:If you've calculated the moment of inertia of each material about it's own neutral axis, you can then combine that info using the parallel axis theorem to calculate the moment of inertia of each material about the resultant neutral axis ( which you've already found ), and then just total the two translated moments of inertia.
42.
:If you've calculated the moment of inertia of each material about it's own neutral axis, you can then combine that info using the parallel axis theorem to calculate the moment of inertia of each material about the resultant neutral axis ( which you've already found ), and then just total the two translated moments of inertia.
43.
Note that this equation implies that pure bending ( of positive sign ) will cause zero stress at the neutral axis, positive ( tensile ) stress at the " top " of the beam, and negative ( compressive ) stress at the bottom of the beam; and also implies that the maximum stress will be at the top surface and the minimum at the bottom.
44.
The stress due to shear force is maximum along the neutral axis of the beam ( when the width of the beam, t, is constant along the cross section of the beam; otherwise an integral involving the first moment and the beam's width needs to be evaluated for the particular cross section ), and the maximum tensile stress is at either the top or bottom surfaces.
45.
I've asked this question before but I'm still not sure which area to use when calculating things like first moment of area, shear flow etc . My understanding is that it should be the area above the neutral axis ( or below as they should be equal ) but when I actually do the calculations, this doesn't seem to be the case . talk ) 21 : 21, 12 May 2014 ( UTC)
