Roof challenge

AIM:

To design a car roof and to do the curvature study to resist heat distortion and snow load condition of the same.

Introduction:

An automobile roof or car top is the portion of an automobile from sun, wind, rain, and other external elements. Because the

automobile roofs used similar materials and designs.

passenger compartment, protecting the vehicle occupant

were designed in an era of horse-drawn carriage, early

Different types of Car Roofs are :

• Convertible roofs
• Hardtops
• Sunroofs
• T-tops
• Targa tops
• Vinyl roofs

The roof of the cars is made up of multiple parts that provide support and strength to the roof components. The actual roof sheet and the

roof rails in a car the front, the center and the rear, While in additional roof rails are called bow roof rails. The number of bow roof rails

depends on the size of the roof. Headroom, visibility criteria, and target region also play a key role in roof design.

Vehicle Roof Structure:

A roof structure for a vehicle body includes a roof opening defined by a pair of spaced apart side rails, each having a flange extending

inwardly and being vertically offset below the roof surface, and by front and rear headers, each having a flange defining a window opening

A roof panel assembly includes a roof outer panel and a pair of inverted hat-shaped reinforcement rails which underlie the outer side edges

of the roof outer panel and include inwardly and outwardly directed legs abutting the underside of the roof outer panel. The outermost

portion of the side edges of the roof outer panel are hem flanged over the outwardly directed flanges of the reinforcement rails so that the

roof outer panel and the reinforcement rails define the roof panel assembly. The roof outer panel has fore and aft end flanges which overlie

the flanges of the front and rear headers and are spot welded thereto. A bead of adhesive is placed on the inwardly extending flanges of the

side rails and the roof panel assembly is lowered into the roof opening with the base wall of the reinforcement rails pressed onto the

adhesive to attach the roof panel assembly to the vehicle body. The subsequent installation of the front and rear windows hides the spot

welds.

Different components of Car Roof:

• Roof
• Front Roof Rail
• Center Roof Rail
• Rear Roof Rail

. Bow Roof 1

• Bow Roof 2

Roof Crush Test:

SO,

Passenger safety is also a very important parameter in front of OEMs. For this reason, strength is a very important criteria for

designing a vehicle roof.

The strength of the roof structure to occupant the protection in real world crashes, requiring the maximum moving distance of the roof

structure should be less than 127mm when the induced load is 1.5 times the vehicle weight.

For the test, the passenger car shall be rigidly placed or positioned on a horizontal surface with the doors locked and the window closed.

This test can be conducted on either side of the roof structure, the front left or front right side but not on both sides in one single test and

still meet the requirements of the test. The rigid plate shall not move faster than 0.5 inches/second and the force applied on the plate shall

not exceed the lesser of 15 times the unloaded vehicle weight (UVW) expressed in kilograms multiplied by 9.8 or 5000lbs

Also, the direction of the forces shall be downward and perpendicular to the lower surface of the rigid plate and such that moves in a

straight line without rotation. The duration of the test shall not exceed 120 seconds. The longitudinal axis of the plate is pitched forward at a

5 angle as viewed from the side of the passenger car.

Rollover accidents of a car are the most occurring accidents that we see in our daily lives. The passengers experience major injuries like neck.

head and spine injuries. So. to reduce the injuries of a passenger from major fatalities it is important to provide safety in the cz. Though

safety is provided by seat belts and airbags during accidents, the passenger must have sufficient space survival in the car during

accidents. The roof of the car must have high strength to resist the crush force to avail the passenger some space for survival Therefore, in

this project we have carried out roof crush test using Federal Motor Vehicle Safety Standards (FMVSS216) standards in Seyna software

We have used Hyper mesh software to mesh the prodel and to apply boundary conditions to it. And the rigid plate is used to crush the car

roof as specified by FMVSS216 standards. The nigilate is oriented on the car roof as specified by Insurance institute of highway safety

(HSAnd an alternate material is used to the car roof structure to the baseline model to check the crashworthiness of new matemal The

outcome of test results of the new material's strength to weight ratio (SWR) was compared to baseline model and the new materials

proposed for the roof (B-pillar) which is found to be more crashworthy.

Roof Master Section:

Bow roofs:

The bow roofs are given to improve the torsional stiffness and load bearing capacity of the roof structure. The number of bow roof present

is depending on the overall size of the roof.

Joining process

Mastics are introduced between the roof outer panel and the reinforcements for joining where ever the mastic are introduced there is

remarkable improvement of strength.

Spot welding is also introduced to join the reinforcements and the outer panel.

Sewing Surface to Ecracted Surface

The string team is provided the sold dump outer panel from that we are extracting the surface to model the necessary reinforcements

Like the Ditch area. Front Roof Rail, Bow Roof Rails and Rear Roof Rail.

Heat Distortion calculations:

W-[1.73 x 10^(-3) x L] + [1.85 x 10^(-8) (R^2)/t] + [ 1.10x10^(-3) xl) - 2.68

Schedule

Judgment Condition : OK< 2.7> 3.1

Where.

L = Roof Length in X-Direction[mm] (Roof dimension in O-Y

Related Courses

R- Roof curvature

R-2/RXRy1/RxRy

Rx - X curvature

Ry -Y curvature

t-Roof plate thickness [mm]

l-Bow Roof Span [mm]

S.No	Bow_Roof	Rx	Ry	R	t	l	L	R^2/t	W	Result
1.	Front to Bow1	5741.089	2456.579	3440.841	0.75	49.92	2040.328	15785849.0	1.196	OK
2.	Bow1 to Center	4794.736	6921.825	5665.198	0.75	49.92	2040.328	42792624.5	1.696	OK
3.	Center to Bow2	3764.577	11696.794	5695.934	0.75	49.98	2040.328	43258218.8	1.705	OK
4.	Bow2 to Rear	3079.510	15947.972	5162.211	0.75	49.98	2040.328	35531229.8	1.562	OK

Section modulus study of the Roof Rails:

The section modulus of the cross-sectional shape is of significant importance in the design of structures. It is a direct measure of the streng

of the structure

A structure that has a larger section modulus than another will be stronger and capable of supporting greater loads.

Section modulus (S) = 1/y

Where.

I = Moment of inertia in (mm)

y = Distance between the neutral axis and the extreme end of the object (mm)

Snow load criteria calculations:

Snow load criteria is useful to justify the bow roof rail position in snow fall regions. Due to snow fall snow will get collected on the top roof

which will tend to bend the roof. Bow roof will be at such position which will provide more strength to roof against bending.

Qr=[ly x t2] / [a x sx [(Rx+ Ry/2]2 x 10-8]

Note: The Qr value given over here is correct. There was a typo error in the formula given in the video.

Where

a = My x Lx2 x 10-12. My - Y(Ly-Y)

Judgment condition - Qr 23.1

250 SS5380

t = Roof plate thickness [mm]

Ly = Distance between the front and rear roof Rails on the Vehicle along with OY [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

ly - Geometrical moment of inertia of Roof BOW (Y cross-section )[mm 4]

Rx - Lateral direction curvature radius of roof panel Y cross-section on Roof BOW [mm]

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

BOW_Roof	Rx	Ry	Lx	Ly	Y	My	ɑ	t	s	Iy	Qr	Status
FR to Bow1	5741.089	2456.579	1155.12	2083.63	574.6	867088.6	0.1156	0.75	288.55	156.5	1.5708	NG
Bow1 to Center	4794.736	6921.825	1096.03	2083.63	540.1	833660.5	1.0014	0.75	269.21	757.8	4.6072	OK
Center to Bow2	3764.577	11696.794	1068.66	2083.63	573.3	865872.1	0.9888	0.75	292.23	757.8	2.4683	NG
Bow2 to Rear Roof	3079.510	15947.972	1056.01	2083.63	398.2	671138.2	0.7484	0.75	175.41	156.3	0.7385	NG

Hence the result of snow load criteria shows there is an improvement required for the bow roof rails placement, So we add Emboss to the Outer Panel Roof For better Strength for the Roof.

Part Pics:

Views Of Roof-

Central Roof Rail:

Rear Roof Rail:

Front Roof Rail:

Draft Analysis:

Bow_Roof & Center Roof-

Front_Roof-

Rear_Roof-

Conclusion-

1. Using all input data we have successfully designed Ditch area flanges, Front roof rail, Bow roof rails, Rear roof rail as per the requirement

2. As per heat distortion criteriawe come to know all bow roof positions are OK.

3. As per Snow load criteria we come to know there is improvement required.
4. All roof rails draft analysis are found OK.