Section Modulus calculation and optimization

Aim :

To find section modulus of the designed car hood and to optimise section modulus to have improved overall section modulus.

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Objective :�

To use section fron hood design and calculate section modulus using given formula S=I/Y for frontal impact.

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Section Modulus :�

Section modulus ia a geometric property for a given cross-section used in the design of beams or flexural members.�

It is a direct measure of strength of any cross sectional area of an object about a reference axis.�

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Formula :

S=I/Y�

where,

S = Section Modulus (mm^3)

I= Area moment of inertia (mm^4)

Y= Distance between neutral axis and outermost fiber (mm)

Moment of inertia is nothing but offering resistance against the moment, bending or twisting. Higher the moment of inertia higher will be its resistance to deformation or bending.�

Thus I is resistance offered by cross section towards bending. At�Y there is neither compression nor tension.

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Steps to calculate section modulus:-

Step 1:- Find location of centriod of cross section.

Step 2:- Find moment of inertia about neutral axis.

Step 3:- Find Y ie half of minimum distance between outermost fibers.

Step 4:- Find Section Modulus by given formula for S.

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Moment of inertia(MOI) is calculated by NX-CAD software.

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MOI before optimisation:

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Value of Y :

Y = Min dist between outermost fibres / 2

Y = 876.8284 / 2 = 438.4142 mm

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Section modulus before optimisation :

S1 = Imin/Y = 1.5695*10^4 / 438.4142

S1 = 35.7994 mm^3

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MOI after optimisation:

• In order to increase section modulus, cross section had to be increased.

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Section modulus after optimisation :

S2 = Imin/Y�= 1.5902*10^4 / 438.4142�

S2 = 36.2716 mm^3

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Conclusion :

Imin2>Imin1 and S2 > S1

Strength of material is directly proportional to the moment of inertia, thus increasing the sectional area increases strength of component. Thus, larger the Section modulus lesser the bending will be obeserved.

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