Section Modulus calculation and optimization

OBJECTIVE : The main aim is to analyse the strength of the hood and try to improve it by doing necessary changes to it.

SECTION MODULUS : Section modulus is a geometric property for a given cross-section used in the design of flexural members. Section modulus is the direct measure of the strength of the steel. Bending a steel section that has a larger section modulus than another will be stronger and harder to bend. Higher the section modulus of a structure, the more the resistive it becomes to bending.

CALCULATION :

The calculation of section modulus is done using S=I/y formula, where

S = Section Modulus

I = Moment of Inertia

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

We will see 3 iterations of calculating the section modulus of car hood.

• According to the Master section : By doing the section analysis in this case, we get following result

Here,

Imax = 4.533652*10^6 mm^4

Imin = 1.330963*10^6 mm^4

y = 432.75 mm

So,

Smax = Imax/y = 10476.37 mm^3

Smin = Imin/y = 3075.59 mm^3

• By increasing gap between panels : In this, the gap between the outer and inner panel in increased by 2mm and that increases the sectional area. The results are as follows

Here,

Imax = 4.551054*10^6 mm^4

Imin = 1.462353*10^6 mm^4

y = 432.75 mm

So,

Smax = Imax/y = 10516.58 mm^3

Smin = Imin/y = 3379.20 mm^3

• By increasing depth in drawing : In this, the drawing depth of the inner section of the panel is increased from 25mm to 28mm. By doing that, the sectional area of the hood increases a little more.

Here,

Imax = 4.574273*10^6 mm^4

Imin = 1.641730*10^6 mm^4

y = 432.75 mm

So,

Smax = Imax/y = 10570.24 mm^3

Smin = Imin/y = 3793.71 mm^3

Conclusion : By comparing the values, we can say that the section modulus of the third iteration is increased almost by 1%. So, basically if we increase the cross-section of the hood by any means, the section modulus will directly increase and that means the strength also increases or the resistance towards bending increases. Just have to make sure, that we do not make the gap more and make it fully hollow as the panels needs to be connected by mastics.