Roof Design

CAR ROOF DESIGN:

Car roof is the part which is protect the parts and passanger of the car from sun,wind,rain and etc.It was placed in above passenger compartment.

TYPES OF CAR ROOF:

AIM:

• Here we are going to design and develope the car roof which is contain front roof,rear roof,bow roof 1,bow roof 2 and central roof with given master section.
• Then we are going to calculate the Snow load condition and heat distortion criteria.

OBJECTIVE:

• We need to study the types of roof style available in the market and design the front roof rail,rear roof rail,bow roof rail 1,bow roof rail 2,certral roof rail with given cross section.
• To study the heat distortion creteria for positioning the bows and cetre roof rail.
• To study about snow load condition.

DESIGNING OF ROOF AND ITS PARTS:

1.ROOF:

• We are getting a styling surface from the styling team and we are creating outer area and slot embosses for increase the strength.
• Then Need to create main roof area with given cross styling surface.
• here we are deside spot welding methode to joining the rail with main body of the roof.
• when design the rails we need to consider the spot weld area,mastic area and thickness of the rails.
• here the thickness of the roof is 0.75mm

DRAFT ANALYSIS FOR ROOF:

We are giving 3 degree positive draft wit perpendicular to the roof for draft analysis.

2.FRONT ROOF RAIL:

• The front roof rail is design with cross section which is given in the challenge.
• we are given front roof rail for strengthen the main body of roof,it is act as a reinforcement for roof.
• The depth of the roof is decided by the visibility creteria of the driver.
• And it was contained the car inside room lamp.
• it is contain mastic region and spot weld area.

DRAFT ANALYSIS FOR FRONT ROOF RAIL:

Here we are doing the draft analysis with positive draft angle of 3 degree and the direction is perpendicular to the front roof rail.

REAR ROOF RAIL:

Rear roof rail was design same as front roof rail first we sketch given the cross section and give guide curve for direction to flow the boundary surface.

DRAFT ANALYSIS FOR REAR ROOF AREA:

Here also we give 3 degree of positive draft with perpendicular to the rear roof rail.

BOW ROOF RAILS:

Here bow roof rails are used for main reinfocement part of roof,it is give more strength to the roof and it protect from frontal crash of the car.

Here we are give two bow rails for more strength,it is also contain welding spot and mastic region to joining the roof main body.

BOW ROOF 1

BOW ROOF 2

DRAFT ANALYSIS FOR BOW ROOF 1 AND 2:

CENTER ROOF RAIL:

This rail placed center of the roof top which is connect with Apillar,give more strength to the top roof.

DRAFT ANALYSIS FOR CENTER ROOF RAIL:

Same as above mentioned method to proceed this roof also.

HEAT DISTORTION CRITERIA:

This creteria had prediction formula and judgemental condition for positioning the rails.

The position of the rails pass the judgemental condition is tells that the strength,visibility creteria,crash test and other safety things ok for the people to use the car.

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

from observation all the position of bow rails pass the heat distortion prediction formula judgmental condition.

SNOW LOAD CONDITION FORMULA:

Snow load condition is used to find the long time load acting on a roof by snow folling area.here also we had snow load prediction formula and judgemental condition.

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

from above data we understood that ctr-bow2 area we need to strengthen that area.

Conclusion:

From this challenge I had learned car roof design with some safty cosideration.from this i had improve my cad skills in Simmens NX and solidworks,heat distortion prediction method,snow load prediction method,material knowledge,Draft analysis,section inertia analysis industrial manufacturing and production of car roof,crash test and safty measures.