Modelling and simulation of themo-mechanical phenomena at the friction interface of a disc brake.An empirically-based finite element model for the fundamental investigation of factors that influence the interface thermal resistance at the friction interface of a high energy sliding pair in a disc brake.

摘要

The fundamental theories of heat generation and transfer at the friction interface of audbrake assume either matching or not matching surface temperatures by having audvarying or uniform heat partition ratio respectively. In the research presented theudbehaviour of heat partition has been investigated in a fundamental study based onudexperimental measurements of temperature and the associated modelling andudsimulation of heat transfer in a brake friction pair. For a disc brake, an importantudparameter that was identified from the literature study is the interface tribo-layerud(ITL), which has been modelled as an equivalent thermal resistance value based on itsudthickness and thermal conductivity. The interface real contact area was also anudimportant parameter in this investigation, and it has been found to affect heatudpartitioning by adding its own thermal resistance.udA 2-dimensional (2D) coupled-temperature displacement Finite Element (FE) model isudpresented, based on which a novel relationship which characterises the total thermaludresistance (or conductance) at the friction interface has been characterised based onudthe ITL thermal properties, the contact area, and the contact pressure at the interface.udUsing the model the effect of friction material wear on the total thermal resistance (orudconductance) at the friction interface was predicted and a comparison of the Archardudand Arrhenius wear laws in predicting the wear of a resin bonded composite frictionudmaterial operating against a cast iron mating surface is presented.udA 3-dimensional (3D) model is also presented. This model has represented a smalludscale disc brake test rig which has been used in parallel with the simulation forudvalidation in a drag braking scenario. Two simulation conditions with different padudsurface states were investigated, the first having a nominally flat surface, and theudsecond an adjusted (worn) pad surface based on bedding-in data. The Arrhenius wearudmodel was applied to significance of including wear on the total thermal resistance atudthe friction interface over a short brake application.udA sensitivity analysis on the interface thermal conductance, the location of heatudgeneration, and the magnitude of contact pressure has identified the importance ofudeach factor in determining the total thermal resistance (or conductance) at the frictionudinterface during any friction brake application. It is concluded that the heatudpartitioning is insensitive on the location of heat generation, and that the mostudsensitive parameter is the contact pressure.