Roof Design

ROOF DESIGN

OBJECTIVE

We need to design the required reinforcment and flanges for the given Class A surface of Roof.Required reinforcments are Front Roof Rail,Rear Roof Rail,Bow Roof 1,Bow Roof 2.After designing the roof assembly completely we need to perform the Heat distortion analysis and the Snow Load Analysis.

ABSTRACT

Safety point of view the roof plays vital role,specially on accident where cars roll overs.Roll over accidents are the causes of many fatalities and several head,neck and spinetrauma around the world.Therefore passenger safety is also very important parameter in front of OEMs now a days.It is not only a marketing strategy but also a obligation stipulated by many governments.For this reason the strength of the roof is very crucial while designing the Vehicle roof.

Roof Assembly
The conventional task of the roof is to provide protection against hard local contact.In case of roll over,compartment integrity is provided by the compartment frames.
Material Used-:There are a wide range of materials available for making Roofs Vehicles. That are-Steel, aluminum, and Thermosetting Plastic sheets.In the case of steel, the usual thickness is in the range of 0.65-0.85mm.In all cases any roof panel material requires braces to prevent panel flexing and vertical waivness, commonly known as oil canning. This is the main purpose of introducing thelightweightt bow roofs which are welded to the body side and bounded to roof panel by smooth flexible adhesive such as MASTIC .Another task of bow roofs is to support the interior roof liner which requires a number of fittings both in central and boundary areas to avoid deflections

Design Of Roof Includes

⦁ FRONT ROOF RAIL
⦁ BOW ROOF 1
⦁ CENTER ROOF RAIL
⦁ BOW ROOF 2

OUTER ROOF PANEL :

FRONT ROOF:

]

BOW ROOF :

FRONT ROOF RAIL MOI :

BOW ROOF RAIL MOI :

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
=1.79733

SLNO	BOWs	RX	RY	R	l	L	t	R^2/t	W	OK/NG
1	FR & 1st	2592.98	10114.96	4128.107	362.17	2114.8	0.75	22721689.8712	1.797	OK
2	1st & CTR	11965.98	4946.122	6999.15	394.5	2114.8	0.75	65317491.11	2.6199	OK
3	CTR & 2nd	48334.307	9959.163	16515.37	393.05	2114.8	0.75	363676782.2	2.598	OK
4	2nd & RR	188498.30	3312.980	6511.51	309.049	2114.8	0.75	56533118.83	2.3643	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)
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

SL NO	BOWs	lY	α	Lx	Ly	y	s	Rx	Ry	t	Qr	Determination (Qr)
1	FR & 1st	807.204	0.9776	1149.4	1970.31	505.02	491.025	2644.34	14122.153	.75	40.03	ok
2	1st & CTR	107.026	0.876	1098.6	1970.31	1047.33	481.0146	11634.77	3768.9	.75	32.23	ok
3	CTR & 2nd	138.789	0.897	1071.5	1970.31	1514.3	498.776	59740.917	4262.151	.75	59.56	ok
4	2nd & RR		0.00		1970.31			4729.56	2520.86	.75

Conclusion

The Roof design is pass all the test that is Heat Distortion & Snow Load and ready to manufacture for all weather conditions.