Development of an optimal impact energy absorber for highway crash cushions

摘要

The objective of this research is to develop a new and efficient method ofabsorbing a vehicle??s kinetic energy for highway safety crash cushions. Avehicle that makes a direct impact with a rigid highway structure traveling athighway speeds can be fatal for its occupants. Crash cushions are implementedon roadways in front of these rigid structures with the intent to ??soften?? theimpact. The cushion will bring a vehicle to a stop at safe rates before it impactsthe rigid structure. The energy absorbing component of the crash cushion mustmeet four main requirements. The cushion must reduce the vehicles speed at arate that does not allow the occupant to impact the vehicle interior at velocitiesgreater than 12 m/s. The cushion must then bring the vehicle to a complete stopwith deceleration rates below 20 g??s. A crash cushion must satisfy theserequirements for an 820 kg vehicle and a 2000 kg vehicle traveling at 100 km/hr.Advanced design methodologies were applied to enable multiple,innovative design concepts. These concepts made use of the deformation ofsteel in structural pipe, structural angle, and structural plate to reduce thevelocity of a vehicle at a safe rate. Critical design parameters were identifiedwhich allowed for efficient and effective numerical experiments to be conducted.The data collected from these experiments were then validated when comparedto physical test data. After the data had been collected, each of the designs wascompared to one another in order to decide upon the best design. The designselected was the deforming plate concept which makes use of steel platemounted in a fashion that created two arms that acted similar to two cantileverbeams. A wedge was forced beneath these arms deforming them upward. This design is effective because the deformation can be easily controlled by thethickness of the plate, the moment arm created by the wedge, and the geometryof the wedge. Steel plate is a readily available material that requires minimalmanufacturing for installation preparation making it cost-effective, and easy toinstall. In the event of impact with the cushion, new parts will be inexpensiveand readily available. Being reusable, easy to repair and low in cost, the energyabsorbing concept presented herein is a cost effective alternative to existingenergy absorbing technology. Due to replaceable parts being readily available,repair time and cost will be reduced compared to other designs that require newparts to be fabricated for replacement. This will make for a competitive design.