Roof Design
INTRODUCTION :
The roof of a car or other vechicle is the top part of it , which protects passengers or goods from the whether .The roof also protects the passenger from any injury when the car gets crashed or is rolloed over or something heavy falls on the roof .
OBJECTIVE :
The main objective of this project is to understand the design process to design the roof with all the roof rails and to understand the calculations behind it .we also get to learn about the different tools used in NX cad for designing .
METHODOLOGY:
We get the model of the roof of the from the styling team .Then we will have to do all the engineering work .We creat the ditch area for the roof and also the roof bows and roofs rails for the roof which would we designed by us considering all the safety norms and regulation.
components of roof :
1.front roof rails :
The front roof rail is located on the front of the roof where the wind shield joins with the roof . The visibility criteria and the head room clearance of the passenger are taken into considerations for the bottom flange . One end of the rail is joined using spot welding while the other end is joined with the roof using mastic sealents for increased strength.with draft analysis
bow roof1
Bow roof is an additional siffening member for the roof to increase the strength and so that it can satisfy the norms .both the ends are together using mastic sealents to increase strength and also since this would not affect the styling of the roof .with draft analysis
centre roof rail:
centre roof rail or the reinforcement centre is located at the centre of the roof .The cross section of this is more since it needs to provide more strength to the roof .here both are ends are joined together using masticsealants with draft analysis.
Bow roof 2
This bow roof also have the same purpose as that of the first one .this one is located between the centre bow roof and rear roof rail.
Rear roof rail
This roof rail joins with the back door and the roof .inputs from the backdoor are taken into consideration for designing this roof rail.
Here one end is joined using spot welding while other end is joined using mastic sealents with draft analysis
HEAT DISTORTION CURVATURE STUDY
This study is used to find out and predict the heat distortion temperature at where the material starts to soften when exposed to a fixed load .so in order to avoid bending or damage of the roof based on this calculation we will decide the position on the roof bows on the roof .
Formula :
W= [1.73x10^(-3)xL]+[1.85x10^(-8)x(R^2)/2]+[1.10x10^(-3)xl]-2.68
judgement condition :ok<2.7>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]
| Bow position | Rx | Ry | R | l | L | T | R2/2 | W | OK/NG |
| FR and BR1 | 5741.00 | 2392.64 | 3377.62 | 347.3 | 2033.2 | 0.75 | 5704158.43 | 2.07 | NG |
| BR 1 and CTR | 98890.5 | 5934.79 | 7417.85 | 423.4 | 2033.2 | 0.75 | 27512249.31 | 2.6 | NG |
| CTR and BR 2 | 19098.93 | 10205.71 | 13302.89 | 423.1 | 2033.2 | 0.75 | 88483441.17 | 5.6 | NG |
| BR 2 and RR | 3310.28 | 14390.75 | 14390.75 | 415.3 | 2033.2 | 0.75 | 103546842.78 | 2 | NG |
Snoe load calculat
bow position Iy my Lx Ly y s Rx Ry t Qr determination
FR and BR1 22.611 652207.01 1058 1923 439.7 469.85 6918.58 3192.34 0.75 153 NG
b1 and CTR 22.58 924041.25 1079 1923 940.5 500 3858.31 52588.95 0.75 3.19 NG
CTR and B2 81.4 69446.09 1121.5 1923 1441 513.5 2275.22 17841.34 0.75 113.21 NG
sction modulus
bow roof 1
center roof
center roof 
bow roof 2
conclusion:
Hence the roof ,front roof rail ,bow roof rails ,central roff rail and the rear roof rail is designed by following the master section and themoment of inertia and draft analysis are carried out to check feasubility manufacturing.