Roof challenge

ROOF DESIGN AND ANALYSIS

What is a roof?

Roof is an automobile BIW component which is used to cover the top portion o a car. It protects the car from from rain, thunder, sun rays etc., It may be made up of aluminium or steel based on the requirements a car needs and hence it must undergo certain analysis and other measures to be perfectly effective.

Some of the Design Criteria are,

1. Material Thickness

2. Draft analysis.

3. Head distortion criteria

4. Snow Load Criteria.

5. Roof Crush study.

6. Section Inertia Analysis.

In these criteriae, all except Roof Crush study can be calculated while or after the designing process.

ROOF COMPONENTS:

1. Roof Top:

Rooftop is the the upper surface of the roof where it attached with the A pillar, backdoor mountings, etc., to cover the upper portion of the car.

2. Front Rail:

Front Rail is a mounting fixed to roof inner side by spot welding or using mastics with the windshield mounting. It provides strength for the roof.

3. Bow Roofs:

Bow roofs are the essential rails which should be added for giving additional strength to the roof and causes less damage when accidents happen. The more bow roofs added, the more strength the roof gets. It is fixed to the roof using Mastics which are placed 80mm away from each points to be effective.

4. Centre Roof Rail:

Center roof rail is placed in the centre of the roof inner side and there is a reinforcement in the inside of it to provide strength against deformaion which could be caused by weather conditions. the reinforcement is spot welded to the centre roof rail and the center rail is fixed to the roof by using Mastics placed 80mm away from each other.

5. Rear Roof Rail:

Rear Roof rail is placed at the end of the roof and it connects the roof end with the backdoor mountings. All these and other rails are always given 0.75 thickness and while designing and necessary tolerances were given.

A BOTTOM VIEW SETUP OF ROOF RAILS:

INSIDE VIEW OF ROOF:

DRAFT ANALYSIS:

Draft Analysis for the roof and its components were taken in order to check the machinabilty of the components when it undergoes manufacturing process like punching etc.,

The minimun draft angle should be 5 degree and the region which has or more degree in angle will be highlighted as green.

Draft analysis of roof:

Draft analysis of Front Rail:

Draft Analysis of Bow Roofs:

Draft Analysis of Center Rail:

Draft Analysis of Centre Rail Reinforcement:

Draft Analysis of Rear Rail:

SECTION INERTIA ANALYSIS:

Section Inertia Analysis is done to check the rails strength to withstand any deformation caused by ay means to avoid deformations

For Bow roofs:

For Center Rail with reinforcement:

CURVATURE STUDY:

Heat Distorion Criteria:

In some regions ther will be hot climate and some regions may experience lless hot climatic zones. Heat distortion Analysis is used to check the roof curvature and analyse the values to be effective under those climatic conditions. Below is the Heat distorion formula and findings of values for this roof.

Formula:

Calculations and Result:

SNOW LOAD CRITERIA:

Snow load criteria is used to determine the strength of the roof in cold climates or snow weather etc., it analyses how much strength does the roof has to withstand the weight of snow when the car remains idle when not in use causing it to deform. Hence the roof must get back to its original shape after the snow is cleared. If this satisfies the criteria it is marked as OK otherwise it will be sent to the styling team to make changes to improve the strength.

Formula For Calculation:

Calculations and results:

CONCLUSION:

It seems that the heat distortion criteria has passed in every region and can be effective but when it comes to Snow load condition only the region from Bow roof to Center Rail satisfies the considerations while other regions arent. To overcome this, the roof design can be sent to the styling team to make changes to the curvature of the roof and can be analysed again. Hence the roof and its rails were sucessfully designed keeping all the necessary considerations in mind and other criteriae like Draft Analysis, Section Modulus and Curvature Studies were made clear.