Improvement in the brake disc design for heavy vehicles by parametric evaluation

Abstract

Design of the brake disc geometry for a given brake disc material provides an opportunity for improvement in the fatigue life of the brake disc. High thermomechanical loads at braking lead to substantial local plastification and also induce tensile residual stresses in certain areas of the brake disc. This contributes to shortening of the fatigue life of the brake disc by possible initiation and growth of cracks. In the present paper, a simulation approach for evaluation of brake disc designs with respect to thermomechanical performance is developed and applied. Brake disc performance is analysed using commercial finite element software by employing a constitutive model for grey cast iron implemented in a Fortran subroutine. The thermal loading consists of consecutive severe braking cycles at a constant brake power and a constant speed, with cooling between the brake cycles. Based on a previous experimental study, three different assumptions are made regarding the spatial distribution of the thermal load at braking. A standard commercial brake disc made from grey cast iron having straight vanes is used as the reference case. Geometrical modifications are introduced in the ventilation arrangement using a design-of-experiments approach, studying both straight cooling vanes and different pillar layouts. A preliminary assessment of the fatigue life of the brake discs is carried out. The results indicate that the introduction of different pillar arrangements instead of straight vanes make it possible to decrease the mass of the brake disc by up to 13% or to increase the fatigue life of the brake disc by about 50%.