Hood design-Week 2

 AIM: 

To Design Hood Outer Panel, Inner Panel and the necessary reinforcements by following the Master Section mentioned with the Design parameters.

INTRODUCTION:

The Hood or Bonnet is an opening body panel that covers the engine in a front-engine vehicle. The hood is also considered as another type of door in a vehicle as it consists of an inner panel and outer panel. The inner panel provides strength while the outer panel functions as the metal cover for aesthetic looks.

HOOD DESIGN: 

The height of the hood is designed based on the country standards as the height of a average person changes from place to place.

The hood of a car is considered as the frontal BIW enclosure component. Hoods are designed to reduce air resistance as the air flows around the car. Apart from this, Hoods are also designed to meet several other requirements. They serve a great deal of purpose in protecting the passengers inside the car & the pedestrians 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 which has developed test specifications & rating systems for assessing pedestrian injuries during impacts with the front of vehicles such test include 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. Test 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 absrob 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 a such a way that the during the collision, the force should travel in the upward direction through the embosses & directed towards the body of car. Thus protecting the occupants inside.

Following parts are using in hood assembly for this report,

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

Inner Panel:

• In the inner panel only we can research & implement the safety of pedestrians & as well as the driver. In this panel only we can attach the reinforcement, embossed, mastic points etc.

• It is an object of the present invention to provide a hood inner panel capable of reduction of a reaction force of the hood inner panel even if a level of deformation of a hood of a vehicle increases, & ensuring a sufficient energy absorption capacity.

Outer Panel:

We can also call it as cover of inner panel. It is the part, which gives luxurious look to the hood or bonnet. Outer & inner panel can not join by any welding process like spot welding or rivet, which spoil the outer look of a car. The outer panel is generally extracted model from the prototype design.

Hinge Assembly:

Hinge is a component that fixes the hood to the fenders of the car. The latch must be fixed perpendicular to the hinge axis so that the hood opens or closes properly.

Striker Assembly:

Latch & striker is used for locking the hood with the car. It is usually placed on the space provided on the inner panel.

The process involved in designing hood as a sheet metal operations are as following:

• Blanking
• Hemming
• Punch cutting or piercing
• Deep drawing
• Embossing

Hemming:

• Double bending operation carried out on the sheet is called as Hemming Operation. 
• Hemming is used in this operation.

Deep Drawing:

The deep drawing is a forming operation in which the plastic deformation produced in the sheet will be used for changing the shape of the component.

                                        

For carrying out the deep drawing operation, the punch and die combination will be used as a tools but the clearance between punch and die is equal to sheet thickness.

When the required shape and size of the component is obtained in one stage itself, the force needed to be applied is larger. Due to this, eventhough the average stresses induced is less than the ultimate stress. But, some of the localized areas will experience the stress greater than the ultimate. Due to this localized cracking will be taking place and this leads to leakages taking place during usage of the components.

To avoid this, it is always recommended to carry out the deep drawing operation in multiple stages or multiple draws.

Embossing:

• The sheet metal embossing operation is commonly accomplished with a combination of heat & pressure on the sheet metal, depending on what type of embossing is required.

• A sheet metal is drawn through the male & female roller dies, producing a pattern or design on the sheet metal. Depending on the roller dies used, different patterns can be produced on the sheet metal.

Hood Assembly Output:

                              

 

                      

Conclusion:

We have designed a hood that falls under the rules & regulations of the manufacturer's standards.