Section Modulus calculation and optimization

Section Modulus:

Ratio of area moment of inertia in neutral axis to distance of outer most fibre from neutral axis. The more the section modulus, the more the strength of the section.

Moment of Inertia - Resistance offered by a body towards bending.

Bending moment is calculated directly from Section modulus. The section modulus can be calculated for a sketch in NX using Section Inertia Analysis.

Bending Moment = Z (Section modulus) * Bending stress

Bending Moment = [I (inertia) / Y (distance from neutral axis)] * Bending stress

Hence Bending moment is directly proportional to Section modulus, which is directly proportional to Moment of Inertia.

Objective: To prove that section modulus improves with the moment of Inertia when a change in sketch is done to improve the strength.

Section Modulus for my Initial hood design:

Moment of inertia = 9.04mm^4 (Max value as seen in the screenshot below)

Distance = 876.805/2 = 438.402 (screenshot below)

Section Modulus = Moment of Inertia/Distance from neutral axis = 9.04mm^4/438.402mm = 0.02062mm^3

Section Modulus of design with increased value:

A slight offset to the design was made as shown below. The inner panel was offset by 0.5mm.

Now Moment of Inertia of the section = 9.0587mm^4 (slight increase)

Distance remains the same

Section Modulus = Moment of Inertia/Distance from neutral axis = 9.0587mm^4/438.402mm = 0.02068mm^3 (a very slight increase)

Hence the section modulus of this section was increased with the offset that we made in the section.

Hence increase in the Moment of inertia results in increase in section modulus.