Roof challenge

TITLE :- AUTOMOTIVE ROOF DESIGN

OBJECTIVE: - To design roof of car and do curvature study for heat distortion and snow load criteria

Introduction:-

An automotive roof is that part of car which sits above the passenger compartment. The main purpose of roof is to protect passenger from rain, sun, and other external element.

Roof of car is made of multiple parts like front roof rail, bow roof, rear roof rail. Reinforcement roof rail and rail for room lamp and dich area which helps roof to join with other part of the body.

Type of roof in the market:-

1. Convertible roofs
2. Roof modules
3. Roof modules
4. Hardtops
5. Sunroofs
6. T-tops
7. Targa tops
8. Vinyl roofs

DESIGN METHODLOGY

As we get the input from styling team, we take an approach to design our roof. These structures are given to the roof to provide support to the roof as it is very long part and also provide strength to the roof in heat distortion and snow load condition.

INPUTS :-

We get roof panel from our styling team and master-section for roof rails.

Input for roof panel

Input for front roof rail

Input for rear roof rail

Input for bow roofs

DESIGN PROCEDURE

1. Roof panel

• As we get styling roof from our styling team . we create a wave geometry linker.
• Now create an extract body of giving surface and untrim the surface to remove the hole.
• Offset the roof by 0mm and trim the roof panel using boundary of extracted surface what we got as a extra portion.
• Now start creating flanges according to the given the input for front panel, dich area and rear panel.
• This is what we do with our roof panel.

2.FRONT ROOF RAIL

• Front roof rail is that part of roof which will come contact with windshield area is responsible for visibility factor of the driver.
• The major design factor that is taken into consideration is headroom clearance.
• It also provides provision for mounting of inner rear view mirror.
• We design the front roof rail from the given master-section.

3. BOW ROOFS

• Bow roof are provided to provide some extra strength to the roof which we will se while calculation of snow load and heat distortion.
• It is spot welded at the dich area because a rubber part has to come over their.
• By using mastic seal it is joined at the roof panel for which we give gap of 5mm between roof panel and bow roof.

4. REINFORCEMENT ROOF RAIL

• It is also called center roof rail which provide stiffness to the roof and it has provision of center room lamp.
• It is joined same as the bow roof , at the dich area we spot weld and in the middle by mastic seal.
• Dimensions used for the reinforcement roof rail is hit and trail to achieve the shape provided as input.

5. REAR ROOF RAIL

• Rear roof rail is important part as it has to come in contact which the back door.
• As we do not have much information about back door therefore we can simply follow the input to design the rear roof rail.

HEAT DISTORTION CALCULATION:-

• When temperature increases there is decrease in stiffness and metal get softer and defect can be seen our roof. To avoid that we calculate the position of roof rails that is correct or not using below formula.

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

Judgment Condition: OK< 2.7> 3.1

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]

SL NO	BOW’S	Rx(mm)	Ry(mm)	I(mm)	L(mm)	R^2/t	W(mm)	Status
1	FRR & BR1	5741.13	2405.09	445.273	1923.238	15322998.8	1.44	OK
2	BR1 & CRR	6187.063	4974.87	354.93	1923.238	30416813.53	1.784	OK
3	CRR & BR2	9668.329	6035.48	310.017	1923.238	55233495.353	2.0082	OK
4	BR2 & RRR	6791.44	3397	405.830	1923.238	27346248.80	1.596	OK

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)

Judgment condition = Qr ≥ 3.1

250 ≤ s ≤ 380

t = Roof plate thickness [mm]

Ly = Distance between the front and rear roof Rails on the Vehicle along with 0Y[mm]

Lx = Distance between the Left and Right end of the roof on the Roof BOW [mm]

Width of the roof panel 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

SL NO	Rx	Ry	t	S	Iy	α	Qr	Status
1.	2435.84	4299.67	0.75	492.554	9309.59	1.054	90.97	OK
2.	4124.97	4253.28	0.75	397.456	51431.48	0.717	580.172	Ok
3.	6878.35	2967.769	0.75	466.5387	4516.68	0.653	34.33	Ok

Here,

Case 1 = FRR & BR1

Case 2 = BR1 & CRR

Case 3 = CRR & BR2

So, our roof can sustain the heat as well as snow load.

ORIENTATION OF ROOF:-

Top view

Side view

Bottom view

SECTION VIEW

CONCLUSION:-

This project show how an automotive industry takes approach towards creating of roof.

The roof has passed the heat distortion and snow load calculation.

LINK TO VIEW MODEL:-https://drive.google.com/drive/folders/1d3_i5Ra2sHI5hPgrqDLfw0V9JUEMtIaO?usp=sharing

THANKYOU