马彪 , 陈飞 , 李和言 , 等 . 换挡频次对离合器平均温升影响的研究 [J ] . 汽车工程 , 2017 , 39 ( 5 ): 535 - 542 .

MA B , CHEN F , LI H Y , et al . A study on the effects of shifting frequency upon average temperature rise of clutches [J ] . Automotive Engineering , 2017 , 39 ( 5 ): 535 - 542 . (in Chinese)

于亮 , 马彪 , 李和言 , 等 . 簧约束对多片离合器温度场的影响分析 [J ] . 兵工学报 , 2018 , 39 ( 4 ): 635 - 644 . DOI: 10.3969/j.issn.1000-1093.2018.04.002 http://doi.org/10.3969/j.issn.1000-1093.2018.04.002 为分析卡簧约束对多片离合器接触应力分布的影响，运用Abaqus仿真软件建立了多片离合器三维有限元模型。通过数值模拟，得到了多片离合器摩擦表面的接触应力分布规律和多片离合器的温度场分布。仿真和试验结果表明：卡簧约束导致了摩擦副接触应力沿径向分布不均匀，越靠近卡簧，摩擦元件的外径接触应力越大，径向应力差异越大；越远离卡簧，径向应力分布差异趋于平缓，并逐渐接近活塞压力；卡簧轴向约束导致了摩擦元件的径向温差加大，外径温升快，内径温升慢，并且轴向不同位置摩擦元件的温度场分布不一致，近卡簧侧的摩擦元件更易发生热翘曲；离合器低速长时滑摩试验验证了该温度场模型的正确性，所建模型能够切实有效地反映离合器的实际温升特性。

YU L , MA B , LI H Y , et al . Effect of circlip constraint on temperature field of multi-disc clutch [J ] . Acta Armamentarii , 2018 , 39 ( 4 ): 635 - 644 . (in Chinese) DOI: 10.3969/j.issn.1000-1093.2018.04.002 http://doi.org/10.3969/j.issn.1000-1093.2018.04.002 In order to investigate the influence of circlip constraint on the contact stress distributions of multi-disc clutch, a 3D finite element model is developed by Abaqus software. The contact stress distribution is obtained by the 3D finite element model, and the temperature distribution is obtained through numerical simulation. The simulated and experimental results show that the concentrated load of circlip results in the uneven distribution of radial contact stress of friction pairs during the clutch engagement process. The closer the friction surface is to the circlip, the larger the contact stress of outer radius of friction surface is, and the more obvious the difference of the radial contact stress is; when the friction pair is away from the circlip, the contact stress gets closer and closer to the piston pressure, and the difference of radial contact stress tends to be ease. The concentrated load of circlip leads to the increase in the radial temperature difference. The temperature in outer radius rises significantly, while the temperature in inner radius increases slowly. Moreover, the temperature fields of friction components in different axial directions are inconsistent, and the friction component near the circlip is more prone to be buckled. The proposed temperature field model is verified effectively by long time, low speed sliding experiments, which can better reflect the actual temperature rise characteristics of the multi-disc clutch.Key

LIANG X T , CHEN L Q , WANG Y M , et al . A proposed torque calculation model for multi-plate clutch considering boundary lubrication conditions and heat transfer [J ] . International Journal of Heat and Mass Transfer , 2020 , 157 ( 1 ): 119732 . DOI: 10.1016/j.ijheatmasstransfer.2020.119732 http://doi.org/10.1016/j.ijheatmasstransfer.2020.119732 https://linkinghub.elsevier.com/retrieve/pii/S0017931019351543 https://linkinghub.elsevier.com/retrieve/pii/S0017931019351543

李和言 , 王宇森 , 熊涔博 , 等 . 离合器配对摩擦副径向温度梯度对接触比压的影响 [J ] . 机械工程学报 , 2018 , 54 ( 1 ): 136 - 143 . DOI: 10.3901/JME.2018.01.136 http://doi.org/10.3901/JME.2018.01.136 针对离合器滑摩过程中摩擦副元件温度场和应力场分布，建立摩擦热流密度与真实接触面积的动态滑摩过程分析模型，通过动态测温和静态比压试验验证了理论模型对接触比压分布研究的适用性。引入了摩擦副元件动态滑摩热弹形变系数K_α、静态不均匀接触系数K_δ和离合器接触比压扰动系数K。K值为接触比压最大值与名义平均接触比压之比，K值越大，配对摩擦副接触界面比压扰动越大，表明配对摩擦副接触特性越差，真实接触面积越小，离合器越可能出现局部高压与高温区。理论分析与试验结果表明：所研究的铜基粉末冶金摩擦材料与65Mn对偶钢片组成的配对摩擦副：在低、中摩擦热流密度时，真实接触面积为名义接触面积的40%～60%；高摩擦热流密度时，真实接触面积约为名义接触面积20%～40%；当达到或超过临界摩擦热流密度时，配对摩擦副真实接触面积仅为名义接触面积的10%～15%。

LI H Y , WANG Y S , XIONG C B , et al . Effect of radial temperature gradient on interface pressure of clutch friction pair [J ] . Journal of Mechanical Engineering , 2018 , 54 ( 1 ): 136 - 143 . (in Chinese) DOI: 10.3901/JME.2018.01.136 http://doi.org/10.3901/JME.2018.01.136 Based on numerical results of temperature field and stress field, a theoretical model is built to investigate thermal flux and actual contact area of the clutch friction pair during slipping process, which is validated by continuous temperature measurements and static pressure tests. Several coefficients are introduced to express slipping process of clutch friction pair:dynamic slipping thermal deformation coefficient <i>K</i>_α, static uneven contact coefficient <i>K</i>_δ, and interface pressure perturbation coefficient <i>K</i>. Occurrence probability of high-pressure and high-temperature areas is greater by the smaller actual contact area which leads to a larger value of interface pressure coefficient <i>K</i> as well. Calculation and experiment results indicate that the actual contact area ratio ranges from 40% to 60% for copper-base friction pair with low and middle friction thermal flux, and 20% to 40% with high friction thermal flux. While the friction thermal flux reaches at or above the limit, the ratio of the actual contact area to the nominal contact area is only 10%-15%.

马彪 , 陈飞 , 李和言 , 等 . 湿式离合器摩擦副平均温升特性研究 [J ] . 兵工学报 , 2016 , 37 ( 6 ): 961 - 968 . DOI: 10.3969/j.issn.1000-1093.2016.06.001 http://doi.org/10.3969/j.issn.1000-1093.2016.06.001 针对湿式换挡离合器结合过程温升特性，基于集总参数法将离合器液压系统各元件简化为节点，建立了系统热阻网络模型与试验系统，研究获得了冷却润滑流量和转速差对离合器温升的影响规律。研究结果表明：在中低摩擦热负荷下，离合器温升对冷却流量的改变不敏感；在中高摩擦热负荷下，冷却流量变化对离合器温升影响显著，但当冷却流量增大到超过某一临界值时，流量增加对离合器温升影响微弱；转速差与离合器结合油压影响摩擦热负荷强度；离合器温升表现为转速差的线性增长关系，在相同冷却润滑状态下，转速差每增加100 r/min，离合器温升增加8.05%. 通过仿真结果与试验数据的对比，验证了所建模型的有效性，该模型能较好反映离合器正常工况的温升特性。

MA B , CHEN F , LI H Y , et al . Research on average temperature rise characteristic of wet clutch [J ] . Acta Armamentarii , 2016 , 37 ( 6 ): 961 - 968 . (in Chinese) DOI: 10.3969/j.issn.1000-1093.2016.06.001 http://doi.org/10.3969/j.issn.1000-1093.2016.06.001 On the basis of the lumped parameter method which simplifies the components in hydraulic system to nodes, a thermal resistance network model of clutch hydraulic system is proposed to investigate the effects of oil flow and rotation speed difference on the temperature rise of wet clutch during engaging. An experimental device is designed to validate the simulation results. The results show that the oil flow rate has a greater influence on the temperature rise of wet clutch under the condition of high heat flux than that under the condition of low heat flux. The oil flow brings a slight effect on the temperature rise when the cooling flow increases to the critical value. Both the relative speed and the pressure have an influence on heat flux. The temperature of wet clutch is a linear function of the relative speed of friction plates. The clutch temperature rises by 8.05 percent with every 100 r/min increment in the relative speed under same cooling condition. The proposed model is verified effectively by comparison of simulated results and experimental data, which can better reflect the thermal equilibrium of wet clutch hydraulic system in normal condition.

BERGLUND K , MARKLUND P , LUNDH H , et al . Prediction of driveline vibrations caused by ageing the limited slip coupling [J ] . Proceedings of the Institution of Mechanical Engineers, Part D:Journal of Automobile Engineering , 2016 , 230 ( 12 ): 1687 - 1698 . DOI: 10.1177/0954407015619505 http://doi.org/10.1177/0954407015619505 http://journals.sagepub.com/doi/10.1177/0954407015619505 http://journals.sagepub.com/doi/10.1177/0954407015619505 The prediction of the wet-clutch service life still remains a challenge for scientists and engineers. Previous research has shown the significance of the wet-clutch friction characteristics on the driveline dynamics. To avoid driveline vibrations an increasing friction coefficient with increasing sliding speed is desirable. Consequently, prediction of the occurrence of driveline vibrations relies on a detailed knowledge of how the friction characteristics are affected by wet-clutch degradation, as well as an understanding of the driveline dynamics. Wet clutches are used in both automatic transmissions and all-wheel-drive systems in cars, where they are referred to as limited slip couplings by manufacturers. Wet clutches used in automatic transmissions are subjected to high slip levels, but for very limited time periods. In all-wheel-drive systems, where the limited slip coupling can be used to control the torque transfer to, for example, the rear wheels, the slip levels are low but continuous. Most wet-clutch research has been performed for clutches in automatic transmissions and not for clutches used in all-wheel-drive systems. Thus, a simulation model was developed to evaluate how different operating conditions of the limited slip coupling influence degradation of the friction characteristics and the tendencies towards driveline vibrations. First, the changes in the friction characteristics with the time of ageing are simulated. The friction characteristics after ageing are used as the input to a simplified driveline model, which is used to evaluate the occurrence of vibrations. It is shown how the developed simulation model can be used as an efficient tool for engineers. The developed simulation model can be used to predict how the operating conditions for the limited slip coupling influence degradation of the friction characteristics.

KIM S , SHIM S . Modeling of heat transfer for a wet multi-plate clutch based on empirical data [J ] . Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering , 2018 , 232 ( 12 ): 1634 - 1647 . DOI: 10.1177/0954407017733184 http://doi.org/10.1177/0954407017733184 http://journals.sagepub.com/doi/10.1177/0954407017733184 http://journals.sagepub.com/doi/10.1177/0954407017733184 A heat transfer model of a wet multi-plate clutch based on empirical data is presented in this paper. Lumped system analysis was used to simplify the complex heat transfer system of the wet clutch. The model has included the effects of various design parameters of the wet clutch, such as rotating speed, flow rate and inlet temperature of the lubricant, clutch sizes, and groove types, by using the correlations of the heat convection coefficient. The correlations were obtained from 96 experiments that were designed to study the effects of the design parameters. The coefficients of the correlations were determined by the non-dominated sorting genetic algorithm (NSGA-II) to minimize errors between the simulated and the experimental results. The simulated results were compared with the experimental results to demonstrate the validity of the model and the correlations by using the percentage error, the root-mean-square error, and the correlation coefficient. The validation parameters were in good agreement with the experimental results.

KONG J , JANG S . Temperature analysis of wet clutch surfaces during clutch engagement processes based on friction pad patterns [J ] . International Journal of Automotive Technology , 2020 , 21 ( 4 ): 813 - 822 . DOI: 10.1007/s12239-020-0079-7 http://doi.org/10.1007/s12239-020-0079-7

吴邦治 , 秦大同 , 胡建军 , 等 . 考虑摩擦副接触应力场和冷却流场的湿式离合器温度场分析 [J ] . 机械工程学报 , 2020 , 56 ( 22 ): 190 - 200 . DOI: 10.3901/JME.2020.22.190 http://doi.org/10.3901/JME.2020.22.190 温度对湿式离合器摩擦副的摩擦特性和热失效具有重要影响。为了获取湿式离合器温度场的分布规律，建立摩擦副接触应力分布有限元模型和摩擦片沟槽内冷却流场数值计算模型，获得了摩擦副接触应力随离合器接合油压的变化规律和冷却流场对流换热随离合器转速的变化规律。在此基础上，提出考虑离合器摩擦副接触应力分布时变特性和冷却流场分布时变特性的离合器温度场数值计算模型。将所建温度场模型的仿真结果与试验结果作对比，验证了所建温度场模型的正确性。通过计算获得了湿式离合器接合过程中不同钢片在半径和厚度方向的温度分布规律，揭示了摩擦副接触应力场和摩擦片沟槽内冷却流场对离合器温度场的影响规律。结果表明，在离合器摩擦副半径方向上，摩擦副的温度分布规律与接触应力分布规律相一致。而摩擦片沟槽内冷却流场的对流换热主要影响离合器同步阶段的温度分布。

WU B Z , QIN D T , HU J J , et al . Analysis of temperature field of wet clutch considering contact stress field and cooling flow field of friction pair [J ] . Journal of Mechanical Engineering , 2020 , 56 ( 22 ): 190 - 200 . (in Chinese) DOI: 10.3901/JME.2020.22.190 http://doi.org/10.3901/JME.2020.22.190 Temperature plays an important role in friction characteristics and thermal failure of wet clutch friction pairs. In order to obtain the distribution of the temperature field of the wet clutch, the finite element model of the contact stress distribution of the friction pair and the numerical calculation model of the cooling flow field in the groove of the friction plate are established. The variation of the contact stress of the friction pair with the clutch engagement oil pressure and the variation of convective heat transfer in the cooling flow field with the clutch speed are obtained. On this basis, a numerical model of clutch temperature field considering the time-varying characteristics of contact stress distribution and cooling flow field distribution is proposed. The simulation results of the temperature field model are compared with the experimental results to verify the correctness of the temperature field model. The temperature distribution of different separator plates in the radius and thickness directions during the wet clutch engagement process is obtained. The influences of the contact stress field of the friction pair and the cooling flow field in the groove of the friction plate on the temperature field of the clutch are revealed. The results show that the temperature distribution is consistent with the contact stress distribution in the radial direction of the clutch friction pair. The convective heat transfer of the cooling flow field in the groove of the friction plate mainly affects the temperature distribution of the clutch locked phase.

吴健鹏 , 马彪 , 李和言 , 等 . 考虑接触面局部散热的湿式离合器摩擦片滑摩温升特性 [J ] . 北京理工大学学报 , 2019 , 39 ( 9 ): 925 - 932 .

WU J P , MA B , LI H Y , et al . Temperature rise characteristic of friction disc in wet clutch considering the local heat dissipation on the contact surface [J ] . Transactions of Beijing Institute of Technology , 2019 , 39 ( 9 ): 925 - 932 . (in Chinese)

鲍和云 , 孔维地 , 谭武中 , 等 . 油液冷却航空湿式摩擦离合器热特性分析 [J ] . 航空动力学报 , 2022 , 37 ( 5 ): 989 - 999 .

BAO H Y , KONG W D , TAN W Z , et al . Analysis of thermal characteristics of oil-cooled aviation wet friction clutch [J ] . Journal of Aerospace Power , 2022 , 37 ( 5 ): 989 - 999 . (in Chinese)

ZHANG Z G , ZOU L , LIU H , et al . Effects of operating and material parameters on the thermal characteristics of a wet clutch [J ] . Advances in Mechanical Engineering , 2021 , 13 ( 7 ): 168781402110341.

王钰明 , 王其东 , 陈黎卿 , 等 . 热负荷特性下的分动器动力传递特性研究 [J ] . 机械工程学报 , 2018 , 54 ( 14 ): 159 - 168 . DOI: 10.3901/JME.2018.14.159 http://doi.org/10.3901/JME.2018.14.159 分动器作为智能四驱汽车的关键部件，关于其性能研究较多从机械传动角度考虑，没有考虑动力传动中摩擦生热的影响。针对这一问题，首先建立基于热负荷特性作用下的分动器力学模型；接着基于Matlab/Simulink软件建立性能仿真模型，分析结果表明热负荷对分动器摩擦片的摩擦因数以及润滑油黏度的影响较大；在此基础上，构建分动器试验平台，获得热负荷条件下总转矩和转矩响应时间的变化规律与仿真值基本保持一致，验证了所建模型的正确性。最后探明峰值黏性转矩约等于峰值总转矩的1/3，达到峰值总转矩需要0.3 s左右；在热负荷条件下，不同摩擦片数和不同压力对所能传递的转矩起决定性作用，不同油槽的宽度对黏性转矩影响较大，对粗糙转矩基本上不起作用。通过对比分析热负荷条件下有无沟槽的分动器传递转矩变化情况，说明了热负荷在分动器工作过程中的重要作用，获得了分动器接合过程中工作特性的变化规律，为分动器的设计提供了理论依据。

WANG Y M , WANG Q D , CHEN L Q , et al . Research on transfer case transmission power of heat load characteristics [J ] . Journal of Mechanical Engineering , 2018 , 54 ( 14 ): 159 - 168 . (in Chinese) DOI: 10.3901/JME.2018.14.159 http://doi.org/10.3901/JME.2018.14.159 As one of the essential components of intelligent four-wheel drive, transfer case has been studied thoroughly in the area of mechanical drive in the past. However, its friction heat during the transmission of power is rarely discussed. In our works, we construct a model of transfer case based on heat load characteristics. Then, a performance simulation model in Matlab/Simulink is built, which shows that heat load has a great impact on frictional coefficient and viscosity of lubricating oil of transfer case. Based on the above inspection, a test platform for transfer case is constructed, and we find out that the relation between total torque and torque response time under heat load is consistent with the theoretical result. The peak viscous torque is one thirds of the peak total torque, and it costs about 0.3 seconds to reach the peak total torque. The number of friction plate and the pressure play major roles to determine transferable torque. The widths of sumps, while affect viscous torque greatly, do not affect asperity torque as much. The difference between transferable torques of transfer case with and without trenches under heat load is analyzed, and we find the important role of heat load in the working process of transfer case and how its operating characteristic varies during connecting process, which can provides a theoretical basis for the designing of transfer case.

赵二辉 , 马彪 , 李和言 , 等 . 转速对湿式离合器局部润滑及摩擦特性影响研究 [J ] . 兵工学报 , 2017 , 38 ( 4 ): 625 - 633 . DOI: 10.3969/j.issn.1000-1093.2017.04.001 http://doi.org/10.3969/j.issn.1000-1093.2017.04.001 针对湿式离合器局部润滑及摩擦特性的影响因素，建立了摩擦副微观混合润滑模型。考虑了微凸峰接触和局部温升的影响，分析了转速对湿式离合器摩擦副局部压强分布、油膜和微凸峰承压比、实际接触面积、局部温升的影响。同时，利用摩擦磨损试验机进行小试样柱销-摩擦盘试验，分析了不同转速下离合器摩擦系数变化规律。结果表明：随着速度的增加，润滑油膜动压作用显著增强，摩擦副实际接触面积明显减小，法向载荷最终主要由润滑油膜承担；摩擦系数主要受微凸峰实际接触面积变化的影响，变化规律与微凸峰实际接触面积呈大致对应关系。

ZHAO E H , MA B , LI H Y , et al . Influence of rotating speed on local lubrication and friction characteristics of wet clutch [J ] . Acta Armamentarii , 2017 , 38 ( 4 ): 625 - 633 . (in Chinese)

YANG W , TANG X L . Numerical analysis for heat transfer laws of a wet multi-disk clutch during transient contact [J ] . International Journal of Nonlinear Sciences and Numerical Simulation , 2017 , 18 : 599 - 613 . DOI: 10.1515/ijnsns-2017-0081 http://doi.org/10.1515/ijnsns-2017-0081 https://www.degruyter.com/document/doi/10.1515/ijnsns-2017-0081/html https://www.degruyter.com/document/doi/10.1515/ijnsns-2017-0081/html This study aims to solve the transmission failure caused by warping and crackling on frictional and steel disks of a wet multi-disk clutch. Thus, a dynamic model is proposed to describe the transient contact process of the disks, as well as the heat transfer laws, during the engagement of the clutch using the commercial software MSC/NASTRAN. Moreover, the heat transfer laws, which varies with engagement time within a contact area, is investigated. On the basis of these results, some rules for heat conduction in a wet multi-disk clutch are developed. By measuring the pressure and temperature of the inlet and outlet of the clutch, the correctness of the theoretical analysis method is indirectly verified.

ABDULLAH O I , SCHLATTMANN J , SENATORE A , et al . Investigation of thermoelastic problem of multiple-disc friction clutches applying different thermal loads [J ] . Heat & Mass Transfer , 2018 , 54 : 3461 - 3471 .

WU W , XIAO B Q , YUAN S H , et al . Temperature distributions of an open grooved disk system during engagement [J ] . Applied Thermal Engineering , 2018 , 136 : 349 - 355 . DOI: 10.1016/j.applthermaleng.2018.03.016 http://doi.org/10.1016/j.applthermaleng.2018.03.016 https://linkinghub.elsevier.com/retrieve/pii/S135943111736893X https://linkinghub.elsevier.com/retrieve/pii/S135943111736893X

BAO H Y , KONG W D , HOU X N , et al . Analysis on temperature field of friction pair of aviation friction clutch based on different groove shapes of friction disk [J ] . Journal of Mechanical Science and Technology , 2021 , 35 : 3735 - 3742 . DOI: 10.1007/s12206-021-0742-6 http://doi.org/10.1007/s12206-021-0742-6

XIONG C B , CHEN M , YU L Y . Analytical model and material equivalent methods for steady state heat partition coefficient between two contact discs in multi-disc clutch [J ] . Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering , 2019 , 234 ( 2/3 ): 857 - 871 . DOI: 10.1177/0954407019846389 http://doi.org/10.1177/0954407019846389 http://journals.sagepub.com/doi/10.1177/0954407019846389 http://journals.sagepub.com/doi/10.1177/0954407019846389 The heat partition coefficient between two finite thickness contact discs during long-time sliding is studied with a coupled finite element method. Results show that the heat partition coefficient varies from its initial value to another steady state value rapidly instead of being a constant all the time. An analytical solution of the temperature field under invariant heat flux input is deduced, which tells that there exists a unique critical thickness ratio between the contact discs that keeps the heat partition coefficient a constant. An equivalent method for single-material contact bodies is proposed that is capable of calculating the steady state heat partition coefficient for any thickness ratio. It reveals that the steady state heat partition coefficient only has relationship with the mass density and the heat capacity of the materials and the thickness ratio. Based on this method, a two-step material equivalent method is further proposed for the contact discs that have friction linings on them. The solution shows that the steady state heat partition coefficient in this situation is also only determined by the material properties and the layer thicknesses. A test bench of multi-disc clutch is set up and a series of sliding experiments are conducted to validate the proposed equivalent methods and solutions of steady state heat partition coefficient. The measured experimental temperature variations show that the temperature level of the separator disc in the clutch is overestimated with the constant heat partition coefficient of semi-infinite model, while it is close to those calculated results with steady state heat partition coefficient. Therefore, the temperature fields of the contact discs during long-time sliding with constant speed can be figured out efficiently using the steady state heat partition coefficient with only small error, and these equivalent methods benefit the multi-disc clutch design and temperature estimation in practical applications.

YU L , MA B , CHEN M , et al . Variation mechanism of the friction torque in a Cu-based wet clutch affected by operating parameters [J ] . Tribology International , 2020 , 147 : 106169 . DOI: 10.1016/j.triboint.2020.106169 http://doi.org/10.1016/j.triboint.2020.106169 https://linkinghub.elsevier.com/retrieve/pii/S0301679X2030013X https://linkinghub.elsevier.com/retrieve/pii/S0301679X2030013X

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