Finite element modelling and simulation for a 'smart' tyre

摘要

This thesis presents an initial Finite Element (FE) based modelling investigation aimed at supporting the development of 'smart' tyre or intelligent tyre technologies. Physical tests carried out with a stationary (non-rolling) and rolling experimental tyre are used to enhance understanding of tyre behaviour in the contact patch and validate the modelling methodology. Simulation results with the explicit FE package LS-DYNA are then used to characterise the internal stresses and strains at several positions in the tyre tread. Two separate FE models are developed to simulate the stationary and rolling tyre behaviour at the macroscopic level. The models differ only with respect to the mesh density in the circumferential direction, the mesh through the cross section is identical. The complex tyre structure is represented as a rubber and reinforced rubber composite, and the mesh specification and the material descriptions used in the models are discussed. The structural behaviour of the stationary experimental tyre under normal load is simulated. The inflation of the tyre, the wheel fit and the normal loading against the horizontal surface are represented. Simulation results are also presented when a subsequent longitudinal or lateral load is applied to the stationary tyre. These analyses were conducted to determine the longitudinal and lateral tyre stifffiesses, respectively. The predicted normal load-deflection characteristics and contact patch dimensions (length and width) are compared with a reasonable degree of success to those obtained in the full-scale physical tests. The longitudinal and lateral simulations also appear to give realistic tyre stiffnesses. The contact patch dimensions give a good trend-wise agreement, but the length and width are greater than the experimental measurements. A parametric study is carried out and this disparity is related to a deficiency in the performance of the contact algorithms. It is concluded that it not straightforward to accurately predict contact patch behaviour, and therefore the internal transient stresses and strains in a rolling tyre in absolute terms. However, the good trend-wise agreement suggests that the modelling methodology should be capable of predicting internal transient responses which are related to the 'actual' deformations in the contact region. To simulate the rolling tyre behaviour on flat bed and drum surfaces, consideration is given to the inflation of the tyre, the wheel fit, the normal loading and the rotation of the tyre. Numerical instabilities are found to occur and these are related to imperfections inherent in version 950d of the code. This version was, at the time, the most up to date release. The current release is version 960 and it does not contain many of the imperfections in the earlier version. Thus, the flat bed simulation is repeated using the current version. The predicted contact patch stresses are presented and a reasonable correlation is achieved with the experimental data. The internal stresses and strains are then characterised at a number of selected positions in the tread region. These stresses and strains are discussed in context with the development of smart tyre technologies and are useful as a guide to the most appropriate location for an in-tyre sensor (or sensors).