# Thread: cross sectional area of circular solid & hollow rod.

1. ## cross sectional area of circular solid & hollow rod.

please send me the formula to find the cross sectional area of fixed end circular solid and also hollow shaft under load "W".

2. Under the theory of teach a man to fish....

Open a web browser
Type "area of circle" into search line.
Hit return

To calculate area of a hollow circle.

Calculate area of outside diameter circle.
Calculate area of inside diameter circle.
Subtract the second area from the first.

3. Originally Posted by Erich
Type "area of circle" into search line.
Hit return
Hmm... this website could be that link!

Ok so the formula for calculating the area of a circle is....

...wait for it...

Area = πr2

What Erich has said is spot on: You calculate the area of the inner & outer diameters then subtract the inner from the outer

4. sorry sir, that's not the question, actually i would like to know "the formula for minimum cross sectional area of a fixed end circular rod ( solid & hollow) under a load (L)."

5. That would involve calculating the maximum bending moment, The area moment of inertia of the cross section, and the bending stress. Also you need to know the yield strength of the material of the beam.

All of those items should have been taught in your classes.

6. Is the load L in the direction of the rod's length ? Is it applied perpendicular to the rod ? Are any of the rod's ends anchored ? Is the rod simply supported ?

Everything you need is here :
http://www.mechanicaldesignforum.com...ollow-cylinder

However, you need to ask yourself these questions and apply the correct variables or else you'll be way off. Let me know if you have any questions.

7. the rod is placed horizontally with fixed ends (anchored) & load L is acting vertically downward.

8. load L is uniformly distributed along the length.

9. Dear Swarnendu,
You know the load, you know the mounting method (from the explanations, I presume it to be cantilevered). any handbook would give you the bending moment at the point of fixing. Else, you can even calculate it from first principles.
Find the Moment of Inertia of the cross section, find the section modulus (Z = I/y) where Z is the section modulus, I area moment of inertia and "y" the distance of the extreme fibre from the CG.
This would give you the bending stress. Based on the Allowable stress (material property), you may now calculate the minimum dia.

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