Objective

To calculate the Section Modulus cation for the Hood section and optimize the section of hood to improve the Section modulus.

Section Modulus:

 A "section modulus is the value of the "moment of inertia of area" related to the neutral axis of the cross-section of a beam multiplied by the distance from the neutral axis to the outer surface". Therefore, the relationship between the section modulus Z and the moment of inertia of area I is as expressed by the following equation.

It is defined as the ratio of the moment resisted by the section to the stress in the extreme fibre.It gives an idea that most of the work in bending is being done by the extreme fibres of the beam, ie the top and bottom fibres of the section.

The distance of the fibres from top to bottom is therefore built into the calculation.If the section modulus increases the moment of resistance increases & hence its load bearing capacity.A section that has longer section modulus than another will be stronger and capable of supporting greater loads.

Calculation of Section Modulus:-

• In this challenge I have taken my designed hood, for calculation.
• To calculate the moment of inertia, I have taken the hood section along the length of hood & find the inertia using 'section inertia analysis' tool in NX CAD.
• Then, the section modulus is calculated using the given formula i.e. 

 S = I/y

Where,

S = Section Modulus

I = Moment of Inertia

y = distance between the neutral axis and the extreme end of the object 

^“Y^” for section of Hood Distance :-

 1.Fig. - Moment of Inertia of hood section

Section inetria Analysis report for condition 1.Fig

From the above analysis, following minimum and maximum moment of the inertia are obtained :-

I_max = 0.5759 x 10^5 mm⁴

I_min = 2.6348 x 10^3 mm⁴

^“Y^” for section of Hood 2 = 274.866 mm

The Section modulus is calculated B

 S = I/y

S_max =  209.5202 mm³

S_min = 9.5857 mm³

2. Fig. - Moment of Inertia of hood section

Section Interia Analysis Report, after modification -2. Fig.

From the above analysis, following minimum and maximum moment of the inertia are obtained :-

I_max = 8.08764 x 10^5 mm⁴

I_min = 2.3831 x 10^3 mm⁴

^“Y^” for section of Hood 1 = 274.866 mm

The Section modulus is calculated 

S = I/y

S_max = 2942.3791 mm³

S_min = 8.6773 mm³

3. Fig. -Moment of Inertia of hood section

Section Interia Analysis Report, after modification 3. Fig

From the above analysis, following minimum and maximum moment of the inertia are obtained :-

I_max = 8.5849 x 10^5 mm⁴

I_min = 2.7347 x 10^3 mm⁴

^“Y^” for section of Hood 3 = 274.866 mm

The Section modulus is calculated 

S = I/y

S_max = 3123.3037  mm³

S_min = 9.9491  mm³

4. Fig. -Moment of Inertia of hood section

Section Interia Analysis Report, after modification-4. Fig.

From the above analysis, following minimum and maximum moment of the inertia are obtained :-

I_max = 8.67721 x 10^5 mm⁴

I_min = 6.7554 x 10^3 mm⁴

^“Y^” for section of Hood 1 = 274.866 mm

The Section modulus is calculated 

S = I/y

S_max = 3155.0282 mm³

S_min = 24.5770  mm³

^{TABLE: OPTIMIZATION CHART OF HOOD SECTION ON EXTENDING THE INNER PANEL'S EDGE} 

CONCLUSION

When compared section values in case 1 and case 4, we can see the how much i improved the model ,i gate the section modulus value are increased.

Thus Section Modulus carried out on BIW Structures provide better undertanding of the Load bearing capcity , bending resitance and forces and stress exerted in the beam and has wider significance of reducing the weight and cost for Automotive OEM's.