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The contact heat conduction problem between the rough sliding surfaces was studied through secondary development of finite element software ABAQUS.The thermal contact conductance was defined as a function of the sliding speed,the local contact pressure,material properties and the surface roughness, and the effeecs of three dimensionless parameters were also analyzed.The results reveal that reciprocating motion has a significant influence on contact heat conduction.When heat conduction between sliding surfaces reach a stable stape,the dimensionless mean heat flux per unit time increases with the rising dimensionless parameters η and ω the heat conduction decreases with the reduction of the contact pressure and the growth of the surface roughness.Besides,the variations of the dimensionless average temperature are consistent with those of the dimensionless average heat flux.

This paper provides a fast method based on static reduction for the solution of the displacements of the piston ring's contact nodes. The nodal displacements and the corresponding nodal forces of the contact nodes are connected by the contact stiffness matrix which is obtained through performing static reduction on a finite element description of the two dimensional model of the piston ring in an internal-combustion engine. Given applied loads, the displacements of the contact nodes can be quickly obtained, and vice versa. The numerical result is compared with that of analytical and the error is less than 2% which indicating the accuracy of this numerical method. Using this method, free shape of the piston ring can be easily designed to ensure the requirements of the contact pressure of the piston ring, which will improve wear resistance and service life of the piston ring.

The dynamics model of a two-speed planetary transmission is established by using the virtual displacement principle,the dynamic shifting processes comparison and simulation analysis between the planetary transmission using tooth brake and friction brake are carried out. The different joint speed effects on the transmission characteristics are also analyzed through the simulation. The simulation results show that the maximum torque impact of the planetary transmission using tooth brake is lower than using friction brake in the same shifting time. The larger the joint speed difference of the planetary transmission using tooth brake is and the smaller the shifting time is,the greater the maximum torque impact is still lower than the planetary transmission using friction brake.

During the sliding process of multi- disc clutch,the heat partition coefficient between friction components is affected by the disc thickness and material property. For the discs with finite thickness,a coupled heat conduction model is established,based on which the disc temperature fields and the heat partition coefficient are obtained at the same time. The results show that,the heat partition coefficient is a constant at the very beginning and varies to another steady- state constant after a short time rise. Comparing this heat partition coefficient with the constant value obtained by the semi- infinite model,it’s found that the latter can only determine the initial heat partition coefficient. Experimental results show that,the temperature field calculated with variable heat partition coefficient is very close to the measured temperatures. However,the temperature field predicted with the constant heat partition coefficient overestimates the separator disc temperature and underestimates the temperature of the friction disc.

The temperature field of the wet clutch is an important factor that influences the vehicle transmission performance. In order to predict and prolong the service life of the wet clutch, a test bench is built, and an accelerated life test is carried out based on the actual working conditions. Then, according to the variation of the friction coefficient and the maximum radial temperature difference, the sliding temperature field is analyzed in different periods. By introducing four evaluation indexes, a temperature field evaluation system is established and verified. With the help of this evaluation system, the temperature fields during running-in and unstable stages are compared, and the thermal failure mechanism of the friction disc is analyzed. In the stable stage, the influence of rotational speed, oil pressure and lubricant flow on the temperature field are investigated. The results of this study can guide the design and control of the friction components in the wet clutch. [ABSTRACT FROM AUTHOR]

An enhanced Cu-based friction material was prepared by the powder metallurgy techniques and proposed for use in the dry clutch system. The friction characteristics and wear rate of this friction material sliding against 65Mn steel are obtained using Universal Material Tester-5. The friction pairs were subjected to two operating variables, which are sliding speed and temperature. The effect of these variables during the engagement process of the friction pairs is investigated. Knowing the normal applied force and dimension of the clutch disc, the dynamic friction coefficient was translated to friction torque capacity with time. It was found that instability can be excited at low operational conditions when the resulting friction coefficient is high. At 25 ℃, the dynamic friction torque oscillates with time likewise at 400 ℃. Generally, a more stable friction torque is obtained when the sliding speed is varied compared to varying the temperatures. Moreover, the influence of the operating temperatures and sliding speeds on thermal buckling and thermoelastic instability of the friction disc is the second consideration in this work. The onset of thermoelastic instability occurs when the sliding speed exceeded 200 r/min and the results for the growth rate of hot spots were found to agree well with the critical speed of the system. Also, thermal buckling was highly dependent on the temperature difference between the inner and outer radius of the friction disc. [ABSTRACT FROM AUTHOR]