Section Modulus calculation and optimization
Section modulus
Objective:
To find the section modulus of the designed hood assembly in Siemens NX.
Introduction:
Section modulus is a geometric property of a cross section. It is a direct measure of the strength of a cross section. Higher the section modulus, better the resistance of a cross section to bending.
The elastic section modulus is defined as S = I / y, where I is the moment of inertia and y is the distance from the neutral axis to the extreme point of the cross section.
Description:
In the field of engineering design, section modulus plays an important role as it helps determine the feasibility of a structure and make changes as required to obtain the desired output. To determine the section modulus various features are provided in different softwares.
To find the section modulus of our hood design in NX cad we use the section inertia analysis. This feature provides the principal moment of inertia, centre of gravity, length and area of the section.
Section modulus calculation:
For the calculation, we use the hood section along y axis. Using the sketch tool we create a sketch of the cross section which can be used to the section analysis. From the section inertia analysis tool we get the following values:
As shown above, the value of moment of inertia is 2.889e+3 mm^4.
Using the formula for section modulus S = I/y,
Where I is the moment of inertia,
Y is the maximum distance of cross section from the neutral axis.
For the cross section of the designed hood, y = 12mm.
Using the values, we get section modulus S as,
S = 240.74 mm^3
To increase the value of the section modulus, certain changes can be made to the cross section itself.
In order to get a better result, the cross section must be made more resilient to bending. That means the regions with flat or plain geometry should be reduced and more emboss definitions must be added.
After adding an appropriate amount of geometry to the section, following results were obtained:
Moment of inertia = 3.5625e+03 mm^4.
Distance Y = 12mm
Section modulus S = 297 mm^3.
Conclusion:
After modifying the cross section of the hood design, the section modulus was increased by 23%.