Roof Design

CAR ROOF DESIGN BY USING CATIA V5:- OBJECTIVE:-

• The objective of this project is to design car roof with essential flanges and reinforcements like ditch area , front roof rail , bow roofs, central roof rail and rear roof rail for the the given styling surface
• Perform a curvature study on the roof and perform the calculations for the heat distortion and snow load criteria to determine whether the bow roofs are at the correct positions.
• Finding moment of inertia and section modulus for Bow roofs , central roof rail . front roof rail and rear roof rail .
  • Perform the draft analysis for each reinforcements WHAT IS CAR ROOF:-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. Roof is the structure above the wind shield glass having the reinforcements to provide the strength to the overall structure and to with stand the over head forces like snow REINFORCEMENTS :If the roof is flat it is very weak and cannot able to with stand the forces like snow , so in order to increase the strength of the roof these reinforcements like front roof rail, central roof rail, rear roof rail and the bow roofs are introduced and joined to the flat surface of the roof with the different joining process. TYPES OF REINFORCEMENTS:-
  • Front roof rail
  • Bow roofs
  • Central roof rail and Rear roof rail FRONT ROOF RAIL:- CENTRE ROOF RAIL :- BOW ROOF 1:- BOW ROOF 2:- REAR ROOF RAIL:-

    HEAT DISTORTION STUDY ON THE ROOF :

    The heat distortion study plays a major role in sheet metal usage . heat distortion temperature is a temperature limit above which the material cannot be used for the structural applications . This study is used to predict the heat distortion temperature at where the material starts to soften when exposed to a fixed load at elevated temperature . In order to avoid bending or damages on the roof, based on the heat distortion temperature , this study will predict the bow roof position which helps to strengthen the roof .

    Bow – roof prediction 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]

    Judgement Condition : OK< 2.7> 3.1 CALCULATIONS : HEAT DISTORTION:-

    SNOW LOAD CRITERIA :

    This test is done to know how is the roof behaving when there is a snow over . normally due to the snow weight the dent will happen. But the roof should be designed in such a way that when the snow is removal the roof should go it its original position . This is the basic requirements for snow load criteria .

    

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

    Where

    α = My x Lx2 x 10-12 , My = Y(Ly-Y)

    Judgement condition = Qr ≥ 3.1

    250 ≤ s ≤ 380

    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 reference point of the front and the rear.

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

    Width of the roof panel 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]

    CALCULATIONS:- SNOW LOAD CRITERIA α & S PARAMETERS :-

    Section Modulus Study

    Section modulus is a geometric property for a given cross-section used in the design of beams or flexural members. There are two types of section moduli, the Elastic Section Modulus and the Plastic Section Modulus. For general design, the Elastic Section Modulus is used, applying up to the Yield Point for most metals and other common materials.

    Section modulus is calculated using the formula

    S=Iy�=��

    Where,

    S = Section Modulus

    I = Moment of Inertia

    Y = distance between the neutral axis and the extreme end of the object