Research On Dissipation And Friction-Wear Performance Of Automobile Brake Disc

Modern car manufacturing companies are paying more and more attention to the safety, comfort, energy saving and environment-friendliness. This requires the friction couple of the braking system to have good friction performance, which includes a high and stable friction coefficient, high anti thermal decay rate and low wear rate, so as to brake smoothly and safely and not to cause in sequel and judder or damage cracks. This dissertation discussed the impact of brake disc structure on the performance of the brake system taking disc-pad couple as the investigating subject.The researches that were done in this dissertation are as follow:Firstly, the impacts of structural designing parameters on the performance of the brake disc including the weight, manufacturing complexity, friction moment and structural stability were discussed such as the rotor outer thickness, adjusting hole position and its diameter, diameter, brake hat thickness, the connecting part between the hat and the outer. Structural analysis was carried out to investigate the structural stress of the brake disc, the result of which was then used to optimize the venerable part of the structure.Secondly, by using the constant speed friction test machine, friction experiments were carried out on brake disc samples with and without macro-grooves with the rotating speed ranging from250r/min to2500r/min and the pressure ranging from1.3Mpa to5.1Mpa, in order to investigate the impact of different brake disc structure on the wear and frictional properties. The results show that the third body of the frictional surface, which influenced the wear and frictional properties, was deeply related to the speed, pressure and the disc structure. With the rotating speed rising from250r/min to2500r/min, third body particles were pressed and crushed into compacted third body and then broke and fell off the surface, which resulted in the changes of the wear and friction coefficient respectively. Compared with that of the brake disc without grooves, the compacted third body of brake disc with grooves appeared and fell off at a lower speed, which makes the friction coefficient higher and wear rate lower at the speed of500-1500r/min. Besides, the friction coefficient change is smaller with the change of the rotating speed.Thirdly, the software Fluent is utilized to simulate the air flow of the vane, so as to calculate the convectional heat by using the empirical equation and to compare the convection ability of different choice of the vane’s length, width, quantity and thickness through single factor experiment. At last, the optimized vane structure which can satisfy the mechanical requirement was decided.Finally, the convection, friction coefficient, rotating speed and pressure were all introduced into the thermal model in ANSYS, which was decided in the previous steps and included the brake structure and the vane, to simulate the temperature distribution. The influence of the grooves, different connecting parts and different vane thickness on thermal stress and mechanical stress was synthesized. Different design was analyzed for different braking conditions and different road conditions.