Hood design-Week 2

Hood Design and Assembly

In Siemens NX 

Hood Design and Component Used.

The hood or bonnet is the hinged cover over the engine of motor vehicles. Hoods can open to allow access to the engine compartment, or trunk on rear-engine and some mid-engine vehicles) for maintenance and repair.

Hoods are typically made out of the same material as the rest of the body work. This may include steel, aluminum, fiberglass or carbon fiber. However, some aftermarket companies produce replacements for steel hoods in fiberglass or carbon fiber to make the vehicle lighter.

The Component used are listed below:

1. Outer Panel
2. Inner Panel 
3. Ripple Plate
4. Support Plate
5. Striker 
6. Hinge Assembly

The hood opening angle is a very important consideration while designing the hood. As the person's height varies accordingly, the hood opening angle varies.  

This could be simply done by drawing a circle from the center of the  linear axis of the hinge. The radius of the circle will constraint the striker and Arc form with the horizontal axis will be the opening and closing curve of the hood. 

The pictorial depiction is given below:

The Mastic Data is also necessary to be considered while designing the hood. It is the gluing of the inner panel with the outer panel. Approximately, One mastic point covers around 80 mm diametrical area. They are mostly kept in the CH and AH impact area of the outer panel.

The embossed feature given to the inner panel with the appropriate mastic points and cuts are for two purpose listed below:

It gives a supporting surface for the mastic points and being embossed makes it light in weight. Thus helps in reducing the overall weight of the vehicle.

The cut emboss diverts the impact in case of accident towards outside to reduce the impact force and safeguards the driver. It also reduces the impact force to the head in case of a person’s head hitting the hood.

Manufacturing Process

Hemming is a metalworking process in which a sheet metal edge is rolled over onto itself. Hemming is the process in which the edge is rolled flush to itself, while a seam joins the edges of two materials. Hems are commonly used to reinforce an edge, hide burrs and rough edges, and improve appearance.

The rollers are passed one after one with the necessary force rolled over the edge to form the bend and finally a hem.

There are two types of hemmed edges: closed hems and open hems. Closed hems are completely flush while open hems have an air pocket in the bend. The major difference is that the tonnage required for a closed hem is much greater than that for an open hem.

Open hem closed hem

Deep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. It is thus a shape transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter. This is achieved by redrawing the part through a series of dies. 

Industrial uses of deep drawing processes include automotive body and structural parts, aircraft components, utensils and white goods. Complex parts are normally formed using progressive dies in a single forming press or by using a press line.

Punches and dies are typically made of tool steel, however cheaper (but softer) carbon steel is sometimes used in less severe applications.

Parameter Considered

The Master Sketch is used for the Modeling of Inner panel 

Taking the outer panel and inner panel thickness as 0.75mm.

Hemming Data:

Rear relief Section:                              Front Relief: