Hood Assembly

Aim:

To design Hood with the following requirements

• Design Outer Panel with the Hem
• Develop the Inner Panel
• Develop all the Necessary Reinforcements
• Mirror and position the Hinge & Striker
• Provide Mastic Data
• Provide the required Emboss definition
• Develop a detailed Report for the Mastic position and Embosses you have placed

Tool used:

CATIA V5R20

Links:

https://drive.google.com/file/d/16tXQrSxhdMRCHtRh_D6ER5sA8WxUffa6/view?usp=sharing

https://drive.google.com/file/d/1Qn_c-iJkfxaKsH-IaWwrSzopd34lXjpk/view?usp=sharing

https://drive.google.com/file/d/1Xy01S-MbbR-F82kh82w_rYzE6qeK7ajd/view?usp=sharing

https://drive.google.com/file/d/1Y2c559MNO8GNIV7qmx1FfRxZUCpU5EBK/view?usp=sharing

https://drive.google.com/file/d/19HYTOmCxrf_AUtwYg-xcb22Himzz-ev0/view?usp=sharing

https://drive.google.com/file/d/1U6qrSu0huoIGInSuwekNk_6HvKt5gz90/view?usp=sharing

Hood:

A car hood also referred to as a bonnet is a hinged cover that rests over the engine of a 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 racecars, 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.

A car hood is meant to protect the performance parts of your vehicle, including the engine, while also providing easy access for repairs and maintenance. It is possible for the hood to incur damage as well. One of the most common types of damage is to the hinge, which is the device that connects the hood to the body of the vehicle.

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, including SUV, crossover, truck, minivan and passenger-car models.

Concerns regarding the severity of a potential pedestrian head injury during a collision with a motor vehicle have led to advanced hood designs on many models. Such designs may include a multi-cone inner hood panel design.

An active structure that is capable of pushing the surface of the hood away from the vehicle\'s hard motor components in the event of a pedestrian crash is also in use. Pyrotechnic or spring force designs are often used in the active-hood design.

Requirements:

• Inner panel
• Outer panel
• Hood stay
• Latch
• Hinge
• Mastic points
• Reinforcement
• Emboss

The following are the guidelines should be considered while designing the hood

• Outer Panel Thickness = 0.75mm
• Inner Panel Thickness = 0.75mm
• Reinforcement Thickness = 1.5mm
• Minimum fillet radius = 3mm+thickness
• No sharp edges
• Provide proper corner relief
• Emboss maximum depth =6-7mm

Master section:

Inner panel:

The inner panel is primarily developed using the master section. The inner panel is offset of the parent surface which is the outer panel. It is the complicated part of the hood design consisting of the elements like mastic points, hinges, latch, emboss, etc.

Outer panel:

The outer panel is generally an extracted model from the prototype design. It is the styling part of the car.

Reinforcement:

The reinforcement basically provides strength to the components. Here, the latch and hinge need reinforcement as they are assembled components and had to carry some load of the hood (weight). It helps in reducing the deformation of the panel. Generally, the thickness of the reinforcement is thicker than the panel(1.50mm). The material used in reinforcement is of a higher grade.

Hemming:

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. Hems are commonly used to reinforce an edge, hide burrs and rough edges, and improve appearance. The hemming process wraps the edges of the hood outer panel featuring a drawn surface around the inner panel with the help of the rollers and holds it tightly. Hemmingcan stiffens the hood border and when adequately sealed it can protect against corrosion. Basically, it is a 3 step process which is explained in the form of a figure below.

Corner relief:

Mastic pads:

Sealants are materials that are for one-time use only. Mastic sealants are widely used in the automotive industry. They provide a permanent seal between the components avoiding welds or revetting as they spoil the look of the component. Seals provide strength locally at a radius of 80mm. At the point of application, there should be a gap of 2mm.

Mastic is commonly used on construction projects as an adhesive and sealant. It is a popular choice where one surface needs to be adhered to another in a durable bond, or where the area needs to be protected.

The most common types of materials that mastic sealant can be adhered to include timber, aluminum, steel, marble, glass and various types of board, although it can be used on nearly all materials.

Embossing:

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.

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.

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.

Latch and striker positioning:

After positioning the hinge assembly and latch the position of the striker need to reset. The trajectory is derived from the hinge axis and the center distance from the striker. It is denoted as a circle. The hood closes properly if the striker is perpendicular to the trajectory.

Final assembly:

sectional view: