THERMAL FATIGUE LIVE ANALYSIS OF BRAKE DRUMS MADE WITH GRAY CAST IRON AND VERMICULAR CASTIRON VIA FEM SIMULATION

The brake drums are designed to convert kinetic energy of the vehicle into thermal energy. The stress originated by thermal transients produced by braking process may nucleate fatigue cracks and lead the component to failure. The aim of this work is to study thermal fatigue life for brake drum made with gray cast iron and vermicular cast iron. The loading transients due to different braking events were determined by thermal analysis, using FEM methods. Stress amplitudes and mean stresses were obtained. The fatigue life of the component has been evaluated and the points with the highest probability for crack nucleation were determined. The highest level of stress was observed in the hoop direction when the brake drum is made in gray cast iron and in the radial direction when it is made with vermicular graphite cast iron. The highest stress levels observed were associated with the braking event where the vehicle goes through successive braking actions during 5 seconds of braking and 4 seconds of free riding. The fatigue life of the components has been evaluated and the points with the highest probability for crack nucleation were examined. The method of rain-flow for counting of cycles had been applied and the Goodman equation used to determine the number of cycles to failure. The results have shown that the section near to the bolting flange is the most probable site for crack nucleation for the two materials. The brake drum made with vermicular cast iron presented higher thermal fatigue endurance than that one made with gray cast iron.