Challenge

Roof challenge

MMangillipally Jhansi5 Jul 2022

ROOF DESIGN

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.

CAR ROOF

The Automobile roof consists of the following parts:

* The outer panel

* Front roof rail

* Bow roof

* centre roof rail

* Rear roof rail

FRONT ROOF RAIL:

The front roof rail is created at the front side of the roof to provide strength to the roof.Headroom clearance and the driver visibility are the two important factors to be considered while designing the front roof rail.The front roof rail is connected to the roof outer panel with the help of mastic seal.

FRONT ROOF RAIL

BOW ROOF:

It is used to give strength to the area between the front roof and the center roof rail. Also it created in the area between the center roof rail and the rear between the centre roof rail and the rear roof rail to provide enough strength. It can be created in any numbers depending upon the roof length but the position of the bow roofs is to be justified by curvature study.

BOW ROOF

CENTRE ROOF RAIL:

It is created at the center of the roof. It is connected to the roof by mastic seal.

CENTRE ROOF

REAR ROOF RAIL:

It is created at the rear end of the roof. The fitment of the backdoor is to be considered while desiging the rear roof rail.

REAR ROOF RAIL

ROOF IMAGES:

ROOF IMAGE 1

ROOF IMAGE 2

ROOF IMAGE 3

HEAT DISTORTION CRITERIA:

Heat distortion temperature is the temperature at which metal softens and deforms under a specified load. While designing the roof, this criteria is taken into consideration. we create bow roofs when the roof is long and flat to increase its strength.The position of the bow roof is to be justified and this justification is done by curvature study:

Bow - Roof prediction formula.

TO MEASURE L:

TO MEASURE L

TO MEASURE Rx:

TO MEASURE Rx

TO MEASURE Ry:

TO MRASURE Ry

TO MEASURE I(BOW ROOF SPAN):

BOW ROOF SPAN

Here we can see that the roof is completely satisfying the conditions of heat distortion.

SNOW LOAD PREDICTION FORMULA:

Snow load is the downward force on a car's roof by the weight of accumlated snow and ice. The roof can fail if the snow load exceeds the weight the roof was designed to shoulder. Or if the roof was poorly designed or constructed.

So there is a formula to predict the strength of the roof.

TO MEASURE Ly:

MEASURING Ly

TO MEASURE Lx:

MEASURING Lx

TO MEASURE Ry:

MEASURING Ry

TO MEASURE Rx:

MEASURING Rx

TO MEASURE s:

MEASURING s

TO MEASURE y:

MEASURING Y

After calculating all these values the Qr is found out.

It is observed that the roof is satisfying the condition only in the area between bow roof 1 and centre roof.In the other areas it is not statisfying the condition. S in order to strengthen the roof at these areas embosses are created on the outer roof.

EMBOSS TO STRENGTHEN THE ROOF

SECTION MODULUS STYDY OF THE SECTION OF THE ROOF RAILS:

The section modulus of the cross sectional shape is of significant importance in designing of structures.It is a direct measure of the strengthof the structure.

A structure that has a larger section modulus than another will be stronger and capable of supporting greater loads.

Section modulus(S)=i/y

Where i=Moment of inertia in (mm4)

y=Distance between the neytral axis and the extreme end of the object(mm)

FRONT ROOF RAIL:

FRONT ROOF RAIL SECTION INERTIA ANALYSIS

I=10871.9mm^4

y=114.28mm/2=57.14mm

S=i/y=190.27mm^3

BOW ROOF 1

BOW ROOF 1 RAIL SECTION INTERTIA ANALYSIS

i=154.8mm^4

y=74.97mm/2=37.49mm

S=i/y=4.13mm^3

CENTRE ROOF RAIL:

CENTRE ROOF RAIL SECTION INERTIA ANALYSIS

i=9154.3mm^4

y=89.99mm/2=44.99mm

S=i/y=203.45mm^3

BOW ROOF 2

BOW ROOF 2 RAIL SECTION INTERIA ANALYSIS

i=160.89mm^4

y=75.84mm/2=37.92mm

S=i/y=4.24mm^3

REAR ROOF RAIL:

REAR ROOF RAIL SECTION INERTIA ANALYSIS

i=3513.54mm^4

y=91.73mm/2=45.86mm

S=i/y=76.61mm^3

DRAFT ANALYSIS:

In the NX to check whether the sheet metal part we have designed can be deep drawn, there is an option called draft analysis. This type of analysis is performed based on color ranges identifying zones on the analyzed element where the deviation from the draft direction at any point, corresponds to specified values.