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Approved by:Richard of uing•Director ofRsa ch FOREWORD Recent developments in defensive weapons systems make it imperative for the combat and support vehicles of the Army to move on the ground with utmost agility. In the case of tracked vehicles, the speed of turning required for evasive tactics to be successful is often limited hy the high turning resistances encountered in soft soils and by the ability of the vehicles to develop the slewing forces necessary to overcome these turning resistances.Simulation of the interaction of terrain and tracked vehicles in the turning mode is essential to the improvement of the agility of the tracked combat and support vehicles of the Army. The applied mechanics approach developed at Grumman over the years for the solution of wheel-soil and tire-soil interaction problems has been applied to the simulation of the steady state turning of tracked vehicles. Track-soil interaction models, simulating the action of flexible tracks used by the Army, have been developed for the driving mode (outer track in turning) and towed or braking mode (inner track in turning). Interactions occurring in the turning mode between vehicle components and soil , such as load transfer from the inner to the outer track, roadwheel load redistribution due to track forces, offset of the yaw center due to limitations on interface shear stresses, etc., have been taken into account. The analytical turning model developed by the applied mechanics approach is suitable for the parametric analysis of the effect of various design variables on turning performance and offers insight into the various interrelationships that qovern the turning performance of tracked vehicles. iii ACKNOWLEDGMENT