Section Modulus calculation and optimization

Section modulus

Section modulus is defined as the ratio of second moment of area or area moment of inertia to the distance to the farthest fibre. This actually defines the structural strength of the section under bending.Greater the section modulus the greater is the strength of the component under bending.

s=I/y

where y is the distance to the farthest fibre

We can find the area moment of inertia for the section through the centre of the body.

In catia we have to first take the intersection through the centre of the hood.

This will give the following geometry.

Then we have to multiple extract the outer lines of both upper and lower panels.

Now we have to connect the end points together using a line as shown below.

Now we have to join all the lines together to make it a closed boundary.

Then fill the boundary as shown below.

Now we can find the area moment of inertia as shown below.

We have to select the below tool and select the area to find the moment of inertia.

We have to select the second option for face.

The moment of inertia can be found out from the image above.The M1 is the minimum moment of inertia and M2 is the maximum moment of inertia.

In this case we have to take the minimum moment of inertia.

so S=I/y

I=8.275 e-007 m4 =8.275 e5 mm4.

now we have to find the y value.

We can create two end points and can find the distance between the two points.

here y= 480.625/2=240.3125

so s=8.275e5/240.3125=3443.43 mm3.

Now we can increase the section modulus by offsetting the bottom line of the extract by a little below.

We have offsetted the bottom line by 1 mm and we have got the moment of inertia =9.097e-007m4=9.097e5

The section modulus will become 3785.48mm3.