Modeling And Experimental Analysis For Steady Rolling Resistance Of Automotive Tire

The mechanical properties of the tire which is the unique part of the vehicle contacting with the road can directly affect the performances of vehicle,including power performance,handling and stability,braking and driving,ride comfort,safety and fuel economy.Tire rolling resistance as one of the tire mechanical properties has a significant impact on the fuel economy,tire lifespan,driving and braking and handling performance,and is also a key research topic on tire structure design.At present,the research of tire steady-state rolling resistance is mainly based on in-house bench test,together with road experiment in outdoor.The experimental method still relies on large-scale experimental equipment importing from abroad and the analysis for rolling resistance could be under standard conditions.At the same time,the theoretical models of tire rolling resistance are guided by an empirical model based on a large amount of experimental data,and it lacks the in-depth research that how to analyze its changes through the theoretical modeling of tire steady-state rolling resistance,coupling with the multi-condition experiments.The flexible deformation of the tire rolling process is the direct cause of tire rolling energy consumption.The methods how to predict the characteristics of tire rolling deformation through theoretical models are still not well resolved.There are many factors influencing the steady-state rolling resistance of tires,the rolling resistance of tires is mostly analyzed by a single influencing factor,and there is a lack of in-depth research on the mechanism of the steady-state rolling resistance of tires under multiple conditions at this stage.There are still deficiencies in the extended research of tire rolling energy consumption under non-standard operating conditions,such as cornering,abrasion and other operating conditions.It is also an urgent problem to develop a new method which has theoretical analysis and is easy to operate.In this paper,a lot of theoretical research,devices built,simulation analysis,experimental analysis and verification are carried out.In view of the above problems,the main research contents and results are as follows:(1)A tire flexible ring model which takes into account arbitrary vertical load pressure distribution,rolling contact between tire and road surface,tread flexible deformation and tire rolling energt loss is established and accurately expresses the rolling deformation and variation law;Based on Hamilton principle of dissipative system,the Lagrange equation of tire flexible ring is derived,and the dynamic equation of tire flexible ring is established;The modal expansion method is used to reduce the order of the deformation model of the tire flexible ring with distributed load.The tire experimental modal devices are estabilshed to identify the parameters of the distributed load flexible ring tire model,such as the stiffness and damping coefficient,which can accurately illustrate the rolling deformation characteristics and variation law of the tire in the plane.The radial deformation and tangential deformation characteristics of the rolling tire under multiple working conditions,such as load,speed,inflation pressure and tangential force,are simulated and analyzed.(2)Based on the deformation model of tire flexible ring in(1),a theoretical model of rolling resistance of tire flexible ring is proposed and the analytical expressions of critical damping and critical speed in tire rolling resistance are derived.The rolling model of tire considering the front and rear contact angle of tire is established,which can predict the standing wave phenomenon of tire at high speed and the mechanism of abrupt change of tire rolling resistance with the increase of speed.The variation of rolling resistance of tire flexible ring changing with damping and the contact angle changing with rolling tire is simulated and analyzed.It is concluded that the increasing damping makes the opposite change of contact angle changing with rolling tire,and the mechanism of damping parameters on tire steady rolling resistance is revealed.(3)On the basis of tire flexible ring deformation theory,a tire rolling damping modal identification method based on single point excitation and single point pick-up frequency response function is proposed.The theoretical basis of single degree of freedom and multi degree of freedom modal analysis of tire is derived.The mechanism of energy loss caused by hysteretic damping is explained.The relationship between system viscous damping and structural damping is established,and the half power bandwidth method is derived to analyze tire frequency response function.Based on the principle of strain mode method,a model of tire modal loss factor is proposed.By building a tire modal test system based on single point excitation and single point pick-up frequency response function method,a tire modal test method of single PVDF(polyvinylidene fluoride)piezoelectric film sensor pick-up and force hammer single point excitation is proposed.Using this method,the modal damping parameters of several tires are obtained,and the modal loss factors are calculated.The modal loss factors are applied to evaluate the rolling resistance characteristics of multiple tires to achieve a fast,efficient and economic evaluation mechanism of tire rolling resistance.The feasibility of obtaining tire modal loss factor by using the proposed method is proved,and it is applied to evaluate tire steady rolling resistance and the feasibility and universality of the proposed tire modal experiment method.(4)In order to obtain the real deformation characteristics and steady-state rolling resistance experimental data during tire rolling and verify the accuracy of the models in(1)and(2),the tire in tire sensing test system and the calculation method between tire rolling contact mark length and acceleration are established.The vehicle multi condition road test with in tire sensor test system was carried out,and the coupling problem of radial acceleration,tangential acceleration and gravity acceleration of rolling tire is solved.The characteristics of radial and tangential acceleration in the contact mark of tire under multiple working conditions are studied.The radial and tangential deformation characteristics of tire during rolling are calculated,and the correctness of the deformation model of tire flexible ring with distributed load is verified.The characteristics of energy and power distribution during tire rolling are studied.The experimental methods and characteristics of tire steady rolling resistance are studied,and the accuracy analysis of drum tire rolling resistance experimental platform is carried out.This paper studies the variation of tire steady-state rolling resistance involving load,speed and inflation pressure,and verifies the accuracy of tire flexible ring deformation model and steady-state rolling resistance model,and a model of tire rolling resistance variation law with inflation pressure is proposed,and verifies the effectiveness of the model through experiments.(5)The tire rolling energy loss expansion research is carried out under driving conditions,including travling time,wheel orientation(slipe angle and camber angle)and wear.Firstly,the energy loss characteristics of tread rubber are analyzed,the viscoelastic hysteresis performance of material are analyzed by compression,impact rebound and DMA experiment.The rubber impact experimental system under large deformation and high strain rate conditions is developed.The collision model of rubber considering energy loss is established and its rationality is verified by experiments.The relationship between material energy loss and tire rolling resistance is obtained;A novel model of tire rolling resistance with driving time and a novel model of tire temperature with testing time are proposed,and the rationality of the two empirical models is verified by experiments.The tire rolling resistnace model with slipe angle and camber angle are derived and the model is verified by experiments;The influence of tire wear condition on rolling resistance is studied,and the relationship between tire wear and rolling resistance coefficient is analyzed quantitatively.