Roof challenge
DESIGN OF AUTOMOTIVE BIW ROOF
AIM :
To design the roof of a car from the given Styling Surface.
OBJECTIVE :
- Design of BiW component Roof from the given styling surface along with Roof rail, Center reinforcement & Bow roof.
- Measure the Heat distorsion & Snow load criteria to find the strength of 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.
Global automotive roof system market can be segmented on the basis of types as
- Sunroof system
- Panorama roof system
- Multi-optional roof system
- Roof system with solar technology
- Light weight roof system.
Global automotive roof system market can be segmented on the basis of vehicle type as
- Passenger cars
- Sedan cars
- Compact
- Executive
- SUV/MUV
- Luxury
- Sports
- Premium
- Light commercial vehicles
The global automotive roof system market can also be segmented on the basis of
- Hard-top roof system
- Soft-top roof system
- Retractable roof systems
- Non-retractable roof systems
Design Consideration :
- Visibility Criteria
- Head Clearance
- Curvature study
- Heat distorsion & Snow load Prediction
- Material thickness
Marerial thickness :
- Roof = 0.75 mm
- Bow Roofs (1,2,3 & 4) = 0.75 mm
- Front & Rear Roof Rial = 0.75 mm
- Center roof Reinforcement = 0.75 mm
Components of Roof :
In the below figure the circle shows the location of mastic seal.
Draft Analysis of roof,
Front Roof Rail :
Front roof rail is used to provide strength to the roof panel front and it also acts as link between windshield glass, roof panel and headliner(interior trim).
Front Roof rails run along the length of the vehicle's roof. Their purpose is to provide an attachment point for crossbars and other devices designed to secure loads carried on the roof of the vehicle. Roof rails are attached to the vehicle's roof by feet or other mounts.
Front Roof Rail Draft analysis,
Rear Roof Rail :
Rear Roof rails run along the length of the vehicle's roof. Their purpose is to provide an attachment point for crossbars and other devices designed to secure loads carried on the roof of the vehicle. Roof rails are attached to the vehicle's roof by feet or other mounts.
Rear Roof Rail Draft analysis,
Bow Roof 1 :
Bow roofs are used to give the strength to the roof.
The below image shows the distance between the roof & bow roof is 4.75 mm for Mastic seal
The below image shows the distance between the roof & bow roof dich area is 0.2 mm for Spot welding.
Bow roof 1 draft analysis,
Bow Roof 2 :
The below image shows the distance between the roof & bow roof is 4.75 mm for Mastic seal
The below image shows the distance between the roof & bow roof dich area is 0.2 mm for Spot welding.
Center Reinforcement :
The below image shows the distance between the roof & Center reinforcement is 4.75 mm for Mastic seal.
The below image shows the distance between the roof & Center reinforcement dich area is 0.2 mm for Spot welding.
Bow Roof 3 :
The below image shows the distance between the roof & bow roof is 4.75 mm for Mastic seal
The below image shows the distance between the roof & bow roof dich area is 0.2 mm for Spot welding.
Bow Roof 4 :
The below image shows the distance between the roof & bow roof is 4.75 mm for Mastic seal
The below image shows the distance between the roof & bow roof dich area is 0.2 mm for Spot welding.
Heat Distortion Study :
Heat distortion study is an engineering design curvature study which is used to predict the position of bow roof & centre reinforcement is correct.
Heat distortion is caused when light is refracted through air of differing densities. Hot air is less dense than cold air, so light waves are bent differently in hot versus cold air. The result is visible heat waves when there is a significant temperature difference between the ground and the air above it.
Heat distortion prediction formula,
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] Distance beteeen the bow roofs
Judgement Condition : OK< 2.7> 3.1
Snow Load Study :
Snow load Prediction formula,
Qr = [Iy x t2] / [α x s x [(Rx + Ry)/2]2 x 10-8]
Where,
α = My x Lx2 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 = L1/2 + 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]
Judgement condition = Qr ≥ 3.1 | 250 ≤ s ≤ 380
Result : The Hear Distortion & Snow Load Criteria condition are satisfied for the roof & Bow roofs.
Roof Assembly Link : ROOF_ASSEMBLY.PRT
CONCLUSION :
Thus design the roof of a car from the given Styling Surface along with Roof rail, Center reinforcement & Bow roof is completed sucessfully. And the measurement of Heat distorsion & snow load prediction tells the position of the Bow roof & centre reinforcement conditions are satisfied.