Hood design-Week 2

HOOD

To Design Hood outer panel, inner panel, and the necessary reinforcements by following the Master section with the design parameter

What is a Hood: Hood is one of the main components of a car at the front portion. It is present at the very front of the car, covering the Engine compartment. It is mainly used to protect the front portion, designed in a way it gives an attractive look to the car. The shape of the Hood is made aerodynamic to minimize the air effect. To access the parts easily such as a radiator, engine, and many other parts, The hood of the car is used. 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. A concealed latch is typically used to hold down the hood. On vehicles with an aftermarket hood and on race cars, hood pins may be used to hold down the car hood. Hoods sometimes also contain a hood scoop, wiper jets, power bulge, and/or hood ornament. Car hoods are typically constructed from steel and sometimes from aluminum. Aftermarket car hoods may be constructed from various other materials, including carbon fiber, fiberglass, or dry carbon. The hood design may vary from one make and model to another.

Attractive looks owed to the Hood

To hold the Hood in its place, the components used are:

1. Support Rod

2. Gas stay

(IMAGE)

Pedestrian -Vehicle Collision

A perfect hood design means it should have a great impact distribution angled outside the car. The European Enhanced Vehicle-Safety Committee (EEVC) & European New Car Assessment Program (euro NCAP) says about the militations of the severity of the head injury of a pedestrian.

In Japan and Europe, regulations have come into effect that places a limit on the severity of pedestrian head injury when struck by a motor vehicle. This is leading to more advanced hood designs, as evidenced by multicore hood inner panel designs.

Design specifications for the automotive hood component

About Inner PANEL, OUTER PANEL, & Reinforcements

The below image shows the fully assembled hood of a car with an Inner panel, and outer panel along with mastic points (circles show the mastics release space)

Designing a Hood:

1. Hood Head for Lock Striker: Fig. 2 shows the hood head for the lock striker From Fig. The opening angle of the hood will give A, C, B, and D concerning the ground. those A, B, C & D are decided in the head zone. The opening angle varies from region to region depending on average human weight. Depending on the standards we are deciding the angle. So from the angle data, the Support rod or Gas stays designed. The position of the Support rod is on the other side of the battery which is shown in fig. below.
2. Latches and Stiffener pad: Latches are added where and all the weight is added. On the inner panel, we have Hinges and striker, which are attached to the inner panel so due to this attachment the strength of the inner panel is going weak. To strengthen the inner panel Latches will play a very important role. A stiffener pad is a sponge-like material placed b/w Inner and outer panels to reduce vibrations.
3. Mastic Seals: Mastic Seals are placed b/w Inner and outer panels to reduce Noise, vibration, and harshness. Every Mastic will have an effect of 80mm Dia locally. shown in fig 3.1. The inner and outer panel gap is 2 to 5mm. They can provide thermal and acoustical insulation, and may serve as fire barriers. They may have electrical properties, as well. Sealants can also be used for simple smoothing or filling. They are often called upon to perform several of these functions at once.

1. Embosses: Embosses are provided in the inner panel of the hood assembly. This helps in a weight reduction of the hood and also dissipates the force during the collision. Force dissipation is shown in fig. 4.1 this project design

• The metal sheet embossing operation is commonly accomplished with a combination of heat and pressure on the sheet metal, depending on what type of embossing is required. Theoretically, with any of these procedures, the metal thickness is changed in its composition.
• A metal sheet is drawn through the male and female roller dies, producing a pattern or design on the metal sheet. Depending on the roller dies used, different patterns can be produced on the metal sheet. The pressure and a combination of heat actually "irons" while raising the level of the image higher than the substrate to make it smooth. The term "impressing" refers to an image lowered into the surface of a material, in distinction to an image raised out of the surface of a material.

Manufacturing a Hood:

There are various processes for manufacturing processes involved in making a hood. Mentioned below are the common ones

1. Deep Drawing: 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 a "deep" drawing when the depth of the drawn part exceeds its diameter.

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

• Conventional die hemming is suitable for mass production. In die hemming, the flange is folded over the entire length with a hemming tool. Normally the actual hemming is a result of a forming operation in which the flange is formed with a hemming tool after the drawing and trimming operations have been completed

• 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.

• If weld or bolts were used to join the hood panels then the design and the aerodynamic features would get damaged & also the aesthetics will be affected, so hemming is more significant to use.

While doing the hemming process, A relief angle is formed as a product of the hem when attaining at the corner of the sheet metals.

Components of a Hood:

Latch Striker:

A hood latch is a very simple component. It's the fastener that keeps your hood closed shut. This latch ensures that your hood is securely connected to your vehicle and that it doesn't pop open unexpectedly

When tension is applied to the cable from the hood release handle, it pivots the secondary latch, which pulls away from a retaining seat located under the hood. By design, the secondary latch then releases the hood a few inches before a safety latch takes over.

Hinge: A hinge is a component that fixes the hood to the fenders of the car. The latch must be fixed perpendicular to the hinge axis so that the hood opens or closes properly.

Latch trajectory motion: There is a path of motion for hood to open and close, called the Latch trajectory. This is defined over an axis connecting to the center point of hinges. While opening or closing the hood, the latch must be perfectly aligned to the fixing or striker point. For that, the latches' trajectory must be perpendicular to the hinge axis.

Impact Force Distribution In Hood design: A hood design must be made in such a way that when a force is impacted in the front of the hood, all the force must be directed outwards from the vehicle. And the distribution of the force must be controlled along with the hood.

• Draft Analysis: 5 degrees of draft analysis are made to the inner panel to find any negative draft. this process is done because we need to develop and submit a positive design to the manufacturers. We can see that there are no negative drafts on the inner panel, hence the design is positive and ready to manufacture.

HOOD DESIGN: