Roof challenge

Roof Design And Optimization

Introduction

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.Because the earliest automobiles were designed in an era of horse-drawn carriages, early automobile roofs used similar materials and designs.A high-quality roof offers assurances that a low-quality roof won’t provide. Weather is the principal challenge as far as roofs go, and our climate has become increasingly intense in many parts of the country. High winds, heavy rain, hail storms, and heavy snowfall all took their toll. A lesser-quality roof may not stand up to the rigors of your regional weather.

The roof panel is attached to the Biw of the car with the help of front and rear roof rail. This attachment is done with the help of sealants. 1-2 bow roofs are attached depending upon the length of the roof along with the central roof rail. Longer the roof, more the number of now roof rail. Other dimensions like strength and material is governed by the factors like headroom, overall space, visibility, ergonomics and the rules and regulation of the states where it is sold.

Objective

• In this project going to design roof components like front roof rail, bows, rear roof rail etc.
• going to perform calculation to justify these component’s positions and role in providing strength to the roof under two conditions “Heat distortion condition “ and “Snowed condition”.
• Section Inertia Modulus Calculation

Design

Given Styling Surface

Images Of Views

Images Of Roof Rails & Bows

Front Roof Rail

Bow 1 & 2

Center Bow

Rear Roof Rail

Curvature study

Heat Distortion Criteria

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

Judgement Condition : OK< 2.75mm ≤ NG

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]

Calcutaion of Heat Distortion Criteria is shown below in the table

Ry Calculations

Rx calculations

Bow Roof Span (I) Calculations

Overall Length (L) Of The Roof

Calculated Sheet For Heat Distortion

Snowed 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]

Calculated Sheet For Snowed Load Criteria

Section Modulus Analysis

Section modulus is a geometric property for a given cross-section used in the design of beams or flexural members. Other geometric properties used in design include area for tension and shear, radius of gyration for compression, and moment of inertia and polar moment of inertia for stiffness. Any relationship between these properties is highly dependent on the shape in question. Equations for the section moduli of common shapes are given below. There are two types of section moduli, the elastic section modulus and the plastic section modulus. The section moduli of different profiles can also be found as numerical values for common profiles in tables listing properties of such.

Front Roof Rail

Bow Rail

Center Bow Rail

Rear Roof Rail

Roof Outer Body

Draft Analysis

Roof Outer Body

Front Roof Rail

Bow Rail

Center Bow Rail

Rear Roof Rail

Conclusion

In this project learnt about the Design of an automobile roof and its components and also learnt about Heat distortion condition and snowed condition why and how they are calculated . The Section modulud analysis study and Draft Analysis also done. Thankyou