Hood Design Mohit Narula

Aim: - To design hood outer and inner panel, position the striker and hinges and providing emboss and mastic points.

Design considerations:

1. Outer Panel Thickness = 0.75mm
2. Inner Panel Thickness = 0.75mm
3. Reinforcement Thickness = 1.5mm
4. Minimum fillet radius = 3+0.75 = 3.75mm
5. Providing reliefs at corners to reduce stress concentration

Theory: - Hood is also called as bonnet. It is the main component of front portion. The shape of bonnet is made aerodynamic in order to minimize the air resistance. It is used to access the parts like radiator, engine and many parts. Hood or bonnet in open position by the support of support rod or gas stay. Support rod is like different curves and bend to made it stronger to support hood.

1. Master Section: -
2. Functional and Safety Requirements:- The important criteria to be considered is during frontal collision, the hood should be designed in such a way that the crash force is dissipated evenly in the outward direction towards the hinge, so that passenger safety is ensured.

Procedure :-

• Creating the hood inner panel using the master section as shown below:-

• Creating embosses so as to dissipate the crash force towards the hinge
• Placing the hinge and striker by providing appropriate embosses
• Providing mastic points for applying mastic which are rubber like material, which when heated spread evenly and help in reducing Noise, vibration and harshness. The mastics have influence area of 80mm diameter. The influence area of 80mm is shown below (red circles).
• Development of hood outer flange by hemming and maintaining the gap as per master sections
• Hemming: Hemming is the process of joining inner and outer panel together. A set of rollers roll the sheet with inner panel 3-4 times to get the desired results. The gap is then filled with sealants to make joint waterproof.
• Providing reliefs at corners to reduce stress concentration

Observations:-

• Development of all necessary reinforcement: Hood reinforcement structure as provided to reduce impact in collisions to passengers. When latch and striker attached to the panel, the strength will be reduced in that area. In order to improve the strength in that area the reinforcement is added.

In between outer and inner panel there will be stiffener pad is also added to avoid NVH (Noise,Vibration,Harness).

Position of hinge and striker:- For positioning hinge and striker, we have to place hinge tentatively and take hinge axis point and place striker position from data taken from parent car or our own. Take a hinge axis point and striker point as radius and draw a circle. From a circle we conclude two points.Whether a circle is trajectory of hood opening and closing.At this position striker is exactly perpendicular to the trajectory locally.

Mastic data :- Mastic seal is a kind of hard rubber glue added between outer and inner panel of hood to join them at different points called mastic points locally around 80mm diameter. There should be minimum 2mm gap between outer and inner panel to make a constant joint.

Conclusion:- Thus, the hood design is completed considering all the master sections and all other requirements

Google Drive LINK:-https://drive.google.com/file/d/1v5hIuf8u9ix1yfMZyIPtE2wN5ZxMAYh2/view?usp=sharing