Research On Several Key Problems Of Thermodynamics Behaviors Of Mechanical Elastic Safety Wheel

As the unique bridge for the interaction between the vehicle system and road surface,the mechanical properties of thermo-mechanical coupling are obviously presented operating actual working conditions,and it will exert an important influence on the handling stability,safety and comfort of the totally vehicle system.However,as typical pneumatic tyres,the hidden hazard exists in the rolling process,involving tyre burst,air leakage and instability of pressure,which are easy to cause the traffic accidents,it could lead to greatly economic losses and casualties.Therefore,tyre manufactures and research institutions focus their attention on the research and investigation of safety tyres.In this paper,a novel non-pneumatic tire called mechanical elastic wheel(MEW)was introduced.The unique suspension hub and hinge units of MEW not only ensure a high bearing efficiency,but also enable effectively solve the safety and reliability problems of vehicles,which are operated under the periodic alternating loads.To provide the basis for the study of the comprehensive mechanical properties of the MEW and its structural optimization,several key problems of thermodynamics behaviors properties of MEW were studied using the combination of theory,simulation and experiment.The main contents of this thesis were listed as follows:1.These aspects were analyzed at first,involving structural properties,working principle,bearing and contact behavior of MEW.The heat generation and heat transfer mechanism of MEW,which was operated under steady rolling condition,were investigated respectively.Then,a theoretical model for predicting surface temperature of wheel was proposed on the basis of the law of conservation of energy,and the proposed theory model has been verified by temperature testing,it can be found that the theoretical model has high reliability in predicting the temperature of the tread and the sidewall surface under different working conditions.2.The theoretical model of mechanical characteristics,which is neglected the influence of thermal effet was derived based on the brush-type tyre physical model,it was suitable to research the mechanical behaviors of MEW under the complex operating conditions(longitudinal-slip and cornering).The ability and reliability of the model to express the key mechanical properties of MEW under the compound condition were verified by experiments.The influences involving load,speed and dynamic friction coefficient,which were closely related to temperature rising,on mechanical behaviors of MEW were analyzed,the obtained results established the foundation for further study of the thermo-mechanical coupling theoretical model.3.The thermo-mechanical coupling theoretical model of MEW,which was included in temperature rising model,material characteristic model,friction model and mechanical model was established.Moreover,the mechanical characteristics of thermo-mechanical coupling were simulated and analyzed under the different working conditions,involving pure longitudinal-slip,pure cornering and the combination of longitudinal-slip and cornering.It was found that the proposed model enabled accurately predict the mechanical characteristics of MEW under the above-mentioned working conditions.4.Thermo-mechanical coupling finite element modeling and analysis of MEW was studied.A thermal-mechanical coupling finite element model(FEM)of MEW was established using the nonlinear finite element analysis software.The steady state temperature field of MEW and its influencing factors were analyzed by FEM.By incorporating the heat transfer and frictional model into a three-dimensional(3D)nonlinear FEA model of MEW through user specific subroutine in Abaqus,the thermo-mechanical coupled FEA model was established subsequently.Furthermore,the thermo-mechanical coupling effect on tyre cornering behaviors under steady-state rolling condition was investigated,and the influences of thermal effect and friction characteristics on lateral force and aligning moment of MEW were analyzed accordingly.5.A combination of finite element method(FEM)and experiment modal analysis(EMA)have been employed here to investigate the thermal modal analysis of MEW.Based on the Timoshenko curved-beam of combinated elastic body,the governing equation of thermal stress and the theoretical model of thermal modal were proposed,the modal simulation analysis of MEW under normal temperature environment and a specific thermal environment were carried out by FEM.The modal test system of MEW was established on the basis of the analysis theory of experimental thermal modal,accordingly,and a series of modal test were made.Comparision between simulated and experimental results involving the modal shape and natural frequency,it demonstrated that the proposed FE model of MEW operating under a specific thermal condition was reliable and the thermal modal test method was feasible.Additionally,the influence of temperature variation on the inherent vibration behaviors of MEW was analyzed.