Integration of geometry and small and large deformation analysis for vehicle modelling: Chassis, and airless and pneumatic tyre flexibility.

The goal of this study is to propose an approach for developing new and detailed vehicle models that include flexible components with complex geometries, including chassis, and airless and pneumatic tyres with distributed inertia and elasticity. The methodology used is based on integration of geometry, and small and large deformation analysis using a mechanics-based approach. The floating frame of reference (FFR) formulation is used to model the small deformations, whereas the absolute nodal coordinate formulation (ANCF) is used for the large deformation analysis. Both formulations are designed to correctly capture complex geometries including structural discontinuities. To this end, a new ANCF-preprocessing approach based on linear constraints that allows for systematically eliminating dependent variables and reducing the component model dimension is proposed. One of the main contributions of this paper is the development of the first ANCF airless tyre model which is integrated in a three-dimensional multibody system (MBS) algorithm designed for solving the differential/algebraic equations of detailed vehicle models. On the other hand, relatively stiff components with complex geometries, such as the vehicle chassis, are modelled using the finite element (FE) FFR formulation which creates a local linear problem that can be exploited to eliminate high frequency and insignificant deformation modes. Numerical examples that include a simple ANCF pendulum with structural discontinuities and a detailed off-road vehicle model consisting of flexible tyres and chassis are presented. Three different tyre types are considered in this study; a brush-type tyre, a pneumatic FE/ANCF tyre, and an airless FE/ANCF tyre. The numerical results are obtained using the general purpose MBS computer program Systematic Integration of Geometric Modelling and Analysis for the Simulation of Articulated Mechanical Systems (SIGMA/SAMS).