• Elastic section modulus
• Plastic section modulus

Elastic section modulus:

The elastic section modulus is applicable up to the yield point of material.It is used in most engineering applications.

Elastic section modulus is the ratio of moment of inertia about a neutral axis(In.a) and the maximum distance between the neutral axis and outermost fiber of beam (Ymax).

Elastic section modulus equation:-

The formula of elastic section modulus is given by,

S=I/Y

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

Plastic section modulus:

The plastic section modulus is generally used for material in which plastic behavior is observed.

The plastic section modulus is necessary to calculate plastic moment capacity of the section.

The plastic section modulus is the addition of moment of area of area under compression about PNA (plastic neutral axis) and the moment of area of area under tensile stress.

Plastic section modulus equation:–

For the above cross-section, the plastic section modulus is given by,

Zp=∑AcYc+∑AtYt

Where,
Ac = Area of cross-section under compression.
At = Area of cross-section under tension.
Yc = Distance from PNA to CG of the areas under compression.
Yt = Distance from PND to CG of areas under tension.

FOR HOOD DESIGN THE GIVEN SECTION MODULUS FORMULA IS:

S = I/y

Where,

S = Section Modulus

I = Moment of Inertia

y = distance between the neutral axis and the extreme end of the object

SECTION 1:

CALCULATION OF SECTION 1:

Y=447/2 ,Imax=5.1531e^06 mm^4 ,Imin=1.5706e^04 mm^4

=223.5mm

Smax=Imax/Y

=5.1531e^06/223.5

=0.023e^06 mm^3.

Smin=1.5706e^04/223.5

=0.007e^04 mm^3.

SECTION 2:

CALCULATION OF SECTION 2:

Y=447/2 ,Imax=6.8685e^06 mm^4 ,Imin=2.1394e^04 mm^4

=223.5mm

Smax=Imax/Y

=6.8685e^06/223.5

=0.030e^06 mm^3.

Smin=2.1394e^04/223.5

=0.009e^04 mm^3.

CONCLUSION:

• By comparing the values we can say that section modulus of the optimized hood is increased.
• If we increase the gap between the inner and outer panel of hood eventually section length will increase thus MOI will increase.
• MOI increases with the increase of section length.
• MOI increases with the increase of section area.