Comparison between a rollover tractor dynamic model and actual lateral tests

Despite the progress in tractor design with respect to safety, one of the most dangerous situations for the driver under operating conditions on agricultural machines is the lateral rollover. Several accidents involving tractor rollover have indeed been encountered, requiring the design of a robust Roll-Over Protective Structure (ROPS). A mathematical model representing the behaviour during a generic tractor lateral rollover, with the possibility of modifying the geometry, the inertia of the tractor and the environmental boundary conditions is herein proposed. The purpose was to define a method allowing the prediction of the elasto-plastic behaviour of the impacts occurring in the rollover phase. In particular, this paper proposes a tyre impact model capable of analysing the influence of the wheels on the energy to be absorbed by the ROPS. Different tractor design parameters that affect the rollover behaviour, such as mass and dimensions, were considered and their influence on the energy absorbed by the ROPS was determined. The model was designed and calibrated with respect to the results of actual tests carried out on a narrow-track tractor. The results of the model showed a good match with the dynamic behaviour and energy absorbed by the ROPS in experimental lateral rollover tests. This should permit good prediction of the amount of energy to be absorbed in some accident situations, and therefore assist in the design of protective structures.