Section Modulus calculation and optimization
SECTION MODULAS :
Section modulus is the direct measure of the strength of the steel. Bending a steel section that has a larger section modulus than another will be stronger and harder to bend. Section modulus is a geometric property for a given cross-section used in the design of flexural members.
To define section modulus, it may be defined as the ratio of total moment resisted by the section to the stress in the extreme fibre which is equal to yield stress.
In elastic bending, the stress distribution in the beam is as follows:
As per theory of pure bending :
Where M= bending moment
I = moment of inertia of the section about the bending axis.
Sigma=fibre stress at a distance ‘y’ from the centroidal/neutral axis.
R = radius of curvature of the bent beam.
E = Young’s Modulus of the material of the beam.
If y is replaced by c, the distance to remotest element, from the neutral axis or centroidal axis, then
Where, Z= section modulus and is given by
This Z is the elastic section modulus used for elastic design for beam. It is usually denoted by Ze.
CASE 1
To Check the section modulas of the Hood i have created the intersection and extracted the outer layer of the Hood outer panel and inner panel. Connected all curves in sketch.
Using Section inertia modulas command moment of interia is finded out.
Here,
Monent of inertia , I = 6.992310438*10^3
Distance between neutral axis and extreme end of fibre, Y = 903.582/2 = 451.791
Section Modulas , S = I/Y
= 6.992310438*10^3/451.791
= 15.47 mm3
CASE 2
To create new section to increase the value of section modulas outer line of inner section of inner panel is offset to 0.5 mm in outside direction.
Here,
Moment of inerta, I = 7.203730724*10^3
Distance between neutral axis and extreme of fibre, y = 903.582/2 = 451.791
Section Modulas , S = I/Y
= 7.203730724*10^3/451.79
= 15.94 mm3
Conclusion :
From above two cases we have two section modulas values, In that section modulas value of improved section is greater than first section.