Summary High-frequency train-track interaction and mechanisms of wheel/rail wear that is non-uniform in magnitude around/along the running surface are surveyed. Causes, consequences and suggested remedies to relieve the problems are discussed for three types of irregular wheel/rail wear: (1) short-pitch rail corrugation on tangent tracks and large radius curves, (2) wheel corrugation as caused by tread braking, and (3) wheel polygonalisation. The state-of-the-art in modelling of dynamic train-track interaction in conjunction with prediction of irregular wear is reviewed.

Train-Track Interaction and Mechanisms of Irregular Wear on Wheel and Rail Surfaces

Thermoelastic instability in an automotive disk brake system is investigated exper­ imentally under drag braking conditions. The onset of instability is clearly identifiable through the observation of nonuniformities in temperature measured using embed­ ded thermocouples. A stability boundary is established in temperature/speed space, the critical temperature being attributable to temperature-dependence of the brake pad material properties. It is also found that the form of the resulting unstable perturbations or eigenfunctions changes depending upon the sliding speed and tem­ perature.

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An Experimental Investigation of Frictionally-Excited Thermoelastic Instability in Automotive Disk Brakes Under a Drag Brake Application

A transient finite element simulation is developed for the two-dimensional thermoelastic contact problem of a stationary layer between two sliding layers, with frictional heat generation. The petrov-Galerkin algorithm is used to discretize the sliding layers because of the high Peclet numbers involved. The results in the linear, full contact regime were validated by comparison with the analytical predictions of Lee and Barber (1993). After separation occurs, there is a non-monotonic transition to a steady state with the contact regions separated by the same wavelength. During the transition, the migration speed exhibits values lower than those in either the linear regime or the final steady state. When several wavelengths are unstable, the final steady state is generally that corresponding to the longest unstable wavelength, even though other modes have more rapid growth rates in the linear regime.

/pdf/nonlinear-transient-behavior-of-a-sliding-system-with-5e6cngfwdk.pdf

Nonlinear Transient Behavior of a Sliding System With Frictionally Excited Thermoelastic Instability

Model and numerical algorithm for sliding contact between two elastic half-planes with frictional heat generation and wear

An analytical frequency domain solution is obtained using the spatial Fourier transform for thermal and thermoelastic fields due to an arbitrary heat source or thermal distribution moving at constant speed over the surface of an insulated, traction free elastic half space. Conversions between the space and frequency domains for the input and output are performed efficiently and robustly using FFT techniques. The method is validated by comparison to the analytical result for the moving line heat source in which it is shown that numerical evaluation of the analytical solution is problematic for large speeds or distances from the heat source. The utility of the method is illustrated on the constant patch moving heat source and discretely distributed multiple heat sources known as the hot spot problem. It is shown, through several examples, that the effect of hot spots on surface displacement and tangential stress is small. Finally, this conclusion is generalized by quantifying the frequency domain solution for the moving heat source problem as a low pass filter.

FFT thermoelastic solutions for moving heat sources

http://www-personal.umich.edu/~jbarber/Wear1985a.pdf

Transient thermoelastic contact problem of two sliding half-planes

http://www-personal.umich.edu/~jbarber/IJMS1985.pdf

On partial contact of a thin-walled circular cylinder and a rigid half-space

We study the partial contact of a long circular cylindrical shell pressed eccentrically by its end face against a rigid half-space, using the theory of thin shells in bending. The elastic displacements are presented in the form of a Fourier expansion, the coefficients of which are found by the variational formulation combined with the penalty method to enforce contact conditions. Results are applied to buckling of a centrally and eccentrically compressed bar, and a bar with an initial inperfection. These solutions are compared with the corresponding results of the strength of materials.

A. Azarkhin

Papers

Transient thermoelastic contact problem of two sliding half-planes

On partial contact of a thin-walled circular cylinder and a rigid half-space

Stability of a Long Cylindrical Shell With Partial Contact at the End Face