Rear Underrun Protection Assembly Design

Shock absorption: Incorporation of shock absorbing structure (auxetic re-entrant hexagonal structure) for collision impact reduction and a wire of appropriate material that extends and allows better energy transmission.

The car hits the front RUPD bar and moves backwards. The wire, attached to the block first moves and stretches to 7 cm after which it breaks and hits the re-entrant shaped auxetic structure cuboid. This ensures maximum energy is absorbed and minimum collision impact is experienced by the car's driver. Since both the wire and the materials (the auxetic structure connected via groove to chassis and the low grade steel inside the RUPD bar) act as energy and shock absorbers, the collision impact is reduced.

We wanted better energy and shock absorption at minimum damage and impact on our device for the longevity of the device. As we can observe above, most part of the RUPD experiences lesser strain (as well as stress), therefore, the mechanism works well and according to our requirements.

We calculated how much collision energy is absorbed by our device (corresponding to a 1200 kg car colliding at 90 kmph to our RUPD device) and therefore how much collision impact is reduced. Total energy absorbed by the device = Energy absorbed by the wire + Energy absorbed by the auxetic block deformation.

The total energy absorbed is around 65% of collision energy. Hence, the device works well and efficiently in real life and shows an optimum energy absorption of 65%. So, efficiency = 65

We calculated how much collision energy is absorbed by our device (corresponding to a 1200 kg car colliding at 90 kmph to our RUPD device) and therefore how much collision impact is reduced. Total energy absorbed by the device = Energy absorbed by the wire + Energy absorbed by the auxetic block deformation.

The total energy absorbed is around 65% of collision energy. Hence, the device works well and efficiently in real life and shows an optimum energy absorption of 65%. So, efficiency = 65