Study On Dynamic Characteristics Of Commercial Vehicle Drum Brake Under Multiple Conditions By Thermo-Mechanical Coupling

Drum brake is a common core component that guarantees the safety of the vehicle.However,the highly nonlinear coupled process of the stress field & temperature field,which is necessary for the work of the brake,could lead to the heat fade failure of the friction lining and fatigue failure of the brake drum.In this paper,based on the thermo-mechanical coupling theory,the necessary simplified modeling of the drum brake is carried out.On the subject of the synergetic mechanism of the temperature field and stress field on the brake drum,the brake drum is simulated and discussed under the three conditions of emergency braking,repetitive braking and continuous braking using the direct coupling method.(1)The emergency braking condition that the vehicle is braked at an initial speed of 60 km/h until it stops is simulated.The simulation results show that the internal surface temperature of the brake drum rises fluctuates greatly,and it is prone to appear the high temperature flash point in initial time.With huge driving force,the brake may appear the phenomenon of brake lock,which seriously affects the braking performance.(2)The repetitive braking condition is simulated according to ‘Trucks and buses-Brake-Bench test methods'(QC/T479-1999).The results show that the maximum temperature of the brake drum reaches above 300°C.The braking performance of the brake will decrease badly with heat fade due to high temperature.And in the alternate effect of tensile stress and compressive stress,the internal surface of brake drum is easy to sprout fatigue crack,eventually leading to brake drum rupture failure.(3)The continuous braking condition that the vehicle continues to brake in long downhill keeping constant speed driving is simulated.Under this condition,the brake drum has been in a state of friction,and its temperature will continue to rise.The high temperature will further increase the internal stress of the brake drum.The heat fade is the main reason for its failure.The results of thermo-mechanical coupling analysis of three common braking conditions show that the friction temperature rise and stress distribution of the brake drum have a great influence on the performance of the brake drum,and the influence mechanism is also different.But the possible forced cooling measures can be used to improve the safety effect of the brake drum.In order to reduce the risk of fatigue fracture of the brake drum,it is necessary to improve the quality of the brake,to pay attention to the speed that cannot be too large,to try to avoid frequent braking,to install heat dissipation devices for brake and so on.