To determine the stability of the road train with a partially filled tanker

Abstract

When designing and manufacturing tanks for the transportation of liquid cargo, it is necessary to take into account the shape of the tank, the level of liquid filling and the natural frequency of splashing of the liquid in the tank, as they are important factors and affect the stability of the movement. Due to the uncertainty of the lateral forces acting in a partially filled tank, the maximum speed of the start of braking, at which the stability of the movement is still ensured, can be taken as the main indicator of the lateral stability of the tank train. When studying the stability of a road train, as a rule, plane-parallel movement of its links is considered. At the same time, it is considered that the normal reactions of the support surface on the starboard and port wheels are the same. Under this condition, stability of movement is considered for a flat model of a road train. However, when the road train is moving with a partially filled tank, the reactions of the support surface on the wheels of the road train links may change significantly. To determine this phenomenon, the equations of the road train were compiled both in plane-parallel motion and in the longitudinal vertical and transverse planes.

The integration of the equations of motion is performed for a road train consisting of a DAF XF95 tractor and a tank semi-trailer filled to 50 % (8000 L) and the same road train with the same rigid load. As a result of the integration of the obtained system of equations, it was established that during braking of a road train with a partially filled tank, due to the movement of liquid in the tank itself, a lateral force arises, which depends on a large number of factors that cannot be determined analytically. This force leads to a change in the normal reactions of the support surface on the wheels of the axles and sides of the road train. At the same time, the reaction on the wheels of both sides of the tractor vehicle increases, and on the wheels of the semi-trailer - decreases. This is explained by the effect of liquid cargo on the walls of the tank. At the same time, it is shown that the generalizing parameter that characterizes the stability of the straight-line movement of a road train with a partially filled tank (50 % of the full volume) in the braking mode should be taken as the initial speed at which the tractor and semi-trailer do not exceed the width of the traffic lane. Based on the selected criterion, the initial braking speeds are obtained, at which the stability of the road train is ensured. These velocities, with a coefficient of adhesion of the wheels to the supporting surface in the range of j = 0.6, were 16.1 and 26.9 m/s for the road train with hard and liquid cargo, respectively. Therefore, it is necessary to provide special devices in the tank structures, in particular internal partitions, which would increase the stability of the road train during the braking process.