Roof challenge

ROOF DESIGN

Objective:

• Create roof model using given master section and styling surface.
• Determine whether the design satisfies the heat distortion criteria.
• Judge the snow condition criteria of roof using prediction formula.
• Prepare section modulus study of bow roof 1, Center bow roof, and bow roof 2.

Software Used:
Siemens NX CAD

Introduction:

An automobile roof or car top is the portion of an automobile that is above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements. The roof must be designed in such way that it will sustain the imapact load of accidents. The roof is an assembly of many parts such as bow roofs, front roof rail, Rear roof rail, Reinforcement center. The number of bow roof depends on length of roof. Roof is attached to the body of car using mastic sealant.

Thickness of Outer panel is 0.75mm whereas the thickness of the different Bows is 1.25mm.

Roof Assembly:

Outer Panel:

Front roof rail:

Bow roof 1:

Bow roof center:

Bow roof 2:

Rear roof Rail:

Heat Distortion Criteria:

Predicting heat distortion for roof is important since it is exposed to heat for long time & high temperature will affect the roof structure. This study helps to determine the positions of bow roof to provide strength to the roof.

SNOW Load Criteria:

Snow load criteria study is done to check the ability of the roof to withstand snowfall and bounce back to its original shape
without any permanent deformation once the load is removed.

Section Modulus analysis:

Bow roof 1:

I = 114.12 mm^4

Y = 42.93mm

S = 2.658 mm^3 ˈˌˈ (S = I/Y )

Bow roof center:

I = 274.29 mm^4

Y = 103.917 mm

S = 2.639 mm^3 ˈˌˈ (S = I/Y )

Bow roof 2:

I = 139.88 mm^4

Y = 49.97 mm

S = 2.799 mm^3 ˈˌˈ (S = I/Y )

Draft Analysis:

Draft Analysis is done to analyze the draft angle. This allows us to verify whether the product will be easily removed from the
tool.

• Outer Panel

• Front Roof Rail

• Bow No.1

• Central Bow

• Bow No.2

• Rear Roof Rail

Conclusion:

In this challenge i learned how to develop the Ditch area and the required Reinforcement. Also i come to know about the curvature of the Roof after calculating the Heat Distortion and the Snow load conditions.