Hood design-Week 2

                                                                                            HOOD DESIGN

Objective:

• To design a passenger model Car Hood with the outer panel, inner panel, hinge and Striker assembled and to understand the reasons and requirements behind all.
• To provide the required emboss definition and its purpose and the mastic sealant and data.

Software Used:

Siemens NX 1855

Introduction:

The Hood is an opening body panel which is the frontal BIW enclosure component in a front engine vehicle. It consist of an outer and inner panel. The inner panel provides strength while the outer panel functions as metal cover. The outer panel is always considered as a stylish panel to attract the customer because inner panel wont visible. The design has several main requirements we need to consider frontal crash requirements and pedestrain and passenger safety requirements. The design of the hood like in aerodynamic shape to reduce air resistance as the air flows around the car. It is design under the regulation of EURO NCAP.

Manufacturing Requirements and Deep drawing:

Deep drawing is one of the most widely used processes in sheet metal forming. Apart from its use in many other sectors, it is applied in the automotive industry for the manufacturing of car body parts. The deep drawing process is a forming process which occurs under a combination of tensile and compressive conditions. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter. The flange region (sheet metal in the die shoulder area) experiences a radial drawing stress and a tangential compressive stress due to the material retention property. These compressive stresses (hoop stresses) result in flange wrinkles (wrinkles of the first order).

 While deisgning the inner panel hood that will be manufactured using the deep drawing process, there are some minimum requirements to attain the desired output,

• No curvature lesser than 5mm.
• Provided appropriate corner on the area of curvature on both sides.
• No sharp corners inside the components.
• Minimum filled radius = 3mm.

Design Methodology Procedure:

The following Tasks are performed 

• Design inner panel for the given outer panel.
• Provide all the necessary Reinforcement.
• Provide the required emboss definition.
• Provide Mastic Data.
• provide reinforcement for the Hinge & Striker
• hemming process for Outer Panel

Data to be used:

• Hood Thickness Infrmation
• Outer panel Thickness = 0.75mm
• Inner panel thickness = 0.75mm
• Reinforcement Thickness = 1.5mm

Designing:

There is always a Master Sketch for every region and design to develop and on different situation which gives us the dimentions of the part to be designed. the inner panel including all its embosses are designed with the considerations of outer panel. The maximum panel gap between the outer panel and the inner panel in the master sketch is 25 mm. This specification is created by the consideration of pedestrain safety.

Purpose of Studying Hood:

An automation engine hood is arranged to be opened for the purposes of inspecting the engine room, replenishing cooling water and engine oil changing parts and making repiars.

Types of Hood Support:

Basically car has two types. They are;

Support Rod: A device for supporting the engine hood of a motor vehicle in its open position by means of a rod.

Gas Stay: A device for supporting the engine hood of a motor vehicle in its open position by means of an actyator which is activated by gas.

Reinforcement:

After the development of the entire inner panel for the hood, we need to develop some additional necessary reinforcements. The latch striker and the hinges will need a reinforcement that needs to be developed because of embosses made on that place. All the reenforcements are made from sheet metal of thickness 1.5mm is to avoid any failure.

Positioning of Hinges and Striker:

To position the latch and striker effectively, first we need to position the hinge and then draw an hinge axis. Now, using the hinge axis as the centre we draw a big circle to the position where we need the latch to be placed. Then, We draw a tangent line to the circle at that point and place the latch in a localized area. Now, we can adjust the latch position with respect to hinge axis wherever we need to align the striker.

Striker position is fixed with the help of hinge axis that shown in the Above figure

Mastic Sealant:

The mastic points are regions where the mastic is put to interface the outer panel to the inner panel and strengthen the panel together. we cant use spot welding or any other welding process as it would give a less elegantly fulfiling result and welding process should affect the outer panel. It behaves like a rubber. It helps the hood outer panel to get its original shape after it gets deformed. The mastic overall sealant's area of 80mm.

Hemming:

Hemming is a forming operation in which the edges of the sheet are folded or folded over another part in order to achieve a tight fit. Normally hemming operations are used to connect parts together, to improve the appearance of a part and to reinforce part edges.

In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming and flanging operations to join two sheet metal parts (outer and inner) together. Typical parts for this type of assembly are hoods, doors, trunk lids and fenders.

After Hemming is done, now we need to provide corner relief on the corners of the hood. So, that part is manufactural.

Embosses:

Embosses are usually required for to improve the strength of the compenent or part. It is an operation mostly for the purpose of stiffening flat surface. The hood's strengthened will be based on the master section creation. We need to consider the frontal crash before designing the hood, when a force impacts the hood from the front, it needs to  travels in an upward direction for that we need to provide a cut section on the hoods centre. The hood has to be deisgned to divert the force away from the passengers into the hinges point, as shown in the figure, as well as we need to consider pedestrain also. the embosses depth is kept at maximum of 5mm to be manufacturable and it should be lesser than 6mm.

Conclusion:

To design a passenger model Car Hood with the outer panel, inner panel, hinge and Striker assembled with its given requirements has been done.