Section Modulus calculation and optimization

Section Modulus

A Structure’s Bending Stress can be calculated with Section Modulus. It can also be said as it is the ratio of moment of inertia of a section and distance of neutral axis to end of section. This is used in designing beams or flexural members. Greater the value of section modulus greater will be the strength of the section.

Here are few different cross section and its respective equation

Types of section Modulus

• Elastic section modulus, S
• Plastic section modulus, Z

Elastic section modulus - Elastic section modulus is applicable up to yield point of the material. It is denoted by S.

Plastic section modulus - Plastic section modulus is used for materials where its acceptable range is till plastic behavior. It is denoted by Z.

I have designed a hood and done the section modulus calculation and optimization.

This is the value i got when i done with my original hood dimension

Zoom view.

So here is the value i got after increasing the cross section by 3 mm downwards.

Zoom view

To calculate the Section modulus we also need the length from its nominal axis. So here is the total end to end distance.

Calculation:

We have, Distance,y = 244.45715mm

For original component:

Imin = 1.619657114x105 mm4

Minimum section modulus = 1.619657114x105 / 244.45715

= 662.55 mm3

For Optimized component:

Imin = 1.822596626x105mm4

Minimum section modulus = 1.822596626x105 / 244.45715

= 745.56 mm3

So here we can see the increase in section modulus before and after optimization. That is the strength of the material is directly proportional to the moment of inertia. Hence the increase in cross sectional area increases the overall mass and also increases the strength. The strength of the component is also differs with material to material.