Area Moment of Inertia for Solid Shafts

[teng125]

for a solid shaft,the area moment of inertia is (pi*d^4) / 64 or (pi*d^4) / 32 ?? i mean in bending and buckling case.

ihave two formulas but don't know which one is correct??


does anybody has those formulas for other cross sections ??
pls help

 

[Meson]

For a shaft with cross section d,

Area moment of inertia is $$I=\frac{\pi*d^4}{64}$$ with unit $$mm^4$$

Widerstandsmoment, $$W=\frac{\pi*di^3}{32}$$ with unit $$mm^3$$

Relation between W and I, for the case of bending and bulking, is given by:
$$W_{by}=\frac{I_{y}}{C}$$ where C is the (maximum) distance from the neutral axis to the outermost fiber or layer of atoms.

Hence, do not be confused as they are different and yet related. If one is known, let's say I, the other can be found, W in this case.