Roof challenge

ROOF DESIGN

OBJECTIVE :

• The objective of this project is to design car roof with essential flanges and reinforcements like ditch area , front roof rail , bow roofs, central roof rail and rear roof rail for the the given styling surface
• Perform a curvature study on the roof and perform the calculations for the heat distortion and snow load criteria to determine whether the bow roofs are at the correct positions.
• Finding moment of inertia and section modulus for Bow roofs , central roof rail . front roof rail and rear roof rail .
• Perform the draft analysis for each reinforcements

SOFTWARE USED :

NX -CAD

FRONT ROOF RAIL:

BOW ROOF 1:

BOW ROOF 2:

CENTER BOW ROOF:

REAR ROOF RAIL:

CAR ROOF DESIGN:

HEAT DISTORTION STUDY ON THE ROOF :

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]

Judgement Condition : OK< 2.7> 3.1

S No	BOWs	Rx	Ry	R	l	L	t	W	OK/NG
1.	Frt & 1st	5589	2650	3595	220	2034	0.7	1.42	OK
2.	1st & CTR	4852	3220	3871	378	2034	0.7	1.65	OK
3.	Center & 2nd	4070	4130	4099.8	290.5	2034	0.7	1.60	OK
4.	2nd & Rear	3418	4776	3984	278	2034	0.7	1.56	OK

SNOWED CRITERIA:

Formula to be used,

(Prediction Formula) Q_r =(ly⋅t)2∝⋅s⋅{Rx+Ry2}2⋅108=(ly⋅t)2∝⋅s⋅{Rx+Ry2}2⋅108

Where α=M_y*L_x²*10^-12 [ M_y = Y(L_y-Y)]

Here,

t = Roof plate thickness [mm]

L_y = Dist. Between the front & rear rails on 0Y [mm]

L_x = Dist. Between the left & right roof ends [mm]

Y = Dist. Between the front & rail center [mm]

s =(L₁/L₂)+(L₂/2) (all in mm)

from the data available we got Y=480mm, t=0.7

Snowed criteria prediction Q_r was found to be Good [PASS]

[as per judgement condition Q_r: OK ≥ 3.1mm & 250 ≤ S ≤ 380]

S No	BOWs	ly	Lx	Ly	Y	α	s	Rx	Ry	t	Qr	OK/NG
1.	Frt & 1st	2213	1127	2034	480	0.95	256	1389	2921	0.7	0.96	OK
2.	1st & CTR	2479	1089	2034	480	0.88	251	2662	6234	0.7	2.26	OK
3.	Center & 2nd	4068	1066	2034	480	0.85	201.25	3684	10854	0.7	2.20	OK
4.	2nd & Rear	-	1052	2034	480	0.82	225.9	4870	15490	0.7	1.99	OK

DRAFT ANALYSIS:

BOW ROOF 1:

Moment of inertia maximum,( MAX) I _max =1.34426 × 10^5 ( mm⁴)

Moment of inertia maximum ,( MIN) I _min =6.6144 x 10^3 ( mm⁴)

SECTION MODULUS

S= moment of inertia /distance from the neutral axis to any given fibre

S = I / y

Y = 34.95 mm

FOR MINIMUM MOI :

S= 6.6144 x 10^3 ( mm⁴)/ 34.95 mm

S _min = 189.2532 mm³

^{BOW ROOF 2:}

Moment of inertia maximum,( MAX) I _max =1.344961 × 10^5 ( mm⁴)

Moment of inertia maximum ,( MIN) I _min =6.70052 x 10^3 ( mm⁴)

SECTION MODULUS

S= moment of inertia /distance from the neutral axis to any given fibre

S = I / y

Y = 34.95 mm

FOR MINIMUM MOI :

S= 6.70052 x 10^3 ( mm⁴)/ 34.95 mm

S _min = 191.2872 mm³

^{CENTRAL ROOF RAIL :}

Moment of inertia maximum,( MAX) I _max =2.21304 × 10^5 ( mm⁴)

Moment of inertia maximum ,( MIN) I _min =1.13004x 10^3 ( mm⁴)

SECTION MODULUS

S= moment of inertia /distance from the neutral axis to any given fibre

S = I / y

Y = 59.96 mm

FOR MINIMUM MOI :

S= 1.13004 x 10^3 ( mm⁴)/ 59.96 mm

S _min = 188.466 mm³