Contact forces in three dimensional nonlinear analysis of tracked vehicle systems

A three dimensional model is developed for the nonlinear dynamic analysis of large scale multibody tracked vehicle systems. In this model, the joint articulations of the track chains are taken into consideration so as to allow the development of a computational procedure for the analysis of the vibrations and the contact forces of the multibody tracked vehicles. The configuration of the vehicle is identified using the absolute Cartesian coordinates and Euler parameters.; The multibody tracked vehicle is modeled as three kinematically decoupled subsystems which include the chassis subsystem and two track subsystems. The tracks of the vehicle are represented as closed loop kinematic chains, each has a number of degrees of freedom equal to the number of chain links plus three. Singular configurations of the closed chains are avoided by making cuts at selected secondary joints and use a penalty function approach to represent the secondary joint compliance. The technique of the velocity transformation which combines the advantages of the augmented formulation and the recursive equations is used to develop the dynamic formulation for the spatial tracked vehicle system. In this approach the augmented formulation is used to define the system topological structure, while the recursive equations are used in order to avoid using the iterative Newton-Raphson algorithm. Nonholonomic constraints that define the rotation of the sprockets are defined and expressed in terms of the time derivatives of the generalized coordinates.; Three dimensional nonlinear contact force models that describe the interaction between the track links and the vehicle complements as well as the interaction between the track links and the ground are developed and used to define the generalized contact forces associated with the vehicle generalized coordinates. These contact force models include the tangential force components which are found to be necessary to maintain the motion stability of the track chains. These tangential force components prevent the slippage of the track that results in the loss of the contact between the track links and the vehicle components. Body and surface coordinate systems are introduced in order to define the spatial contact conditions. These conditions provide the forces necessary for driving the tracked vehicle. A computational three dimensional finite element procedure for the deformation and stress analysis of the chain links of spatial multibody tracked vehicles is presented. The dynamic forces including the contact forces used in the finite element procedure developed in this investigation are evaluated.