# Youngs Modulus Yield Points

1. Nov 20, 2013

### Mattheo

1. The problem statement, all variables and given/known data
I had a Young's Modulus experiment in lab. Our specimen, which was used, was mild steel. After plotting the graph I realized that there was only one yield point. However, as I read from many sources, there must be two yield points for mild steel(upper and lower). I am pretty sure that I didn't to any mistakes since the data were recorded by a computer.

Can anyone explain to me how that is possible to get a one yield point from mild steel.

2. Relevant equations

E = (ΔL/L)/(F/A)

3. The attempt at a solution

2. Nov 20, 2013

### Staff: Mentor

Were you plotting the engineering stress strain curve (force divided by original cross sectional area) or the true stress strain curve (force divided by deformationally reduced cross sectional area)?

3. Nov 20, 2013

### Mattheo

Hello,

Engineering stress curve, force divided by original cross sectional area. The graph I got was exactly like this

http://www.benbest.com/cryonics/sscurve.gif

However, what I think is I should have got a graph like this with upper and lower yield points included

http://www.etomica.org/app/modules/sites/MaterialFracture/Images/SSPicture3.jpg

So there is a mistake?

4. Nov 20, 2013

### Staff: Mentor

5. Nov 23, 2013

### Mattheo

I learnt that our equipment should have been more sensitive to measure the second yield point.

Cheers.