DESIGN OF ROOF
DESIGN OF ROOF
OBJECTIVE:
1.To perform the section modulus study for the Master sections and create for the Front roof rail, Rear roof rail, Bow Roof Rail and Rear Roof Rail.
2.To create the Ditch area,and to perform the draft analysis.
DESIGN CONSIDERATION:
- VISIBILITY CRITERIA
- HEAD CLEARENCE
- CURVATURE STUDY
- HEAT DISTORTION AND SNOW LOAD CRITERIA
- MATERIAL THICKNESS
INTRODUCTION:
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. Because the earliest automobiles were designed in an era of horse-drawn carriages, early automobile roofs used similar materials and designs.
MAIN COMPONENTS OF ROOF:
FRONT ROOF RAIL:
Front roof rails are used in the assembly of a roof in which it provides mounting provisions to windshield glasses and the changes in the front roof rail influences the frontal visibility of the passenger. The major design factor considered is the headroom clearance. The front roof rail also provides provisions for mounting the inside rearview mirror.
BOW ROOF1:
BOW- Roof center 1 is an additional stiffening member used in the roof assembly for the localised strength improvement and it is join directly to roof itself with several spot welding or even with the mastic sealent.
CENTER ROOF RAIL(REINFORCEMENT CENTER:
The reinforcement center is used as a cross member between bodyside LH & RH respectively. In some cases, the reinforcement center is not joined with the roof and in some other cases, it is made to join in both roof and bodyside. The reinforcement center and BOW roof are joined either spot weld or by mastic sealants and provisions for the same are given.
BOW ROOF2:
The bow roof center 2 is similar to that of bow roof center1 which serves the same purpose as the previous but with a limited extend and hence it is used with a smaller cross section.
REAR ROOF RAIL:
The rear roof rail is the one of the importent component of roof assembly which is used for the back door mounting.similar to front roof rail importen design consideration include rear passanger head clerance rear visibility of the vehicle.
CURVATURE STUDY OF THE ROOF:
maxmimam moment of inertia = 7.19054303e+07mm^4.
minimum moment of inertia = 2.801083112e+05mm^4.
MOMENT OF INERTIA OF BOW ROOFS:
FRONT ROOF RAIL:
CENTER ROOF:
REAR ROOF RAIL:
Heat Distortion Curvature study:
The heat distotion study play an important role in sheet matal usage. Heat distortion temperture is a temperature limit above which the material cannot be used for structural applications.
This study is used to predict the heat distortion temperature at where the material start to soften when exposed to a fixed load at elevated temperature. In order to avoid bending/damages on roof, based on heat distortion temperature, this study will predict the bow roof position on the roof to strengthen the roof.
Bow - roof prediction Formulae:
W =1.73*10^-3*L+1.85*10^-8*(R^2)/t+1.10*10^-3*I-1.26
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]
I - Bow roof span [mm]
Judgemegnt Condition : OK<2.7mm
Where NG- Not good
SNOW LOAD CRITERIA:
This evalution is performed in cold regions where snow occurs.roof design must pass through these calculations to ensure that it has sufficent stiffness to withstand the load due to accomalation of snow over the roof.
FOR STRENGTH:
conclusion:
The section modulus study for the Master sections and create for the Front roof rail, Rear roof rail, Bow Roof Rail and Rear Roof Rail and creation of the Ditch area,and to perform the draft analysis all are sucessfully done by using nx software.