Hood design-Week 2

Hood design consideration:-
The hood of a car is considered as the frontal BIW enclosure component. Bonnets are designed to reduce air resistance as the air
flows around the car. Apart from this, bonnets are also designed to meet several other requirements. They serve a great deal of
purpose in protecting the passengers inside the car & the pedestrians in the event of an accident. It also acts as the cover for the
engine.

The European New Car Assessment Programme (Euro NCAP) is a European car safety performance assessment program which
has developed test specifications & rating systems for assessing pedestrian injuries during impacts with the front of vehicles
such test include a series of tests using impacts designed to bio-mimic a collision at speed of 40 km/h.
They describe a situation in which a pedestrian is situated laterally & a car first hits one of his legs. Test are conducted on the
leg, upper leg & most importantly the head, as head trauma is most commonly responsible for casualties.
So to avoid severe injuries to the head, the high impact area for adults & children are subjected to less thickness. Also no
reinforcement should be provided in that area as during head collision, the hood will absrob the head impact energy leading to
collapse of the hood & thus protecting severe head injury.
Another important criteria for the hood design is the protection of the occupants inside the car during front collision. The design
of the hood should be in a such a way that the during the collision, the force should travel in the upward direction through the
embosses & directed towards the body of car. Thus protecting the occupants inside.

Following parts are using in hood assembly for this report,
1. Hood outer panel
2. Hood inner panel
3. Hinge assembly
4. Striker assembly
Hood thicknessOuter panel thickness= 0.75 mm
Inner panel thickness= 0.75 mm

first all the part files are added into the assembly workbench and then all the operations are done accordingly.

making inner panel:

first the outer hood is offested to 0 mm and all the operations are done that panel

our first moto is to make flanges for the inner panel according to the given data the flanges are made. by using the commands offset face in curve, face blends, laww extensions and trim and extended.

now to came emboses we to draw a sketch so that the stricker area and the hinge area are covered and are embosed.

all the sketches are made and are projected to the inner hood surface respectively and then are embosed withe desired draft angle.

these emboses are to made to increase the stiffness of the hood and to absorb the forces so that the passengers inside the car are minial affected.

this is how the inner hood panel is made.

Hood outer panel work;

The hood outer panel is made to have hemming so that it wraps around the inner panel this hemming process is made so that the asthetic appearnce of the car is not spolied.

now to make hemming the outer hood is curve offsted and since it as to be rolled in the manufacturing process the hood is offseted downwards to thickness of the hood plus the gap between the oter surface and inner surface of the hood and plus the thickness of the inner panel.

after that face blend is given to have the feature of curved side.

since the edges are given relief the edges are sketched and are given relief.

Assembly work:

now the outer and inner hood are fixed later the hinges are given constraints of touch anf aligh withe axis where it sits on the hinge emboss.

now to align the striker draw a circle of desired radius in the inner panel hood and draw a liine tangent to the circle top and give constraints in such a way that change in angles of the tangent line with circle also changes.

now smiliarly draw a line perpendicular to striker hook which helps in making assembly constarints to the hood and striker

after making now aligh th tagent line of circle and the perpendicluar line of striker

and also create emboss for the striker by taking wake geometry linker and select the face of strikers which sits oas emboss and now create the emboss on the inner hood with that face,.

In the inner panel only we can research & implement the safety of pedestrians & as well as the driver. In this panel only we can
attach the reinforcement, embossed, mastic points etc.
It is an object of the present invention to provide a hood inner panel capable of reduction of a reaction force of the hood inner
panel even if a level of deformation of a hood of a vehicle increases, & ensuring a sufficient energy absorption capacity.
Outer PanelWe can also call it as cover of inner panel. It is the part, which gives luxurious look to the hood or bonnet. Outer & inner panel can not
join by any welding process like spot welding or rivet, which spoil the outer look of a car. The outer panel is generally extracted model
from the prototype design.
Hinge AssemblyHinge 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.
Striker AssemblyLatch & striker is used for locking the hood with the car. It is usually placed on the space provided on the inner panel.

The process involved in designing hood as a sheet metal operations is
Blanking
Hemming
Punch cutting or piercing
Deep drawing
Embossing

Hemming

Hemming is a sheet metal forming process in which sheets are joined by bending it usually to 180 degree. Automotive body
panels & parts such as deck-lids, trunk-lids, doors, hoods & tailgates are formed by hemming processes.
Roll hemming is carried out incrementally with a hemming roller. An industrial robot guides the hemming roller & forms the
flange. Roll hemming operation can also be divided into several pre-hemming & final hemming process steps.
Coventional 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 & trimming operations have been completed.

Deep Drawing:

Deep drawing is a manufacturing process that is used extensively in the forming of sheet metal into a cup or box-like structures.
Pots & pans for cooking, containers, sinks, automobile parts, such as panel & gas tanks, are among a few of the items
manufactured by sheet metal deep drawing.
A deep drawing of sheet metal is performed with a punch and die. The punch is the desired shape of the base of the part, once
drawn. The die cavity matches the punch and is a little wider to allow for its passage, as well as clearance. For many
calculations, the sheet metal thickness is assumed to remain constant. There are changes in thickness in certain areas, due to
force involved.
EmbossingThe sheet metal embossing operation is commonly accomplished with a combination of heat & pressure on the sheet metal,
depending on what type of embossing is required.
A sheet metal is drawn through the male & female roller dies, producing a pattern or design on the sheet metal. Depending on
the roller dies used, different patterns can be produced on the sheet metal.
Latch trajectoryWhile 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.