A novel approach to analyzing thermoelastic behavior of brake disc under the combined action of thermal and mechanical loads

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Friction hot spots have been troubling the industry and academia as the root cause of a series of brake NVH and thermal fatigue problems. Previous experimental and simulation studies on hot spots have focused only on the role of thermal load but lacks consideration of mechanical load. And there are few methods for transient simulation of brake hot spots under thermal and mechanical loads, leading to a lack of consensus on the mechanism. In this paper, the idea of ’combined but not coupled’ is adopted to investigate the thermoelastic behavior of a simplified brake disc under combined thermal and mechanical loads through both experiments and simulations. A new test method for the thermoelastic behavior of brake disc under thermal and mechanical loading has been designed, and the hot spots are successfully reproduced. The evolution process and spatial distribution of temperature and deformation fields are analyzed, revealing that the deformation field evolves earlier than the temperature field. To replicate the hot spots observed in the experiment, a novel finite element (FE) model based on a modified Riks algorithm and thermomechanical coupling is established. The simulation results align with the experimental results. The number of hot spots is found to correspond to the main order of the deformation, and their locations coincided with the peaks of the waviness distortion. The effects of heating method, rotation speed, initial distance (representing braking pressure), wrap angle, and phase difference between the thermal load and the mechanical load are analyzed. It is found that there is a critical rotation speed and a critical braking pressure for the emergence of hot spots. Finally, a new mechanism for the generation of brake hot spots is proposed. This study may provide a valuable reference for revealing the mechanism of brake hot spots and the theory of progressive waviness distortion. The research is also valuable for automotive brake design and safety.