Roof challenge

ROOF

INTRODUCTION

An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements. Because the earliest automobiles were designed in an era of horse-drawn carriages, early automobile roofs used similar materials and designs.

the roof is a styling part surface which is fixed with the BIW body through the rools and pannels inside the upper part to provide strength and stifness

Ditch area plays an major role in here to fix the reinforcement on the component

the required tool opening angle is minimum 3 deg

Factors considered before creating ditch area ia

. head room clearance

. visiblity

. wind shield glass

. back door

class A input

after the fillet is opend the roof part is not jointed together but at the individual surface

the surface is symetrical in shape therefore half we can work on the half of the portion and we can reflect it

Components of roof

. front roof rail

. rear roof rail

. bow roof

. center roof rail

. ditch area

front roof rail

it is created by using given master surface

front roof rail is used to provide strength to the roof pannel front and also it act as the linkage between windshield glass,roof pannel and head liner

REAR ROOF RAIL

it is created by using the given master section

rear roof rails are used to provide strength to the roof rails and also act as the linkage between the backdoor and the roof

CENTER ROOF RAILS AND BOW ROOF RAILS

center roof rails will be placed at the center of the roof to provide strength and stability to the roof . Here the center roof rail is joined to the roof through mastic sealent

DITCH AREA

ditch area is the extended area from the main roof concelled by other BIW parts

SECTION VIEW

all the components are created with thickness 0.75

curvature study of the roof

after getting the final body of the roof it has to been checked wheter it passes through the standards

Analysis

it is done to justify the bow roofs

1: Roof crash test

2: snow load test

3: Heat distortion test

Heat distortion criteria

Heat distortion analysis plays a pivotal role in the strength of the roof panel. It is the temperature above which material cannot be used for structural applications. This study is used to predict the heat distortion temperature where the material starts to soften when exposed to a fixed load at elevated temperature.

. to measure the heat distortion by the bow roof formula

. we need to creat the sketrch on the top of the face and a line is drawn in the center on OY direction

. draw a line 300mm from the oy line

. from the 300 mm draw 100 mm line on the both sides

.take the intersection poin from the roof rails and draw a line of 100 mm line on both sides

. now the lines we draw intersects and we get the points for measuruing

. roof curvature (Rx & Ry) radius is measured by creating 'Three point arc'

Between	L	RX	RY	R=2(RX.RY)/ (RX+RY)	t	I (mm)	R^2/t	w	OK/NG
front roof rail and bow roof 1	2032.73	5724.7170	2749.8791	3715.29	0.75	386.0039	18404.506	1.36	ok
Bow roof 1 to center roof rail	2032.73	4864.72	6629.5223	5611.63	0.75	359.33	41987188.34	1.64	ok
center roof rail to bow roof 2	2032.73	3985.1625	10542.0018	5783.86	0.75	463.35	44604648.66	1.80	ok
bow roof 2 to rear roof	2032.73	3293.987	14497.46	5368.247	0.75	403.55	38424000.93	1.62	ok

the test value infer that the design is good under the limit and standards

Snow load criteria

BOW	I Y	α	LX	LY	Y	s	Rx	Ry	t	Qr	ok/NG
front roof rail to 1 st roof rail	2199.71	0.98	1130.734	2028.1785	509.9096	509.45	4408.0067	2786.2007	0.75	19.16	ok
first roof rail to center roof rail	2935.12	0.91	1080.8532	2028.1785	519.3676	460.05	3790.859	6557.8347	0.75	14.72	ok
center roof rail to bow roof 2	6249.08	0.72	1050.2212	2028.1785	407.7859	453.68	4272.0500	11033.071	0.75	18.37	ok
bow roof 2 to ditch area	2898.96	0.82	1042.0697	2028.1785	499.5985		4028.1156	16267.4758	0.75

section modulus

section modulus is a direct measure of strength of any sectional area of an object about an reference axis . strength is nothing but capable of supporting greater loads, so higher the strength it has a high capable of support greater load

S = I / Y

S= section modules

I = distance from the reference line to one of the extreme end of the object

Bow roof 1

center roof rail

Bow roof 2

Draft Analysis

it is done to check if the feature designed clear the minimum draft 5 degree for manufacturability . this type of analysis performance based on colour ranged identifying zones on the analyzed element where the deviation from the draft direction at any point , corresponds to specification value

it is seen that the features designed cleares the minimum draft angle which denoted in green

.Conclusion

. Essention roof component such a bow and center rails required with flanges and reinforcement are designed

. curvature study on roof was analysed with heat distration and snow load standard

. draft analysis was done to check toolability