Roof challenge
Aim- To develop the essential flanges and reinforcements with appropriate dimensions and checking draft by performing Draft analysis, Calculating Section inertia, Heat distortion and Snow load on the roof.
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.
Reinforcements and Design
The Ditch Area is the extended portion of the main Roof concealed by other BIW panels. The rail supports of the roof are attached to the Ditch Area using Spot welds. since it is not a styling surface and remains concealed.
Front Roof Rail
It is the support that is joined the windshield glass. Body side outer and the inner panels. Its thickness is usually 0.75mm. The windshield end flanges are the extract offset of the roof surface. The bottom-most flanges is decided after taking into consideration the visibility criteria. Spot weld is applied at the windshield end of the other end is joined with the roof using Mastics sealants which also contributes to increases strength.
Rear roof rail
It is the support that is joined to the back door and the Body side outer and the inner panels. it is usually made from body side outer scrap and therefore the thickness of the rail is 0.75mm. Similar to the Front roof rail design. We have to take into consideration the rear headroom clearance and the rear visibility criteria while designing the rear roof rail from the backdoor design and also taken into consideration od the required clearance. Spot welds are applied at the back door end of the rail and the other end is joined with the roof using Mastic sealants.
Bow Roof Rails
Similar to the other design, we have to take into consideration of the headroom clearance and the visibility criteria while designing the centre roof rail and bow roof rail. Here spot weld is not applied for joining these rails of the roofs. Instead mastic sealants are used are introduced at both ends since centre Roofs are fully positioned under the styling surface of the roof. For increasing the strength of the rails, Embossing is done. To reduce the weight of the material used, different styling has been followed with a thickness of 0.75mm.
Reinforcement centre rail
It is the main supporting rod for the roof. Their purpose is to provide an attachment point for crossbars and other devices designed to secure loads carried on the roof of the vehicle, it absorbs energy at the time of the crash. Its thickness is 1mm.
Analysis
1. CURVATURE STUDY:
It is done to justify the positioning of the bow roofs. There are mainly two criteria to fulfil
- Heat distortion criteria
- Snow load criteria
Heat distortion formula :
Draft Analysis: Draft analysis is a method of checking the draft angle on various faces of a part in a particular direction. it should be more than 7 degrees. draft analyzing command which lets you know if your model or design has a draft angle in a given tool direction.
If the part lies within the conditions it shows in green colour if not shown in blue or red colour.
The below figures show the draft analysis for Roof, Front Roof Rail, Rear Roof Rail, Bow Roofs and Reinforcement Center.
Results: The Design of Roof, Front roof rail, Rear Roof Rail, Bow Roofs, and reinforcement roof center by following the Master section with the design parameter for the given class A surface is done
DRAFT PICS
Roof
Bow Roof 1
Bow Roof 2
Center Roof
Front Roof
Rear Roof
ASSEMBLY
SECTION INERTIA
Bow Roof 1
Bow Roof 2
Center Roof
PARTS FILES
Front Roof
Bow Roof 1
Bow Roof 2
Center Roof
Rear Roof
| BOW ROOF PREDICTION FORMULA | |||||||||||||
| W1 | 1.73 | 0.001 | 2015 | 3.48595 | 1.85 | 0.00000001 | 19895622 | 0.368069 | 1.1 | 0.001 | 500 | 0.55 | 1.724019 |
| W2 | 1.73 | 0.001 | 2015 | 3.48595 | 1.85 | 0.00000001 | 43047856 | 0.796385 | 1.1 | 0.001 | 396 | 0.4356 | 2.037935 |
| W3 | 1.73 | 0.001 | 2015 | 3.48595 | 1.85 | 0.00000001 | 44034591 | 0.81464 | 1.1 | 0.001 | 366 | 0.4026 | 2.02319 |
| W4 | 1.73 | 0.001 | 2015 | 3.48595 | 1.85 | 0.00000001 | 37478675 | 0.693355 | 1.1 | 0.001 | 318 | 0.3498 | 1.849105 |
| Rx | Ry | R^2/t | |||||||||||
| R1 | 5705 | 2920 | 3862.864 | 19895622 | |||||||||
| R2 | 4761 | 7045 | 5682.068 | 43047856 | |||||||||
| R3 | 3879 | 11084 | 5746.82 | 44034591 | |||||||||
| R4 | 3265 | 14094 | 5301.793 | 37478675 | |||||||||
| Snow Load Prediction Formula | |||||||||||||
| Alpha | s | 10^-8 | (Rx+Ry/2)^2 | Final | |||||||||
| Qr1 | 217 | 0.5625 | 122.0625 | 0.2939 | 534 | 0.00000001 | 13144250 | 20.62893 | 5.917055 | ||||
| Qr2 | 286 | 0.5625 | 160.875 | 0.2301 | 460.5 | 0.00000001 | 29637136 | 31.40382 | 5.122784 | ||||
| Qr3 | 215 | 0.5625 | 120.9375 | 0.1499 | 399.5 | 0.00000001 | 63736272 | 38.1685 | 3.168516 | ||||
| Alpha1 | 841584 | 1E-12 | 349281 | 0.293949 | |||||||||
| Alpha2 | 1011396 | 1E-12 | 227529 | 0.230122 | |||||||||
| Alpha3 | 760536 | 1E-12 | 197136 | 0.149929 | |||||||||
| s | |||||||||||||
| My1 | 2015 | 591 | 841584 | Lx1 | 591 | 349281 | 534 | ||||||
| My2 | 2015 | 1068 | 1011396 | Lx2 | 477 | 227529 | 460.5 | ||||||
| My3 | 2015 | 1512 | 760536 | Lx3 | 444 | 197136 | 399.5 | ||||||
| Lx4 | 355 | ||||||||||||
| Rx1 | 4380 | Ry1 | 2871 | 3625.5 | 13144250 | ||||||||
| Rx2 | 3833 | Ry2 | 7055 | 5444 | 29637136 | ||||||||
| Rx3 | 4311 | Ry3 | 11656 | 7983.5 | 63736272 | ||||||||