Section Modulus calculation and optimization

Aim

To calculate section modulus of hood and optimize the design to have improved section modulus.

Section modulus:-

Section modulus is a direct measure of a strength of any cross sectional area of an object about an reference axis.

The formula of section modulus is given by,

S=I / Y

Where,
I = Moment of inertia (mm^4)
Y = Distance between neutral axes and outermost fiber (mm)

Steps to calculate section modulus:-

• Step 1:- Find location of centroid of given cross section.
• Step 2:- Find moment of inertia about neutral axis (INAINA)
• Step 3:- Find YmaxYmax from neutral axis.
• Step 4:- Find elastic section modulus using the formula provided above.

Case 1: Original cross section of the hood.

Using the Intersection Curve command, the cross section of the hood is obtained.

Now, to obtain the value of 'y', the distance from the neutral axis (construction line) and the extreme edge of the hood is measured.

In this case, the distance is approximated to 440 mm.

The calculation for finding the area is made using the Section Inertia Analysis within NX CAD. The result of the software is given below.

From the data above:

`Imax = 94089695 mm^4 & Imin = 288960 mm^4`

`Using the formula S = I/y, S max = 94089695/440 = 213840.2 mm^3 S min = 288960/440 = 656.73 mm^3`

Case 2: Modified hood cross section.

The original cross section curve is modified by offsetting the lower half of the cross section loop 1mm downwards. This simulates the increase of the depth of emboss within the drawing operation by 1mm.

Running the command on the modified cross section, the results obtained are as follows:

Calculating the maximum and minimum section modulus:

`Smax = 93246986/440 = 211925 mm^3 Smin = 294250/440 = 668.75 mm^3`

Result :

1) The increase in Minimum Section Modulus is 1.83%.

2) Section Modulus increases with increase in cross section area.

3) Section Modulus can be increased by incresing the gap between the outer and inner panels.