Bronze Orig
Posted in Garden Antiques on 07/02/2008 09:58 pm by adminhelp with this stress-strain problemt please?
http://www.physicsforums.com/attachment.php?attachmentid=22016&d=1259009682
Bronze a=10.1e-6, original length = 12"
Al a=12.8e-6 orig = 15"
so after 200f,
Al = 200*10.1e-6 * 15 = 0.0303 extra, so 15.03 total
Br = 200*12.8e-6 *12 = 0.0307 extra, so 12.03 total
total extra length = 0.061 an we only have 0.02 so we have 0.041 extra compression providing the stress
The force in both bars must be the same - otherwise they would move!
εtot=(0.02) / 27
=7.407407e-4
σ=ε*E
F=ε*E*A
F=al*10e6*3
F=br*15e6*2.5
al*15+br*12=0.02
after solving i get
F=24390.2439
al=8.13e-4
br=5.65e-4
still no good
i can see where this might be wrong, nowhere here do i take into account the amount that each material expands.
but i have no idea how to fix it
I cannot access physics forum. Can you post as a jpg somewhere?
OK I registered.
Initially assume that the bars can expand without being restrained.
You already know the overall unrestrained expansion so now just apply a force to the end to reduce the lengths by the difference 0.041.
As you have said the force is the same in both bars so you can write an equation for the combined compression for a force F.
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