Roof Design

Roof :

Roof is the part of all types of automobile which is fixed in a top side of the compartment which provide the vehicle occupants from sunlight, rain, wind and other external factorsthat comes for envirnment or in accident. While roll-over accidents it protect the passengers for geting a harm and death on the accident. So, strength of the roof is very important factor.

DESIGN OF ROOF

For designing the roof with flanges and reinforcement of the car with given skin data and mastersection.

Roof materials :

There are so many range of materials are using for making a roof such as steel, Aluminium, Thermosetting plastic sheet.

In case of steel usual thickness is range of 065 – 0.85mm.

Reinforcement Fixing :

Spot welding and flexible adhesives such as mastic are used to fix reinforcement with roof.

Manufacturing process of Roof :

Deep drawing

For making of a roof we use one of the process Sheet metal forming process and Widely used Sheet metal forming process.

It is classified into three types depands on load application.

1. Deep drawing using tools.

2. Deep drawing using active media.

3. Deep drawing by means od active energy.

Deep drawing method using tool is mostly used in sheet metal forming.

Deep drawing process:-

Deep drawing of sheet metal is performed with a punch and die. The punch is the desired shape of the base of the part, once drawn.

The die cavity matches the punch and is a little wider to allow for its passage, as well as clearance.

This setup is similar to sheet metal cutting operations. As in cutting, clearance is the lateral distance between the die edge and the punch edge.

The sheet metal work piece, called a blank, is placed over the die opening. A blankholder, that surrounds the punch, applies pressure to the entire surface of the blank, (except the area under the punch), holding the sheet metal work flat against the die. The punch travels towards the blank. After contacting the work, the punch forces the sheet metal into the die cavity, forming its shape.

Embossing

Sheet metal embossing is a stamping process which is used for producing raised or sunken designs or relief in sheet metal. In this process we can be made by means of matched male and female of the rollers dies or by passing the sheet or a strip of metal between rolls of the desired pattern. It is often combined with foil stamping to create a shiny, 3D effect.

Embossing process

The metal sheet embossing operation is commonly accomplished with a combination of heat and pressure on the sheet metal, depending on what type of embossing is required.

Metal sheet is drawn through the male and female roller dies, producing a pattern or design on the metal sheet. Depending on the roller dies used, different patterns can be produced on the metal sheet.

Part Inside Roof Design:-

1. Roof.
2. Front Roof Rail.
3. Rear Roof Rail.
4. Bow Roof Rail.
5. Centre Bow Roof Rail.

	For 1 Section	For 2 Section	For 3 Section	For 4 Section
Rx	2757.7202mm	6405.8229mm	10574.7760mm	2349.6812mm
Ry	3036.8393mm	4919.4089mm	4036.3543mm	3329.0412mm

For 1 Section (R) = 2890.55728283mm

For 2 Section (R) = 5565.07146919mm

For 3 Section (R) = 5842.6065202mm

For 4 Section (R) = 2754.91033746mm

t = 0.75mm

	For 1 Section	For 2 Section	For 3 Section	For 4 Section
l	397.0773mm	363.3614mm	363.9587mm	383.9373mm

L = 2025.2665mm

	W
For 1 Section	1.4665939912mm
For 2 Section	1.9873357373mm
For 3 Section	2.0660881993mm
For 4 Section	1.4332505004mm

	Rx	Ry	R	L	t	l	W	Passese / Not
For 1 Section	2757.7202mm	3036.8393mm	2890.5572mm	2025.2665mm	0.75mm	397.0773mm	1.4665mm	Passese
For 2 Section	6405.8229mm	4919.4089mm	5565.0714mm	2025.2665mm	0.75mm	363.3614mm	1.9873mm	Passese
For 3 Section	10574.7760mm	4036.3543mm	5842.6065mm	2025.2665mm	0.75mm	363.9587mm	2.0660mm	Passese
For 4 Section	2349.6812mm	3329.0412mm	2754.9103mm	2025.2665mm	0.75mm	383.9373mm	1.4332mm	Passese

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

Bow Roof Rail 1 Section of Inertia.

Bow Roof Rail 2 Section of Inertia.

Center Roof Rail 1 Section of Inertia.

1 case = L1 :- 526.7891mm
L2:- 446.1530
2 case = L1 :- 446.1530
L2 :- 446.0746mm
3 case = L1 :-446.0746mm
L2 :-552.5059mm
4 case = L1:- 552.5059mm
L2 :- x

For 1 case My:-761,241.3300569mm

For 2 case My:- 680,693.4459503mm

For 3 case My:-680,608.8037031mm

For 4 case My:-784,194.93961898mm

	For 1 Section	For 2 Section	For 3 Section	For 4 Section
Rx	1281.4858mm	1361.3487mm	1308.6662mm	1321.2716mm
Ry	2793.2382mm	6322.7022mm	10711.5447mm	15939.8846mm

	α	t	Ly	Lx	Y	S	Iy	Rx	Ry	QR	Passes or Not
For 1 Section	0.9767800677mm	0.75mm	1971.8481mm	1132.7582mm	526.7891mm	486.47105mm	775.309069623mm^4	1281.4858mm	2793.2382mm	4.65321769E-18	pass
For 2 Section	0.8011054284mm	0.75mm	1971.8481mm	1084.8484mm	446.1530mm	446.1138mm	778.716229411mm^4	1361.3487mm	6322.7022mm	2.32332838E-18	Failed
For 3 Section	0.7640603895mm	0.75mm	1971.8481mm	1059.5344mm	446.0746mm	499.29025mm	957.976323148mm^4	1308.6662mm	10711.5447mm	1.02506538E-18	Failed
For 4 Section	0.8558809842mm	0.75mm	1971.8481mm	1044.7074mm	552.5059mm	...........	.........	1321.2716mm	15939.8846mm	............

Now since we these values for the snow load values it does not satisfy the condition.So to make the roof stronger we create embossses on the roof to strengthen the roof.

Roof

Front Roof Rail

Rear Roof Rail

Bow Roof Rail 1 &2

Center Roof Rail

Iso. view

Front View

Left side Vide

Right Side View

Bottom View