Section Modulus calculation and optimization

SECTION MODULUS CALCULATION AND OPTIMISATION

OBJECTIVE

To improve the section modulus of the hood by making necessary changes using NX CAD software.

SECTION MODULUS

Section modulus is a geometric property for a given cross-section used in the design of beams or flexural members. Other geometric properties used in design include area for tension and shear, radius of gyration for compression, and moment of inertia and polar moment of inertia for stiffness.

It is indicated as

S = I/Y mm3

S = Section modulus,

I = Moment of inertia,

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

Here section modulus is directly proportional to the moment of inertia, therefore if moment of inertia increases then section modulus also increases. MOI depends on the cross-sectional area of the object.

An asymmetric section has two value for top and bottom of centroid, the maximum section modulus (S_max) and minimum section Modulus (S_min) important of Section Modulus. Section modulus is vital factor for designing beam and flexural members. Higher the section Modulus, higher will be the resistance to bending.

The S_min is defined as the point at which the object starts to deform and the one which starts to rupture and break into two objects is known as maximum section modulus.

CALCULATION OF SECTION MODULUS

• Here we are calculating the section inertia of present hood.

here from the above figure

MOI(min) = 1.3824*10^4 mm^4

MOI(max) = 4.7559*10^6 mm^4

Y = 881/2

= 440.5 mm

Hence section modulus S = I/Y

= 1.3824*10^4 /440.5 here minimum moment of inertia is considered as (I) while calculating the section modulus.

= 31.3825 mm^3

SECTION INERTIA OF HOOD AFTER OPTIMISATION

• In this case we have extended the lower edge of inner panel to increase the overall crossection of the hood, so that we can improve the section modulus of the hood.
• Here i made the changes by extending the lower edge by 0.5mm distance outwards.

here we can see the section inertia values after optimisation

MOI(min) = 1.4010*10^4 mm^4

MOI(max) = 4.7472*10^6 mm^6

Y = 440.5 mm

therefore the section modulus is S = I/Y

= 1.4010*10^4 /440.5

= 31.8047 mm^3

TABLE.. OPTIMISATION CHART FOR HOOD SECTION

S.no	Extension	Maximum moment of inertia (MOI)max (mm4)	Minimum moment of inertia (MOI)min (mm4)	Distance (Y) (mm)	Section modulus (S) (mm3)
01	00	4.7559*10^6	1.3824*10^4	440.5	31.3825
02	0.5 mm	4.7472*10^6	1.4010*10^4	440.5	31.8047

CONCLUSION

Hence we can conclude that by increasing the cross-section area of hood, we can improve the section modulus of the hood. In this report we have increased the section modulus value to 31.8047 mm^3 by changing the offset distance of inner panel edge by 0.5mm.