Cargo load shift and its influence on tank vehicle dynamics under braking and turning

Abstract

Dynamic behaviour of a partly filled tractor-tank-semitrailer vehicle is investigated under simultaneous application of cornering and braking manoeuvres. A three-dimensional quasi-static model of a partly-filled tank of circular cross-section is developed and integrated into a comprehensive three-dimensional vehicle model to study its dynamic performance as a function of steering and braking input, and the fill volume. The liquid load movement occurring in the roll and pitch planes of the tank under combined steering and braking is derived as a function of the longitudinal and lateral accelerations, and the corresponding load shift is expressed in terms of instantaneous c.g. coordinates and mass moments of inertia of the liquid bulk, assuming negligible influence of fundamental slosh frequency and viscous effects. The response characteristics of the partly-filled tank vehicle are evaluated in terms of load shift, forces and moments induced by the cargo movement, dynamic load transfer in the lateral and longitudinal directions, directional and roll response, and braking performance of the vehicle. The dynamic response characteristics of the partly filled tank vehicle are further compared with those of an equivalent rigid cargo vehicle to demonstrate the impact of the liquid load shift under combined turning and braking manoeuvres. The results of the comparative study reveal that a partly filled tank vehicle is more susceptible to rollover during a braking-in-a-turn manoeuvre.