Roof challenge

Automotive Roof

OBJECTIVE:

To design an Automotive Roof for the Given Roof styling, and to Develop the essential flanges and reinforcements. Do a curvature study on the roof and perform calculations to determine the position of the Bow-roof. Do a section modulus study for the Master sections you create for the Front roof rail, Rear roof rail, Bow Roof Rail and Rear Roof Rail.

INTRODUCTION:

In this project, we will be designing and developing an automotive roof with all its components. By doing draft analysis you will check the manufacturability of the part and with that feedback change the model design accordingly. This projects also require you do perform two sets of calculations depending on the region and weather conditions, and finally study the curvature of the roof and its strength with respect to its components.

DESIGN PROCESS:

• In this project, you first start with getting the styling data and then fix the surface if any geometry clean-up required
• Then according to the master section provided and by following the parameters for designing roof you will create the front, side, and the rear flange of the roof outer panel
• After completing the roof outer panel design, you will start with creating the respective roof rails in the front and rear section of the roof by simultaneously analysing the manufacturability of each part
• Now by assuming the approximate positions of the centre roof rail. you will model the bow roof rails. While designing the blow roofs of the component you will learn how these components are joined to the roof outer panel and the side body of the car
• The next step will be assembling all the components together and then performing respective calculations for curvature study and to finalizing the positions of the bow roof.
• Analysing the styling surface and designing the respective flanges
• Designing the Bow roof and the centre roof rail for the roof
• Assembling all the components together
• Curvature study through heat distortion criteria
• Curvature study through snow load criteria

Roof Design:

Design of Roof rails:

Section Inertia Analysis on Roof Rail:

Section Inertia Analysis on Bow Roof Rail-1:

Section Inertia Analysis on centre Bow Roof Rail:

Section Inertia Analysis on Bow Roof Rail-2:

Draft Analysis of Roof and Roof rails:

Draft Analysis of Roof:

Draft Analysis of Front Roof rails:

Draft Analysis of Bow Roof rails-1:

Draft Analysis of Centre Roof rails:

Draft Analysis of Bow Roof rails-2:

Draft Analysis of Rear Roof rails:

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< 2.7> 3.1

Were

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]

S.NO	ROOF RAIL	RX (mm)	RY (mm)	R (mm)	l (mm)	L (mm)	t (mm)	W	OK/NG
1	FRR & BR1	5768.73	2522.86	3510.47	413.43	2030.35	0.75	1.56	OK
2	BR1 & CRR	4935.813	4458.66	4685.11	474.83	2030.35	0.75	1.89	OK
3	CRR & BR2	3951.12	9299.93	5545.99	474.98	2030.35	0.75	2.11	OK
4	BR2 & RRR	3254.53	11421.22	5065.59	382.02	2030.35	0.75	1.88	OK

SNOWED CONDITION:

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.

Were

α = My x Lx² x 10^-12

My = Y(Ly-Y)

Judgement condition = Qr ≥ 3.1

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 centre 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]

S.NO	ROOF RAIL	IY	LY	LX	α	Y	MY	S	RX	RY	t	Qr	OK/NG
1	RRR & BR2	2683.7	1039.67	2030.5	0.778	458.4	720670	484.2	3988.8	8210	0.75	10.7	OK
2	CRR & BR2	8514.2	1039.67	2030.5	O.838	510	775384	509.8	4131.9	6674	0.75	19.1	OK
3	CRR & BR1	2826.4	1039.67	2030.5	0.8378	509.7	775135	496.9	3474.9	6263	0.75	16.1	OK

CONCLUSION:

The Automotive Roof for the Given Roof styling is been designed with the essential flanges and reinforcements. The curvature study on the roof and perform calculations for the Front roof rail, Rear roof rail, Bow Roof Rail and Rear Roof Rail are been done and passed in the test so it can be sent to further production.