A three-dimensional numerical model based on a semianalytical method in the framework of small strains and small displacements is presented for solving an elastic-plastic contact with surface traction. A Coulomb’s law is assumed for the friction, as commonly used for sliding contacts. The effects of the contact pressure distribution and residual strain on the geometry of the contacting surfaces are derived from Betti’s reciprocal theorem with initial strain. The main advantage of this approach over the classical finite element method (FEM) is the computing time, which is reduced by several orders of magnitude. The contact problem, which is one of the most time-consuming procedures in the elastic-plastic algorithm, is obtained using a method based on the variational principle and accelerated by means of the discrete convolution fast Fourier transform (FFT) and conjugate gradient methods. The FFT technique is also involved in the calculation of internal strains and stresses. A return-mapping algorithm with an elastic predictor∕plastic corrector scheme and a von Mises criterion is used in the plasticity loop. The model is first validated by comparison with results obtained by the FEM. The effect of the friction coefficient on the contact pressure distribution, subsurface stress field, and residual strains is also presented and discussed.

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This study is focused on a bearing arrangement made of two tapered roller bearings and a shaft, supporting a combination of axial and radial loads. The paper is divided in two parts. This part presents first a numerical procedure to obtain the internal load distribution within tapered roller bearings. The internal load distribution is required to estimate the bearing fatigue life. Afterwards, a numerical method and the related algorithm for a load support system constituted of a shaft and two tapered roller bearings are described. The effect of the initial axial preload (or total axial compression) is taken into account. In consequence the method proposed can be used to select an adequate axial preload in order to increase the system survivability. An example of model implementation, i.e. application to the transfer shaft of an automobile automatic transaxle, is presented in Part 2 of the paper.

A mineral oil of low viscosity was additivated with different concentrations of low-density polyethylene. The wear behaviour of the additivated samples and the base oil was evaluated using a four-ball wear tester at constant speed and variable load. Steel and ceramic (silicon nitride) were chosen for the balls. The scuffing resistance of the ceramic balls was higher than that of the steel balls. No scuffing appeared i n the case of a n upper steel ball in contact with lower ceramic balls. As far as the minimum wear-scar diameter on the lower balls was concerned, a n optimum concentration of polymer added to the base oil was found from the experimental data, for both types of ball. For the systems investigated, the optimum concentration was about 1.0% polyethylene.