Contact And Thermal Parameterized Finite Element Analysis On Automotive Drum Brake

Drum brake, which is widely used in the front and rear wheels of medium and heavy trucks and buses as well as the rear wheels of cars, is one of the important components to driving safety. For its hard work conditions which contain complex mechanical state and thermal state, research on the drum brake involves multi-body mechanics, tribology, contact mechanics, heat transfer theory and so on. Domestic software design of the braking system has been made great progress. Lots of work on the three-dimensional parametric modeling of drum brake and the theoretic computing platform of braking system has been accomplished, achieving good results in application. However, the software rarely involves finite element modules on non-linear contact analysis and thermal analysis of drum brake, besides, the finite element model developed from the software is relatively simple, which can not reflect the actual working condition of brake very well. Therefore, the development of parametric finite element analysis module for simulation of mechanical properties and thermal characteristics on the brake has important significance in improving the domestic backward state of brake products R&D with the method of experience and analog design, enhancing the R&D capacity of drum brake and heightening the products competitiveness of drum brake manufacturers.In this thesis, finite element method is the theoretical basis, and the finite element analysis platform of drum brake is established using the secondary development language APDL and UIDL of finite element analysis software ANSYS, in which parametric design is applied to the finite element analysis. The analysis of E260 drum brake is completed using that platform, which included contact analysis and transient thermal analysis. Deep analysis of the brake in stress field, deformation, temperature field and contact pressure of the linings is investigated. The main research work of automotive drum brake carried out in the thesis is presented as following:⑴A parameterized finite element model of automotive drum brake is established. Implementing process of parametric design technology is analyzed in the finite element analysis, and parametric design technology, the general principles of finite element modeling, the principle of meshing and the principle of modeling using APDL are described. Considering the above-mentioned principles, a parameterized finite element model of automotive drum brake is established using APDL,which controlled by 56 independent geometry parameters and three meshing-controlled parameters. Different finite element model can be established by changing the geometric parameters and meshing- controlled parameters.⑵The boundary conditions of structure and thermal are determined during braking process. Three types of structure-nonlinear problems in engineering are described.The difficulty to solve contact problem is emphasized.The force state of the drum brake is analyzed,and the braking torque is calculated using the efficiency factor method, and The boundary conditions of contact analysis is determined.The process of imposing contact boundary conditions is described in detail. The contact problem is solved through three load steps:a small displacement is applied in order to eliminate the rigid body displacement in the first load step,so the problem is easy to converged;then, the braking force is imposed in the second load step;at last, a small angle displacement is imposed on the positions at bolt connection for a simulation of the brake's friction braking process in the third load step.The theory of heat conduction and the three types of boundary conditions for solving heat transfer are introduced.The allocation process of braking energy is described ,and the thermal boundary conditions is determined under the emergency braking conditions of the drum brake, which include heat flux and convective heat transfer coefficient.⑶A finite element Analysis platform of automotive drum brake is established using secondary development language APDL and UIDL of the software ANSYS,which includes contact analysis and transient thermal analysis Module.The menu system and dialog box of each module are introduced in detail.The application of modules are described combined with the analysis process of the drum brake in this paper.Using the platform,we can achieve parameterized solid modeling, parameterized meshing generation, parameterized material definition, parameterized boundary conditions imposing, parameterized solving, parametric solving and parametric post-processing, which greatly shorten the product design cycle and lay a foundation for the future optimal design and the research of brake material match.⑷A non-linear contact analysis is carried out for E260 drum brake. The braking torque of the contact analysis model was extracted and compared with the experimental datas. The error of comparison was 9.8%, proving the contact analysis model had a certain accuracy.The magnitude and distribution of mechanical stress of the brake shoe,brake lining and brake drum caused by braking was analyzed; analysis of the brake drum stress field and deformation was emphasized;The max value and location of equivalent stress are got through the contact analysis on the inner surface, and its causes is analyzed;The deformation of the brake drum is deeply analyzed,and its max value and location are got;The magnitude and distribution of the contact pressure on the leading shoe and trailing shoe is analyzed deeply.The above analysis has a guiding significance in the intensity design of the brake.⑸A transient thermal analysis is carried out for E260 drum brake under one emergency braking condition. The research contents are as follows: The law of heat generating ,heat dissipating of the brake drum;The stresses histories of the two nodes in the inside and outside cylindrical surface of the brake drum;The stresses histories of the node of the casting flange fillet root in the junction of flange; The law of thermal stress variation in the radial direction of the cylindrical part;Stress distributions in the inner surfaces at some time stages during simulation period;Thermal distortions of the brake drum.