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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.

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 transient thermal and thermoelastic analysis of an automotive multidisc clutch is performed to investigate the thermal deformation and the contact pressure distribution of the friction surfaces. An alternating finite volume method (FVM) and finite element method (FEM) for temperature distribution and contact pressure distribution, including the coupling between temperature, displacement, and contact pressure, is employed in MATLAB. A penalty function method is used to impose the constraints on the contact boundary. The computational results indicate that the contact pressure distributions on the surfaces near the pressure plate are more uniform than those near the opposite plate, and the nonuniformity is enlarged with the temperature rise. The contact pressure and temperature distributions on the two friction surfaces of the separate plate are dissimilar and asymmetric, which is in good agreement with the test results. The results further show that the contact pressure peaks diminish and the noncontact regions reduce due to the heat conduction and convection when the engagement ends. [ABSTRACT FROM AUTHOR]

This paper deals with the effects of friction material properties on thermoelastic instability (TEI) and the associated dominant deformation mode. Both analytical and finite element models are constructed for determining the variation of the critical speed and the dominant TEI mode. Some important factors, e.g. the nonconductive friction material as well as the symmetric and anti-symmetric TEI deformation modes, are investigated. It has been found that the dominant TEI deformation mode is strongly dependent on the properties of frictional material. The results show that the symmetric mode can be dominant in the condition when the friction material has either a sufficiently large elastic modulus or a sufficiently small thermal conductivity. These research findings are useful for vehicle clutch and brake designs. [ABSTRACT FROM AUTHOR]

A finite element model is developed for the frictionally excited thermoelastic instability problem in intermittent sliding contact with finite geometries and realistic friction materials. The existing analytical solutions are used to validate the method in several limiting cases. It is concluded that some caution must be taken for the commonly used strategy of assuming time-averaged frictional heat generation for intermittent contact. The predictions made by the half-plane analytical solution that assumes thermally nonconductive and rigid frictional surface considerably overestimate the dimensionless critical speeds of realistic brake or clutch systems. Longer wavelength perturbations become unstable at a dimensionless sliding speed approaching zero, as opposed to the converged value of unity in the half-plane solution. Averaging the heat input over the entire circumference is appropriate only when the period of frictional contact is longer than that of separation. These results merit the use of the finite element method in more general applications involving intermittent contact. [ABSTRACT FROM PUBLISHER]