Roof Design

OBJECTIVE :

• The objective of this project is to design car roof with essential flanges and reinforcements like ditch area , front roof rail , bow roofs, central roof rail and rear roof rail for the the given styling surface
• Perform a curvature study on the roof and perform the calculations for the heat distortion and snow load criteria to determine whether the bow roofs are at the correct positions.
• Finding moment of inertia and section modulus for Bow roofs , central roof rail . front roof rail and rear roof rail .

SOFTWARE USED

CATIA V5

ROOF

The Automobile roof consists of the following parts:

• The outer panel
• Front roof Rail
• Bow Roof
• Centre Roof Rail
• Rear Roof Rail

FRONT ROOF RAIL:

The front roof rail is created at the front side of the roof to provide strength to the roof. Headroom clearance and the driver visibility are the two important factors to be considered while designing the front roof rail. the front roof rail is connected to the roof outer panel with the help of mastic seal.

BOW ROOF:

It is used to give strength to the area between the front roof and the centre roof rail. Also it is created in the area between the centre roof rail and the rear roof rail to provide enough strength. It can be created in any numbers depending upon the roof length but the position of the bow roofs is to be justified by curvature study.

CENTRE ROOF RAIL:

It is created at the centre of the roof. It is connected to the roof by mastic seal.

REAR ROOF RAIL:

It is created at the rear end of the roof. The fitment of the backdoor is to be considered while designing the rear roof rail.

CURVATURE STUDY OF THE ROOF:

MOMENT OF INERTIA OF BOW ROOFS:

FRONT ROOF RAIL:

CENTER ROOF:

REAR ROOF RAIL:

Heat Distortion Curvature study:

The heat distotion study play an important role in sheet matal usage. Heat distortion temperture is a temperature limit above which the material cannot be used for structural applications.

This study is used to predict the heat distortion temperature at where the material start to soften when exposed to a fixed load at elevated temperature. In order to avoid bending/damages on roof, based on heat distortion temperature, this study will predict the bow roof position on the roof to strengthen the roof.

Bow - roof prediction Formulae:

W =1.73*10^-3*L+1.85*10^-8*(R^2)/t+1.10*10^-3*I-1.26

L - Roof Length in X-Direction[mm] (Roof Dimension in 0-Y)

R - Roof Curvature

R = 2(Rx*Ry)/(Rx+Ry)

Rx - x Curvature

Ry - y Curvature

t - Roof Plate thickness[mm]

I - Bow roof span [mm]

Judgemegnt Condition : OK<2.7mm

Where NG- Not good

SNOW LOAD CRITERIA:

This evalution is performed in cold regions where snow occurs.roof design must pass through these calculations to ensure that it has sufficent stiffness to withstand the load due to accomalation of snow over the roof.

CONCLUSION :

Hence the roof , front roof rail, bow roof rails , central roof rail and the rear roof rail is designed by following the master sections and the moment of inertia , section modulus and draft analysis are carried out to check feasibility manufacturing.