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C. Baron Saiz et alii, Frattura ed Integrità Strutturale, 34 (2015) 608-621; DOI: 10.3221/IGF-ESIS.34.67 608 Thermal stress analysis of different full and ventilated disc brakes C. Baron Saiz, T. Ingrassia, V. Nigrelli, V. Ricotta Università degli Studi di Palermo, Dipartimento di Ingegneria Chimica, Gestionale, Informatica, Meccanica – 90128 Palermo, Italy tommaso.ingrassia@unipa.it A BSTRACT . During the braking phase, the heat produced by friction between pads and disc cannot be entirely dissipated. Consequently, the brake disc, especially if very hard braking occur, can accumulate large amounts of heat in a short time so producing high gradients of temperature on it. Under these conditions, functionality and safety of the brake system can be compromised. The object of this study is to investigate, under extreme working conditions, the thermomechanical behaviour of different brake rotors in order to evaluate their efficiency and stability and to identify any compromising weakness on them. In particular, by means of FEM thermo-mechanical coupled analyses, one full disc and three ventilated rotors with different shapes have been studied. A very hard (fading) test has been used to evaluate the performances of the discs in terms of temperature distribution, stresses and strains. Obtained results demonstrate that the analysed ventilated discs, unlike the full rotor, can be effectively used in very hard working conditions, always ensuring high safety levels. Among the studied rotors, the curved-vanes disc was found to be the best solution. K EYWORDS . Ventilated disc; Brake rotor; Thermomechanical analysis; FEM; Fade. I NTRODUCTION uring a braking, most of the kinetic energy of a car is converted into thermal energy due to the dry friction effects and, successively, the generated heat is dissipated in the surrounding environment [1-2]. For this reason, one of the main problem of a braking system is how to handle the thermal energy generated during its action. Although the heat dissipation mechanisms could be different (conduction, radiation and convection), the major portion of the generated heat flows out to the air and, consequently, it is dissipated by convection. However, on high-demand repeated braking applications, convection mechanism is unable to dissipate the great amount of incoming heat, so causing overheating of the components and inducing potential failures. Previous studies, in fact, showed that thermally induced cyclic stresses strongly affect the crack initiation in the brake discs [3]. Nakatsuji et al. [4] studied how cracks, which form around small holes in the flange of one-piece discs, propagate in overloading conditions, whereas Gao et al. analyzed the thermal fatigue fracture in brake discs [5-6]. High temperatures during braking, moreover, could cause the brake fade [7], which means losing both efficiency and security during the stopping process. High thermal loads, in fact, can determine considerable distortions of the brake rotor [8], so modifying the system response and increasing the brake judder propensity. For all these reasons, increasing the thermal efficiency and the integrity of the brake components has become an essential objective in the modern automotive engineering field [9]. With this aim, innovative rotors have been designed to improve D