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mh1985
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Homework Statement
Determine
a)where the greatest stresses are
b) overall change in length
That is meant to be a hollow cylinder on the bottom section inbetween the dotted lines
E = 200 GPa
Homework Equations
σ = Fn / A
ε = dl / lo = σ / E
The Attempt at a Solution
The book gives the answer as the top of the rod having the greatest stress = 7.64 MPa
So working back from that answer the force on the top of the rod = 15 kN
I assumed this was because -20+10-5 = -15 kN, but when I used -15 kN for the rest of the sections the stress was much higher due to the smaller area.
ie. 15e3/[(pi 25 mm^2)] = 7.64 MPa (top section)
15e3/[(pi 20 mm^2)] = 11.94 MPa (middle section)
15e3/ [(pi 10mm^2)] = 47.75 MPa (bottom section)
So my problem is that I don't know whether to include all the forces when calculating strain for each section or not..Thanks
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