Roof challenge

ROOF DESIGN

Aim: - To Develop the Roof flanges and reinforcement from the given styling surface.

About Roof

An automobile roof is a portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements. Under the styling surface that is seen on the outside, there are many other structures under the roof that contribute to its strength and stability. The number of such structures/supports differ with respect to the size of the vehicle. They are primary installed on flatter areas of the roof to enhance the strength. These are the Front Roof Rai, Rear Roof Rail, Centre Roof Rail and Bow Roofs and they are joined to the roof by the Ditch Area.

Ditch Area

The Ditch Area is the extended portion of the main Roof concealed by other BIW panels. The rail supports of the roof are attached to the Ditch Area using Spot welds since it is not a styling surface and remains concealed. Headroom Clearance, visibility criteria, clearance for Windshield and Back door are some of the factors to be considered while designing the Ditch Area. It is given a thickness of 0.75 mm.

given

creating top surface and ditch area

offseting one side of the top surface

creating edges by using sweep command

Ditch area

symmetry to other side and join

creating thick surface draft analysis

creating front rail

extract top surface and offseting

using parallel curve and split the top surface

then using sweep command creating front rail creating symmetry

creating embosses

draft analysis

creating rear rail

same way of front rail creating rear rail giving thickness

draft analysis

CREATING BOW ROOF 1

extracting top surface and giving offset then using sweep command creating bow roof 1

creating mastakes extruding the sketches and spliting

using MSS and create the part then join and symmetry

giving thickness Draft analysis

section modulus for bow roof 1

CREATING BOW ROOF 2

bow roof 1 and bow roof 2 are same procedures Draft analysis

CREATING CENTRE BOW

Draft analysis

CREATING REINFORCEMENT CENTRE

Draft analysis

centre bow should not extended outside

Multi views

SECTION MODULUS

section modulus for bow roof 1

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Product : Face...Fill.3...Part1
Date : Thursday, 15 April 2021 05:03:46
Author : Admin
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Component | Sub-Component | Area[m2] | Gx[mm] | Gy[mm] | Gz[mm] | M1[m4] | M2[m4] | IoxG[m4] | IoyG[m4] | IxyG[m4] |
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Face...Fill.3...Part1 | | 0.000171863 | 1673.707 | 1419.012 | 8.05856e-09 | 1.23205e-08 | 1.19439e-07 | 1.232e-008 | 1.194e-007 | 1.452e-019 |
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section modulus for centre bow and centre reinforcement

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Product : Face...Fill.4...Part1
Date : Thursday, 15 April 2021 05:16:36
Author : Admin
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Component | Sub-Component | Area[m2] | Gx[mm] | Gy[mm] | Gz[mm] | M1[m4] | M2[m4] | IoxG[m4] | IoyG[m4] | IxyG[m4] |
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Face...Fill.4...Part1 | | 0.003 | 2156.864 | 1425.711 | 1.12209e-05 | 2.20618e-07 | 6.10837e-06 | 2.206e-007 | 6.108e-006 | -8.627e-019 |
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section modulus for bow roof 2

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Product : Face...Fill.5...Part1
Date : Thursday, 15 April 2021 05:22:20
Author : Admin
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Component | Sub-Component | Area[m2] | Gx[mm] | Gy[mm] | Gz[mm] | M1[m4] | M2[m4] | IoxG[m4] | IoyG[m4] | IxyG[m4] |
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Face...Fill.5...Part1 | | 0.000174006 | 2639.230 | 1415.060 | 6.75253e-06 | 1.26972e-08 | 1.21413e-07 | 1.27e-008 | 1.214e-007 | 2.604e-020 |
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CALCULATING HEAT DISTORTION CRITERIA

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

Judgement Condition : OK< 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]

CALCULATIONS:

1. FOR FRONT RAIL ROW TO BOW ROW 1

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68

L = 2033.705mm

t = 0.75mm

Rx = 2803.388mm (by measuring the X-direction arc )

Ry = 5759.619mm (by measuring the Y-direction arc)

l = 313.199mm (distance between extreme ends of front rail row and bow row 1)

R = 2(Rx*Ry)/(Rx+Ry)

= 2(2803.388*5759.619)/(2803.388+5759.619)

= 3771.209mm

(R^2)/t = (3771.209^2)/0.75

= 18962689.762

W = [1.73 x 10^(-3) x 2033.705] + [1.85 x 10^(-8) x 18962689.762] + [1.10 x 10^(-3) x 313.199] - 2.68

= 1.532

so the value is less than 3.1

Judgement Condition : OK< 3.1

2. BOW ROOF 1 & CENTRE REINFORCEMENT

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68

L = 2033.705mm

t = 0.75mm

Rx = 4946.194mm (by measuring the X-direction arc )

Ry = 6306.001mm (by measuring the Y-direction arc)

l = 329.33mm (distance between extreme ends of bow row 1 & centre reinforcement)

R = 2(Rx*Ry)/(Rx+Ry)

= 2(4946.194*6306.001)/(4946.194+6306.001)

= 5543.932mm

(R^2)/t = (5543.932^2)/0.75

= 40980245.774

W = [1.73 x 10^(-3) x 2033.705] + [1.85 x 10^(-8) x 40980245.774] + [1.10 x 10^(-3) x 329.33] - 2.68

= 1.958

so the value is less than 3.1

Judgement Condition : OK< 3.1

3. CENTRE REINFORCEMENT & BOW ROOF 2

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68

L = 2033.705mm

t = 0.75mm

Rx = 4012.304mm (by measuring the X-direction arc )

Ry = 10436.981mm (by measuring the Y-direction arc)

l = 329.37mm (distance between extreme ends of centre reinforcement & bow roof 2)

R = 2(Rx*Ry)/(Rx+Ry)

= 2(4012.304*10436.981)/(4012.304+10436.981)

= 5796.320mm

(R^2)/t = (5796.320^2)/0.75

= 44796434.910

W = [1.73 x 10^(-3) x 2033.705] + [1.85 x 10^(-8) x 44796434.910] + [1.10 x 10^(-3) x329.37] - 2.68

= 2.006

so the value is less than 3.1

Judgement Condition : OK< 3.1

4. BOW ROOF 2 & REAR ROOF ROW

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68

L = 2033.705mm

t = 0.75mm

Rx = 3324.853mm (by measuring the X-direction arc )

Ry = 14407.706mm (by measuring the Y-direction arc)

l = 315.32mm (distance between extreme ends of bow roof 2 &rear roof row)

R = 2(Rx*Ry)/(Rx+Ry)

= 2(3324.853*14407.706)/(3324.853+14407.706)

= 5402.886mm

(R^2)/t = (5402.886^2)/0.75

= 38921575.302

W = [1.73 x 10^(-3) x 2033.705] + [1.85 x 10^(-8) x 38921575.302] + [1.10 x 10^(-3) x315.32] - 2.68

= 1.904

so the value is less than 3.1

Judgement Condition : OK< 3.1

Table for all the values of Heat distortion criteria:

S.NO	POSITIONS	Rx (mm)	Ry (mm)	R (mm)	l (mm)	L (mm)	t (mm)	R^2/t	W	OK/NG
1	FRR & BR1	5759.619	2803.388	3771.209	313.199	2033.705	0.75	18962689.762	1.532	OK
2	BR1 & CR	4946.194	6306.001	5543.932	329.33	2033.705	0.75	40980245.774	1.958	OK
3	CR & BR2	4012.304	10436.981	5796.320	329.37	2033.705	0.75	44796434.910	2.006	OK
4	BR2 & RRR	3324.853	14407.706	5402.886	315.32	2033.705	0.75	38921575.302	1.904	OK

CALCULATING SNOW LOAD CRITERIA

Snow load Prediction formula

Qr = [Iy x t²] / [α x s x [(Rx + Ry)/2]² x 10^-8]

Where

α = My x Lx² x 10^-12 , My = Y(Ly-Y)

Judgement 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]

Length of Roof panel with the center point between Roof rail Front /Rear as the reference point of the front and the rear.

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

Lx , Ly and Y values

Rx and Ry values

CALCULATIONS

1. FOR FRONT RAIL AND BOW ROW 1

Qr = [Iy x t²] / [α x s x [(Rx + Ry)/2]² x 10^-8]

α = My x Lx² x 10^-12

^{My = Y(Ly-Y)}

^{s = L1/2 + L2/2}

Where

Rx = 4419.102mm

Ry = 2828.46mm

Lx = 1135.145mm

Ly = 2033.705mm

Y = 454.763mm

t = 0.75mm

Iy = 1.23 x 10^4

My = 454.763(2033.705-454.763)

= 718044.400mm

α = 718044.400 x (1135.145)^2 x 10^-12

= 0.925

s = L1/2 + L2/2

L1 = 454.763mm

L2 = 489.459mm

s = (454.763/2) + (489.459/2)

= 472.111mm

Qr = [1.23 x 10^4 x 0.75^2] / [0.925 x 472.111 x[(4419.102+2828.46)/2]^2 x 10^-8

= 120.649

Judgement condition = Qr ≥ 3.1

The Qr value is greater than 3.1

2. FOR BOW ROOF 1 AND CENTRE REINFORCEMENT

Qr = [Iy x t²] / [α x s x [(Rx + Ry)/2]² x 10^-8]

α = My x Lx² x 10^-12

^{My = Y(Ly-Y)}

^{s = L1/2 + L2/2}

Where

Rx = 3770.72mm

Ry = 6218.89mm

Lx = 1089.304mm

Ly = 2033.705mm

Y = 489.459mm

t = 0.75mm

Iy = 2.206 x 10^5

My = 489.459(2033.705-489.459)

= 755845.102mm

α = 755845.102 x (1089.304)^2 x 10^-12

= 0.896

s = L1/2 + L2/2

L1 = 489.459mm

L2 = 483.168mm

s = (489.459/2) + (483.168/2)

= 486.313mm

Qr = [2.206 x 10^5 x 0.75^2] / [0.896 x 486.313 x[(3770.72+6218.89)/2]^2 x 10^-8

=1141.485

Judgement condition = Qr ≥ 3.1

the value is greater than 3.1

3. CENTRE REINFORCEMENT & BOW ROOF 2

Qr = [Iy x t²] / [α x s x [(Rx + Ry)/2]² x 10^-8]

α = My x Lx² x 10^-12

^{My = Y(Ly-Y)}

^{s = L1/2 + L2/2}

Where

Rx = 4265.151mm

Ry = 10901.41mm

Lx = 1062.38mm

Ly = 2033.705mm

Y = 483.168mm

t = 0.75mm

Iy = 1.27 x 10^4

My = 483.168(2033.705-483.168)

= 749169.861mm

α = 749169.861 x (1062.38)^2 x 10^-12

=0.845

s = L1/2 + L2/2

L1 = 483.168mm

L2 = 487.446mm

s = (483.168/2) + (487.446/2)

=485.307mm

Qr = [1.27 x 10^4 x 0.75^2] / [0.845 x 485.307 x[(4265.151+10901.41)/2]^2 x 10^-8

= 30.294

Judgement condition = Qr ≥ 3.1

the value is greater than 3.1

table for all the values of snow load criteria

S. NO	POSITION	Rx (mm)	Ry (mm)	Lx (mm)	Ly (mm)	t (mm)	Y (mm)	My = Y(Ly-Y) (mm)	α = My x Lx2 x 10-12	L1(mm)	L2 (mm)	s = L1/2 + L2/2	Iy (mm^4)	Qr	OK/NG
1	FRR & BR1	4419.102	2828.46	1135.145	2033.705	0.75	454.763	718044.400	0.925	454.763	489.459	472.111	1.23*10^4	120.64	OK
2	BR1 & CR	3770.72	6218.89	1089.304	2033.705	0.75	489.459	755845.102	0.896	489.459	483.168	486.313	2.206*10^5	1141.48	OK
3	CR & BR 2	4265.151	10901.41	1062.38	2033.705	0.75	483.168	749169.861	0.845	483.168	487.446	485.307	1.27*10^4	30.294	OK
4	BR2 & RRR	4058.865	16142.957	1047.891	2033.705	0.75