Research On The Steady-state Tire Model Under The Roll Condition Based On The Brush Model

Tire is an important component of automobile.It is also the unique medium of contact between automobile and ground.In addition to air force,all kinds of vehicle motions are accomplished by rolling tires acting on the ground.However,modern automobile might be collided on the bad and complicated road surface in the process of movement,and the tire will have a certain roll angle accordingly.The existence of roll angle causes the deformation and complication of inner tire tread element in tire tread imprint,which makes the all composite operating conditions of rolling,cornering and longitudinal-slip become the key factors to study the mechanical properties of tire.The research and modeling on the coupling properties of cornering and longitudinal slip under the condition of anisotropic stiffness while the tire is under large load in reality,and the research and modeling on tire dynamic in all composite operating condition including the influence of large roll angle are insufficiency.In addition,the experiment of tire dynamic under composite operating condition is difficult,costly and has long cycle.Therefore,it is also a difficulty to construct a tire steady-state model considering the effect of rolling under composite operating condition.This paper studies the tire steady-state model around the problems mentioned above as follows:1.The background and significance of this research,the relationship and classification between tire dynamic properties and vehicle dynamics are explained.The development history and research status of tire steady-state model at home and abroad are introduced.2.The theoretical basic modeling knowledge of steady-state dynamic properties of tire is introduced in detail,including the coordinate system of tire tread imprint,the relationship between tire model input and output,the slip ratio of tire model definition and vertical pressure distribution in grounding imprint.Secondly,the physical structure of the tire is simplified.The tread is regarded as the formation of a series of elastic bristles.The elasticity is concentrated on the tread,and the carcass is regarded as rigidity.The longitudinal force generation process of the steady-state brush model of the tire is introduced from the deformation mechanism of the tire.The prediction results of the relationship between tire longitudinal force and slip ratio of brush model and the magic formula are compared.However,the brush model is an assumption based on the elastic tread and rigid carcass,which has certain limitations on the expression of the elastic carcass' s tire dynamic.3.A tire steady-state brush model under the composite condition of cornering and longitudinal-slip taking no account of the complex deformation of the elastic carcass is established.Under the composite condition of cornering and longitudinal-slip,the friction coefficient of the brush model is assumed to be the constant,the relationship between the longitudinal-slip ratio and the longitudinal force at different side angles.The lateral force and the aligning torque are symmetrically distributed.Under the large side angle,the aligning torque almost approaches zero.A brush model of the steady-state cornering characteristic of tire considering rolling was established on account of the rolling influence.The presence of the rolling causes the position of the slippage within the imprint to change,which caused the force and torque curves asymmetry.When analyzing the influence of the rolling on the characteristic of cornering,the lateral force is decomposed into the sum of the lateral force generated by the slip angle and the lateral force generated by the roll angle,so that the aligning torque while rolling and cornering can be accurately analyzed.4.On account of the complex deformation of elastic carcass,the change mechanism of the total force direction under anisotropic stiffness is analyzed.Based on this,combined the complex deformation of the carcass and the lateral cartilage deformation of part of carcass,the tire steady-state brush model of the cornering and longitudinal-slip at all composite operating conditional was simulated on account of tire elasticity under rolling operating condition for the simulation analysis of the mechanical properties of tires under various sub operating conditions.The effects of carcass elasticity and time-varying tire pressure on the mechanical properties of the tire are analyzed: the elasticity of the tire carcass changes the direction of internal stress in the imprint.The lateral elastic flexure and torsional elasticity of the carcass reduces the lateral stiffness of the carcass.This phenomenon affects the steering performance of the vehicle.The existence of the carcass elasticity makes the longitudinal slip ratio under the cornering and longitudinal-slip composite operating condition affect the lateral stiffness of the tire.The rolling causes the internal joint force point to deviate from the center of the original imprint,and the aligning torque is greatly affected by the longitudinal force.Due to the torsional elasticity of the carcass,the lateral force is distorted under the combined working condition to exhibit the S shape.Different tire pressure will show different mechanical characteristics.When the load and roll angle are fixed,as the tire pressure increases,the cornering stiffness decreases and the maximum lateral force decreases.For different loads and roll angles,as the tire pressure increases,the maximum peak value of the positive moment decreases.5.Using the self-designed processed static mechanical properties test bench to measure the tire tread imprint of different tire pressures and loads under static under static load conditions of selected 215/65R16 98 H tires.Using the six-component force test bench of the US MTS flat-trac high-speed tires to complete the steady-state mechanical dynamic test of the pure longitudinal-slip,rolling and cornering working conditions of the selected tire at 60km/h.The experimental data obtained were in contrast with the simulation results of the built tire model.