Research and modeling of tire cornering characteristics considering tread wear based on UniTire model

In view of the complexity of tire structure and working conditions, tire models are often based on complete and accurate test data. In combined with the theory of tire dynamics, the empirical and semi-empirical tire models are built. In order to accurately measure the tire mechanical properties, it is necessary to strictly control the wear state of the tire tread during the tire test. But there is still a certain amount of wear, which does not guarantee the consistency of the data. In order to study the influence of wear on the mechanical properties of the tire, based on the tire footprint pressure distribution model and brush model theory, combined with the brush model theory and the rubber block shear stiffness deformation theory, the tire cornering stiffness model under different wear conditions is established. The footprint pressure distribution model is built based on the results of footprint test under different wear conditions. And combined the test result with different tread wear conditions and the theory of brush model, the tire brush model considering tread wear conditions is built. Based on the above theoretical model, the UniTire tire cornering slip model considering the tread wear state is established. To verify the accuracy of the model, the UniTire cornering slip model is obtained by using the cornering slip data in three tread wear states, and the tire mechanical properties of the other tread wear conditions are predicted. The error between the simulation results of the model and the experimental results is small, which effectively prove the predictive ability of UniTire cornering slip model considering tread wear. This study will help to improve the UniTire tire model and provide theoretical and technical support for the UniTire indoor and outdoor expansion applications.

Research and modeling of tire cornering characteristics considering temperature based on UniTire model

Based on the results of tire handling test, the cornering properties of the tire at small side slip under different temperature are obtained, and the variation law of the parameters of tire cornering characteristic with the temperature is obtained. By establishing a tread temperature model and finite element tire model considering the influence of temperature, the mechanism of tire mechanical properties with temperature is clarified, and the expression of tread stiffness and aligning stiffness considering temperature is obtained. Then, based on the above expression and the tire mechanical characteristics with temperature, a complex brush model is established and the relationship between the temperature and the tire cornering properties is obtained. The relationship is used as the basic expression formula to establish the UniTire cornering model considering tire temperature. In order to verify the correctness of the model, four kinds of temperature state cornering data are used for parameter identification, and the tire cornering properties in the other two temperature states is predicted. The error between the simulation results of the prediction model and the experimental results is very small, which effectively proves the predictive ability of the UniTire cornering model considering tire temperature. This research is helpful to improve the application of UniTire model under different temperature condition.

Three-dimensionally preserved ‘Stage IIIb’ fossil down feather supports developmental modularity in feather evolution

We describe a unique three-dimensionally preserved fossil down feather from the Late Cretaceous of Myanmar. It’s morphology is highly congruent with Stage IIIb of the widely accepted Prum and Brush model of feather evolution-development. This makes the new specimen the first evidence of this developmental stage in the fossil record. The Stage IIIb diagnosis is robustly supported by the absence of a central rachis and by its paired barbules emanating from radially positioned barbs that are attached to a short calamus. Prum and Brush’s model hypothesises a bifurcation in the evolution-development pathway at Stage III. Stage IIIa involves rachis development and branching into barbs. Stage IIIb involves branching of the barbs from the calamus and then further branching of the barbules from the barbs. These two pathways then converge into Stage IIIa+b where feathers produce a rachis, barbs and barbules in nested order, finally leading to Stage IV. Evolution-development studies on the morphogenesis of feathers have unequivocally shown that such feather branching can be controlled by BMP, Noggin, Shh and several other proteins. Therefore, molecular crosstalk can convert a barb into a rachis and vice versa. The topology of this down feather, consistent with specific patterns of modular protein-protein signalling already observed, provides the first definitive evidence that such signalling was responsible for the evolution of a diverse inventory of feather morphologies in non-avialan dinosaurs and early birds since the middle Jurassic.

In-Plane Bending and Shear Deformation of Belt Contributions on Tire Cornering Stiffness Characteristics

ABSTRACT In radial tires, belt structure plays a role of minimizing the lateral deflection of carcass, which has a significant influence on the cornering and wear properties of a tire. The deflection of carcass affects the magnitude of tread block deformation when the tire is under the slip angle. As a result, it can change the cornering stiffness characteristics of the tire, especially when the vertical load is high. During tire development, a tire design engineer tries to find the optimal belt ply angle that satisfies the various performance requirements simultaneously, but it is not an easy task because the effect of belt angle change is different depending on the size of the tire. There have been many attempts to construct a mathematical model that represents the structural properties of the belt package, including the string-based model and the beam on elastic foundation model. But, in many cases, only the in-plane bending of belt is considered and the shear deformation is not taken into consideration. In this study, the effect of belt angle change on belt stiffness is analyzed using a mathematical model based on the Timoshenko beam theory. This model can account for the in-plane bending and shear deformation of the belt structure at the same time. The results of the analysis show how the contribution of bending and shear is changed depending on a tire design parameter, herein the belt cord angle. The effect of belt ply angle change on cornering stiffness is investigated by means of the brush model including belt flexibility. The prediction by the brush model is compared with the measurement using a Flat-trac machine, and the validity of the model is discussed.

Study on the Influence of Temperature on Tire Cornering Stiffness and Aligning Stiffness

Based on the results of tire handling test, the cornering properties of the tire at a small range of steer angles under different temperature are obtained, and the variation law of the tire cornering characteristic parameters with the tire temperature is obtained. By establishing a tread temperature model and finite element tire model considering temperature, the mechanism of tire mechanical properties with temperature is clarified, and the expression of tread stiffness and aligning stiffness considering temperature is obtained. Then, based on the above expression and the tire brush model considering the tire temperature state, a complex brush model is established. Through the model derivation, the relationship between the temperature and the tire cornering stiffness is obtained. The relationship is used as the basic expression formula to establish the UniTire cornering model considering tire temperature. In order to verify the correctness of the model, four kinds of temperature state cornering data are used for parameter identification, and the tire cornering properties in the other two temperature states is predicted. The error between the simulation results of the prediction model and the experimental results is very small, which effectively proves the predictive ability of the UniTire cornering model considering tire temperature. This research is helpful to improve the application of UniTire model, and provide theoretical and technical support for UniTire model indoor and outdoor expansion applications