Yintao Wei

Analysis of Tire Rolling Contact Response by REF Model

Abstract Analysis for tire dynamic response rolling over an obstacle is important to study automobile NVH (Noise‐Vibration‐Harshness), determine vehicle fatigue load, investigate combined longitudi...

Dynamic Mechanical Properties of Aged Filled Rubbers

Abstract It is well known that the macromolecular structure and the microstructure of the fillers play an important role in the mechanical properties of filled rubbers. This paper focuses on the dependence of the complex modulus of aged natural rubber vulcanizates on the filler network and polymer structure. Dynamic mechanical analysis (DMA) at 30°C, 50°C, and 70°C on the aged rubbers with/without prestrain showed the Payne effect, i.e., a storage modulus drop with increasing amplitude, and the appearance of a loss tangent maximum at strain of about a few percent. The storage modulus increased with the aging time at 70°C, 24 < 72 < 240 hr, in the case of nonprestrain. When the prestrain was applied, strain‐induced crystallization was generated that enhanced the storage modulus. As time passed, the prestrain relaxed and the crystalline structures began to disappear. After 72 hr, the crystalline structures had almost disappeared, and they had only a weak effect. Consequently, there existed a higher modulus for an aging time of 24 hr than 72 hr at testing temperatures of 30°C and 50°C. It was concluded that the storage modulus was determined by the postvulcanization, strain‐induced crystallization, aging, and relaxing time.

Tyre rolling kinematics and prediction of tyre forces and moments: part II – simulation and experiment

There are two aims for the second part of this paper: verifying the theory presented in the first part through parameter variation and comparison between simulation and experiment, and to study the effect of the belt structure on the cornering properties of radial tyres. Research has been carried out with a passenger car radial tyre and two different kinds of truck or bus radial tyres using both simulation and experiment. This second part of the paper shows that belt structure plays an important role in the generation of tyre forces and moments in addition to the effects of the tread stiffness and friction coefficients. The theory and method presented in this paper opens a new robust way to predict the tyre forces and moments from the tyre design and provides a reliable model for a generation mechanism.

Tyre rolling kinematics and prediction of tyre forces and moments: part I – theory and method

A new method to describe tyre rolling kinematics and how to calculate tyre forces and moments is presented. The Lagrange–Euler method is used to calculate the velocity and contact deformation of a tyre structure under large deformation. The calculation of structure deformation is based on the Lagrange method, while the Euler method is used to analyse the deformation and forces in the contact area. The method to predict tyre forces and moments is built using kinematic theory and nonlinear finite element analysis. A detailed analysis of the tyre tangential contact velocity and the relationships between contact forces, contact areas, lateral forces, and yaw and camber angles has been performed for specific tyres. Research on the parametric sensitivity of tyre lateral forces and self-aligning torque on tread stiffness and friction coefficients is carried out in the second part of this paper.

ANALYSIS OF EXTENSION PROPAGATION PROCESS OF INTERFACE CRACK BETWEEN BELTS OF A RADIAL TIRE USING A FINITE ELEMENT METHOD

Abstract A radial tire is a very complex structure made from rubber elastomers and fiber–rubber composite materials. During its use, extension propagation of interface crack between belts can occur, which obviously affects its durability and life. In the present paper, a new mathematical model of extension propagation of interface crack in complex composite structures is presented. The model can reveal the extension propagation dependence of interface crack on the relative size of energy release rates at the left and right crack tips and on the interfacial material properties. The extension propagation model of interface crack, Irwin’s virtual crack close technique and the finite element analysis method are used together in simulating numerically the extension propagation process of a interface crack between belts of a radial tire. The present study numerical results show that the extension propagation model of interface crack proposed in this paper can more realistically characterize the complexity of the extension propagation process of interface crack in complex composite structures.

A theoretical model of speed-dependent steering torque for rolling tyres

ABSTRACT It is well known that the tyre steering torque is highly dependent on the tyre rolling speed. In limited cases, i.e. parking manoeuvre, the steering torque approaches the maximum. With the increasing tyre speed, the steering torque decreased rapidly. Accurate modelling of the speed-dependent behaviour for the tyre steering torque is a key factor to calibrate the electric power steering (EPS) system and tune the handling performance of vehicles. However, no satisfactory theoretical model can be found in the existing literature to explain this phenomenon. This paper proposes a new theoretical framework to model this important tyre behaviour, which includes three key factors: (1) tyre three-dimensional transient rolling kinematics with turn-slip; (2) dynamical force and moment generation; and (3) the mixed Lagrange–Euler method for contact deformation solving. A nonlinear finite-element code has been developed to implement the proposed approach. It can be found that the main mechanism for the speed-dependent steering torque is due to turn-slip-related kinematics. This paper provides a theory to explain the complex mechanism of the tyre steering torque generation, which helps to understand the speed-dependent tyre steering torque, tyre road feeling and EPS calibration.

Nonlinear Finite Element Modeling of Delamination Crack Growth Process between Belts of a Radial Tire

A radial tire is a very complex structure made from rubber elastomers and fiber rubber composite materials. During its use, a delamination crack growth between belts can occur, which obviously affects its durability and life. In the present paper, a new numerical model of the delamination crack growth in complex structures is presented. The model can reveal the crack growth dependence on the relative size of energy release rates at the left and right crack tips and the interfacial material property. The crack growth model, the Irwin’s virtual crack close technique and finite element analysis method are together used in simulating numerically the growth process of the delamination crack between belts of a radial tire. The numerical results show that the crack growth model proposed in the present paper can more really characterize the complexity of the delamination crack growth process in complex composite structures.

Lifetime Prediction of Tires with Regard to Oxidative Aging5

Abstract It is a challenging task in the design of automobile tires to predict lifetime and performance on the basis of numerical simulations. Several factors have to be taken into account to correctly estimate the aging behavior. This paper focuses on oxygen reaction processes which, apart from mechanical and thermal aspects, effect the tire durability. The material parameters needed to describe the temperature-dependent oxygen diffusion and reaction processes are derived by means of the time–temperature–superposition principle from modulus profiling tests. These experiments are designed to examine the diffusion-limited oxidation (DLO) effect which occurs when accelerated aging tests are performed. For the cord-reinforced rubber composites, homogenization techniques are adopted to obtain effective material parameters (diffusivities and reaction constants). The selection and arrangement of rubber components influence the temperature distribution and the oxygen penetration depth which impact tire durabilit...

FM-BEM evaluation for effective elastic moduli of microcracked solids

A fast multipole boundary element method (FM-BEM) was applied for the analysis of microcracked solids. Both the computational complexity and memory requirement are reduced to O(N), where N is the number of degrees of freedom. The effective elastic moduli of a 2-D solid containing thousands of randomly distributed microcracks were evaluated using the FM-BEM. The results prove that both the differential method and the method proposed by Feng and Yu provide satisfactory estimates to such problems. The effect of a non-uniform distribution of microcracks has been studied using a novel model. The numerical results show that the non-uniform distribution induces a small increase in the global stiffness.

Investigation of the carbon-black network in natural rubber under cyclic deformation

Carbon‐black (CB) filled rubbers are often subjected to cyclic deformation in service, particularly in tire applications. To improve resistance to fatigue, better understanding of how the meso‐ or microstructures evolve under cyclic loading is necessary. The presence of a CB network for reinforcement of rubber has been proposed. We describe the study of a CB network in natural rubber by an analysis of the impedance spectrum. The characteristic frequency of the filled rubber is used to characterize the junction width of the CB network. As the junction width of the CB network decreases, theoretically the characteristic frequency will increase. When the CB concentration was less than 10%, the nonfatigued rubbers had normal frequency characteristics, i.e., the measured frequency increased with an increase of the CB concentration. However, rubber with higher CB loading had an abnormal frequency response, whose the origin has been unclear until now. Much work will be done to clarify it. By examining the characteristic frequency, the dependence of the CB network in natural rubbers on the deformation cycle was studied. In general, the higher the number of fatigue cycles, the lower the characteristic frequency that was obtained. Although the rubber specimens showed little change in length in the tension direction before and after the fatigue cycles, the predicted change (different from the recoverable change) in the CB network did occur.