| Tire dynamic model is the basis of vehicle dynamic analysis and research.To obtain the parameters of tire dynamic model,it usually requires a large number of tire tests for parameter identification.As the currently widely used experiential tire model Magic Formula,more tire tests are required due to the wide range of model parameters.However,the tire test conditions in domestic are limited,and there are few enterprises and scientific research institutions have tire test platforms(only 13 MTS Flat-Trac test platforms are in China at present).The test costs are high,and relevant test specifications and test technology research have not been conducted basically,which cannot meet the existing tire parameter identification requirements.Moreover,the commonly used tire dynamic models at present usually need experience fitting,the physical meaning of the parameters is not clear,the range of applicable working condition is narrow,the expression ability is rapidly deteriorated when the work conditions beyond the range of test conditions,and there is basically no tire force predictive ability.This kind of models cannot simulate the special dynamic properties under some extreme conditions,and even impossible to analyze mechanism of the dynamic properties.As a class of complete physical models,the finite element model does not have the above shortages,but the required parameters are numerous and difficult to obtain.Moreover,the modeling cycle is long,and the calculation efficiency is low.Therefore,this paper developed a semi-physical tire model with less test data required for identification,less parameters and clear physical significances,wide range of operating conditions,strong predictive ability,high computational efficiency,and easy to study the variation mechanism of dynamic properties of tires.Firstly,the effect of tread patterns on the tire contact patch characteristics was studied by using the finite element models with different tread patterns.Then,based on the simulation data of the finite element models,a tire contact patch characteristic model and a tire body complex deformation model under varying tire pressure and load were established.Finally,a semi-physical tire model was established based on the above tire contact patch characteristic model and the tire body complex deformation model,and the expression ability of the semi-physical tire model to the dynamic properties under different tire pressures and loads was verified,the tire force predictive ability of the model with variable pressure and load was verified and compared with Magic Formula.The main research contents and conclusions of this paper are as follows:1.Several finite element models are designed and tested based on two types of tires.The types of the tires were 205/55R16 and 235/60R18.These two classes of tire models both have three different types of tread: flat tread,longitudinal grooved tread and complex tread.These two classes of tire models have the same parameters except for different tread pattern types.Based on the static stiffness test and contact patch characteristic test with different pressures and loads,the finite element models with complex tread have been verified.The results show that the finite element models with complex tread tires have high accuracy,and they can provide sufficient simulation data for the modeling of subsequent ground mark characteristics and tire body complex deformation tire body.2.The static contact patch characteristics of tire have been tested and studied.The characteristics of the tire contact patch have been defined.The characteristics were related to the half width of the contact patch,the 2D half length of the contact patch and the 2D pressure distribution on the contact patch.Four methods for testing the pressure distribution of grounding mark have been briefly introduced,and the test method for static ground mark characteristics used in this paper has also be introduced.According to the test data,the static tire contact patch pressure distribution has obvious non-uniformity.Especially under the overload and under standard pressure conditions,the non-uniformity of the static tire contact patch pressure distribution is more obvious.3.The influence of tread pattern on the static tire contact patch characteristics has been studied.Based on the finite element models of 205/55R16 flat tires,longitudinal grooved tires and complex tread tires,the influence of tread patterns on the static grounding impression pressure distribution was studied.The results show that the tread pattern does not affect the variation of the ground mark characteristic,therefore the ground mark characteristic model based on the finite element model of longitudinal groove tire is suitable for any tread pattern tire.4.The contact patch characteristic model has been established based on the FEM model of 205/55R16 longitudinal grooved tire.The contact patch characteristic model has also been verified based on the simulation data from FEM model of 235/60R18 longitudinal grooved tire.Based on the results,this model can be used to accurately express the half-width of the ground mark under the static load condition,the pure off-side condition,the pure longitudinal sliding condition and the side-to-longitudinal sliding combined condition,the half-length of the ground mark at different tire widths and the distribution of the pressure on the two-dimensional ground mark.The model has the ability to predict the combined condition and degrade the conbined condition to the pure condition.Finally,the parameters and identification methods of the model have been introduced,and the simulation data of the FEM model of 235/60R18 were used to verify the tire force prediction ability of the model under different tire pressures,different loads and even overload conditions.Since the model was designed based on the theoretical framework and the mechanism,it has a strong tire force predictive ability.Moreover,few parameters and less experimental data are required for parameter identification.5.The deformation characteristics of the tire body under longitudinal force,lateral force,positive torque and the above combined forces have been studied.Based on the analysis above,a complex matrix deformation model has been established,the accuracy of the model and the tire force predictive ability of tire pressure and load were verified.The following conclusions are mainly obtained: the longitudinal translational stiffness,lateral translational stiffness and torsion stiffness of the tire body are not affected by the load,and they are only linearly and positively correlated with tire pressure,the bending stiffness of the tire body is linearly and positively correlated with tire pressure,and is quadratic function related to the load.The relationship between complex deformation model and tire pressure and load is simple,this makes the complex matrix deformation model have strong tire force predictive ability.The tire deformation at different tire widths is basically the same.Therefore,the 2D tire deformation can be equivalent to the tire deformation at the center line of the grounding mark.Under the effect of complex force,the deformation characteristics of the tire body are less coupled.6.A semi-physical tire model has been established based on the contact patch characteristic model and complex tire deformation model.The ability of this model has been studied and the results showed that the model could accurately express longitudinal sliding stiffness,lateral slant stiffness and return stiffness with changing tire pressure and load.The model can also accurately express the asymmetric phenomenon of the lateral force curve,the "double peak" phenomenon,and the inclination phenomenon of the return positive moment curve under the combined condition of side offset longitudinal sliding.The identification method for the parameters was also introduced.The prediction ability of the model has also been verified and its prediction ability has been compared with the Magic Formula,the results showed that the model uses data under pure conditions for identification,the identified parameters can be directly used in the combined conditions.This model has better tire force prediction ability for the characteristics of combined working condition,other tire pressures,loads and even overload working condition,and the tire force prediction accuracy is higher than that of Magic Formula tire model.The main innovations of this paper are as follows:1.A new tire contact patch characteristic model has been proposed,which can accurately express the half width of the tire contact patch under different tire pressures and loads,static condition,pure off-side condition,pure longitudinal sliding condition and lateral off-longitudinal sliding combined condition,the 2D half-length of the contact patch and the distribution of the pressure on the 2D contact patch.The model has strong tire force predictive ability of tire pressure and load.Moreover,it also has the ability of predicting combined condition under pure condition,and the degradation of ombined condition to pure condition.The model also provides theoretical basis for quantitative analysis of tire wear,noise and road damage.2.The complex deformation characteristics of the tire body have been studied and a model of the complex deformation of the tire body has been presented.This model can accurately express the 2D tire body deformation under different tire pressures and loads,longitudinal forces,lateral forces,aligning torques and the deformations,and has a strong tire force predictive ability of tire pressure.3.Based on the tire contact patch characteristics model and complex tire deformation model above,a semi-physical tire model has been proposed,it can accurately express the mechanical properties of steady and unsteady tires under different tire pressures and loads.With a small number of parameters and clear physical significance,it is convenient to study the variation mechanism of tire mechanical properties and has strong tire force predictive ability under different tire pressures and loads. |
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