Section Modulus calculation and optimization

Aim:

Using the Section from the Hood design and calculate the section modulus and compare it with a new section with higher sectional modulus for optimization.

Sectional Modulus:

Section modulus is a geometric property for a given cross-section used in the design of beams or flexural members.

• Sectional modulus is a direct measure of strength of cross-section of a object about an reference axis
• It gives us an idea about how much load the given structure can take.
• Section modulus is directly proportional to moment of resistance/ inertia. Thereby, if inertia/section modulus increases , its strength with load bearing capacity increases

It is denoted by below formula

S=I/Y

where , S= 'Sectional Modulus'

I = 'Moment of Inertia'

Y ='distance between the neutral axis and the extreme end of the object'

• Moment of inertia is nothing but offering resistance against of moment, bending or twisting, i.e if we applied any external load on the body, how much resistance its offering to tend to deform.
• So, higher the value of moment of inertia , have higher resistance to deform under certain load, hence we can say that moment of inertia directly proportional to the strength of the material , and strength of the material can be calculated with the help of section modulus.
• If we vary the neutral axis towards positive or negative side the overall strength of the body will decrease , because when nuetral axis line lies on the middle of the section only have higher strength at particular point, so, here 'Y' value was inversely proportional to section modulus.

Using NX 'Section Inertia Analysis' of the hood section

(Section of the hood panel)

(Sectional inertia Analysis -1)

(length from neutral axis to end point)

Considering minimum moment of inertia

I_MIN= 1.531x10⁴mm⁴

Y = 438.26mm

S = I/Y = 1.531x10⁴mm⁴ /438.26 mm

= 34.93 mm^3 (Minimum Section modulus)

Creating a new modified section with increased cross sectional area with additional embosses

(new section with additional embosses of the Hood)

(Sectional inertia Analysis -2)

Here we infer that the MOI is larger than previous hood section.

Considering minimum moment of inertia

I_MIN= 2.316x10⁴mm⁴

Y = 438.26mm (same length)

S = I/Y = 2.316x10⁴mm⁴ /438.26 mm

= 52.8mm^3 (Minimum Section modulus - more sectional area)

Conclusion

• By comparing both sections, Increased area of Cross section of the modified section increases the moment of inertia thereby increases section modulus
• Increased moment of resistance and section modulus increases the stiffness and strength of the structure for the load bearing capacity.
• Hence, Modified section -2 has better mechanical properties than section-1.