Hood design-Week 2
HOOD DESIGN using SEIMENS UG NX :
In this report the flow of information will be as follows :
A) Hoods Function & Purpose
B) Design consideration & Data given
C) Procedure
D) Draft Analysis
E) Conclusions
A) Hoods Function & Purpose :
1) The hood or bonnet is the hinged cover over the engine of motor vehicles that allows access to the engine compartment for maintenance and repair also protects the main parts of car like engine
2) Its main function is to direct access to the engine, battery and other crucial parts of the cars for repair and maintenance and to protect these parts from direct sunlight and dust. It also gives good looks and help to design car aerodynamically stable.
3) The car’s hood consists of an inner and an outer panel. The inner panel provides strength, while the outer panel is just a metal cover
4) Regulations have come into effect in recent years that place a limit on the severity of pedestrian head injury when struck by a motor vehicle, this is leading to more advanced hood designs.
B) Design consideration & Data given :
1) Head clearance zone :
a) Head clearance zone depends on the height of the individual in certain countories,
for example : In a country in which average height is above 6 feet then the head clearance zone will be more as compared to country with average height as 5 feet
2) Consideration of Noise Vibration Harshness (NVH):
a) 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, particularly cars and trucks.
b) Its perfrable to keep NVH as low as possible for the comfort of passengers inside.
3) Pedestrian safety :
a) Pedestrian safety is important consideration while designing the hood.
b) According to the wrap around distance and pedestrian head impact zone hood is designed.
c) Safety is the most important criteria in automobile designs which concentrates on both pedestrian and occupant safety.
d) The pedestrians are the most vulnerable road users and are at high risk of traffic accidents, the major reason for the fatality of the pedestrian in traffic accident is due to the head injury resulting from the hard impact of the head against the stiffer hood or the ground.
e) This leads to the necessity of new inner hood panel which is less stiffer and pedestrian friendly.
f) The area at the head impact zone is made softer to reduce the impact force during accident.
Fig : Head Impact Zone
Fig : Hood Master Section
4) Outer panel thickness : 0.75mm
5) Inner panel thickness : 0.75mm
6) Reinforcement thickness : 1.5mm
C) Procedure :
1) Inner panel : The inner panel supports the outer panel it consists of embosses & holes, embosses provide stiffness as well as it dissipates energy towards reinforcement.
Fig : Hood Inner Panel
2) Outer panel : Outer panel is nothing but a outside cover for engine and its a used to make a car looks good.
Fig : Hood Outer Panel
3) Hemming Process :
1) The outer panel & Inner panel can't join by any welding process if we did it will leave a spot on the outer panel and it will spoil the look of a car. so, to join inner and outer closure panels together we use the Hemming process.
2) It is the process of bending/folding the flange of the outer panel over the inner one.
3) The flange of the outer panel is bent over the inner panel in progressive steps by means of the roller hemming head.
Fig : Hemming Process
4) Corner Relief :
1) There are many types of Hemming process but in Hoods Roller hemming is used.
2) In this process the roller will be rolling over the edges of the Outer panel to close it with the inner panel.
3) These roller will be rolling over 2-3 time for perfect closing. so, the certain force is being used by rollers to all the corners
4) But there are some areas where the roller cannot tighten the part properly so thats why we give some relief to the corners.
Fig : Conner reliefs
5) Mastic sealant :
1) The Mastic sealant or mastic points is a elastic compound that behaves like a rubber.
2) It is applied between Hood's outer panel and inner panel, it has an influence area of about 80mm.
Fig : Mastic Sealant Points
6) Hinge & Striker :
1) Latch & striker is used for locking the hood with the car. it's usually placed on the space provided on the inner panel.
2) Hinges are used to connect the hood & cowl panel of an automobile.
3) It enable the opening & closing operation of the hood.
4) the hinge should be made strong enough to to handle the weight of the hood and also to handle the force action on it during the collision.
Fig : Hinge & Striker
7) Positioning of Hinge & Striker :
1) The hinges should be usually placed on both sides of the hood in such a way that the strike fits exactly into the hole provided.
2) To ensure these conditions both the hinges should be on the same axis, & the centre of the striker's circular trajectory should be always perpendicular to the hinge axis.
Fig : Hinge & Strikers Alingement
Fig : Hinge & Striker Alingment
8) Embos :
1) Embosses are the projections made on sheet metal using deep drawing techniques.
2) The operation is carried out the mostly for the purpose of stiffening flat surface and design in the inner panel.
3) The major function of embossing is to dissipate the force acting on the hood during the collision of the car toward the hinges as early as possible.
4) This helps to reduce the impact of the force on the passenger sitting inside.
Fig : Embosess
9) Shock flow Analysis : Embosses were designed to dissipates the force outdie the structure and toward the hinges.
Fig : Shock Flow In case of a crash
D) Draft Analysis : Once the design was ready, the inner panel of the hood was anaylzed for manufacturability, here draft analysis shows that all parts are clearing when core is removed from cavity.
Fig : Draft Analysis
E) Conclusion :
1) All the parts of the hood are designed based on the required conditions & given dimensions.
2) With the completion of hood design & analyzing for successful manufacturability.
3) we can conclude that the hood can be utilized for the vehicle.