Section Modulus calculation and optimization

Aim :

The aim of the project is to Calculate the section modulus of the designed hood and to Come up with the new section that has improved section modulus by optimising the previously designed hood.

Introduction :

Section modulus is a geometric property for a given cross-section used in the design of beams or flexural members. Other geometric properties used in design include area for tension and shear, radius of gyration for compression, and moment of inertia and polar moment of inertia for stiffness.

There are two types of section modulus :

• Elastic section modulus
• Plastic section modulus

The Elastic Section Modulus is defined as,
S = I/y
Where,
S: is the Section Modulus
I: is the second moment of area(or area moment of inertia, not to be confused with the moment of inertia)
y: is the distance from the neutral axis to any given fiber. It is often reported using y = c, where c is the distance from the neutral axis to the most extreme fiber.

Section Modulus Calculation for Initial hood design :

From the above analysis, following minimum and maximum moment of inertia are obtained

Imax = 4.740445379 mm^4
Imin= 1.347995545 mm^4
y = 440 mm

For Maximum MOISmax= I / y = 4.740445379 / 440 = 10,77.37 mm^3

For Minimum MOI,
Smin = I / y = 1.347995545 / 440 = 30.63mm^3

Section Modulus Calculation for optimised hood :

The hood inner panel width was increased to 1.5 mm to downwards than the original one.

From the above analysis, following minimum and maximum moment of inertia are obtained

Imax = 4.725967619 mm^4
Imin= 1.43422915 mm^4
y = 440 mm

For Maximum MOISmax= I / y = 4.725967619/ 440 = 10,74.08 mm^3

For Minimum MOI,
Smin = I / y = 1.43422915 / 440 = 32.59mm^3

conclusion :

Thus the section modulus of the Front Hood of a car was calculated and compared with the optimized hood and found the better result. Hence I’m concluding that when the sectional area of the hood increases the stiffness and resistance of the hood strength will also be increased.
From the result, we can conclude and say that off-setting the cross-section of the inner panel 1.5 mm downward(Optimized) would give a better section modulus and this would help in increasing the strength of the hood.