Numerical Evaluation of a Closed Cabin of Earthmovers for Structural Rigidity and Safety

Heavy vehicles like tractors and loaders with high centre of gravity, when working on slopes and uneven terrain, are very susceptible to dynamic instability. Under these conditions, risk of vehicle rollover, which results in many injuries and fatalities to operators, increases. Earthmovers are equipped with protective structure which even under rollover, provide safe zone (no intrusion by the structure) for operators. Such Rollover Protective Structures (ROPS) are expected to meet minimum performance criteria to ensure occupant safety. The presented work aims at developing a systematic approach for assessment of ROPS and for its redesign.

Phenomena of experimental testing and performance parameters required for tractor cabin were used as per SAEJ2194 in mathematical model. Meshed model was created using Hyper Mesh and 1D mesh model was created using Hyper Beam. Methodology for simulating the rollover conditions was validated and then non-linear quasi-static analysis was carried out using Radioss Bulk and Block on structure using beam elements and full shell mesh model. Displacement control method was used for simulating the rear and front longitudinal crushing, rear and front vertical crushing and lateral crushing.

Design of the cabin structure used in the analysis was safe under rollover, pitch over and crushing loading. Obtained results show that middle post contributes significantly to the resistance of the structure to vertical crushing loads. Hence, a six posts design is better over four posts structure. Structure using beam elements analysis, though it requires less computation time, over-predicts displacement than full shell mesh model analysis. It was observed that crushing of beam sections causes more energy absorption for less overall deflection of the structure.