ROOF AND RAIL REINFORCEMENT DESIGN

ROOF AND RAIL REINFORCEMENT DESIGN

INTRODUCTION TO ROOF

The roof is part of an automobile, essential to protect passengers from harsh weather & climatic conditions, accidents, etc.

Figure 4a

IMPORTANT TYPES OF ROOF REINFORCEMENTS:

• Front roof rail reinforcements
• Central roof rail reinforcements
• Bow roofs reinforcements
• Rear roof rail

Refer to Figure 4b for Roof reinforcements

Figure 4b

ANALYSIS OF THE FOLLOWING ROOF:

There are mainly two type’s conditions that the roof needs to pass to hold the design criteria good, they are.

• Heat distortion condition
• Snow load condition

1. Heat distortion criteria :

Heat distortion criteria are the calculation used to find the distance between the bow roof reinforcements.

It is given by the condition: HOLDS GOOD<2.7mm

FORMULA-

w=1.73x10^-3xL+1.85x10^-8x(R²/t)+1.10x10^-3xI-2.68

L-Roof length in the x-direction (mm) (WRT 0-Y direction)

R-Roof curvature

R=2(Rx*Ry)/(Rx+Ry)

Rx-X Curvature

Ry-Y Curvature

t- Roof plate thickness in mm

I-Bow roof span in mm

W-Displacement in mm

According to the above formula, the calculations have been made for the roof design

Refer to Figure 4c for the heat distortion value chart

Figure 4c

NOTE:

1. The first data(Sl no 1) was considered, ie. The Rx and Ry values are considered to be zero between the front and central roof rail because of the presence of the sunroof cut out.
2. In the second data(Sl no 2), the bow roof 1 is present within the central roof rail; hence the bow span is considered zero. The bow roof 1 is added to provide additional support to the roof due to the presence of a sunroof

Figure 4d

All the above W values are below 2.7mm,

Hence the span of bow roofs 1 & 2 holds good for heat distortion conditions.

SECTION MODULUS AND MOMENT OF INERTIA DETAILS:

1. FRONT ROOF RAIL REINFORCEMENT
2. CENTRAL ROOF RAIL REINFORCEMENT
3. BOW-1 ROOF RAIL REINFORCEMENT
4. BOW-2 ROOF RAIL REINFORCEMENT
5. REAR ROOF RAIL REINFORCEMENT

• FRONT ROOF RAIL REINFORCEMENT:

Figure 4e

THICKNESS=1.5mm

WIDTH=221.7mm

MOMENT OF INERTIA

1. MAX=4.001874312e^4 mm^4
2. MIN=1.003361346e^3 mm^4

SECTION AREA: 15.3424 mm^2

• CENTRAL ROOF RAIL REINFORCEMENT:

Figure 4f

THICKNESS=1.5mm

WIDTH=160mm

MOMENT OF INERTIA

1. MAX=3.68033097e^4 mm^4
2. MIN=591.932411755 mm^4

SECTION AREA: 15.257 mm^2

• BOW-1 ROOF RAIL REINFORCEMENT:

Figure 4g

THICKNESS=1.5mm

WIDTH=160mm

MOMENT OF INERTIA

1. MAX=3.84835e^4 mm^4
2. MIN=238.113381513 mm^4

SECTION AREA: 13.737 mm^2

• BOW-2 ROOF RAIL REINFORCEMENT:

Figure 4h

THICKNESS=1.5mm

WIDTH=160mm

MOMENT OF INERTIA

1. MAX=3.252898673e^4 mm^4
2. MIN=453.415319695 mm^4

SECTION AREA: 14.987246992 mm^2

• REAR ROOF RAIL REINFORCEMENT:

Figure 4i

THICKNESS=1.5mm

WIDTH=mm

MOMENT OF INERTIA

1. MAX=2.661093142e^4 mm^4
2. MIN=3.031216308e^4 mm^4

SECTION AREA: 14.915 mm^2

SECTION MODULUS OF THE ENTIRE ROOF:

Figure 4j

MOMENT OF INERTIA

1. MAX=6.027050395e^7 mm^4
2. MIN=1.787259e^3 mm^4

Figure 4k

ROOF EMBOSSING:

Roof embossing is an additional roof reinforcement, strengthening the outer surface.

Figure 4l