Roof challenge

REPORT:

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

Front roof rail.

Bow Roof 1

Center Bow roof.

Bow roof 2.

Rare Roof rail

Roof Arrangement.

Heaat 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 to withstand high temperature with respect to the positioning of the reinforcements which contribute to increased strength.

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

From the table we can conclude that roof design satisfies heat distortion criteria.

Snow Load Prediction Formula

 The snowload formation process, which depends both on the macro- and microclimates of such meteorological variables as the depth of the snowfall, the snowfall density, wind speed, air temperature etc., as well as, the size and geometry of particular roofs

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

We can observe from the table roof satisfies coonditiononly in the region front roof and bow roof 1.Apart from that condition doesnt satisfies, so in order to improve our design we provide embosses on the roof.

Embosses on the roof.

Section Inetria Analysis.

Front roof 

I=10855.27 mm^4

Y=114/2=57

S=I/Y = 190.44 mm63

Bow roof 1 and 2

I=132.01 mm^4

Y=72/2=36 mm

S=I/Y = 3.66 mm^3

I=132.625 mm^4

Y=36 mm

S=I/Y=3.68 mm^3

Center roof.

I=141.105 mm^4

Y=80/2=40 mm

S=I/Y=3.52 mm^3.

Rare roof.

I=3508.11mm^4

Y=92/2=46 mm

S=I/Y=76.26 mm^3

Draft Analysis.

With draft analysis, you can verify draft angles, examine angle changes within a face, as well as locate parting lines, injection, and ejection surfaces in parts.

Front roof rail.

Bow roof 1.

Center reinforcment roof rail.

Bow roof 2

Rare roof rail.

Assembly.