A new procedure for the analysis of tracked vehicle suspension system under track length constraint has been presented. The detailed behavior of the contact between the track and the ground and the wheel is taken into account utilizing a frictional contact problem formulation. All the conditions such a s impenetration condition, inextensible and unilateral behavior of track and friction conditions are expressed in complementarity form. The formulation has provided not only a theoretical basis but also a convenient method of numerical analysis. The static equilibrium equations are derived by using the principle of minimum potential energy. The resulting problem is then amenable to efficient numerical algorithms such as the modified simplex method. An incremental analysis is made because of nonlinearity and nonuniqueness of the solution to a given level of external load in the frictional contact problem. At each loading step, the Newton-Raphson method is adopted to find the equilibrium configuration of the suspension system.
The approach has been demonstrated through numerical applications to a model of a tracked vehicle suspension system when it sits on a ground of various shapes such as a level, a slope, a sinusoidal and a step obstacle. The selection of a proper size of the load increment is important in getting the physically correct solution. It is in turn dependent on the number of nodal points of the track. A stepsize of 10\% of the total weight used was checked suitable for the present discretization in the sense that there is no change in the solution of the final stage for different stepsizes.
Since no reference solution of this nature is available, no direct comparison is possible. However the results agree well with intuition. In the contact region between track and ground, it is seen that the distribution of track tension and friction force are largely influenced by the friction coefficient while the normal pressures remain the same shape. It is also seen that the direction of relative slip and the location of sticking point have significant influence on the distribution of track tension. It is also confirmed that the shape of contacting ground and track length constraint have direct influence on the deformation of the torsion bar. Such is the case especially with the obstacle.
The model numerical examples have shown the difficult nature of the problem and system behaviors in terms of slope, frictional coefficient and ground shape. It is illustrated that the approach is new and theoretically capable of describing the nonlinearities of the problem. It may be concluded that the suggested method can very well be applied to practical analyses of tracked vehicle suspension systems. However, the efficiency of the method and the poor convergence when the track starts to slack require further study.
