Challenge

Hood design-Week 2

MMayank Tiwari17 May 2023

HOOD-DESIGN

- MAYANK TIWARI

AIM - THE MAIN OBJECTIVE IS TO DESIGN HOOD BIW FOLLOWING MASTER SECTIONS CONSIDERING DESIGN PARAMETERS.

SOFTWARE USED - SEIMENS NX

BRIEF INTRODUCTION OF HOOD - Hood is the engine cover hinged to the car's body (front-engine automobile). It gives you access to the vehicle's engine and is also vital for the safety against the frontal impact of the car.

A car hood, also referred to as a “bonnet” in some countries, is the hinged cover that rests over the engine bay of a front-engine vehicle. The car hood protects the engine and connected parts from the elements while providing easy access for repairs and maintenance.

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.

A concealed latch is typically used to lock the hood in place while driving. A release for the mechanism can be accessed from the dash below the steering wheel. On race cars and vehicles with an aftermarket hood, exposed pins may be used to secure the car hood.

* Types of hoods support

There are two types of support available for the hood support

Gas Stay
Support Rod

Gas Stay - Gas Stay Gas stay is the device for supporting the engine hood of a motor vehicle in its open position using an actuator activated by gas. This is mainly used when the car hood is heavy. In this, no men's power is required. Spring stays are designed to be used on upward-lifting doors; once the door is open n slightly, the spring will push the entrance to the fully open position. Euro fits stock various size springs depending on the door size requirement.

Support Rod - A support rod is a device for supporting the engine hood of a car in its open position using a rod. This is mainly used where the car bonnet weight is negligible. We have to lift the hood ourselves and place the support provided either in the hood or the engine component.

Passenger Safety Whenever a frontal crash occurs in the car, the first part affected will be the hood. So must be designed in such a way that it should not come from the body of the vehicle and must absorb the energy as far as possible ad divert the force towards the side panel of the car so that the amount of force which is sent to the cabin is lesser since the force lesser the passenger will experience less amount of force so that passenger safety is ensured.

Pedestrian Safety Safety of the pedestrians needs to be considered during the design as per the NCAP Euro assessment. Hood is of two types based on the side reference line. The side reference line is an imaginary line drawn from the ground at an angle of 45degree. If this line falls on the fender, then the hood is inlaid, and if the line falls on the hood, the hood is wrapped around the hood.

Child and adult impact areas on the hood are defined by wrap-around distance. The space between the wrap-around length of 1000- 1500mm in the child head impact zone and from 1500-2100 WAD is the adult head impact zone. We know the area where the pedestrian going to be hit; as a design engineers, we must make sure that they are exercising the most minor force such that they were not getting any serve injury without compromising the strength of the hood so that passenger safety must be assured.

The Head impact area is defined as the side reference line and wrap-around distance. This zone will get a red, yellow, and green rating using the head injury criteria calculated using the expression. For this reason, the inner panel kept 25mm from the outer panel and created the embosses to improve the strength of the hood.

# Components of Hood

1. Outer Panel
2. Inner Panel
3. Hinge
4. Latch
5. Reinforcement

Outer Panel - A car hood panel is one of the most important components of the BIW (body in white), it is considered the closure sheet-metal component. The outer panel has the aesthetic look to it but on its own is very weak and not capable of handling force during impact. Most automobile hood outer panels are made of traditional steel plates, and their quality does not meet the needs of lightweight development. For this reason, it is necessary to obtain lightweight effects through the application of automotive aluminium sheets. The most widely used car aluminium alloys in the market are deformed aluminium alloys of 6111, 6016, and 5182. The production process of the outer panel of the hood mainly includes blanking, deep drawing, trimming, turnup, and side turnup. Among them, deep drawing is a key process to ensure the quality of parts.

Inner Panel – The inner panel of the hood is not visible to the customer, but this is the engineering feature of the outer panel. The hood panel is required to have a high initial reaction force against the impact exerted on the hood to enhance the energy absorption capacity. The hood is further required to minimize a reduction of a reaction force by deformation in a collision. A hood inner panel according includes an inner panel main body forming part of a hood of a vehicle, a front bead provided on the inner panel main body and extending along a vehicle width direction, and a rear bead provided on the inner panel main body, located on a rear side of the front bead and extending along the vehicle width direction. The front bead includes a centre portion in the vehicle width direction that is curved toward the front of the vehicle and located in front of each end portion in the vehicle width direction, and the rear bead includes a centre portion in the vehicle width direction that is curved toward the back of the vehicle and located behind each end the portion in the vehicle width direction.

Hinge - A hinge is a machine element that connects two bodies allowing angular movement about a fixed axis of rotation, all the while preventing translations and rotations on the remaining two axes. A hinge can be considered as a journal bearing with only one degree of freedom where a shaft is rotating in a hole. Hinges only allow one rotation, either yawing (the most common), pitching, or rolling. Hinges are a jointed and flexible device that is attached to any swinging part. Hinges are mechanical bearings that are used to connect two swinging objects or points and give them the freedom to move relative to each other. Hinges have limited movement, allowing the joint to move only at one angle and restricting the other movements of swinging parts.

Latch - Latchesare mechanical components that allow the temporary joining of parts that are moving relative to each other. They are actuated to release the coupling and allow the two parts to separate. Latches are mostly seen on doors and enclosure openings. They are also used in devices such as seat belts, clamps, straps, and objects with retractable parts. Different designs feature various methods of actuation, holding style, and mounting. The hood latch is extremely simple. When the hood is closed, the latch slides over what is called a catch, and spring covers the latch to keep it snug. When we pull the knob inside the car to open the hood, the hood latch cable opens the latch, allowing it to bypass the catch and open.

Hood Thickness

Outer Panel thickness=0.75 mm
Inner panel thickness-0.75 mm
Reinforcement thickness =1.5 mm

Master Sketch : -

Design Approach: -

The styling gathering will give us the skin data. The arranging engineer will mull over the engineering common sense of the part with furthermore considering the NCAP standards and will provide analysis so they can change the styling of the hood properly.

The master sketch territory is obliged different areas. Moreover, various predefined values are given to us as demonstrated by which we need to engineer and plan the sketch and model the hood.

Starting there forward, the CAE engineer will do an examination and testing on the part shown and subsequently report analysis to the hood engineer and make the significant changes.

Parts description: -

Deep drawing In this corporation, a sheet is pulled into the ideal shape using a punch and pass-on gadget. The sheet is outlined in the condition the pass on by driving the punch down on it. To avoid the sheet wrinkling itself, the sides of the sheet are held someplace close to folios. In the automotive industry, deep drawing is usually carried out using rigid tools.

Latch Trajectory The latch trajectory shows the striker's way when the hood is opened and shut on a vehicle. The range of the round Trajectory is controlled by the set standard dependent on the typical stature of an individual. The range is estimated from the pivot hub up to the Latch. It is the Trajectory on which the movement of the hood (opening and closing are dependent). This circular Trajectory has a radius equal to the length from the centre point of the centre axis of the Hinge to the striker point on Latch. The striker point is also tangent to the Trajectory.

Mastic sealant: The mastic points are regions where mastic interferes with the outer panel to the inner board. We can't use spot welding because this gives less elegantly fulfilling results. Accordingly, mastic is used to join the panel as it doesn't modify the actual metal.

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. It is often combined with foil stamping to create a shiny, 3D effect.

The design of embosses is done by the force distribution of frontal impact. It is designed so that the reduction of force starts when it is directed till the corner, i.e., up to the hinges, and loses the maximum amount (of force) till the end.

Reinforcement: - The Zone near the turn and Latch has more chances of disillusionment in the hood panel. Consequently, to avoid any failure to rotate and latch region upheld with extra materials whose thickness is regularly directed by the vehicle. The reinforcements give additional fortitude inner panel of the centres where various parts, for instance, the lock and rotate, will be put. The reinforcement ensures that the turns and the snare have better assistance to avoid frustration.

Hemming: - The Heming process involves joining the outer and inner panels of the hood by bending their corner curvature areas to 180 degrees. There is also some corner relief given to the sheet to get stationed so that the rollers that do the Heming of sheets can roll appropriately in the required area. Hemming is a sheet metal operation widely used in the automobile sector because the welding or joining process can not be done on styling parts as it may affect the car's aesthetics

Reliefs: - Reliefs are provided at the front and side portion of the panel for smooth rolling operation .so that no tearing of the sheet happens when the roller passes through a specific portion.