Finding the tensile modulus E11

[helpinghand]

Hey guys,

Really basic question, how do I find the tensile modulus E11 from a set of data?

Let the data be:

stress(GPa) 0.050 0.300 0.454 0.800
strain(mm/mm) 0.002 0.0025 0.004 0.0087

I know how to find young modulus E=strain / stress

When finding E for each of the data points, I keep getting different values, so how would I go about finding E11?

Thanks for any help

 

[SteamKing]

It's probably because you're using the wrong relation for E.

E = stress / strain

 

[helpinghand]

oops... I get finding E with stress / strain (Massive typo in the previous post)

But how do I find E from the data?

 

[Travis_King]

What exactly is the data?

From your notation, it looks like you are looking for E by examining stresses and strains in the axial direction? Are the measurements all the same trail but different points, are they different trials same points, is it a force machine and those are incremental steps?

If the last is the case (which seems most logical to me), then plot your results, and you should get a graph that looks like a Stress/strain curve. Then depending on whether you are accounting for the offset or just looking for the standard modulus, you look at the linear part of the slope only (this you may have to interpolate) and do your math from that.

 

[helpinghand]

What exactly is the data?

From your notation, it looks like you are looking for E by examining stresses and strains in the axial direction? Are the measurements all the same trail but different points, are they different trials same points, is it a force machine and those are incremental steps?

If the last is the case (which seems most logical to me), then plot your results, and you should get a graph that looks like a Stress/strain curve. Then depending on whether you are accounting for the offset or just looking for the standard modulus, you look at the linear part of the slope only (this you may have to interpolate) and do your math from that.

say that I've found the linear part of the slope and it comes out to be y = 0.00478 + 159.495x

would it mean that the E = 159.495GPa ?

 

[Travis_King]

Yup, if I'm reading your question correctly. I don't know how far you've gone into this stuff, so I don't know if you need to consider the offset, but if all you were given was data and told to find the E, then this is how you do it.

 

[helpinghand]

alright... cool thanks