Roof challenge
AUTOMOBILE CAR ROOF DESIGM USING CATIA
AIM For the Given Roof styling, Develop the essential flanges and reinforcements and front roof rail rear roof rail bow roof 1 and 2 and create mastic , Provide appropriate dimension and check for Draft analysis and section modulus .
introduction
An automobile roof or car top is the portion of an automobile that sites above the passenger compartment , protecting the vehicle occupants from sun ,wind,rain,and other external elements.
material used for roof : aluminium, steel,composite plstics etc.
types of roof design
1 - convertable roofs
2 - hardtops
3 - sun roofs
4 -T- tops
5 - targa tops
6 - vinyl roofs
objectives:
* select the proper matreal which reduce the weight, cost and increase effeciency.
* measure the section modulus of the inertia to know the performance of it in runing condition.
* The roof to be compliant with the relevent standards in automotive engineering.
* TO measure strain and deformation at critical location in the vehicle roof support structure and provide strenthening solutions inceitical areas
Design of roofs.
1 - front roof rail
2 - rear roof rail
3 - reinforcement roof
4 - bow roof 1
5 - bow roof 2
6 - ditch area.
Thickness of the roof is =0.75mm
draft angle is = >0.7
1 - front roof rail
2 - rear roof rail
3 - reinforcement roof
4 - bow roof 1and 2 are same
there are three types of criteria design of car roof
1 - heat distortion criteria
2 - snowed criteria
1 - heat distortion criteria. why we need this heat distortion criteria.
* This is nothing but the curvature study and bow roof position justification. at certain tempreture material start softening ,when exposed to fixed load at elevated tempreture above this tempreture matreal not stable it can be deformed or loses its strength and this is unsafe to the passenger.
* in order to know whether the matreal or roof is in a safer zone according to the position of the bow roof (whether its position is right or wrong) we need to perform some formula criteria as shown above.
ROOF BOW CALCULATION.
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
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]
| ROOF | L (length | RX | RY | t (thickness) mm | l (width) (mm) | W |
| FRR AND BR1 | 2147.648 | 2660.637 | 3240.072 | 0.75 | 409.66 | 1.29 |
| BR1 AND CRR | 2147.648 | 6328.372 | 4008.044 | 0.75 | 447.891 | 2.426 |
| CRR AND BR2 | 2147.648 | 10442.431 | 4945.153 | 0.75 | 446.052 | 2.198 |
| BR2 AND RR | 2147.648 | 14867.196 | 5736.753 | 0.75 | 370.714 | 2.343 |
SNOWED CRITERIA.
calculate snowed criteria
in north india there is continous snowfall and it causes a door jam in the car to optimise this problem. we need to justify the snowed criteria theoretically. to know whether tha bow roof position is correct or not according to snowed load condition.
Snow load Prediction formula
Qr = [Iy x t^2] / [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.
Where
α = My x Lx^2 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/L2 + 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.
| ROOF | LX | LY | S | Y | MY | α (ALPHA) | RX | RY | IY | QR | STATUS |
| FRRTOBR1 | 1106.018 | 1990.815 | 496.5742 | 409.692 | 647773.44 | 0.79 | 953.436 | 4601.902 | 106.8 | 4.269 | OK |
| BRITOCR | 1072.312 | 1990.815 | 493.9111 | 443.155 | 685853.62 | 0.78 | 2325.772 | 3851.864 | 272.7 | 7.419 | OK |
| CRTOBR2 | 1036.539 | 1990.815 | 530.444 | 443.934 | 686713.06 | 0.73 | 2510.007 | 4171.24 | 652.8 | 16.42 | OK |
| BR2TORR | 0 | 1990.815 | 0 | 362.882 | 590747.58 | 0 | 804.207 | 2863.228 | MG |
BOW ROOF RAIL 1
CENTER ROOF RAIL
BOW ROOF RAIL 2
EMBOSESS ON THE ROOF
An automobile roof or car top is the portion of an automobile that sits above the ... Ditch area may or may not having emboss at top (which may vary car to car ... It have a mastic point, which is used to make attached to the roof .
SUMMERY
From the above calcualtion we summeries that this roof stisfy the therotical heat distortion criteria as well as snowed criteria by maintaining W value in heat distortion criteria and QR value is snowed criteria