Integration of a Continuum-Based Finite Element Tire Modeling Framework in Multibody Dynamics Algorithms
thesisposted on 25.07.2018 by Mohil D Patel
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
Flexible multibody systems (MBS) are systems of interconnected rigid and flexible bodies and are typically characterized by large reference translations and rotations. Examples of such systems include automotive vehicles, trains, aircrafts and musculoskeletal systems. The flexible bodies found in MBS models can be characterized by small and large deformation. The MBS dynamics literature consists of various methods of formulating the governing equations of motion, describing the MBS models and incorporating component flexibility. In case of flexible MBS models, the fidelity, accuracy and efficiency of the model will depend on the formulation and numerical methods used by the MBS software, which keep evolving and improving over time. The goal of this thesis is to develop a new computational framework for the modeling and integration of finite element (FE) tires in MBS dynamics algorithms. Historically tire modeling techniques used in MBS computer programs have consisted of curve-fitted analytical formulations, discrete/compliant-type elastic tire models and co-simulated classical FE models. This thesis proposes a new method of FE-based tire modeling that utilizes the absolute nodal coordinate formulation (ANCF) elements and can be systematically implemented in non-incremental MBS dynamics algorithms. The advantages of such a type of tire modeling are two-fold: the distributed inertia and elasticity of the tire can be successfully represented, and the model can exploit the existing MBS dynamics algorithms for obtaining efficient and reliable solutions. Along with the overall structural modeling aspects of tires, a new approach for the inclusion of surface geometry within ANCF FEs is developed, with tire tread details being a good example of such type of geometry. This thesis also reviews and discusses locking phenomena in classical FEs and fully parameterized ANCF beam and plate/shell elements and proposes a new locking alleviation technique called the strain split method. Finally, this thesis demonstrates the feasibility of developing new and detailed vehicle models that include many interconnected rigid and flexible bodies that could have structural discontinuities and are subjected to small and large deformation. The vehicle models developed and studied in this thesis includes a flexible chassis which is modeled using the floating frame of reference (FFR) formulation and pneumatic and airless tires which use the ANCF approach.