Roof challenge

AIM : To develop Roof outer panel flanges along with bow's and reinforcement and perform calculation and draft analysis.

OBJECTIVE :

• To create flanges on given roof using input roof styling and master section.
• To create Bow's and Reinforcement using input roof styling and master section.
• To do curvature study on the roof and perform calculation to determine the position of the bow roof.
• To determine Heat destortion criteria and Snow load criteria for roof.
• To find the section modulus on the 0-Y section of the roof and also for all the component of it.
• To perform draft analysis on the final CAD model.

INTRODUCTION :

ROOF :

• An Automobile Roof or Car top is the portion of the automobile that sit above the passenger compartment protecting the vehicle occupants from Sun, Wind, Rain and other external element.

TYPES OF ROOF :

• Convertable roof

• Hardtops

• Sunroof

• T-tops

• Targa top

• Vinyl top

DESIGN COSIDERATION OF THE ROOF :

• Visibility Critera
• Head Clearance
• Heat Distortion Criteria and Snow Load Criteria
• Draft Analysis
• Safety Parameter

GIVEN INPUT DATA :

The styling surface & master section is provided by styling team

• Roof surface along with the railing rack

• Font roof rail master sketch

• Rear roof rail master sketch

• Mater section for Bow's and Reinforcement

DEVELOPMENT OF BOW'S & REINFORCEMENT :

• Outer surface of Roof

• Front Roof Rail

• Rear Roof Rail

• Bow Roof-1

• Center Roof and Reinforcemet

• Bow Roof-2

HEAT DISTORTION CRITERIA :

• The heat distortion from the sun cause the roof of the car to change in the metallic regions.
• Heat distortion criteria determines at what temperature material start when exposed to a fixed load at elevated tempetaure.

• Heat distortion Formula

`W` = `[1.73 * 10^(-3) * L] + [1.85 * 10^(-8) * (R^2)/t] + [ 1.10*10^(-3) * 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]

Heat Distotion Calculation :

Where,

FR = Front Roof,

BR-1 = Bow Roof-1,

CR = Center Roof,

BR-2 = Bow Roof-2,

RR = Rear Roof.

From above calculation roof passes the Heat Distortion Criteria.

SNOW LOAD CRITERIA :

• During the winter season the snow get clogged over the top surface roof for the car and snow has some mass it.
• Due to this, the roof can fail if the snow load exceed the capacity of the roof was that esign to sustain.

Snow load Prediction formula

`Qr` = `[Iy * t2] / [α * s * [(Rx + Ry)/2]2 * 10-8]`

Where

`α` = `My * Lx^2 * 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 front and rear reference point.

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]

Roof panel X curvature radius of length s in Side view

Snow Load Calculations :

Where,

FR = Front Roof,

BR-1 = Bow Roof-1,

CR = Center Roof,

BR-2 = Bow Roof-2,

RR = Rear Roof.

From above calculation roof passes the Snow Load Criteria.

SECTION MODULUS :

Section modulus is a geometric property for a given cross section used in a design of a beamor flexural members, it is also reffered to as the Polar Modulus or Torsional Section Modulus.

Other Geometric Properties used in Design include area for tension and shear, radius of gyration for compression, and moment of inertia and polar moment of inertia for Stiffness.

Any reletionship between this properties is highly dependent on the in equation.

Equation for the section moduli of common shapes are given below,

S = I/Y ,

here,

S = Section modulus.

I = Moment of Inertia.

Y = Distance from Neutral axis to the extreme end.

Front Roof :

Moment of Inertia (Max) = 1.73*`10^4`

Moment of Inertia (Max) = 0.0943*`10^4`

Y = 125/2 = 62.5 mm

S = I/Y

S = 0.0943*`10^4`/62.5

S = 15.09 `mm^3`

Bow Roof-1 :

Moment of Inertia (Max) = 1.372*`10^3`

Moment of Inertia (Max) = 0.0172*`10^3`

Y = 57/2 = 28.5 mm

S = I/Y

S = 0.0172*`10^3`/28

S = 0.6 `mm^3`

Center Roof and Reinforcement :

Moment of Inertia (Max) = 2.92*`10^3`

Moment of Inertia (Max) = 0.069*`10^3`

Y = 57/2 = 28.5 mm

S = I/Y

S = 0.069*`10^4`/28.5

S = 2.42 `mm^3`

Bow Roof-2 :

Moment of Inertia (Max) = 770.45

Moment of Inertia (Max) = 12.83

Y = 47/2 = 23.5 mm

S = I/Y

S = 12.83/23.5

S = 0.545 `mm^3`

Rear Roof :

Moment of Inertia (Max) = 5.10*`10^3`

Moment of Inertia (Max) = 274.71

Y = 86/2 = 43 mm

S = I/Y

S = 274.71/43

S = 6.39 `mm^3`

DRAFT ANALYSIS :

FRONT ROOF

REAR ROOF

CENTER ROOF & RE-INFORCRMENT

BOW ROOF-1

BOW ROOF-2

CONCLUSION :

In this way, we conclude that Roof pass the Heat Distortion & Snow Load Criteria and Calculate the Section Modulus for each part.