Roof challenge

Design of Roof Using NX CAD

Aim/Objective:

• The Main objective of this project is to design a Car Roof with Some Flanges, Reinforcement, Roof Rails (Front & Rear), Ditch Area Bow Roof rails
• Calculate the Heat Load (Extreme Heat Distortion Study) & Snow Load (Extreme Cold Condition Study)
• Study about section Modulus of Front Roof rail, Rear Roof rail, Bow Roof & Center Bow Roof
• Study the Draft Analysis of all part

Roof: A Roof is the Important Part of the Car which is the upper portion of Car. It Provide the protection of Passenger from Wind, Heat, Dust, Noise & Other hurdles

Design Consideration:

• Visibility Criteria
• Head Clearance
• Curvature Study
• Heat Distortion & Snow Load Criteria
• Draft Analysis

Roof Assembly

Image:

Components of Roof Assembly:

1. Front Roof Rail: The Front Roof rail are Located on the front of the roof where it is joined with wind Shield. The Design Criteria for Head Clearance & Visibility are taken into Consideration. One end of the Rail are Joined by Spot Welding & the Other end are joined with Mastic Sealant between outer panel and Rail

2. Rear Roof Rail: This Roof Rail is provided to the rear side of the Roof. One end is Joined with the backdoor by some spot welding & Other end are joined with Mastic Sealant

3. Bow Roof: The Reason for Providing the Bow Roof is that it provides the better strength to the roof & it is joined with the roof by Mastic Sealant so that the Look of the styling face of roof isn’t affected and strength increased more

4. Center Bow Roof: In this Roof we have to provide reinforcement to the roof at the center position because the center position bears the max. Load so by the reinforcement the strength increased.

Calculation:

1. Heat Distortion Curvature Study: In this study we generally find out that how roof will distort or soften in the extreme temperature Condition when exposed to a fixed Load. So in order to avoid any damage of the roof after calculation we can decide the position of Bow roof

Bow Roof prediction Formula:

w = [1.73×10^(-3)×L]+[1.85×10^(-8)×(R^2)/t]+(1.10×10^(-3)×1] - 2.68

Judgment Condition:- OK<2.7

Where

L = Roof Length in X – Direction (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)

Result:-

Bow Position	Rx	Ry	R	l	L	t	R²/t	w	Result
FR Roof Rail and 1st Bow Roof	2720.9108	5727.3586	3689.1892	448.7418	2033.7	0.75	18146822.6	1.18	OK
1st Bow Roof and Center Bow Roof	5308.0513	7477.9473	6208.8741	465.0217	2033.7	0.75	51400156.8	1.79	OK
Center Bow Roof & 2nd Bow Roof	10677.8252	3958.5620	5775.8560	429.6581	2033.7	0.75	44480688.5	1.66	OK
2nd Bow Roof & Rear Roof Rail	14367.8153	3313.7958	5385.4827	349.2031	2033.7	0.75	38671231.9	1.55	OK

2) Snow Load Condition Curvature Study: This Criteria follow for doing the curvature study of Roof when there is an extreme

Cold condition the purpose of this study is knowhow will be the roof curvature deflect when there was snow on Roof.

Snow Load Prediction Formula:

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

α = My×Lx^2×10^ (-12)

My = Y(Ly-Y)

Judge Condition = Qr≥3.1

250 ≤ s ≤ 380

Where

t = Roof panel thickness (mm)

Ly = Distance B/W the Front & Rear Roof Rails on the vehicle along with 0-Y(mm)

Length of roof Panel with the center Point b/w Roof Rail front /Rear as the Ref. Point of the Front & rear

Lx = Distance b/w the Left & right end of the Roof Bow (mm)

Width of the roof Panel exposed on the Surface

Y = Distance from 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 (mm) (Y – Cross Section)

Rx = Lateral direction curvature radius of Roof panel on roof Bow (mm) (X- cross Section)

Section	Iy	t	Y	Lx	Ly	My	α	L1	L2	s	Rx	Ry	Qr	Result
FR Roof Rail-1st Bow roof	1308.89	0.75	541.8	1140.71	2033.7	808311.42	1.1	541.8	502.44	508.4	2639.18	4503.80	10.51	OK
1st Bow roof – Center Bow Roof	1191.54	0.75	1044.25	1087.56	2033.7	1033233.16	1.2	502.4	411.9	482.1	6497.31	3786.55	4.54	0K
Center Bow Roof -2nd Bow roof –	1225.36	0.75	1481.10	1061.66	2033.7	818454.65	0.9	411.9	510.7	475.1	11217.52	4285.26	2.70	NG

Section Inertia and Moment of Inertia Analysis:-

• Front Roof Rail :

Imin = 9.19984541 ×10^3

Ymin = Y/2 = 120.72 / 2 =60.36mm

Zmin = 1.52 mm3

• Bow Roof 1:

Imin = 1.308898295 ×10^3 mm4

Ymin = Y/2 = 84.96 / 2 = 42.48

Zmin = I/Ymin = 30.81 mm3

• Bow Roof 2:

Imin = 1.225362×10^3 mm4

Ymin = Y / 2 = 84.98/2 = 42.49 mm

Zmin = I/Ymin = 28.83 mm3

• Center Bow Roof:

Imin = 1.192549410 ×1o^3 mm4

Ymin = Y/2 = 89.98/ 2 = 44.99 mm

Zmin = I/Ymin = 25.50 mm3

• Rear Roof Rail:

Imin = 8.74435 × 10^4 mm4

Ymin = Y/2 = 255.93/2 = 127.96 mm

Zmin = I/Ymin = 68.33mm3

Draft Analysis

1. Front roof Rail

2. Bow Roof 1

3. Center Bow Roof:

4. Bow Roof 2

5. Rear Roof Rail

Conclusion:

1. By the end of Conclusion we first made the Different component of Roof and then assembled together
2. After that we have done the curvature study by Heat distortion and Snow Load Criteria.
3. The heat distortion Criteria has followed all the Condition so it is passed
4. But the Snow load Criteria does not follow(only the third section) the require Condition so it is failed to satisfy the criteria

Note: For improving this we have three method from which enhancing strength of Roof

1. By increasing the width of Bow Roof

2. by increasing Depth of Bow Roof

3. by imposing some embosses to the Bow roof