Roof Challenge
OBJECTIVE:
To design the roof parts and its ditch area with their requirement on quality testing, calculate the curvature for designed roof parts.
INTRODUCTION:
CATIA is a multi-purpose software, used in Computer Aided Designing, Computer Aided Manufacturing, Computer Aided Engineering, PLM and 3D. It is used to design, simulate, analyse and manufacture products in variety of industries.
In our design, we use CATIA as the software to create various functioning operations and features to create the parts and their assembly.
ROOF:
Roof is part of car, fixed over the compartment of passenger. The main purpose of roof is to protect the passenger and vehicle from sunlight, rain, wind, dust, heat and other mediums. There are many types of roof available according to its cost and style of the vehicle. In some car models, solar panel is also added for helping the cost reduction and electrical consumption. Some roofs have cutout section on the top, embossed surfaces to have more durability and strength.
Roof may seem to be a easily designed and produced part, but it has many conditions to be met. Roof should meet the requirements for crash test, rollover test, heat distortion test and the load that could withstand. Some cars have design in a way that it could hold the luggages on it. So all the measures should be calculated and changes should be done if needed before sending it for producing.
There can be many parts on the roof body. Roof may have different numbers of bow roofs and reinforcements on the center which is totally based on the car length. In this design, we have Front roof rail, Bow roof 1, Bow roof 2, Reinforcement roof and Rear roof rail.
FRONT ROOF RAIL
Front roof rail should be attached to the roof with no ditch area gap whereit may get spot welded or other kind of welding. Some gap is left between the inner roof surface and front roof rail which will get joined using mastic sealent. The thickness is of 0.75mm. Front roof rail is attached on the front of roof assembly, for adding some attachments like rear view mirror, sun visors, antennas.
BOW ROOF
BOW ROOF 1
BOW ROOF 2
The number of bow roofs are added according to the design, to increase the strength and withstanding capacity of the roof design. The bow roofs are attached with less gap to increase withstanding pressure of roof assembly. Basically, the thickness of bow roof should be around 0.6mm to 1mm. It should be chosen according to its requirement of strength and the length of roof.
REINFORCEMENT ROOF
Reinforcement roof plays a vital role on the strength of roof assembly. As it is fixed with the pillar assembly of car, it gives a rigid strength to the whole assembly. The reinforcement roof is comparatively thicker than the bow roofs. Ditch area is attached to surface of roof ny the same method bow roof gets attached to the roof surface. The embossing is created to improve the look and design on the parts.
REAR ROOF RAIL
Rear roof rail looks similar with the design of front roof rail but rear roof rail is comparatively bigger in size. The gap between the surface of rear roof rail and roof surface is also higher. The thickness is same of the front rail roof, 0.75mm.
ASSEMBLY
The assembly of roof should pass all the tests like heat distortion test, snow load test, crash test and rollover test.
CALCULATIONS:
Here, we are discussing about the heat distortion test and snow load test.
HEAT DISTORTION
The formula for calculating the heat that could withstand heat load on roof is,
W= [1.73*10^-3*L]+[1.85*10^-8*(R^2/t)]+[1.10*10^-3*l]-2.68
where,
L is length of the roof in X-direction on 0Y line,
R is the curvature of roof,
R= 2(Rx*Ry)/(Rx+Ry)
Rx is the curvature of roof in X direction,
Ry is the curvature of roof in Y direction,
t is the thickness of roof and
l is the distance between the each roof parts.
The explanation for the above values are given in the image
SNOW LOAD CONDITION
The formula for calculating the total amount of snow load it could withstand on the top of roof is,
Qr=(Iy*t^2) / a*s*[(Rx+Ry)/2]^2 * 10^-8
where,
t is the thickness of roof plate
Ly is the distance between the styling end of front and rear roof rail on 0Y [mm]
Lx is the distance in X axis between the ends of the part
Y is the distance from front roof rail center to the bow roof center
s= (L1/L2) + (L2/2)
Here in L1 and L2 three parts are taken for measuring.
L1 is the distance between the first part center to the second part center,
L2 is the distance between the second part center to the third part center,
Rx is the radius of roof panel in Y cross section between the three centers of roof,
Ry is the radius of roof panel in X cross section between the ends and center of the bow roof.
CONCLUSION:
The roof and ditch area is successfully designed, along with the heat distortion test and snow load test. All the requirements are calculated and gets passed through them, so it could be sent to further steps of production.