Multi-field Coupling Analysis And Optimization Of Wet Multi-disc Brake

With the wide application of wet multi-disc brakes in heavy-load construction machinery,thermal failure problems such as ablation,cracks,warpage seriously affect the performance and life of the brake.The main cause of thermal failure is the local high temperature and thermal stress under the coupling of the temperature,stress,and lubricating oil flow field during the working process of the brake.Therefore,it is important to study the multi-field coupling problem of wet multi-disc brakes.As the friction pairs and lubricating oil of the wet multi-disc brake are located in a sealed housing,it is difficult to obtain the changes of the physical fields during operation by experimental measurement.With the development of finite element technology,the numerical model can be used to study the brake performance intuitively.Based on the above background,this paper takes the pressure-loss wet multi-disc brake applied to electric deck cranes as the research object,and studies the multi-field coupling phenomenon and thermal failure of the brake during operation.The main research contents and conclusions are as follows:(1)Research on the multi-field coupling theory and modeling method of wet multi-disc brakes.According to the structure and working principle of wet multi-disc brakes,based on the tribology,heat transfer,thermoelasticity,and computational fluid dynamics(CFD),the coupling relationships of temperature,stress and lubricating oil flow field of the friction pair under different working conditions are discussed,and a method for establishing multi-field coupling models of the wet brakes under different working conditions is proposed.(2)The multi-field coupling models of the brake under different working conditions are established in ABSYS Workbench.The geometric models of each numerical model are determined,the important parameters required for the simulation are obtained through experiments and calculations,and the analysis and solution settings are clarified.(3)The multi-field coupling simulation results of the brake under different working conditions are analyzed.The heat dissipation characteristics of the friction disc oil groove are studied through the heat flow field of the brake lubricating oil,and the thermal reliability of the brake disc during emergency braking is analyzed through the temperature and stress fields of the brake disc.The results show that the heat generation during emergency braking is much higher than the heat dissipation.The lubricating oil plays a role in the uniform temperature field of the brake discs during braking.The flow rate in radial grooves of the friction disc is faster,and the heat exchange in spiral grooves is more complete.Under normal conditions,the temperature rise of the brake disc is low,and the structural stress is mainly due to mechanical stress.The coupling relationship between temperature and contact pressure in emergency conditions results in local high temperature from the middle diameter to the outer diameter of the contact surface,and the structural stress of the brake pads is mainly due to thermal stress.The friction disc warps and its deformation mode is wavy in the circumferential direction and arc-shaped in the radial direction.(4)According to the heat dissipation characteristics of the friction disc oil groove,the size of the oil groove is optimized based on CFD.After optimization,the temperature distribution of the friction contact surface is more uniform,while the maximum temperature remains almost unchanged,which improves the thermal failure caused by local high temperature and extremely high thermal stress during emergency braking.