W.Z. Golinski
Safety Development, MIRA Ltd, Nuneaton, United Kingdom
Keywords: computer aided design, finite element, LS-DYNA, simulation, kerb, impact, BSI PAS68, BS EN 12767, BS EN 1317.
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Road restraints are tested in the United Kingdom to the specifications defined in BS EN 12767 and BS EN 1317 whereas BSI PAS68 defines the requirements for impact testing of security systems. However finite element modelling can be utilised to reduce both the product development cost and the development time.
Products such as road barrier parapets or bollards can be installed behind a kerb. In such circumstances, the simulation will require inclusion of the kerb, as the vehicle interaction with the kerb may affect the impact with the product. Unfortunately, even correlated crash vehicle models will not correctly represent the kinematics of the vehicle while mounting the kerb. To address this issue, it was decided to initially correlate the 2.5t pickup truck model to kerb impacts. Kerb impact tests were performed at the MIRA High Energy Facility (HEF). A Toyota Hi-Lux was selected as a representative vehicle for the 2.5t vehicle model. The 45 degree impacts with 250mm kerb at 20mph (~32km/h) and 50mph (~80km/h) were performed.
The 2.5t pickup truck finite element model was taken from MIRA's library of vehicles models purposely built for road restraint or vehicle security barrier system simulations. The vehicle models were correlated to rigid bollard and flat rigid wall tests to improve their accuracy.
During the correlation to kerb tests, the exact locations of all the joints in the front suspension including steering arms were measured with a FaroArm and the model updated accordingly. The front suspension and steering arms were modelled with beam elements. The tyre's tread and side walls were modelled as elastic shell elements whereas the reinforcements were modelled as elastic beam elements. The correct tyre pressure was achieved by modifying the input for an airbag model included in each tyre.
To verify the kinematics of the vehicle model mounting the kerb, the global rotations of the model (roll, pitch and yaw) were compared against gyroscopic data taken from the test vehicle.
As a result of this project, the 2.5t pickup truck model represents well the overall kinematics of the kerb impact compared with the original crash model response. During the correlation only the suspension and wheels, in particular the tyres, were modified therefore the crash capability of the model was not affected.
Although some discrepancies remain between the model and the tests, it is believed that the current model can be successfully used to develop and assess kerb profiles or road restraint - security systems installed behind a kerb.
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