Section Modulus calculation and optimization

AIM

To calculate and compare a section modulus value of hood oh car.

SECTION MODULUS

Section modulus (s) is a geometric property for a given cross-section used in the desine of beam of flexural members.

The section modulus of the cross-sectional shape is of significant importance in designing beam. A beam that has a longer section modulus than another will be stronger and capable of supporting greater loads.

It is known that the stress in a fiber is proportional to distace from the neutral axis. If y is the distance of the extreme fiber from neutral axis then. Here, S represents section modulus or modulus of section , S=I/Y.

S - Section modulus

I - The moment of inertia

Y - The distance between the neutral axis and the end of the object.

MOMENT OF INERTIA

Here we are considering the area moment of inertia also known as the second moment of inertia. it is used in a sectional mechanical application, usually involving a section of any structure. the shape of the object and the plane of the section will give us the 2d part it is called the section.

when the area of the section increases the moment of inertia also increases. so the final result which is the section modulus also increases.

so we could say section modulus is proportional to the moment of inertia.

OBJECTIVE

To find a section modulus of the hood, and optimizing the section modulus value using NX_cad.

SECTION MODULUS CALCULATION AT SECTION OF THE HOOD:

MOI (Max) = 4.859164874e+06[mm^4]

MOI (Min) = 1.473158303e+04[mm^4]Y

As per the section modulus equation,

S=I/Y

I = MOI (min) value is considered

Y = Total distance /2,Total distance

= 877.02mm/2

Y=438.51mm

Therefore, S = 14731.583mm^4/438.51mm

S = 33.594mm^3

DESIGN OPTIMIZATION BY INCREASING THE DEPTH OF THE INNER PANEL BY 0.5MM:

MOI (Max) = 6.757678726e+06[mm^4]

MOI (Min) = 2.217382028e+04[mm^4]Y

As per the section modulus equation,

S=I/Y

I = MOI (min) value is considered

Y = Total distance /2,Total distance

= 877.02mm/2

Y=438.51mm

Therefore, S = 22173.8203mm^4/438.51mm

S = 50.566mm^3

Final result: Thus the stiffness of the car hood has been increased by increasing its area moment of inertia.

Conclusion:
Section modulus is directly dependent on the area moment of inertia and the distance from the neutral axis. Hence, to improve the geometry of the carry more bending load, the section modulus can be improved by increasing the area MOI of a given section.
We can increase the section modulus just increasing the gap between the outer & inner panel.