# Mechanics of Materials Bending Stres Problem

1. Jul 10, 2005

### Delta-One

Mechanics of Materials Bending Stress Problem

Hi,

I have a homework problem for mechanics of materials involving bending stress. Here is the exact wording:

"Show that the maxiumum bending stress for a beam of rectangular cross-section is Omax = Mc/I [(2n + 1) / (3n)] if instead of Hooke's law, the stress-strain relationship is O^n = Ee, where n is a number dependent on the material."

--NOTE: Omax is the maxiumum bending stress

Essentially the diffence is not using Hooke's law: O = Ee (e is the strain). Using Hooke's law yields the flexure formula: Omax = Mc/I.

So far I have got O^n = Omax^n * (y/c)
but when I insert this into the equation dM = ydF or dM = yOdA I am uncertain how to obtain I (the moment of Inertia)

Any help would be greatly appreciated.

Last edited: Jul 10, 2005
2. Jul 10, 2005

### mathmike

the moment of inertia is calculated by the eq. [1/12*b*h^3]