Section Modulus calculation and optimization

Section Modulus calculation and optimization

Objective

To calculate the section modulus of the previously designed hood for analyzing its strength and also optimizing the design to improve section modulus compared to the previous one.

Section modulus

Section modulus is a direct measure of any sectional area of an object about an reference axis. Strength is nothing but, capable of supporting greater loads, so higher strength it has a high capable of supporting greater loads.

Changing the position can show the difference in bending which is because of the centroid distance from extreme fiber end. Section modulus is defined as the ratio of total mount resisted by the section to the stress in the extreme fiber which is equal to yield stress.

Section modulus,

S = I/y

Where,

S = Section Modulus.

I = Moment of Inertia.

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

Moment of inertia is a measure of the resistance of a body to angular acceleration about a given axis that equal to the sum of the products of each element of mass in the body and the square of the element distance from the axis.

Section modulus of hood

Here, we use section of the hood. It is difficult to calculate manually because of its complecated geomentry. so, here NX software will calculate max and min moment of inertia. By this data we able to find section modulus using the above formula.

Maximum moment of inertia- 8.25 X 10^5 mm^4

Minimum moment of inertia- 4.97 X 10^3 mm^4

Distance between the neutral axis and the extreme end of the object, Y = Total distance / 2

y = 487.4/2

=243.7mm

Section modulus , S = I/Y

=(4.97 X 10^3)/243.7

Hence, S=20.39 mm^3

Hood Design Optimization

I have calculated the section modulus of each section which i optimize to increase the value of section modulus. I extending the lowermost edge of inner panel & then calculated the moment of inertia for each extension.

The lower most edge of inner panel extended to 0.5mm.

The lower most edge of inner panel extended to 0.7mm.

The lower most edge of inner panel extended to 0.9mm.

Tabulation:

S.No.	Extension in mm	Min moment of inertia (mm^4)	value of "Y" (mm)	Section modulus "S" (mm^3)
1	0	4.97 X 10^3	243.7	20.39
2	0.5	5.14 X 10^3	243.7	21.09
3	0.7	5.21 X 10^3	243.7	21.38
4	0.9	5.28 X 10^3	243.7	21.67

As Moment of inertia is directly proportional to the Section modulus, thus the value of section modulus is increasing with the value of moment of inertia.

Conclusion

The Section modulus of my hood section is calculated and by extending lower most edge of the inner panel in the hood section we able to increase section modulus. So, the strength also increases. Here, we extended lower most edge of the inner panel maximum of 0.9mm and the section modulus increases from 20.39mm^3 to 21.67mm^3.