Section Modulus calculation and optimization

SECTION MODULUS AND CALCULATION

INTRODUCTION:

The section modulus of the cross-sectional shape is of significant importance in designing beams. It is a direct measure of the strength of the beam. A beam that has a larger section modulus than another will be stronger and capable of supporting greater loads.

OBJECTIVE:

The objective is here to calculate the section modulus of hood that we have designed and how to optimize it more.

DESCRIPTION:

The elastic section modulus is defined as S = I / y, where I is the second moment of area (or area moment of inertia, not to be confused with moment of inertia) and y is the distance from the neutral axis to any given fibre.

So here we are going to calculate the section modulus by using NXCAD and the feature which we are going to use it is called as the Section Inertia Analysis. Which will give us the moment of inertia of the section we wanted so to find the moment of inertia first we are going to make the section and we are going to include hood upper panel outer layer and hood inner panel lower layer and we are going to make it a closed sketch and join the part by using line and studio line.

This is a intersection curve of the hood outer and inner panel on which we are going to calculate the sectional modulus.

So for calculating the sectional modulus we need to have moment of inertia and the neutral axis distance from the extreme point.

Neutral axis distance

So as you can see we have calculated the distance of the neutral axis from the extreme point of it.

And we did that on the X-Y plane and the value we got is 876.2mm.

And we are going to take the half value of it so we will get the neutral axis value which is 876.2/2=438.1mm

The neutral axis doesn’t change so this value is going to remain constant all the time.

Now we have to calculate the moment of inertia.

For that we are going to use the section inertia analysis in NXCAD which will give us the inertia of the section we want.

So as you can see we got the moment of inertia values so now we are going to take the minimum moment of inertia because the minimum moment of inertia will tell us that this the breaking point where the hood is going to start undergo loading.

Minimum moment of inertia = 1.345539891e+04mm^4

So as per formula of sectional modulus (Z) =I/Y,

Z = (1.345539891*10^4)/438.1 = 30.7130 mm^3

So now we have calculated the sectional modulus now we will try to optimize the design so for that we are going to offset the geometry and will see what changes we can expect.

So for the first optimization we are going to offset the hood inner panel curve by 1mm downwards.

Moment of inertia at 1 mm downward offset

So now we are going to calculate the sectional modulus for 1mm downward offset we got minimum moment of inertia of 1.972543527e+04 mm^4

S _min = 1.972543527*10^4/438.1 = 45.0252 mm^3

And for the second optimization we are going to offset the hood inner panel line upwards by 0.5 mm

Moment of inertia at 0.5mm upwards direction

Minimum moment of inertia is 1.925475177e+04 mm^4

S _min = 1.925475177*10^4/438.1 = 43.9505 mm^3

And we are going with the case 2 as we can see we get more section modulus value more the value more the bearing capacity of the hood will become.

CONCLUSION:

As we have successfully done the sectional modulus, calculation and optimizing of the hood in NXCAD.