Roof challenge

Objective:-For the Given Roof styling, create an ASSEMBLY by developing the essential flanges for the outer roof and creating the reinforcements.Provide appropriate dimensions and check for Draft analysis.Do a curvature study on the roof and perform calculations to determine the position of the Bow-roofs.

Introduction:-An automobile roof is the portion of an automobile that sits above the compartment, protect the vehicle occupants from sun heat, rain, wind and other external factor.

The roof itself may be constructed of soft or rigid material. Soft-tops are made of vinyl, canvas or other textile material; hard-top convertibles have roofs made from steel, aluminium, plastic or carbon fibre composites.

Design Procedure:-Import the file from system. File>open>browse file and select the given product as show in the figer below..

Given surface is class-A and we have to design roof surface with the help of this class-A and the help of master section which is show below.There are two master section for front rail roof and the next one for the rear rail roof section..

Reinforcements design:- The ditch area is the extended portion of the main roof concealed by other BIW panels. The rail suppoert of the roof are attached to the ditch area using spot welds.Since it is not a styling surface and remains concealed.

Front Roof Rail:-It is the support that is joined the winshield glass. Body side outer and the inner panels. its thickness is usually 0.75mm. The windshields end flanges are the extract offset of the roof surface. The bottom most flanges is decided after talking into consideration the visibility criteria. Spot weld is applied at the windshield end of the other end is joined with the roof using mastics sealents which also contributes to increases strength.

Rear Roof Rail:-It is the support that is joined to the back door and the body side outer and the inner panels. It is usually made from body side outer scrap and therefore the thickness of the rail is 0.75mm similar to the front roof rail design. we have to take into consideration the rear visibility criteria while designing the rear roof rail from the backdoor design and also taken into considerationod the required clearance. Spot welds are applied at the back door end of the rail and the other end is joined with the roof using mastic sealants.

Bow Roof Rail:- Similar to the other design, we have to take into consideration of the headroom clearance and the visibility criteria while designing centre roof rail and bow roof rail. Here spot weld is not applied for joining these rails of the roofs. Instead mastic sealanes are used are introdused at both end since centre roof are fully positioned under the styling surface of the roof. For increasing the strength of the rakes, embosing is done.thickness of the bow roof rail is 0.75mm.

Centre Roof Rail:-It is the main supporting rod for the roof. Their purpose is to provide an attachment point for cross bars and other devices designed to secure load carried on the roof of the vehicle. It absorb enery at the time of the crash. It thickness is 1mm.

Analysis

Curvature Study:-It is done to justify the positioning of the bow roofs. There are mainly two criteria to fulfill-

1. Heat Distortion Criteria.
2. Snow Load Criteria.

Heat Distortion Formula:-

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]

Judgment Condition

OK< 2.7

For the model we get some value show in figure-

So, After intersecting point on the line, we create 4 point and project them on the roof surface then joint by 3 point arc.

The Horizontal line is Rx and verticle line is Ry.

Calculation are done and its given below-

Snow Load Prediction Formula

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

Note: The Qr value given over here is correct. There was a typo error in the formula given in the video.

Where,

α = My x Lx² 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 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]

The width of the roof panel is 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

Judgment condition

Qr ≥ 3.1

For the model we get some value show in figure-

So, After intersecting point on the line, we create 4 point and project them on the roof surface then joint by 3 point arc.

The Horizontal line is Rx and verticle line is Ry.

For Moment Of enertia we create intersection of the bow and then fill then calculate it..

Calculation are done and its given below-

Draft Analysis:-Draft Analysis is a method of checking the draft angle on various faces of a part in a particular direction. It should be more than 7 degree. Draft analysis command which lets you know if your model or design has a draft angle in a given tool direction.

If the part lies within the condition it shows in green colour if not shown in blue or red colour.

Various View of Roof