Roof challenge
Roof:
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. The roof must be designed in such way that it will sustain the imapact load of accidents. The roof is an assembly of many parts such as bow roofs, front roof rail, Rear roof rail, Reinforcement center. The number of bow roof depends on length of roof. Roof is attached to the body of car using mastic sealant.
Objective:
Create roof model using given master section and styling surface.
Determine wether the design satisfies the heat distortion criteria.
Judge the snowed condition criteria of roof using prediction formula.
Preapare section modulus study of bow roof 1, Center bow roof , bow roof 2.
Roof Assembly:
Bow roof & Rails:
Front roof rail:
Bow roof 1:
Bow roof center and Reinforcement Center:
Bow roof 2:
Rear roof Rail:
Heat Distortion Criteria:
Predicting heat distortion for roof is important since it is exposed to heat for long time & high temperature will affect the roof structure. This study helps to determine the positions of bow roof to provide strength to 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
Judgement Condition : OK< 2.7> 3.1
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]
SNOWED 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]
Roof panel X curvature radius of length s in Side view.
Section Inertia analysis:
Bow roof 1:
Bow roof center:
Bow roof 2:
