Bus rollover event is one of the most crucial hazards for the safety of passengers and the crew riding in a bus. In the past few years it has been observed that after rollover accidents the deforming body structure seriously threatens the lives of the passengers. Hence, rollover strength of the bus bodies has become an important issue for bus and coach manufacturers.

Methodology:

During physical testing, the bus placed on platform is tilted about the rotation point (specified as per standard) with the angular velocity of not more than 0.087 rad/sec.  At some specific angle, the bus C.G. imbalances and the bus rolls into the ditch of depth 800 mm due to its own gravity. The intrusion of the side structure into the residual space is checked manually and regulation pass/fail is decided based on regulatory criteria. The CAE is a cost effective & less time consuming process. Moreover, bus rollover simulation in comparison to physical testing provides enough scope for optimizing the bus body structure which further helps in reducing the overall weight of the bus.

For bus rollover simulation we require final angular velocity of the bus during impact on ground and the residual space as per AIS definition.

Result interpretation and Physics:

Bus rollover happens due to collision or high speed during cornering. As a vehicle rounds a corner, three forces act on it: tire forces (the centripetal force), inertial effects (the centrifugal force), and gravity. The cornering forces from the tire push the vehicle towards the center of the curve.

This force acts at ground level, below the center of mass. The force of the vehicle’s weight acts downward through the center of mass in the opposite direction. When the tire and inertial forces are enough to overcome the force of gravity, the vehicle starts to turn over.