Section Modulus calculation and optimization

Aim

To calculate the section modulus of the previously designed hood for analysing its strength and do optimization as per requirement to have more resistance towards bending.

Literature

Section modulus is defined as the ratio of the moment resisted by the section to the stress in the extreme fibre. There are two types of section moduli, the elastic section modulus and the plastic section modulus.

It gives an idea about the work in bending is being done by the extreme fibres of the beam.If the section modulus increases the moment of resistance increases and thereby its load bearing capacity.

Calculation of Section Modulus:

The section modulus is calculated using the given below formula.

S=I/Y where,

S = Section Modulus

I = Moment of Inertia

y = distance between the neutral axis and the extreme end of the object

Observation & Calculations

Now, for calculating the section modulus of hood from last challenge in NXCAD, the procedure is as follows.

• The Intersection of the HOOD design was taken and made into a closed figure using sketch tools.
• Now, using the Section Inertia Analysis tool from Analysis window, section modulus of the hood is calculated.

The Figure 1 shows the Moment of Inertia of the hood section of the last challenge.

Figure 1 Moment of Inertia of the Hood section

Figure 2 :Maximum length of the Hood section

With reference to the above Figures 1 & 2 ,

I = moment of inertia(min.) = 2.0905*10^5 mm^4

y = distance from neutral axis to extreme end = 487.41/2=243.70 mm

Therefore, S = 8.58 mm^3

In order to optimize the section modulus, the lowermost edge of inner panel is extended by 2mm and calculated the moment of inertia for the same. (Figure 3)

Figure 3: Optimized Moment of Inertia

S=2.3180×10^5/243.70= 9.51 mm^3

Conclusion

Moment of inertia is directly proportional to the section modulus. Therefore, by changing the design parameters, section modulus can be changed and thereby, can change the value of moment of inertia and thereby can increase the strength of the material.