Section Modulus calculation and optimization

SECTION MODULUS OF THE CROSS-SECTION OF THE HOOD

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

• Types of section modulus
• elastic section modulus
• plastic section modulus

• Formulas for calculating section modulus are

1. For Elastic Section modulus

S = I/y

S - Elastic modulus

I - Area moment of inertia

Y - Distance between the center axis and the endpoint of the component.

2. For Plastic Section modulus

Zp = AcYc + AtYt

Z – Plastic modulus.

Ac or At – Areas of cross-sections.

Yc or Yt – Distance from the local centroids of the two areas.

• For calculating Section modulus for my hood design, I will be using the Elastic section modulus formulae because it is the general formula for all section modulus calculations.

Taking sketch from the hood

2d Section of the Hood

Calculating Section Modulus of the sketch by using ' Section Inertia Modulus' command.

Here I got a Maximum and Minimum area moment of inertia which are,

I max = 8.168768567 x 10⁵mm⁴

I min = 3.954969670 x 10³ mm⁴

Y = 486.6/2

= 243.3 mm

By obtaining all the values, now we can calculate Section modulus of the hood.

S (max) = 8.168768567 x 10⁵mm⁴ / 243.3 mm

= 3.357.488 x 10³ mm³

S (min) = 3.954969670 x 10³ mm⁴/ 243.3 mm

= 16.2555 mm³

• Optimization of the 2D sketch for better results

by offsetting the inner panel's outer line to about 0.5 mm outwards, let us see if there is an increase in inertia resistance. Basically the idea is to increase the gap between the inner and outer panel distance.

Now performing the 'section inertia modulus' command

Here I got a Maximum and Minimum area moment of inertia which are,

I max = 8.145332888 x 10⁵mm⁴

I min = 4.131859934 x 10³ mm⁴

Y = 486.7/2

= 243.3 mm

By obtaining all the values, now we can calculate Section modulus of the hood.

S (max) = 8.145332888 x 10⁵mm⁴ / 243.3 mm

= 3.347855 x 10³ mm³

S (min) = 4.131859934 x 10³ mm⁴/ 243.3 mm

= 17.08256 mm³

• Conclusion

By doing the calculation I have observed that there is a better-withstanding capability to the new optimized hood by increasing the distance of the inner panel by 0.5 mm to the outer panel. And the optimized hood is better than the original one. By this process, we can gradually outcome the specifications taken from the parent component.

So we can clearly see that if we increase the gap between the inner and outer panel, the Modulus of inertia increases comparatively to the distance. That means modulus increases with the increase in section area. so I conclude that the section modulus is totally dependent on the area moment of inertia of the section.

THANK YOU