Roof Design

ROOF DESIGN :An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements.

ROOF RAIL CONSIST THE FOLLOWING PARTS

• The Outer Pannel
• Front Roof Rail
• Bow Roof Rail 1
• Center Roof Rail
• Bow Roof Rail 2
• Rear Roof Rail

The Heat Deflection Temperature (HDT), or Heat Distortion Temperature, is a measure of a polymer's resistance to alteration under a given load at an elevated temperature

Bow–Roof Prediction CALCULATION

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

Rx

Ry

SECTION MODULUS STUDY OF THE SECTION OF THE ROOF RAILS:

The section modulus of the cross-sectional shape is of significant importance in designing of structures. It is a direct measure of the strength of the structure

A structure that has a larger section modulus than another will be stronger and capable of supporting greater loads.

Section modulus (S) = I/y

Where,

I = Moment of inertia in (mm⁴)

y = Distance between the neutral axis and the extreme end of the object (mm)

BOW ROOF RAIL 1

CENTER ROOF RAIL

BOW ROOF RAIL 2

CALCULATE HEAT DISTORTION TABLE

Snow Load Prediction Formula

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

Rx

Ry

Lx

Ly

SNOW LOAD CALCULATION TABLE:-

it is observed that area it is not satisfying the condition so in order to strengthen the roof at least these area EMBOSSES are created on the outer roof.