# Homework Help: Elastic recovery-can you just check if i've got it right

1. Nov 22, 2006

### maha

Hiya
Im doing material science as part of my dental technology course. I've got a question, and i'm fidning it hard to tackle.If anyone can help or set me in the right direction, i would be most grateful

Wire, of diameter 0.46 mm, length 100mm.it is subjected to tensile force of 2356 N, taking it beyond its yield point.
Calculate, in mm, the elastic recovery that would occur upon removal of the tensile load

Info given: Modulas of elasticity 67 GPa
Yield Strength 698 MPa
Tensile Strength 1379 MPa

okies, i think i got it. so, to calculate elastic recovery, i can only use the elastic range, so in order to work out elastic strain, i use yield strength/modulas of elasticiy. that gives me an answer of 1.041791045 N
Then, strain = extension/original, so to work out extension, i caluclate, strain x original length, which gives me 1.041791045 x 10-3 m
So answer is 1.04 mm of elastic recovery?

So then , i do not need to calulate the cross-sectional area or the stress value?

Can somebody just check this for me please :)

2. Nov 22, 2006

### Pyrrhus

Didn't we have this discussion already?

3. Nov 23, 2006

### maha

yes, but i wasnt sure if i was right thats why i posted it back up. How come the inforamtion of information of the tensile force and tensile load is not used. Is this because they are related to plastic part of the graph?

Thank you for your help :) hope i get the 4 marks

4. Nov 23, 2006

### Pyrrhus

Because the elastic recovery will only be upto the Elastic limit, if it goes after such limit, there will be permanent deformations on the material, like i said on your other thread.