i have a bit of a retarded question which im quite frankly embarrassed to ask, but given that im in the middle of exams, i havent done any strengths for about a year, and im too stressed (no pun intended) to care about a token lab report for a token module.
so, i have a plot of strain against load for a cantilever beam, and i have to use it to find E for the beam.
i have the equation [sigma] = (y * W / EI )*(x-L)
where, x = distance of gauge along beam from the built in end y = distance through the beam's thickness from the centreline of the beam to the gauge. W = load E = youngs modulus. (aluminum beam so should be about 70Gpa) I = 2nd moment of area = bd^3/12 L = length of the beam.
im trying to find E, so i figured on my graph, [sigma] = gradient * W
comparing that to the equation above, i guessed that gradient = (x-L) * y / (EI)
rearranging to give
E = (x-L)*y/MI ......
..... except it doesnt. i know im going wrong somewhere..... obviously. can someone give me a kick up the ass in the right direction.
ta.