Roof

A Roof is the portion of an automobile that sits above the car, protecting the Passengers from sun, wind, rain, etc. The Roof is attached to front and back rail.

There are Re inforcements used in roof. Types of roof inforcements are as follows:-

Front roof rail inforcement

Centre roof rail inforcement

Bow roof rail inforcement (2 Bow Roof depend on Roof Length)

Rear rail inforcement

roof rail inforcement

Figure 1:-Outer Roof

Figure 2:-Inner Roof

Figure 3:- Re-inforcement

Analysis of Roof Design:-

There are 2 condition to pass the design

• Heat Distortation Condition
• Snow Load Condition

1-Heat Distortation Condition

Bow – roof prediction Formulae:

W = 1.73x10^-3 x L+1.85x10^-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]

Judgement Condition : OK<2.7mm<NG

Position	L (mm)	Rx (mm)	Ry (mm)	R (mm)	I (mm)	t (mm)	w	Judgment
FRR & BR1	2116.57	4351	2257	2972.21	329.66	0.7	1.57	OK
BR1 &CRR	2116.57	3916	4135	4197.63	212.35	0.7	1.67	OK
CRR & BR2	2116.57	3017	6948	4207.15	311.31	0.7	1.79	OK
BR2 & RRF	2116.57	2537	10676	5294.16	239.02	0.7	1.68	OK

Table 1:- Heat Distortion

2-Snow Load Condition

Snow Load Condition curvature calculation will perform to predict the position of bow roofs in the roof design.

Snow criteria predicted formula:

Q_r= l_y*t² /α*s*[(R_x+R_y)/2]²*10^8

Where

α=M_y*L_x²*10^-12

M_y=Y(L_y-Y)

l_y=Geometrical moment of inertia of roof bow

t=thickness of plate

Y=distance between bow roof centers

L_y=length of roof in O-Y section

L_x=width of roof

S=distance for which roof bow bears divided load

S=L₁/L₂+ L₂/2

Judgement Condition : Q_r>3.1

Position	Iy	alpha	Lx	Ly	Y	My	L1	L2	S	Rx	Ry	t	Qr	OK
FRR & BR1	4044.11	0.722772226	1036.99	1918.72	461.12	672128.512	461.12	520.83	261.3004	3565.95	3994	0.7	73.43443	OK
BR1 &CRR	2004.74	0.782921333	1036.99	1918.72	520.83	728063.0487	520.83	421.37	211.921	4098.99	7968	0.7	16.26387	OK
CRR & BR2	3093	0.678478478	1036.99	1918.72	421.37	630938.3695	421.37	542.79	272.1713	4106.4	12529	0.7	11.86291	OK
BR2 & RRF	3216.43	0.803114218	1036.99	1918.72	542.79	746841.0447	542.79	-------		4756		0.7	#DIV/0!	OK

Table 2(A):- Snow Load

t	Iy*t*t	Alpha*S*10^-8	(Rx+Ry/2)	Power	(Rx+Ry/2)^2
0.7	1981.6139	1.88861E-06	3779.975	2	14288211
0.7	982.3226	1.65918E-06	6033.495	2	36403061.92
0.7	1515.57	1.84662E-06	8317.7	2	69184133.29
0.7	1576.0507	0	2378	2	5654884

Table 2(B):- Snow Load

SECTION MODULUS REPORT OF ROOF:

SECTION MODULUS:

It is termed as the ratio of second moment of area and distance from N.A (Neutral axis) to the extreme fiber. Also it is the measure of strength of given member. The stress in the outermost section of beam is computed with the help of section modulus.

Figure 4:- Section Modulus

Figure 5:- Section Modulus of Front Roof

Figure 6:- Section Modulus of Bow Roof 1

Figure 7:- Section Modulus of Centre Roof

Figure 8:- Section Modulus of Bow Roof 2

Figure 9:- Section Modulus of Back Roof