Why does copper wire bend smoothly while steel wire kinks?

[drew1.0beta]

hi everyone..
my lecturer gave each of us a task..we have to give a short presentation next week. everyone have a different topic..mine is this:

"Explain the observation that a copper wire will bend smoothly around a finger, whereas a mild-steel wire will kink and deform to a polygonal shape"

Is these the cause of residual stress? i read from my textbook and search the internet to understand better...but i couldn't put 'residual stress' and wires together..can anyone explain to me?

THANKS a lot!
-andrew-

 

[rmw228]

This doesn't sound like residual stress to me. Consider that copper has an FCC crystal structure and steel generally has a BCC crystal structure. Do these structures have different slip systems?

 

[Astronuc]

hi everyone..
my lecturer gave each of us a task..we have to give a short presentation next week. everyone have a different topic..mine is this:

"Explain the observation that a copper wire will bend smoothly around a finger, whereas a mild-steel wire will kink and deform to a polygonal shape"

Is these the cause of residual stress? i read from my textbook and search the internet to understand better...but i couldn't put 'residual stress' and wires together..can anyone explain to me?

THANKS a lot!
-andrew-

Please review the stress-strain curve/diagram for mild steel and copper. Pay close attention to what happens when the materials depart from strictly elastic behavior. What is the significance of the increasing strain at constant stress for the mild steel?

One reference -
http://www.optics.arizona.edu/optomech/references/OPTI_222/OPTI_222_W4.pdf
http://www.phy.hr/~atonejc/mehanickaSvojstva.pdf