Roof challenge
ROOF ASSEMBLY
OBJECTIVE:
We need to design the required reinforcement and flanges for the given Class A surface of the Roof.Required reinforcements are Front Roof Rail,Rear Roof Rail,Bow Roof 1,Bow Roof 2.After designing the roof assembly completely we need to perform the Heat distortion analysis and the Snow Load Analysis.
ABSTRACT:
Safety point of view the roof plays vital role,specially on accident where cars roll overs.Roll over accidents are the causes of many fatalities and several head,neck and spinetrauma around the world.Therefore passenger safety is also very important parameter in front of OEMs now a days.It is not only a marketing strategy but also a obligation stipulated by many governments.For this reason the strength of the roof is very crucial while designing the Vehicle roof.
Roof Assembly:
The conventional task of the roof is to provide protection against hard local contact.In case of roll over,compartment integrity is provided by the compartment frames.
Material Used-:There are wide range of materials are available for making Roofs Vehicle.That are-Steel,Alluminium,Thermosetting Plastic sheet.In case of steel the usuall thickness is in the range of 0.65-0.85mm.In all cases any roof panel material requires braces to prevent panel flexing and vertical waivness,commonly known as oil canning.This is the main purpose of introducing the light weight bow roofs which are welded to the body side and bounded to roof panel by smooth flexible adhesive such as MASTIC.Another task of bow roofs is to support the interior roof liner which requires a number of fittings both in central and boundary areas to avoid deflections.
Design Of Roof Includes
- FRONT ROOF RAIL
- BOW ROOF 1
- CENTER ROOF RAIL
- BOW ROOF 2
Designing of the Parts of the Roof Assembly
Front Roof rail:
Front roof rail is an additional part attached to the roof which gives the reinforcement and also having certain features in it which helps in attaching the bracket map lamp and the room lamp.
The inputs for the Front roof
The physical shape that came out of these inputs that are given by the styling team is shown below.
Rear Roof Rail:
While designing the rear roof rail we need to take care of the head clearance of the passenger & the Rear Visibility Criteria.
Center Roof Rail:
Here the minimum thing we need to take care is the width of the Center Roof Rail should be between 80-110.By following the master section by styling team the physical shape shown below.
BOW ROOFS:
- Mastics are applied between roof and the roof rail and bow roof.When the mastic gooses out it joins the roof rail and bow roof with the Roof.
- As we have curvature in front and more flat in the back side of the roof,it is sufficient to have reinforcement in the center of the roof.
- If the roof was small with better curvature we need to use only one reinforcement (center) that wiil act as bow roof.
- No.of bow roof increases if the car size becomes longer and taller.If flat region increases bow roofs also increases.
HEAT DISTORTION CRITERIA:
The consideration we need to take for this test is shown below.
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 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]
The values for my designs are:
As the condition for this is -W<2.7
So as per my design, the roof will pass the HEAT DISTORTION CRITERIA.
SNOW LOAD CRITERIA:
The consideration we need to take for this test is shown below.
The condition for this test is Qr>3.1
Conclusion:
The Roof design is pass all the test that is Heat Distortion & Snow Load and ready to manufacture for all weather conditions.