Roof Design

ROOF DESIGN:

Obiective:

To develop a roof structure with all components like front roof rail, rear roof rail, bow roof, center roof with the given master section, considering all design requirements as per the OEM standards.

Introduction:

An automobile roof or car top is the portion of a vehicle that sits above the passenger compartment. The main function of the roof top is to protect vehicle occupants from sun, rain, wind, dust and other external elements.

Components of roof assembly:

• Outer panel
• Front roof rail
• Rear roof rail
• Bow roof
• Center roof

Inputs for developing roof assembly:

Design considerations:

• Visibility criteria
• Head room clearance
• Mastic distance
• Drawability
• Weight and strength
• Positioning of reinforcements
• Material selections

Roof crush test for car:

Each and every component of an automobile rerquires saety point of view as per their requirements. The roof of a car plays a vial role when a car is subjected to roll over accidents, in the roof of the vehicle crashes and cause head, neck and spine trauma around the world. So the roof should be designed with required strength to withstand the accidents.

Heat distortion criteria:

Heat distortion temperature is the temperature at which the metal softens and deforms under a specific load. This study is done to check the ability of the roof roof to withstand high temperature considering the position of the reinforcements which helps to increase the strength and stiffness.

Formula:

W = [1.73x10^(-3) x L] + [1.85x10^(-8) x (R^2)/t] + [1.10x10^(-3)x l] - 2.68

Where,

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)

l = Bow roof span (mm)

Judgement condition

OK < 2.7

Design of roof:

1.) Outer roof panel:

2.) Front roof rail:

It joints with the windshield glass as well as body side outer and inner. The front roof is designed with the given master section.

3.) Rear roof rail:

4.) Bow roof and center reinfircement:

Roof assembly:

Bow roof prediction study:

From the above formula the value which we got are good for the judgment condition

Snow load prediction study:

Draft analysis for roof structure:

Draft analysis helps to find the sheet metal can be easity removed from the punch.

The minimum draft value is 7°

1.) Outer panel:

2.) Front roof rail:

3.) Bow roof 1:

4.) Center reinforcement:

The draft value can be adjusted.

5.) Bow roof 2:

6.) Bow roof 3:

7.) Rear roof rail:

Conclusion:

The roof assembly design is completed with all design standards. The NX file for roof design has been attached.