Roof challenge

#Challenge 5 Roof Design

Name: Sri Gokul P

Course: Automotive Sheet Metal Design using Siemens NX CAD / CATIA V5

CAR ROOF:

• A car roof is part of a car and is used to protect passengers from side-impact and improve pedestrians’ safety. During the accident, the roof will absorb energy during impact and it has a reinforcement area for safety.
• The roof will help passengers not only accidents and also protect them from sun, rain and other external factors.

Types Of Roofs:

They are three different types of roofs available.

1. Convertible roofs.

2. Hardtops.

3. Sunroofs.

4. Targa tops.

1. Convertible roof:

• It is also called a stack. This type of roof is used in a luxury car and opening and closing will be in automatically.
• Single door car mostly has a convertible roof and are quite expensive compared to all other cars.

2. Hardtop:

• In modern cars, hardtops are typically constructed from metal, and they are rigid forms of automobile roofs. Fixed hardtop roofs are not removable, while detachable ones can be stored separately, or retractable ones can be stored within the vehicle.

3. Sunroof:

• An automobile sunroof is a movable panel that opens up to reveal a window on the roof, letting in fresh air and light. A variety of shapes, sizes, and styles are available for sunroofs that are either manually operated or motor-driven.

4. Targa tops :

Basically, a Targa car is a semi-convertible car with a reversible roof section and a full-width roll bar behind the seats

MAIN PART OF THE CAR ROOF:

1. ROOF
2. FRONT RAIL
3. REAR RAIL
4. BOW-1
5. BOW-2
6. CENTER BOW

Design Parameter:

ANALYSIS:

Therefore, it is essential for OEMs should consider passenger safety under perspective. In addition to being essential to implement a marketing strategy for commercial purposes, it is also essential to worldwide standards and various national laws.

1. Roll over test on roof Analysis.

In a rollover, the far side structure of the vehicle experiences a more severe load. When a roof structure is intruded upon during a rollover, more damage is caused.

2. Roof crush test Analysis.

Roof crush is the failure and displacement of an automobile roof into the passenger compartment during a rollover accident.

Draft Analysis
BOW-1
BOW-2
CENTRE BOW

CURVATURE STUDY:

HEAT DISTORTION CRITERIA:

W = [1.73 x 10^(-3) x L] + [1.85 x 10^(-8) x (R^2)/t] + [ 1.10x10^(-3) x l] - 2.68

Where,

L = Roof Length in X-Direction [mm]- (Roof dimension in 0Y)

R = Roof curvature

Rx = X curvature

Ry = Y curvature

t = Roof plate thickness [mm]

l = Bow Roof Span [mm]

Judgment Condition: OK< 2.7

L = Roof Length in X-Direction [2117.11mm, Roof dimension in 0Y]

t = Roof plate thickness - 0.75 mm

Rx = X curvature: Ry = Y curvature- Lateral direction curvature radius of roof panel Y cross-section at -3Y

ANSWER: HEAT DISTORTION CRITERIA S.NO BOWS Rx Ry R I L t (Rᶺ 2)/t W OK/NG 1 FR & BR1 3744.42 5791.12 4548.119 263.46 2117.11 0.75 27580515.83 1.782646 OK 2 BR1 & CR 4352 4887.52 4604.241 579.26 2117.11 0.75 28265376.63 2.142696 OK 3 CR & BR2 1590.11 3022.08 2083.8 378.93 2117.11 0.75 5789627.192 1.506531 OK 4 BR2 & RR 1426.99 2622.46 1848.263 279.38 2117.11 0.75 4554767.895 1.374182 OK

SNOW LOAD CRITERIA:

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

Where,

α = My x x 10-12; My = Y(Ly-Y)

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 centre point between Roof rails 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]

The width of the roof panel is exposed on the surface.

Y = Distance Front Roof Rail to Roof BOW [mm]

s = Distance for which Roof BOW bears divided load [mm]

s =L1/2 + L2/2

ly = 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

y = 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

Judgment condition

250 ≤ S ≤ 380

t = Roof plate thickness - 0.75 mm

Rx = X curvature: Ry = Y curvature - Lateral direction curvature radius of roof panel Y cross-section at 0Y

Ly = Distance between the front and rear roof Rails on the Vehicle along with 0Y [mm]

Lx = Distance between the Left and Right end of the roof on the Roof BOW [mm]

Geometrical moment of inertia of Roof BOW (Y cross-section) [mm4]	ly
Section#: bow-1 Type: Hollow CG: (1.543991080e+03, 1.420800154e+03, 0.000000000) [mm] MOI (Max):2.125236528e+03[mm^4] MOI (Min):17.461221569[mm^4] Principal Directions: Max: (-0.107537243, 0.994201057, 0.000000000) Min: (0.994201057, 0.107537243, 0.000000000) Section Length:294.059180332[mm] Section Area:5.881072431[mm^2]
Section#: bow-2 Type: Hollow CG: (2.717407622e+03, 1.419161358e+03, 292.327421746) [mm] MOI (Max):2.153589591e+03[mm^4] MOI (Min):17.801136221[mm^4] Principal Directions: Max: (0.065554226, 0.994894285, 0.076733332) Min: (0.988037509, -0.075474652, 0.134482187) Section Length:295.321331308[mm] Section Area:5.906419375[mm^2]
Section#: centre Type: Hollow CG: (2.229822158e+03, 1.442477113e+03, 202.713529877) [mm] MOI (Max):3.128277000e+03[mm^4] MOI (Min):35.853979305[mm^4] Principal Directions: Max: (0.018978129, 0.998785639, 0.045465126) Min: (0.999819343, -0.019006444, 0.000190542) Section Length:332.918353447[mm] Section Area:6.658386574[mm^2]

ANSWER:

MANUFACTURING TECHNIQUE:

Bending: The act of bending involves applying force to a sheet metal workpiece to produce a curvature. In general, bends are used to produce simple curved surfaces instead of complex ones. In a mechanical press, a punch forces sheet metal into a simple die under enough pressure to permanently change its shape. The amount of pressure is important.

Drafting: The sheet metal is pressed against a die that has been specially shaped to take on the three-dimensional, frequently curved shape in which the sheet metal is designed to behave. In principle, the metal is moulded using the die. This method can create rather intricate shapes. A hydraulically or mechanically driven punch is used to apply pressure to the workpiece once more

Stamping: Stamping is the process of cutting and forming metal using a stamping press and a series of dies. The material is commonly used to make auto parts like hubcaps and fenders.

Extrusion: Extrusion is a process that is used to create long metal shapes. To make a rod, for example, the metal is pushed into a steel tube. The rod is then "extruded" through the tube to make it longer.

Forging: This process utilizes both the force of a mechanized hammer and the surface of an anvil to forge a piece of metal. This allows the metal to be shaped, bent, and twisted into a more complex shape than could be done with the hammer alone In general, cold metal is used for the above processes.

Conclusion:

The roof design is done using NX Siemens software and the design has been created under given parameters and calculated curvature studies using heat distortion and snow load criteria.