate and reasonable simulation results for correlational dynamic researches.

应用滑动轴承的风电齿轮箱行星轮系动力学建模及解耦方法

在行星轮系动力学建模中,常以非线性油膜力或线性刚度-阻尼形式考虑其对系统动力学特性的影响,前者仿真精度高但计算成本也高,后者计算效率高却忽略了油膜力和轴颈-轴套偏心量的时变性,仿真精度有限。为此,以2MW级风电齿轮箱为研究对象,建立滑动轴承时变线性刚度-阻尼模型,提出计入轴颈-轴套时变偏心量的滑动轴承附加偏心修正力计算方法;利用行星架销轴-行星轮变形协调关系,将时变线性刚度-阻尼模型与附加偏心修正力进行耦合;建立应用滑动轴承的风电齿轮箱行星轮系动力学模型,对比了工况和轴承参数对模型计算精度与系统动态响应的影响,并通过试验加以验证。研究结果表明,齿轮副动态啮合力波动会使滑动轴承刚度-阻尼系数和附加偏心修正力产生周期性变化;在稳定和瞬态工况下,提出的模型可以很好地预测系统响应,尤其是行星轮振动响应;减小滑动轴承宽径比与间隙、增大输入转矩可以改善系统均载性能。

斜齿轮啮合弯矩对风电齿轮箱行星轮滑动轴承瞬态润滑性能影响分析

风电齿轮箱行星轮滑动轴承常被设计为以行星轮内孔和销轴分别作为轴套和轴颈,然而斜齿轮啮合弯矩容易使行星轮与销轴之间产生轴线不对中,导致边缘接触风险高,影响运行寿命。以6 MW级传动链齿轮箱行星轮滑动轴承为研究对象,考虑滑动轴承径向载荷、弯矩以及转速的动态影响,建立了行星轮滑动轴承瞬态摩擦-动力学耦合模型,并以风电机组传动链SIMPACK动力学模型提取的行星轮动态啮合力与时变转速作为行星轮滑动轴承的载荷与运动边界输入,分析了斜齿轮啮合弯矩、输入扭矩和滑动轴承半径间隙对行星轮滑动轴承润滑性能的影响规律,并进行了实验验证。研究结果表明,行星轮动态啮合力及其产生的啮合弯矩会造成行星轮轴心位置与偏斜角产生动态循环变化,并且随着载荷的增加,行星轮滑动轴承油膜/固体接触压力与不对中弯矩会逐渐增大;减小行星轮滑动轴承半径间隙可以有效提高其瞬态润滑性能。

凸棱非平面聚晶金刚石齿的破岩机理及在含砾地层中的应用

为提高聚晶金刚石复合片(PDC)钻头在含砾、软硬交错等不均质地层中的抗冲击性能,开展了凸棱非平面PDC齿的研究。通过仿真和室内实验对比分析了凸棱非平面齿与常规平面齿的破岩机理。与平面齿相比,凸棱非平面齿与岩石的接触应力分布更均匀,切削破岩过程中的载荷波动幅度明显更小,切削稳定性更高。凸棱齿特殊的非平面结构改变了切削齿与岩石的互作用方式,在不均质地层得到成功应用。

基于HMFDE和t-SNE的旋转机械故障诊断方法

针对旋转机械的故障特征提取较难,以及单一类型的特征无法全面反映故障特性的问题,提出了一种基于混合多尺度波动散布熵(HMFDE)、t分布-随机邻域嵌入(t-SNE)和郊狼优化算法(COA)优化极限学习机(ELM)的旋转机械故障诊断方法。首先,采用特征加权提出了混合多尺度波动散布熵方法,并将其用于提取旋转机械振动信号的故障特征;随后,采用t-SNE方法对混合故障特征进行了特征降维,挑选出了最能够反映故障特性的特征子集,构建了敏感特征样本;最后,采用郊狼优化算法对极限学习机的输入权重和隐含层阈值进行了优化,完成了旋转机械的故障识别和分类;以齿轮箱和滚动轴承故障数据集为对象,对基于HMFDE、t-SNE和COA-ELM的故障诊断方法进行了实验,验证了方法的有效性。研究结果表明:采用HMFDE-t-SNE-CAO-ELM故障诊断方法可以取得100%的故障识别准确率,该方法能够有效地诊断旋转机械的不同故障类型和损伤;相较于基于单一类型特征的故障诊断方法,其准确率分别可以提高0.68%、22.42%、29.18%(齿轮箱)和1.43%、8.23%、23.67%(滚动轴承),虽然牺牲了一定的计算效率,但准确率得到了明显的提高;相较于其他常规故障分类器,COA-ELM的故障识别准确率具有明显的优势。

基于维纳滤波的风电机组齿轮箱轴承故障诊断

存在轴承故障时,风电机组齿轮箱振动信号的幅度与频率都会发生明显改变,通过信号变化行为的测量能够判定出具体的轴承故障等级。为实现对轴承故障的准确判定,设计基于维纳滤波的风电机组齿轮箱轴承故障等级判定方法。通过获取轴承振动波的IMF分量,并完善维纳滤波算法,在此基础上,处理故障数据,实现基于维纳滤波的轴承故障特征提取。定义轴承故障特征的伪四阶矩,通过求解特征角度的方式,确定故障等级基准的判定范围,完成基于维纳滤波的风电机组齿轮箱轴承故障等级判定方法的设计。实验结果表明,利用上述方法,能够根据幅度和频率的变化行为,判定风电机组齿轮箱轴承的故障等级,符合实际应用需求。

滚动轴承波纹度对齿轮动态传递误差的影响

为了研究轴承波纹度制造误差对轴承-齿轮传动系统中齿轮动态传递误差的影响,构建了轴承滚道表面时变波纹度误差表征模型,建立了考虑轴承内外圈滚道表面波纹度幅值、波数以及时变齿轮啮合刚度的轴承-轴-齿轮系统耦合动力学模型,研究了齿轮传动系统支撑轴承内外圈滚道表面波纹度幅值和波数对齿轮动态传递误差的影响规律。仿真结果表明:输入轴支撑轴承存在波纹度误差时,其外圈滚道波纹度对齿轮动态传递误差的影响大于内圈滚道;输出轴非负载端支撑轴承存在波纹度误差时,其内外圈滚道波纹度对齿轮动态传递误差的影响相似;输出轴负载端支撑轴承存在波纹度误差时,其外圈滚道波纹度对齿轮动态传递误差的影响大于内圈滚道。

尾减速器轴承预紧对锥齿轮接触印痕和齿隙的影响规律研究

尾减速器是直升机传动系统的重要部件,轴承预紧是尾减速器装配的关键环节,直接影响直升机尾旋翼的平稳性、寿命及噪声。根据轴承支撑构型建立预紧螺栓的受力模型,得到螺栓的拧紧力矩及施加在支撑面上的轴向力;基于受力关系建立尾减速器轴承预紧有限元分析模型,根据分析结果提取了锥齿轮副的安装误差,处理得到:弧齿锥齿轮副的齿面间隙随着力矩的增大而减小,印痕位置随着力矩的增大有逐渐向大端移动的趋势;试验结果与有限元计算结果吻合性较强,方法可进一步推广到其他类型减速器中。

航空非正交偏置面齿轮分汇流系统非线性动力学

在面齿轮传动系统研究领域,研究对象多为单级面齿轮副,针对面齿轮分汇流传动系统动态特性的研究内容相对较少.聚焦航空非正交偏置面齿轮分汇流系统的非线性动力学特性,建立轴承滚动体变形、齿侧间隙以及综合传递误差的数学模型,推导出包含轴承在内的非正交偏置面齿轮传动多自由度耦合弯扭组合动力学模型.利用数值方法求解航空非正交偏置面齿轮分汇流系统的振动微分方程,结合时域图、频域图、相图、Poincaré映射、李雅普诺夫指数以及分岔图研究复杂系统非线性动态特性.研究了激励频率和啮合阻尼比变化对分流级与汇流级齿轮副之间啮合线位移的影响,结果表明:系统分流级与汇流级在特定参数下表现出不同的非线性特性,随激励频率增大,分流级出现单周期、多周期以及混沌现象,而汇流级无混沌现象产生;随啮合阻尼比增大,分流级状态变化近似于逆倍周期分岔过程,而汇流级在较小的阻尼比也可能保持周期运动状态;合理的激励频率和啮合阻尼比能使得系统跳出混沌并保持稳定.

基于应变测试的风电齿轮箱行星轮轴承载荷作用中心的确定

行星轮轴承是风电齿轮箱的关键部件,因其位置的特殊性和受载的复杂性,在风电齿轮箱的设计开发过程中,如何准确分析行星轮轴承的载荷作用中心往往成为设计难点。根据当前风电齿轮箱的设计规范,在10MW负荷试验台上,对两台3MW风电齿轮箱进行背靠背测试,试验中对行星级齿轮进行了应变测试。以此次测试的输入级行星轮轴承为例,基于齿轮的应变测试结果,进一步挖掘应变测试数据的应用,使用最小二乘法原理,给出了确定行星轮轴承载荷作用中心的精确方法。

考虑中心距变化的齿轮接触应力计算方法

齿轮制造/安装误差和轴承径向间隙导致齿轮中心距变化,改变齿面的接触特征,影响齿面的磨损和疲劳寿命。本文基于考虑制造/安装误差和轴承径向间隙影响的2种齿轮中心距模型,结合赫兹接触理论和齿轮啮合原理,建立了考虑中心距变化的齿面接触应力计算模型,并通过将该模型所得结果与有限元接触模型结果对比,验证所提出模型的准确性。此外,进一步研究了齿轮中心距变化对齿面接触应力的影响。研究结果表明:随着实际中心距的增大,本文模型结果与有限元模型结果的误差减小。随着齿轮中心距的增大,单齿对啮合区沿啮合线方向左移,齿面接触应力减小,但齿轮重合度也减小。因此,合理控制齿轮中心距变化对齿面接触性能的提升具有重要意义。

新型行星式回转支承动力学特性研究

传统单齿轮式回转支承存在偏载、传动精度低和非正常磨损等问题,无法满足坦克及火炮系统等高负载装备对回转支承高精度,长寿命的要求。结合行星式传动与回转轴承的特点,设计了一种新型行星式回转支承,并进行了力学性能研究和理论验证。基于Hertz接触理论,考虑接触弹性变形与实际接触角的耦合作用,推导了回转轴承在纯轴向载荷下的力学平衡方程。考虑倾覆角度与径向位移的耦合作用,建立了联合载荷下回转轴承的力学模型,运用Newton-Raphson迭代方法对回转轴承精确的接触角、最大载荷和载荷分布规律等进行了数值计算。运用ADAMS仿真平台,考虑钢球和套圈滚道的四点动态接触作用和轮齿动态啮合作用,分别建立了回转轴承、单齿轮式回转支承和新型行星式回转支承的多体接触动力学仿真模型,计算分析了3种模型的动态啮合力、动态接触力和振动位移等动态特性和振动响应。结果表明:回转轴承的接触角和载荷分布规律等仿真结果与精确的理论结果具有较好的一致性。研发的新型行星式回转支承呈现平衡对称和均载分布的周期性啮合力和轴承内部接触力,消除了单齿轮式回转支承的啮合冲击和偏载现象,显著降低轮齿啮合力、轴承内部载荷和系统振动响应,提高了行星式回转支承的传动力学性能和运动平稳性。提出的新方案和动力学模型为研发高性能军事装备的新型回转支承产品及其动态设计提供了理论指导。