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Homework Statement
node1 node2
O---------------------------------------O
a rod with 2 nodes:
x1=axial force at node1
x2=axial force at node2
u1,axial deflection at node1
u2,axial deflection at node2
l=elements length
E=young's modulus
A=cross sectional area of rod element
e=strain
I don't understand why at node 1:
e=(u1-u2)/l
and from equilibrium considerations at node 2:
e=(u2-u1)/l
Homework Equations
The Attempt at a Solution
From what i understand, if one end is fixed say node2 then strain at node 1 will be:
u1/l
and if node1 is fixed then strain at node2:
u2/l
at node 1, if i assume that the direction of force/displacement from node1 to node2 is positive isn't that supposed to be negative because of compression?
and i don't understand how u1-u2 or u2-u1 works? Can somebody explain it to me and give me an example?