Roof challenge

Aim: For the given roof styling, develop the essesntial flanges and reinforcements, provide appropriate dimensions and check for draftanalysis and to perform roof curvature study using catia v5.

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

The roof is a styling surface part which is fixed with the BIW body through the rails and panels inside the upper roof to provide itstrength and stiffness.

Ditch area plays an important role here to fix the reinforcement on the component.

The rails and reinforcements are joined to the ditch area with a spot weld where it's not the styling part.

The required tool opening angle is minimum 3 Degrees.
Factors which is considered before creating Ditch area,
Headroom clearance
Visibility criteria
Back door assembly
Windshield assembly

Software Using CATIA V5:

Class A Styling Input

After the file is opened, the roof part is not joined together but as the individual surfaces.
It is also seen as the surface is perfectly symmetrical in shape which helps us to work on the half of the portion and reflect it which creates the whole roof Wework on the half of the surface and mirror to complete the rest.

Components of roof:
Front roof rail
Rear roof rail
Bow roof
Centre roof rail
Ditch area
Front roof rail:
It is created using Given reference master section

Ditch area:
Ditch area is a extended portion of the maim roof concellled by other BIW pannels.The rails support of the roof are attached to theditch area using spot weld

SIDE FLANGE

DRAFT ANALISIS OF TOP SURFACE

FRONT ROOF RAIL

draft Analysis

Rear roof rail:

Rear roof rail is again used to strengthen the roof and it acts as a link between back glass and roof which connected to the backdoorof the car.Spot welds are applied at back doorend of the rail and the other end is joined with roof using mastic sealent

It is created using Given reference master section

Draft Analysis

Center Roof rail and Bow roof rails:
Center roof rail will be at the centre of the roof to provide strength and stability to the roof. Here the centre roof rail is joint with the roofthrough mastic sealent

Draft Analysis

BOW ROOF

ASSEMBLT

SUNROOF DESIGN AND ASSEMBLY

CALCULATION

Curvature study on the Roof:
After getting the final body it has to be checked and justify that it passes the standards.

Analysis:
It is done to justify the position of the bow roofs.
1.Roof crash test.
2.Snow load test.
3.Heat distortion criteria

Heat distortion criteria:
Heat distortion temperature is a temperature at which the metal softens and deform under a specific load.This study is done to checkthe ability of the roof to withstand high temperature with respect to the position of the reinforcement which contribute to the increase strength.

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

SMALL l CALCULATION

CALCULATE THE HEATE DISTORTION ON ROOF

CALCULATE VALUE OF R USIN FORMULA IN EXCEL SHEET

CALCULATE VALUE OF W USING FORMULA

CALCULATE SNOW LOAD

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

CREATE CURVE ON MIDDLE OF ROOF FOR CALCULATION

FIND MOMENT OF INERTIA OF BOW ROOF AND CENTRE ROOF

lx DISTANCE

calculation

My calculate usin formula in excel sheet

alpha calculate using formula in excel sheet

s calculate using formula in excel sheet

Qr calculate using formula in excel sheet

Conclusion:
Essential roof components such as bow and center rails required with flanges and reinforcements are designed.
Curvature study on roof was analysied with heat distortion and snow load standards
Draft analysis was done to check toolablilty.