Section Modulus calculation and optimization

Objective

To explain briefly about section modulus and determine the section modulus of the designed hood section which was drafted in the previous challenges, and to optimize the section modulus of the section by making necessary changes in the section for better strength and rigidity.

Section Modulus

Section Modulus is the geometric property of the given cross-section of any shaft or beam structures. It is the direct measure of the strength of the shaft section or the beam section. Higher the section modulus of a structure, the more the resistive it becomes to bending.

The section modulus is defined as S = I / y, where I is the second moment of area (or area moment of inertia, not to be confused with moment of inertia) and y is the distance from the neutral axis to any given fiber. It is often reported using y = c, where c is the distance from the neutral axis to the most extreme fiber.

Unmodified sectional analysis

Here we can easily see the analysis results

Max Moment of inertia=5043039.590mm^4

Min Moment of inertia=16812.15953mm^4

As the section is mirrored and is uniform around the axis

Distance from the neutral axis=886.381/2=443.190mm

Now in this case we have to take the minimum moment of inertia into consideration because if we can increase the minimum moment of inertia of the section we can make the section more safer and more rigid in terms of strength..

so , section modulus

Section Modulus S =I\y

Smax=5043039.590\443.190

=11378.95mm^3

Smin=16812.15953/443.190

=37.93mm^3

Modified Sectional analysis by increasing the depth of the inner panel section by 1.5mm

Here we can easily see the analysis results

Max Moment of inertia=5034751.004mm^4

Min Moment of inertia=17536.3914mm^4

As the section is mirrored and is uniform around the axis

Distance from the neutral axis=886.381/2=443.190

Now in this case we have to take the minimum moment of inertia into consideration because if we can increase the minimum moment of inertia of the section we can make the section more safer and more rigid in terms of strength.

So section modulus=

Section Modulus S =I\y

Smax=5034751.004\443.190

=11360.25mm^3

Smin=17536.3914/443.190

=39.56mm^3

So by simply increasing the depth of the inner panel section by 1.5mm the difference in the section modulus changes drastically

=4.20699%difference between the modified and the unmodified section.

Report Prepared By

Rishabh Soni