1991-09-01

Influence of Design and Material Factors on Thermal Stresses in Multiple Disc Wet Clutches and Brakes 911883

Temperatures and thermal stresses in multiple disc clutches (brakes) are greatly affected by normal pressure distributions on particular friction surfaces. When the pressure distributions are non-uniform, the distributions of heat flux generated on friction surfaces are also non-uniform. This can result in high local temperatures and high thermal stresses.
The pressure distributions depend on a number of design and material factors. They can also be subject to changes during the clutch engagement due to the thermal deformations. The paper presents a theoretical model of a multiple disc clutch (brake). Using this model, the initial distributions of normal pressure have been examinated as well as their changes which occur due to the thermal deformations. Then temperatures and stresses in the cross-sections of friction discs have been calculated.
It has been found out that the initial pressure distributions are greatly affected by the stiffness of the structural elements closing a pack of discs and the mode in which one of these elements is supported. The modulus of elasticity of friction material, in turn, has a considerable effect on changes in pressure resulting from the thermal deformations.
The study indicates that under non-uniform pressure distributions stresses in discs can reach values several times higher than those reached under uniform distributions.

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