Section Modulus calculation and optimization

Section Modulus calculation and optimization of car hood

Introduction to section modulus:

It is defined as the ratio of moment of inertia of a section about its centroidal axis and to the distance of extreme layer from neutral axis.

Mathematically, S=I/y

Where,

S=Section modulus (Unit mm3)

I=Moment of inertia (Unit mm4)

y=The distance of extreme layer from neutral axis (Unit mm)

Moment of inertia: The product of the initial moment of area and the centroidal distance of the area from a given axis is the moment of inertia.

Fig(a)

Fig(b)

The figures above indicate that the beams in figures (a) and (b) have the same area and even the same shape. Beam in figure (b) is stronger then beam in figure (a) because it has a higher moment of inertia. The moment of inertia can be altered via oriantation.There is more material from the axis to the specified direction in the oriantaion of beam figure (b) to resist the load, resulting in less bend and improved strength.

Aim: Calculate the section modulus of the hood and optimize the section modulus.

Case 1:

The section analysis was done by using the intersection curve of a hood.

Y Distance: 880.5mm

Moment of Inertia(Max) = 9.03372x10^7(mm^4)

Moment of Inertia(Mim) = 2.60994x10^5(mm^4)

Y = 880.5/2 = 440.225 mm

S = I/y

S = 2.60994x10^5/440.2 = 59.2 mm^3

Case 2 Optimization hood design:

Changes made:

1. Offsetting the inner panel to 0.5mm changed the spacing between the inner and outside panels.
2. The new embosses have been added.

Moment of Inertia(Max) = 9.02556x10^7(mm^4)

Moment of Inertia(Mim) = 2.70837x10^5(mm^4)

Y = 880.5/2 = 440.225 mm

S = I/y

S = 2.70837x10^5/440.2 = 61.5 mm^3

Conclusion:

Section Modulus of Case 2 > Section Modulus of Case 1 so the difference in moment of inertia can be observed in the above case study, and the change in section modulus can be noticed by changing the dimension between the inner and outer panel by 0.5mm and adding embosses to the design.