Hood design-Week 2

Introduction:

The Hood is the outer panel covering the front engine of the vehicle. It opens to allow access to the engine compartments for the ease of maintenance or repair of the vehicle. The Hood is also considered another door as it consists of the outer panel, an inner panel like the side doors of a vehicle.

Outer Panel: It is the aesthetic part of the hood. In other words, it is the outer skin of the hood which provides a luxurious look to the vehicle.

Inner Panel: The hood inner panel provides strength & rigidity to the hood. It also directs the force of the collision outwards instead of into the engine compartment of the car.

Striker: It is a U-shaped bend that attaches to the latch to lock the hood & prevent any loose movement during the car motion.

Hinge: It is the pivoting point from which the hood opens & closes.

Materials:

Conventional car bonnets today are mostly made of steel or aluminum. Such car bonnets weigh about 10 kgs. This is considered too high & the potential for improvement by weight reduction is expected. The greatest change for weight reduction is material changes & redesign of the inner panel of the bonnet. The most important criteria to be considered is reducing pedestrian head injury.

Design Considerations:

The hood of a car is considered the frontal BIW enclosure component. Bonnets are designed to reduce air resistance as the air flows around the car. Apart from this, bonnets are also designed to meet several other requirements. They serve a great deal of purpose in protecting the passengers inside the car & the pedestrian in the event of an accident. It also acts as the cover for the engine.

The European New Car Assessment Programme(Euro NCAP)is a European car safety performance assessment program that has developed test specifications & rating systems for assessing pedestrian injuries during impacts with the front of vehicles such test includes a series of tests using impacts designed to bio-mimic a collision at speed of 40 km/h.

They describe a situation in which a pedestrian is situated laterally & a car first hits one of his legs. Tests are conducted on the leg, upper leg & most importantly the head, as head trauma is most commonly responsible for casualties.

So to avoid severe injuries to the head, the high impact area for adults & children are subjected to less thickness. Also no reinforcement should be provided in that area as during head collision, the hood will absorb the head impact energy leading to collapse of the hood & thus protecting severe head injury.

Another important criteria for the hood design is the protection of the occupants inside the car during front collision. The design of the hood should be in such a way that during the collision, the force should travel in the inward direction through the embosses & directed towards the body of car. Thus, protecting the occupants inside following parts are using in hood assembly for this project:

1. Hood Outer panel
2. Hood Inner panel
3. Hinge assembly
4. Striker assembly

Hood Thickness:

• Outer panel thickness = 0.75 mm.
• Inner panel thickness = 0.75 mm.
• Reinforcement thickness = 1.5 mm.