Hood design-Week 2

Hood Design –

Using Euro NCAP Design Regulations

• Objective: -

1. The main objective of this project is to design a hood using a design software - Catia
2. To design each individual part of hood with fully defined sketches.
3. To assemble all the individual parts that are designed with the suitable constraints.

• Introduction: -

Product design starts with requirements. The designer will sketch the product based on your requirements. He then uses advanced CAD software to transform the 2D sketch into his 3D model with proper dimensions. Another important aspect of design is that any designed product is manufacturable.

Therefore, the designer's role is to design products that are easy and inexpensive to manufacture.

This is where Design for Manufacturing [DFM] and Design for Assembly [DFA] play an important role in product development.

The design development process continues until the design meets the customer's requirements. The product to be developed this time is hood.

The hood is the main part of the car at the front that covers the engine compartment. The hood is designed to open to allow access to the engine compartment for maintenance and repairs. The soft top consists of an outer panel and an inner panel, which are hemmed together. The inner panel of the hood provides strength while the outer panel acts as a metal cover. The hood panel is one of the most important components of BIW (Body in White) and is considered an end panel component.

• HOOD PARTS: -

1. Hood Inner Panel
2. Hood Outer Panel
3. Latch and Striker Reinforcement
4. Hinge Reinforcement
5. Stiffener Pad

The hood designer's role is to design the hood so that more energy is absorbed by the hood and less energy is transferred into the vehicle during a frontal collision of the vehicle. This is only possible if the soft top is designed in such a way that energy is dissipated from the interior via the pillars, roof, and sides.

Points to consider before designing a hood: -

1. Hood head Zone Criteria
2. EURO N-CAP crash test
3. Lap distance
4. NVH (Noise, Vibration, Harshness)

Head Zone Criteria: -

Head zone criteria is one of the most important parameters when designing a hood. The opening angle of the hood varies from person to person and from country to country. For example, the average Indian height is 5.8 feet while the average European height is 6 feet.

Based on this size, the angle of the hood opening may vary from country to country. The opening angle of this hood is considered important. This is because a small opening angle poses a risk of head injury to humans. The hood needs another support strut to adjust the opening angle according to the average human height in the country.

There are two types of supports to hold the hood:

• Supportrods
• Gas Stay

Design considerations: -

We must layout the live rod in one of these manners that it must now no longer collide any every other element withinside the engine compartment, due to this collusion the rod produces the noise while the vehicle in movement these reasons the NVH (NOISE, VIBRATION AND HARSHNESS).

Rod with the bends is extra favoured due to the fact an immediately rod will through wobbling, wherein because the equal element with bent is rigid. those established rod offers power to the element.

Every other critical aspect that must be taken into consideration whilst designing the rod is, the rod must be set up on the alternative facet of the battery due to the fact, this rod must now no longer produce any interface whilst putting in the battery.

SAFETY REQUIREMENT: -

Safety is one of the maximum critical standards withinside the vehicle designs which concentrates on each the pedestrians and occupants’ protection.

We must layout the hood now no longer handiest offering the protection for the occupants with inside the vehicle however additionally to the pedestrians who're on foot at the roads.

EURO NACP: -

The European New Car Assessment Programme (Euro NCAP) is a European voluntary vehicle protection overall performance evaluation programme primarily based totally in Leuven (Belgium) fashioned in 1996.

They put up protection reviews on new cars, and awards `big name ratings ‘ primarily based totally at the overall performance of the cars in several crash tests, together with front, facet and pole influences, and influences with pedestrians.

Different testing measurement criteria & tests performed under Euro NCAP testing are shown below (in snaps provided): -

WRAP AROUND DISTANCE:

When a car collides with a pedestrian, the entire human body wraps around the front of the car and the head hits the hood or windshield. The distance your head hits the car from the ground is called the throwing distance

The severity of damage from frontal collision analysis is

1. Vehicle shape
2. Vehicle speed

Pedestrian movement relative to vehicle Crash analysis creates two test areas based on the wraparound distance.

1. Child head impact zone
2. Adult impact zone

The wrapping distance for child's head impact zone is 1000-1500 mm.

Adult head impact zone lap distance is 1500-2100 mm.

This study helps designers soften the outer panels and remove material from the inner panels in specific sections of the head impact area in children and adults to ensure the minimal damage to pedestrians.

NVH (Noise, Vibration, Hardness): -

Noise, Vibration and Harshness (NVH), also known as Noise and Vibration (N&V), is the study and modification of the noise and vibration characteristics of vehicles, especially cars and trucks. Interior NVH deals with noise and vibration experienced by the occupants inside the vehicle, while exterior NVH deals primarily with noise emitted from the vehicle and includes drive-by noise testing.

Reduction NVH of Hood: -

NVH The hood also causes NVH on the body, but this can be mitigated with the use of reinforced pads.

Stiffener Pad: -

This pad is inserted between the inner and outer panels of the top for added localized strength. The bonnet shakes while the car is running, causing noise. Reinforcement pads are introduced to eliminate these vibrations and reduce NVH.

Hood thickness information

Outer plate thickness = 0.75mm

Inner panel thickness = 0.75mm

Reinforcement thickness = 1.5 mm

Inner plate design: -

The interior panel is designed based on the master section. The master section is created based on the requirements received from the marketability team and manufacturing requirements.

Master section: -

Procedure:

• Hood internal panel is created with inside the Top -down assembly approach.
• Import the hood outer panel and call it for reference.
• Offset the panel to the zero mm , in order that we can use the offset panel as connection with create a hood internal panel.
• Trim the sheet to the 1/2 of deciding on the desired plane.
• Offset the trimmed sheet to two mm downwards.
• Offset the curve on the threshold of the sheet to twenty mm and trim the sheet the use of the offset curve.
• Now once more offset the principle sheet to four mm downward and offset the curve on the threshold to 35 mm.
• The use of the trim sheet command trims the sheet via way of means of deciding on the curve.
• Join the 2 offset sheet via way of means of the use of the via curve command.
• Offset the principle sheet to the 25 mm downwards and offset the threshold of the sheet to 55mm.
• Trim the sheet and make certain to preserve the desired vicinity.
• With the assist of extension extend the sheet to top sheet.
• With the assist of trim and extend command put off the undesirable sheet.
• Create a emboss via way of means of sketching on the lowest confronted sheet.
• Draw a sketch at the face and mission it to the embossed sheet and make the emboss to the positive value.
• Mirror the geometry via way of means of deciding on the desired plane as reference.
• Create a emboss for the hinge and striker also.

Mastic data design: -

The beauty of the appearance of the outer plate is considered first, and it is not possible to join the outer plate and the inner plate with welding or bolts because it will spoil the appearance. This can be done with the help of rabbets and mastic sealants.

MASTIC SEALANT: -

A small piece of rubber glue that is placed between the outer and inner panels of the hood, and when the hood is placed in the hot bath oven, it hardens and joins the outer part of the hood to the inner panel. Give strength to the hood before location.

Reinforcement for latch and hinge: -

Additional hinges and striker reinforcements have been added to the bonnet to further reduce the impact on the interior of the car in the event of a crash. Attaching a latch or striker to the bonnet inner panel reduces the local strength of this area, so stiffeners are added to compensate for this local strength.

• Outer panel design:

Procedure:

Create an offset curve by selecting the edge of the original slab face and choosing the Curve on Face command Select the offset curve as reference to trim the sheet. Create a hem that connects the outer panel to the inner panel A part or component is released to relieve stress in a designated area. Sharp corners that occur when folding is performed. Corners are rounded or chamfer.

Hemming :

Hemming is the process of creating the edges of the sheet to create a rounded, safe edge.

There are 4 types of hems: -

1. Open hem
2. Roll hem
3. Teardrop fringe
4. Closed hem.Top of FormBottom of Form

• Hinge position:

The latch and striker must be in the correct position for the hood to open and close properly. To measure the correct position of the hinge axis for the latch and striker plate, take a reference line and draw a circle with the center point of the hinge axis as the center of the circle. Then place the latch using the circle drawn above. This circle should be perpendicular to the hood track/trajectory. One position creates an embossment in the inner panel by pulling out the latch face.

• Snaps for Door Design: -

Outer Panel Design:

Inner Panel Design:

Hemming Relief Design:

Hinge & Latch Mtg Points Design:

Hinge & Latch Mtg reinf. Design:

Top of Form

Bottom of Form

• Conclusion: -

Finally, the Hood is designed using CATIA software which complies with EURO NCAP regulations.