Section Modulus of Solid Circular Rod of Diameter d
The section modulus of a solid circular rod of diameter d is a measure of its strength against bending. It is a property of the cross-sectional area of the rod and is defined as the ratio of the moment of inertia of the cross-sectional area about the neutral axis to the distance from the neutral axis to the outermost point of the cross-sectional area.
Formula for Section Modulus
The formula for the section modulus of a solid circular rod of diameter d is:
Z = πd^3 / 32
where:
- Z is the section modulus
- d is the diameter of the rod
- π is the mathematical constant pi (approximately 3.14159)
Explanation of Formula
The formula for the section modulus of a solid circular rod can be derived using basic calculus. The moment of inertia of the cross-sectional area of the rod about the neutral axis is given by:
I = πd^4 / 64
The distance from the neutral axis to the outermost point of the cross-sectional area is simply half the diameter of the rod, or d/2. Therefore, the section modulus can be calculated as:
Z = I / (d/2) = (πd^4 / 64) / (d/2) = πd^3 / 32
This formula shows that the section modulus of a solid circular rod increases with the cube of its diameter. Therefore, a larger diameter rod will be stronger against bending than a smaller diameter rod.