The Research Of Nonlinear Dynamic Modeling And Braking Characteristics On Braking Process Of Wet Brake

Wet brake is attracting engineering machinery vehicle manufacturer's attention and research gradually.As a new brake,it has the advantages such as a big brake torque,a big friction contact area,stable braking performance,free from external influences and so on.In this paper,based on scientific and technological project,CAE reliability analysis and design of G6 axles,we make a deep research on braking characteristics of wet brake's braking process by combining simulation and bench test supported by China Automotive Engineering Research Institute and Chongqing DajiangXinda vehicles Limited company.We have made the following research.(1)Dynamic analysis on of braking process wet brake.We first describe the three stages of fiction,extrusion,pressing,asperity contact,and analyses the factors concerning the wet brake's braking torque.Considering all the factors,we analyses the dynamic characteristics of oil film between the fiction plates on the braking process and establish a nonlinear mathematical model of the three friction stages.(2)Using MATLAB/Simulink to finish the simulation analysis on the oil film thickness,the viscous torque,the rough torque,the dynamic characteristics of braking torque and a further analysis on the simulation results' influential factors like different the braking pressure,the friction material permeability and the surface roughness.Simulation results show that the thickness of oil film becomes thinner quickly with the joint of the friction plates and then tends to be stable.The increasing of the brake pressure and the friction material permeability,the decrease of the surface roughness will lead to the smaller of the oil film thickness.The viscous torque begins to increase gradually from the engagement of friction plates and reaches a peak in a relatively short time,then decreases to zero eventually.The increasing of the brake pressure and the friction material permeability,the decrease of the surface roughness will lead to an increased peak and a decreased lasting time of the viscous torque.The rough torque begins to increase quickly in a short time from the engagement of friction plates and reaches a stable value,lasts until critical end of braking and decreases to zero.The increasing of the brake pressure will lead to an increased peak and a decreased time of reaching to the peak.But the increasing of the friction material permeability and the surface roughness has no effect on the peak.The braking torque of the wet brake is composed of the viscous torque the main part,and the rough torque.The increasing of the brake pressure will lead to an increased peak and a decreased time of reaching to the peak while the increasing of the friction material permeability and the surface roughness will only lead to a decreased time of reaching to the peak,having no effect on the peak.(3)The experimental data of wet brake from bench test based QC/T 239-1997? automobile brake performance requirements ? and GB/T 13826-2008 ? wet(non-metallic)friction materials? and QC/T 479-1999?method for automobile brake bench test? is mainly in agreement with the simulated results.