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Title: Analytical and finite element modelling of the dynamic interaction between off-road tyres and deformable terrains
Author: Bekakos, Chrysostomos-Alexandros
ISNI:       0000 0004 7971 0071
Awarding Body: Loughborough University
Current Institution: Loughborough University
Date of Award: 2017
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Automotive tyres are one of the main components of a vehicle and have an extremely complex structure consisting of several types of steel reinforcing layers embedded in hyperelastic rubber materials. They serve to support, drive - accelerate and decelerate - and steer the vehicle, and to reduce transmitted road vibrations. However, driving is associated with certain types of pollution due to CO2 emissions, various particles due to tyre wear, as well as noise. The main source of CO2 emissions is the tyre rolling resistance, which accounts for roughly 30% of the fuel consumed by cars. The phenomenon becomes more pronounced in off-road conditions, where truck vehicles are responsible for about a quarter of the total CO2 emissions. Appropriate legislation has been introduced, to control all of these pollution aspects. Therefore, tyre simulation (especially in off-road conditions) is essential in order to achieve a feasible design of a vehicle, in terms of economy and safety. After a concise literature review and critical evaluation of the state-of-the-art models related to simulation and analysis of off-road tyres, the various limitations of the existing tyre models in terms of representing the rolling response and driving behaviour of actual tyres have been identified (e.g. utilization of non-invariant soil parameters). Finite element models for the terrain have been developed in which invariant soil parameters have been designated which are used for the description of the tyre-terrain interaction. Similar to the development of the soil models, a realistic tyre model was established via a novel coupled MATLAB-ABAQUS optimisation algorithm. The agreement of the tyre structure with reality was achieved through matching of its eigen properties with analogous data from actual tyres. Subsequently, the interaction between a 235/75R17 tyre and a road - which is considered to be either rigid or deformable - was modelled with the finite element method and the rolling response of towed and driven wheels under various driving conditions was investigated. Regarding the limitations of the models used, it should be noted that the soil material is described by the linear Drucker-Prager constitutive model and the tyre parameters have been obtained via an optimisation procedure. More accurate soil constitutive models and calibration of their corresponding parameters, as well as realistic tyre properties can be used for further development of the various models involved in the thesis, the results of which can be validated with experimental data. Additionally, a novel semi-analytical solution for the estimation of the response of a pneumatic tyre rolling on deformable terrain has been introduced, which involves substantial improvements compared to other existing semi-analytical solutions. Among others, lateral forces as well as the effects of treaded pattern and multi-pass have been taken into account. Although the developed analytical model is based on invariant soil parameters, it remains a semi analytical approach, as it involves empirical parameters such as the shear deformation modulus and empirical parameters related to distribution of the pressures between the tyre and the soil. Furthermore, it is assumed that the pressures at the tyre-soil interface are uniform along the width of the tyre which can lead to significant deviation of the results, especially for low inflated tyres (< 15kPa) with large contact area.
Supervisor: Not available Sponsor: Jaguar Land Rover ; EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Engineering not elsewhere classified ; Tyres ; Finite element method ; Tyre-soil interaction ; Off-road tyres ; Terramechanics