Roof challenge

TYPES OF ROOFS

1. Convertible:A convertible ,cabriolet or spyder is a passenger car that can be driven with or without a roof in place.
2. Hardtop:A hardtop is a rigid form of automobile roof,which for modern cars typically constructed from metal.A hardtop roof can be either fixed,detachable for separate storing or retractable within the vehicle itself.
3. Sunroof:An Automotive sunroof is a movable panel that is operable to uncover a window in an automobile roof.which allows light and fresh air into the passanger compartment.
4. T-top: A T-top is an automobile roof with a removable panel on each side of a rigid bar running from the center of one structural bar between pillars to the center of the next structural bar. The panels of a traditional T-top are usually made of auto grade safety glass.
5. Targa Top: Itis a semi-convertible car body style with a removable roof section and a full width roll bar behind the seats.
6. Vinyl roof:Vinyl roof refers to a vinyl converting for a automobile’s top.This converting was orginally designed to give the appearance of a convertible to models with a fixed roof but eventually,it evolved into styling statement in its own right.

Design Consideration:

• Visibility criteria
• Head clearence
• Curvature study
• Heat distortion and snow load condition

Components 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)

• Rear roof rail. - Roof rails are provided to give strength to the outer panel and also provide support to other commodities present in a car.

• Bow roof - To control strong induced current of winds the we use bow roofs. These bow roof’s shape decides their resistance towards the bending load.

• Centre roof rail - Reinforcement center or center roof rail is used as a cross member between Left hand and right-hand bodysides.

• Ditch area - A roof ditch area extending in a generally longitudinal direction of a vehicle is fixedly coupled to a body member and form a longitudinal water management channel on a lateral side portion of a roof of the vehicle.

Heat distortion criteria:

Heat distortion temperature is a temperature at which the metal softens and deform under a specific load.This study is done to check the ability of the roof to withstand high temperature with respect to the position of the reinforcement which contribute to the increase strength.

Prediction formula: W=[1.73×10^-3×L] + [1.85× 10^-8×R²/t]+[1.10×10^-3×l]-2.68

Judgemental condition: Ok<2.7

Where

• L=Roof length in X-direction in mm (Roof dimension in O-Y)
• R=Roof curvature
• R=2(R_X×R_Y)/(R_X+R_y)
• R_X=X Curvature
• R_y=Y Curvature
• T =Roof plate thickness in mm
• L =Bow roof span in mm

Snow Load criteria:

Snow load criteria study is done to check the ability of the to withstand snowfall and bounce back to its orginal shape without any permenant deformation once the load is removed.

Snow load prediction formula :Q_r =[(I_y × t²)/(α × s×(R_X+R_Y/2)² × 10^-8)]

Where

• α = M_y× L_x²× 10^-12 ,M_y=Y(L_y -Y)
• t=Roof plate thicness in mm
• L_Y =Distance between Front and rear roof rail on vehicle O-Y in mm i.e length of the roof panel with the centre point between roof rail FR/RR as the referance point of the front and rear
• Y=Distance from front roof rail centre to bow roof in mm
• S - Distance for which BOW bears divided load in mm
• S= L₁/2+L₂/2
• I_y=Geometrical moment of inertia of roof BOW (Cross-section)mm⁴
• R_x=Lateral direction curvature radius of roof panel Y cross section on Roof ROW in mm
• R_y =Longitudinal direction of the curvature radius of roof panel X cross section on BOW roof (mm)

Judgement Condition:Q_r≥3.1

Here the centre & 2nd Bow roof is failed it can be overcomed by changing position,increasing thickness and also creating additional embosses.

Draft analysis:

The Draft Analysis command enables you to detect if the part you drafted will be easily removed.

Rear Roof Rail

`I = 6.20*10^3` mm^4

Y= 61.02 mm

Bow roof 1

I = 601.4884 mm^4

Y= 29.45 mm

Bow roof 2

I = 481.9 mm^4

Y = 24.26 mm

CENTRE Roof Rail

I = 2.205*10^3 mm^4

Y= 36.78 mm