Analytical and finite element modelling of the dynamic interaction between off-road tyres and deformable terrains

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. [Continues.

Terramechanics and soil–wheel interactions for road vehicle applications

The current research concerns the analysis and development of a soil-wheel interaction model intended for application in road vehicles, in order to support virtual vehicle development processes. As a first step, a review of the literature is conducted which reveals the absence of a reliable tyre model for off-road applications. In addition, it highlights two critical performance items for the soil-wheel interaction; tractive effort and rolling resistance. The rolling resistance is generated by soil compaction, horizontal soil displacement and tyre flexibility, while the tractive effort is generated by the soil shearing behaviour at the soil-wheel interface. Existing models for soil compaction (i.e. pressure-sinkage) are initially evaluated for their accuracy and applicability using literature data, but their performance is unsatisfactory. In addition, a large experimental campaign is conducted using two soil types and various experimental processes such as pressure-sinkage on flat and curved plates, shear tests, rolling wheel tests. [Continues.

Real-time Physics Based Simulation for 3D Computer Graphics

Restoration of realistic animation is a critical part in the area of computer graphics. The goal of this sort of simulation is to imitate the behavior of the transformation in real life to the greatest extent. Physics-based simulation provides a solid background and proficient theories that can be applied in the simulation. In this dissertation, I will present real-time simulations which are physics-based in the area of terrain deformation and ship oscillations. When ground vehicles navigate on soft terrains such as sand, snow and mud, they often leave distinctive tracks. The realistic simulation of such vehicle-terrain interaction is important for ground based visual simulations and many video games. However, the existing research in terrain deformation has not addressed this issue effectively. In this dissertation, I present a new terrain deformation algorithm for simulating vehicle-terrain interaction in real time. The algorithm is based on the classic terramechanics theories, and calculates terrain deformation according to the vehicle load, velocity, tire size, and soil concentration. As a result, this algorithm can simulate different vehicle tracks on different types of terrains with different vehicle properties. I demonstrate my algorithm by vehicle tracks on soft terrain. In the field of ship oscillation simulation, I propose a new method for simulating ship motions in waves. Although there have been plenty of previous work on physics based fluid-solid simulation, most of these methods are not suitable for real-time applications. In particular, few methods are designed specifically for simulating ship motion in waves. My method is based on physics theories of ship motion, but with necessary simplifications to ensure real-time performance. My results show that this method is well suited to simulate sophisticated ship motions in real time applications

Predictive semi-empirical analysis for tire/snow interaction

Thesis (M.S.) University of Alaska Fairbanks, 2004A semi-analytical method is presented to predict the shear stress and motion resistance at the tire/snow interaction. The shear stress model is a function of normal pressure and slip. The main goal was to develop a simplified model by reducing the number of parameters in the model, so that the computational time could be reduced towards real time simulations. Motion resistance is calculated by integrating the horizontal component of normal pressure along the tire/terrain contact surface. The motion resistance obtained is slip dependent because the sinkage is a function of slip. The calculations of motion resistance and sinkage were done using the presented model and an existing model. Also the calculated results were compared with the FEA (Finite Element Analysis) data, which matched reasonably well. In the second part of the thesis shear force is expressed as a function of normal load, slip and slip angle. Shear force parameters tire stiffness, friction coefficients, and contact pressure constants were assumed as the functions of normal load and the coefficients of parameters were found through curve fitting using FEA data. These functions were used to calculate tire stiffness, friction coefficient and contact pressure constant. The calculated results matched well with FEA simulation results for the same tire and snow conditions. Pure shear force and the combined shear force were compared, and the pure shear force is always greater than the combined shear force for the same slip and slip angle.1. Introduction -- 2. Review of tire/snow interaction models -- 3. Parametric analysis of shear forces -- 4. Semi- analytical shear stress model for shallow snow -- Conclusions and future work -- References -- Appendix

Off-road tire-terrain interaction: an analytical solution

A novel semi-analytical solution has been developed for the calculation of the static and dynamic response of an off road tire interacting with a deformable terrain, which utilizes soil parameters independent of the size of the contact patch (size-independent). The models involved in the solution presented, can be categorized in rigid and/or pneumatic tires, with or without tread pattern. After a concise literature review of related methods, a detailed presentation of the semi-analytical solution is presented, along with assumptions and limitations. A flowchart is provided, showing the main steps of the numerical implementation, and various test cases have been examined, characterized in terms of vertical load, tire dimensions, soil properties, deformability of the tire, and tread pattern. It has been found that the proposed model can qualitatively capture the response of a rolling wheel on deformable terrain

Pneumatic tyres interacting with deformable terrains

In this study, a numerical model of a deformable tyre interacting with a deformable road has been developed with the use of the finite element code ABAQUS (v. 6.13). Two tyre models with different widths, not necessarily identical to any real industry tyres, have been created purely for research use. The behaviour of these tyres under various vertical loads and different inflation pressures is studied, initially in contact with a rigid surface and then with a deformable terrain. After ensuring that the tyre model gives realistic results in terms of the interaction with a rigid surface, the rolling process of the tyre on a deformable road was studied. The effects of friction coefficient, inflation pressure, rebar orientation and vertical load on the overall performance are reported. Regarding the modelling procedure, a sequence of models were analysed, using the coupling implicit – explicit method. The numerical results reveal that not only there is significant dependence of the final tyre response on the various initial driving parameters, but also special conditions emerge, where the desired response of the tyre results from specific optimum combination of these parameters

The peat swamp:Productivity, traficability and mechanization

The Peat Swamp: Productivity, Traficability and Mechanization has been written with emphasizing the fundamental engineering principles underlying the peat characteristics, importance of peat,peat environmental affect, determination of the mechanical properties of peat terrain, mechanization of peat based on the vehicle for highland, moderate peatland and worst or peat swamp . The mechanization of peat has been discussed with the way to the development of peat vehicle and their performance. Specially, intelligent vehicle development discussion is one of the cores of this book. This book is intended to introduce senior undergraduate and postgraduate students to study on the peat terrain and theory of peat vehicle mobility. The green house gas (GHG) emission from the peat which is mainly incurred due to the aggressive agricultural planned implemented on the peat is discussed. An analytical framework for determining the mechanical properties of peat in view of predicting the tractive performance of vehicle is presented. The measuring techniques of the stiffness of peat’s surface mat and underlying weak peat are also presented. An intelligent control system is presented in this book with air-cushion tracked vehicle which is more enhancing the vehicle mobility over the swamp terrain. The intelligent advanced hybrid air-cushion tracked vehicle for peat swamp is presented in this book which is developed with incorporating the depth knowledge of terramechanics and different discipline of engineering to make this book more attractive to the automotive professional