Design of Car Hood Inner Panel using the Euro-NCAP regulations /Outer Panel/ Draft Analysis/ Latch and striker position study

DESIGN OF HOOD PANEL FROM THE GIVEN STYLING SURFACE USING CATIA V5 (EURO-NCAP REGULATIONS)

Introduction:

A car hood panel is one of the most important components of the BIW (body in white), it is considered as the closure sheet-metal component. A hood panel consists of two panels that are hemmed together to form the automotive hood assembly.

Fig 1 Hood panels of the car

The inner panel of the hood is not visible to the customer but this is the engineering feature of the outer panel. The outer panel has the aesthetic look to it but on its own is very weak and not capable of handling force during impact. This puts the passenger’s life in danger, so we need to design the inner panel so as to provide strength to the outer panel.

DESIGN METHODOLOGY

Objective

The objectives of the project are as follows

• Check the given styling surface for any discontinuities
• Develop the inner panel and outer panel from the given styling surface according to the Euro-New Car Assessment Program.
• Develop the necessary reinforcements for the inner panel.
• Develop the necessary embosses on the inner panel
• Develop the hem for the outer panel
• Check the manufacturing feasibility of the inner panel by draft analysis
• Check the position of the latch with respect to the hinge axis

Given :

• Master-section of the hood panel.
• Hood Hem data
• The thickness of the inner panel, outer panel, and reinforcements
• Styling surface

Fig 2 Master Sketch for the hood inner panel

Fig 3 Hemming data

Fig 4 Relief data 1

Fig 5 Relief data 2

Fig 6 Hood Styling Surface

DESIGN METHODOLOGY

1. Design of inner panel:
   
   To design the inner panel we need to extract the given styling surface and break any link with the given surface. This will act as a reference surface for the inner panel. Before proceeding further we need to follow certain design guidelines in design.

• Create an origin point and place an axis system on it. All the sketches in the design will be linked to this axis system.
• Maintain a structure tree as many other designers will work on this project and it will be easier for them to understand how we have created a particular part.
• First, we need to develop the master section of the inner panel. The master-section is a very important part of the design procedure as it is made using all the information from the car. For example, how is the engine placed, how much depth is required for the inner panel, etc.

Fig 7 Design of inner panel surface using the master-section

• Embosses on the inner panel
  The embosses on the inner panel are designed to distribute the impact forces on the outside which protects the passenger during a crash. These embosses are designed in a particular shape (Y or V shape). The shape mostly depends on the output from the CAE team.

Fig 8 Design of embosses on the inner panel

Euro NCAP standards followed:

We design the hood panel for the safety of the passengers inside the cars but at the same time, we have to protect the pedestrian walking on the road. This is what improves the standard and quality of the car. Whenever the car hits a pedestrian it should cause minimum damage to the pedestrian. For this, we have to remove material from the inner panel at specific portions.

Fig 9 Collision of the car and pedestrian

Fig 10 Head impact zones for adults and children

Here the wrap around distance comes into the picture, the wrap-around distance is the area covered by the hood on the car. This distance is used to differentiate the adult impact zone and child impact zone.

Fig 11 Wrap around distance

Fig 12 European New Car Assessment Program

We design the embosses on the inner-panel to reduce the material from the areas which lie on the Adult Head Impact Zone and Child Heat Impact Zone. By removing the material from these areas, we intend to weaken it, anything that hits the bonnet on these positions will experience minimum impact possible. This improves the safety of the pedestrian in an unfortunate event.

Fig 13 Embosses with mastic points

Mastic Points:

Mastic points are areas where the inner hood panel is joined with the outer panel hem using a mastic glue. This mastic glue keeps the inner panel stuck to the outer panel.

Fig 14 Mastic glue join

Inner panel design:

Fig 14 Isometric View of the Inner panel

Fig 15 Front View

Fig 16 Master section of the inner panel

Fig 17 Mastic points for joining the inner and outer panel

OUTER PANEL DESIGN:

Fig 18 Outer panel

Fig 19 Hem data

Fig 20 Relief data

Fig 21 Relief data 2

HEM FOR OUTER PANEL

The inner panel and outer panel are joined using mastic which is applied on the hem of the outer panel and edge of the inner panel.

Fig 22 Hem for the outer panel

Fig 23 Hem at the OY section

DESIGN FOR MANUFACTURING (DRAFT ANALYSIS)

Whenever we design a particular component it is very important to consider the manufacturing process. If we design a component that is not manufacturable then it is a waste of time. Design engineering is about bringing ideas into life. As this is a sheet metal component, it is manufactured by a deep drawing process. For the deep drawing process to take place we need to ensure that the inner-panel has an angle of a minimum of 5 degrees as the tool will come out easily after the drawing process.

Tooling axis: It is the axis along which the deep drawing tool moves

Fig 24 Draft analysis on the inner panel

LATCH AND STRIKER POSITION CHECK

Checking the position of the latch and striker assembly:

To check we need to create an axis from the hinge assembly. Tentatively we have to position the hinges and extract the axis. On the axis, a point is placed at the center of the axis and a circle is drawn taking the point as the center. To check for the correct position of the hinge it has to be tangent to the circle. This study is conducted to check the location for the latch and striker mechanism to make the hood manufacturable.

Fig 25 Latch and striker position study

DESIGN OF REINFORCEMENTS FOR THE HOOD PANEL

At certain positions in the hood panel, we need to provide more strength to the inner panel as these areas are prone to loading and unloading. The two main positions which tend to be under stress a lot are

• The latch and striker joining area
• The hinge joining area

The latch is attached to the inner panel and this adds more weight to the inner panel at one particular point. This region is under stress whenever we close the hood with force to lock the latch into the striker. We need to provide reinforcement is this region to handle all the loading cases.

The hinge joining area is again a functional area of the hood panel. This means that we need to provide reinforcements there in order to strengthen the component and make the functioning smooth.

Fig 26 Inner panel Reinforcements

Hood panel assembly parts

Fig 27 Outer panel

Fig 28 Hood Inner panel

Fig 29 Hinges

Fig 30 Latch

Fig 31 Hinge Reinforcement

Fig 32 Latch Reinforcement

FINAL ASSEMBLY

Fig 33 Hood panel Assembly

Conclusion

The inner panel, the outer panel has been designed from the given styling surface according to the Euro-NCAP standards. The inner panel was checked for its manufacturing feasibility using draft analysis. The latch and striker positions were studied. Necessary reinforcements were developed for the inner panel.