Hood design-Week 2

HOOD DESIGN REPORT

Objective

To built inner panel ,latch & striker mount, reinforcement according to the standards, hem the outer panel with the inner panel and provide mastic data.

Hood

A car hood is also referred to as a bonnet in some other countries. Generally, it is used to cover the engine and its accessories. Hood also considered as another door which is used to repair and helped to maintenance engine.

Hood parts

• Outer panel .
• Inner panel.
• Hinge assembly.

Design Methodology

• The method used in this project is top down method using master section.

Design considerations

• Pedestrian rating.
• Force distribution.
• Ensuring dfm (sheet metal process).
• Hood standards.
• Force distribution.
• Passenger safety.
• Collision reduction.

Pedestrian rating

The most important thing is a safety regardless of anything. So there are times that pedestrians will be hit by the hood of a car. While the head is laid on the hood that specific portion should absorb the energy instead of resisting. To prevent causes.

The hitting zone will be different because of so many factors like ages, country, etc.

Wrap around distance

When a car crashes on a pedestrian the whole body wraps around the front shape of the car. And the head impact on the windscreen.

The distance on which the head impacts the car from the ground is called (wad).

Child's head impact zone=1000mm to 1700 mm (3.5 kg)

Adult head impact zone = 1700mm to 2100mm (4.5 kg)

Force distribution

When the force is acting on the center of the hood the force should be spread like a wave instead of a single direction, it will drastically reduce the impact on the passengers by adding emboss we can achieve this shown in figure.

Emboss

Sheet metal embossing is a stamping process for producing raised or sunken designs or relief in the sheet metal. This process can be made by means of matched male and female roller dies or by passing sheet or a strip of metal between rolls of the desired pattern. It is often combined with foil stamping to create a shiny, 3d effect. To provide strength to the inner panel and to distribute the forces 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 data

Mastic seals are used as a bond between the inner and outer panels.it is also used to improve the stiffness of the area. It plays a vital role which is reducing the nvh, the gap between the inner and outer panel is 5 mm. Mastic seal will occupy the 5 mm gap.

Hinge & striker

The Hinge Act As A Mechanism To Open And Close The Hood And The Striker Is Used As A Lock By Creating A Reference Circle By Using Th Hinge Axis We Can Find The Striker Trajectory And Place There

Hemming

Hemming is a forming operation in which the edges of the sheet are folded or folded over another part in order to achieve a tight fit. Normally hemming operations are used to connect parts together, to improve the appearance of a part and to reinforce part edges.

In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming and flanging operations to join two sheet metal parts (outer and inner) together. Typical parts for this type of assembly are hoods, doors, trunk lids and fenders.

The accuracy of the hemming operation is very important since it affects the appearance of the surface and surface quality. Material deformations, which occur during the hemming process, can lead to dimensional variations and other defects in parts. Typical hemming defects are splits or wrinkles in the flange, material overlaps in the corner areas or material roll-in. This is why it is important to provide required reliefs at the corners.

There are two types of hemming operations,

Conventional die hemming

In conventional die hemming, the flange is folded over the entire length with a hemming tool.

Roll hemming

It is the roll hemming process that is used for automotive sheet metals. Roll hemming is carried out incrementally with a hemming roller. An industrial robot guides the hemming roller and forms the flange. Roll hemming operation can also be divided into several pre-hemming and final hemming process steps. Roll hemming is very flexible to use and tool costs are significantly lower as compared to those of conventional die hemming. However, the cycle times are much higher since the hemming is realized using a hemming roller which follows a defined path.

Hem relief

Hem relief are being given to reduce the stress concentration on the edges during hemming process.

CONCLUSION

In this challenge Hood is created successfully in Top-Down Assembly approach with Hood Outer Panel, Hood Inner panel, Hinge Assembly and Striker with the given sketch and all the design considerations.