Challenge

Hood design-Week 2

VVaishak C3 Jun 2022

HOOD DESIGN

Aim: To design Hood outer panel, inner panel and the necessary reinforcements by following the Master section mentioned with the design parameter.

Hood and its components

A car hood also referred to as a bonnet in some other countries is the hinged cover that rests over the engine of a front-engine vehicle. Its purpose is to provide access to the engine for repair and maintenance. Car hoods are typically constructed from steel and sometimes from aluminum. On front-engined cars, the hood may be hinged at either the front or the rear edge, or in earlier models it may be split into two sections, one on each side, each hinged along the centerline. The hood release system is common on most vehicles and typically consists of an inner hood latch/lock handle, a hood release cable, and a hood lock assembly. The hood lock handle is usually located under the steering wheel, next to the driver’s seat, or in the door frame.

1. Hood Inner Panel

The hood inner panel for a vehicle is provided to improve rigidity, durability, and pedestrian protecting performance by comprising a composite structure in which a multi-cone structure and a frame structure are individually arranged on the front and the rear.

2. Hood Outer Panel

A car hood, also referred to as a bonnet in some other countries, is the hinged cover that rests over the engine of a front-engine vehicle. Its purpose is to provide access to the engine for repair and maintenance.

3. Hinge

Drivers can raise and lower their vehicle's hood thanks to the hood hinges that serve as the body panel's pivoting point. These hinges also hold the hood closed on their end, and most vehicles have two hood hinges, one for each side.

4. Latch

In general, the hood latch system starts with a release handle located on the left side of the driver's area. This handle is connected to an insulated cable that runs towards the front of the vehicle. The other side of the cable is connected to a latch under the hood that keeps the hood flush against the car's body.

Latch Trajectory

The latch trajectory is the path which the striker will follow when the hood is open/closed while pivoting on the hinge axis. The latch trajectory is taken as a circle with the hinge axis as the center of the circle. The striker is placed 90 degree such that it is tangent to the circle.

Mastic Data

Mastic sealants are used here to join the hood outer panel and inner panel together. While considering their asthetic features, we can't just bolt or revet these panels together, so we use mastic sealants. The become hard rubber after drying and also helps in reducing vibrations.

Emboss Definitions

Sheet metal embossing is a stamping process for producing raised or sunken designs or relief in 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.

Deep Drawing

Deep drawing is a metal forming process in which sheet metal is stretched into the desired part shape. A tool pushes downward on the sheet metal, forcing it into a die cavity in the shape of the desired part. The tensile forces applied to the sheet cause it to plastically deform into a cup-shaped part. Deep drawn parts are characterized by a depth equal to more than half of the diameter of the part. These parts can have a variety of cross sections with straight, tapered, or even curved walls, but cylindrical or rectangular parts are most common.

Deep drawing is most effective with ductile metals, such as aluminum, brass, copper, and mild steel. Examples of parts formed with deep drawing include automotive bodies and fuel tanks, cans, cups, kitchen sinks, and pots and pans. The process requires a blank, blank holder, punch, and die. The blank is a piece of sheet metal, typically a disc or rectangle, which is pre-cut from stock material and will be formed into the part. The blank is clamped down by the blank holder over the die, which has a cavity in the external shape of the part.

A tool called a punch moves downward into the blank and draws, or stretches, the material into the die cavity. The movement of the punch is usually hydraulically powered to apply enough force to the blank. Both the die and punch experience wear from the forces applied to the sheet metal and are therefore made from tool steel or carbon steel. The process of drawing the part sometimes occurs in a series of operations, called draw reductions. In each step, a punch forces the part into a different die, stretching the part to a greater depth each time. After a part is completely drawn, the punch and blank holder can be raised and the part removed from the die. The portion of the sheet metal that was clamped under the blank holder may form a flange around the part that can be trimmed off.

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.