Hood design-Week 2

AIM-To design the car hood and understand the mechanism behind the design of hood, then development& its safety features as per the design consideration.

The following task is performed:

• Design Outer Panel with the Hem
• Develop the Inner Panel
• Develop all the Necessary Reinforcements
• Mirror and position the Hinge & Striker
• Provide Mastic Data
• Provide the required Emboss definition
• Develop a detailed Report for the Mastic position and Embosses you have placed.

CAR  HOOD

INTRODUCTION:

Bonnet is main component of a car at the front portion. The Hood or the Bonnet of a car is considered as the frontal BIW enclosure component. Bonnets are designed to reduce air resistance as the air flows around the car. It is used to decorate the car and add luxurious look. The shape of the bonnet is made aerodynamic in order to minimize the air effect. Bonnet is generally used to access the parts easily such as radiator, engine and many other parts. In automotive world the weight optimization plays an important role.

In recent years, the work has been done on the bumper and hood design of the vehicle front end to reduce the injuries to the pedestrians in the event of a pedestrian vehicle collision. The front portion of the vehicle gets damaged including bonnet when met with an accident. So there is need to change the existing design of bonnet or by changing the material. The bonnet is the hinged cover over the engine of motor vehicles that allows access to the engine compartment for maintenance and repair.

PARTS OF AN HOOD:

Basically the hood has the inner pannel, outer panel and reinforcement (it will provide the strength) and emboss. Latch and striker mechanism is used to open and close the hood whenever is needed. Latch and hinge is needed some reinforcement for strength.

TYPES OF HOOD SUPPORT:

There are two types of support is there.

1. Gas stay
2. Support rod

1.Gas stay

spring stays are designed to be used on upward lifting doors, once you have opened the door slightly the spring will push the door to the fully open position, Euro fit stock various size springs depending on the door size requirements. This is mostly used for where the car bonnet weight is heavy.

2.Support rod

This is widely used in many car, because this very easy and cheap. In this type we have to lift the hood by ourselves and place the support rod in the space provided either in the hood or engine component. This is mostly used for where the car bonnet weight is small.

Inner panel:

Inner panel supports outer panel. It consists of different embosses and hole at different places. Embosses provide stiffness as well as dissipate energy towards hinges. To determine the most effective position of hole, the method of modal stiffness is employed. Inner pannel is offset of the parent work surface.inner pannel thickness is 0.75mm.

OUTER PANNEL:

Outer panel is nothing but a outer skin of inner panel. Otherwise called as a cover of inner panel. It is the part, which gives luxurious look to the hood or bonnet. Outer pannel and inner pannel cannot join by any welding process like spot welding or rivet, which spoil the outer look of a car.The outer pannel is generally extracted model from the prototype design.

EMBOSS:

The geometry is created based on the master section that was designed above. After performing the initial stages of design, we will provide local embosses to strengthen the component. The component will be strengthened based on the master section. When a force impacts the hood from the front, it travels in an upward direction. The component is designed to divert the force away from the passengers into the hinges, as shown in the image belowThe embosses in the inner panel are made according to the diversion of the load path. The emboss depth is kept at a maximum of 5mm to be on the safer side so that the part is manufacturable.

To provide strength to the inner pannel and to distribute the force produced during the impact with pedestrian or other obstacles to ensure the safety of the passengers. The forces are directed outwards through the embossing path

Mastic Sealant:

The Mastic sealant or the Mastic point is elastic compound that behaves like a rubber. The mastic points are defined on the hood inner panel where the hood can easily deform. They help the hood outer panel to come back to its original shape after it gets deformed. The mastic has an influence area of 80mm.

Hemming:

Hemming is the process of joining both the outer and inner panel together. The hemming process roles and wraps the hood outer panel around the inner panel and holds it tightly together. The following are the dimensions followed for hemming,

POSITION OF HINGE AND STRIKER:

For positioning hinge and striker, we have to place hinge tentatively and take Hing axis point and place position from data taken from the parent car or our own. The other major functional of the hood is the opening and closing of the hood. This is done with the help of the latch and striker. To position the latch and striker effectively, we position the hinge and draw the hinge axis. Now, using the hinge axis as the center we draw a big circle to the position where we need the latch to be placed. Then, we draw a tangent line to the circle at that point and place the latch in that region

 

Building re-enforcements and crash bead:

After the development of the entire inner panel for the hood, we need to develop some additional necessary re-enforcements. The Latch striker and the hinges will need a re-enforcement that needs to be developed. All the re-enforcements are made from sheet metal of thickness 1.2mm.

The re-enforcements are attached to the hood inner panel using the spot welding method. The positions to be spot-welded are provided by the design team.

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ASSY VIEW

CONCLUSION:

All the parts of the hood are designed based on the required condtions& given values and assembled togather to complete the hood design.