Section Modulus calculation and optimization

SECTION MODULUS OF AN HOOD

Objective: To find the section modulus of the hood and optimisation to improve the overall section modulus.

Section Modulus: Section modulus is a direct measure of strength of any sectional area of an object about an reference axis(neutral axis).

S = I/Y, Where

S = Section modulus (mm^3)

I = Moment of Inertia of the section about the bending axis. (mm^4)

Y = Distance between the neutral axis and extreme end of the object (mm)

Neutral axis: When beam is subjected to pure bending the top most fibres of the beam are subjected to maximum compression, while the bottom most fibres of the beams are subjected to maximum tension.

Material Data: Stainless steel AISI 302 – cold rolled

Where yield strength of stainless steel is 520MPa = 520 N/mm^2

Calculation:

CASE 1: Before Optimization

The Hood which was already created is imported and the section inertia analysis is done.

We have to make sure that the curve obtained is a single/closed curve.

MOI (max) = 8.510473886e+05 (mm^4)

MOI (min) = 8.709833186e+03 (mm^4)

As per the section modulus equation,

S = I/Y

I = MOI (min) value is considered

Y =488.4929 / 2

= 244.24645mm

Therefore, S = 8709.833186 mm^4/244.24645mm

S = 35.66 mm^3

CASE 2: After optimization

The hood inner panel’s curve is offset by 0.5 mm outwards and section inertia analysis is done same as case 1 for a closed curve.

MOI (max) =8.974311796e^05 mm^4

MOI (min) = 8.931556017e^03 mm^4

As per section modulus equation,

S = I / Y

I = MOI (min) value is considered

Y = 244.24645mm

Therefore, S = 8931.55601 mm^4 / 244.24645 mm

S = 36.56 mm^3

Conclusion:

Hence when comparing case 1 & case 2,

1. The section modulus value of case 2 is higher than the case 1

2. As we increase the section area, the moment of inertia & section modulus increases which means strength and load material also increase