Effect of Design Geometry on the Thermal Fatigue Strength of Brake Drum Made in Vermicular Cast Iron

Brake drums are components designed to dissipate kinetic energy of vehicles, converting it, mostly, into thermal energy. The stress state originated by thermal transients produced by braking cycles may nucleate fatigue cracks and lead the component to failure. The aim of this work is to analyze and compare thermal fatigue strength for brake drums, made in vermicular cast iron, with different design geometry. Firstly, fatigue life has been evaluated for the original geometry. The same analysis has been performed after reducing the thickness of the brake drum. From thermal and structural analisys, via finite element method, temperature evolution and loading history for the component have been obtained. The life of the component has been estimated for the region with the highest probability for crack nucleation by thermal fatigue. The rain-flow method of counting cycles has been applied and Goodman equation has been used to evaluate the fatigue life of the component. In the original drum geometry, the highest level of stress has been observed in radial direction, near the bolted flange. In the drum geometry with reduced thickness the highest level has occurred in axial direction, near the surface in contact with the shoes. The fatigue analysis has shown that the drum with reduced thickness presented higher thermal fatigue endurance than the original design.