Section Modulus calculation and optimization

                                             SECTION MODULUS CALCULATION AND OPTIMIZATION

AIM :

To calculate the section modulus of the designed hood and try out another way to increase the section modulus of the hood.

THEORY :

Section modulus is the total moment resisted by the section to the stress in extreme fibre. It gives an idea about how much load the structure can take. A high section modulus means better load bearing capacity.

The formula for S is :

S  = I/Y

Where S is the section modulus, I is the moment of inertia, and Y is the distance between neutral axis and extreme fibre.

SCENARIO 1 :

 This is the designed hood. Make a plane (front plane) on the surface. This is the plane with which the section is to be done.

 

Using intersection command, intersect the hood with this newly made plane.

Extract the outer curve of the outer panel and the inner curve of the inner panel. These are the two curves to be used for finding the section modulus.

 

Extracting the inner curves of the inner panel intersection.

Hiding all the unwanted curves

Connect the gaps with the lines

Join the ends.

Next fill the closed sketch using "FILL" command.

Measure the moment of inertia using "Measuring Inertia" tool.

M1 and M2 are the inertia values. Convert those values to mm^4. For calculating section modulus, we take smaller value of M (which is M1 here)

To get the Y value we need to take the overall length of the section. For that, we can make a sketch and create 2 lines/axes and measure the distance between them. Half of the distance will be the value of Y.

Making an axis from the created point (similarly on the other side too)

The distance was found to be 884.146 mm

Finally calculating the section modulus value (S)

M1 = 2.638x10^(-6)m^(4)

     = 2.638x10^(-6)x10^(12)mm^(4)

     = 2.638x10^(16)mm^(4)

M2 = 9.846x10^(8)mm^(4)

we need to take the lowest value of M1. The lowest value of M determines the starting point of breakage. here M1

so, M1 will be used.

Y is the distance between the neutral axis and extreme end of the object. The overall length was found to be 884.146 mm .

Taking half of this value will give us Y value.

Y = 884.146 mm / 2

   = 442.073 mm

I/Y = 2.638x10^(6)mm^(4) / 442.073

    so,  S1 = 5967.34 mm^(3)

SECANRIO 2 :

We have to find a way to increase the section modulus of the hood by changing the section.

Make a parallel curve of the inner panel curve downwards for 0.5 mm. Then try measuring M1 again.

 

In this secnario, M1 has slightly increased to 2.742x10^6 mm^4 and M2 becomes 0.001x10^12 mm^4

Doing the calculation

M1 = 2.742x10^(-6)m^(4)

     = 2.742x10^(-6)mm^(4)

Therefore, M1=2.742x10^(6)mm^(4)

M2 = 0.001x10^(12)mm^(4)

Here M1

Y value remains the same.

Hence, 

S2 = (2.742x10^(6)mm^(4)) / 442.0.73 mm

therefore, S2 = 6202.595 mm^3

From this we can see that S1 = 5967.34 and S2 = 6202.595

Hence we have succesfully improved the section modulus by offsetting the inner panel curve downwards/inwards to 0.5mm