Hood design-Week 2

HOOD DESIGN- CHALLANGE

Introduction:-

Hood is main component of a car at the front portion. It is used to decorate the car & add luxurious look. The shape of the bonnet is made aerodynamic in order to minimize the air effect.

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 thickness-

Outer panel thickness= 0.75 mm

Inner panel thickness= 0.75 mm

Reinforcement thickness= 1.5 mm

Inner Panel-

• 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.

• The input design for the input panel is given below :

• Master Section:

• The outer panel given is shown below :

    

  So according to the input design given the outer model should be modified to get the final input panel model.

  First the outer panel should be exactley halfed into middle using mid plane and should work on the half anel.

  Then all the features should be mirrored and and sewed together.

  Now the features are to be built up like embosses, mastic points, embosses for hinges and latch.

  The law extension command is used to combine upper edge and the offseted surface.

    

  Through curves command is used to join between the both upper face and the lower offset faces.

    

  Now embosses should be created on the inner panel for removing material to get a light weight component.

• 

To stick the inner panel with the outer panel mastic points were created and the maximum distance between them should be 5mm.

So after completing the mastic points the inner panel should be mirrored and sewed together.

Then the sewed feature should be examined with geometry to check any cracks were built in between.

Here geometry check is performed the green colour is shown so that no errors were present and if it is shown in red marks then it indicates there present some errors in joining the mirrored part.

Now the Hinges should be attached at the ends of the embossed inner panel edges.

HINGE PLACEMENT :

First hinges are placed on to the embosses and as inner panel is applied with fixed constraint hinge is placed parallel and touch constaint.

Then the hinge is mirrored with assocative connection to other side to get the same hinge position on other side of the inner panel.

LATCH ATTACHMENT :

The latch/Striker is position from the basis of hinges centre point.

Two points is marked from the two hinge axis and a line is drawn from the two points.

A midpoint is taken from the line for positioning the latch.

Now a circle is drawn as that point as a centre with a radius of approximately 300 mm(based on the hood designer) and the tagent line is drawn on that circle.

Then latch is coincided with that tangent line.

 

So after latch position is fixed then the emboss is created from the latch surface using wave geometry linker in to the inner panel file.

Striker emboss is shown in the below image.

    

Striker Assembly-

Latch & 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.

While doing the hemming process a relief angle is formed as a product of hemming when attaining at the corner of the sheet.

 

FINAL HOOD MODEL DESIGN :

• Conclusion-

  We have designed a hood that falls under the rules & regulations of the manufacturer's standards.

• CAD DATA-
• https://drive.google.com/drive/folders/1YDMfdZagsZ-SJn6J1IeFYWGaiQ9hDVH7?usp=drive_link