Roof Design

Roof design:

• AIM: To Design the automotive car Roof using the master section and OEM's design standards.

What is a Roof?

• The roof is one of the components of the automotive vehicle.
• The roof is one of the top surfaces in automotive vehicles.
• It protects the person who sits in the vehicle from weather conditions such as sun rays, dust particles, wind, etc. 

Design consideration:

• Visuality criteria
• Head clearance
• Heat Distortion
• Snow load criteria
• The minimum Draft angle should be 7 degrees.

Manufacturing and Joining Method:

• Stamping
• Mastics
• Spot welding

Types of reinforcements required in the roof:

• Front roof rail
• Bow roofs
• Central roof rail and
• Rear roof rail

Why we need reinforcements in the roof:

• Reinforcement in terms of the metal sheet means adding an extra sheet to increase the strength of the component.
• In the case of the roof, as the roof is a flat surface, and if any load is applied to it.
• It will be bent because of that load.
• So, to increase the strength of the Roof we are adding the above reinforcement types in the roof.

1. FRONT ROOF RAILS:

• To design the front roof rails, we will follow the master section. (Refer to the given pic below)

2. REAR ROOF RAIL:

• To design the Rear roof rails, we will follow the master section. (Refer to the given pic below)

3. BOW ROOF RAIL-1:

• To design the bow roof rails-1, we will follow the master section. (Refer to the given pic below)

4. CENTER ROOF RAIL:

• To design the center roof rails, we will follow the master section. (Refer to the given pic below)

5. BOW ROOF RAIL-2:

• To design the bow roof rails-2, we will follow the master section. (Refer to the given pic below)

•  BOW ROOF PREDICTION FORMULA:

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-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]

Judgment Condition

OK< 2.7

 

• SNOW LOAD CRITERIA:

Qr =  [Iy x t²] / [α x s x [(Rx + Ry)/2]² x 10^-8]

Note: The Qr value given over here is correct. There was a typo error in the formula given in the video.

Where,

α = My x Lx² x 10^-12 , My = Y(Ly-Y)

t = Roof plate thickness [mm]

Ly = Distance between the front and rear roof Rails on the Vehicle along with 0Y[mm]

        Length of Roof panel with the center point between Roof rail Front /Rear as the front and rear reference point.

Lx = Distance between the Left and Right end of the roof on the Roof BOW [mm]

        The width of the roof panel is exposed on the surface.

Y = Distance front Front Roof Rail to Roof BOW[mm]

s = Distance for which Roof BOW bears divided load [mm]

        s = L1/2 + L2/2

Iy = Geometrical moment of inertia of Roof BOW (Y cross-section )[mm4]

Rx = Lateral direction curvature radius of roof panel Y cross-section on Roof BOW [mm]

        Roof panel curvature Radius of the Length Lx in Front view 

Ry = Longitudinal Direction curvature radius of the Roof panel X cross-section on Roof BOW [mm]

        Roof panel X curvature radius of length s in Side view

Judgment condition

Qr ≥ 3.1

250 ≤ s ≤ 380

• SECTIONAL INERTIA ANALYSIS:

1. BOW-ROOF RAILS-1:

2. CENTER ROOF RAILS:

3. BOW ROOF RAILS-2:

• DRAFT ANALYSIS OF ROOF AND ITS RESULT: