Calculating Steel Properties. 2

[vtmike]

Hi,

I got the following properties for steel from a manufacturer,
Tensile Strength = 135000 psi
Yield Strength = 130000 psi
Elongation in 2 inches = 16% minimum
Reduction in Area = 50% minimum
Hardness (Rockwell C) = 29 - 34Rc

From above properties I need to calculate the Elastic modulus & Poisson's ratio. This is how I went about it,
1. strain = (change in length)/(original length) = .16
2. Elastic modulus, E=stress/strain=135000/.16=843750 psi
3. Poissons ratio=lateral strain/axial strain=.16/.5 = .32

I don't think above procedure is correct because the modulus of elasticity should be somewhere around 30e6 psi. There seems to be some problem with the strain calculation. Am I reading it wrong?

Thanks,
Mike

 

[HgTX]

For what purpose are you calculating these properties?

Hg


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[CoryPad]

Elastic modulus and Poisson's ratio are elastic properties, while elongation is a plastic property. You do not have enough data to calculate these two properties. Why not use 30e6 and 0.3? Both are within 10 % of a wide variety of materials and conditions.

Regards,

Cory

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[vtmike]

So I guess strain cannot be calculated with the given data because we don't know what stress value was reached during the elongation (as it could have entered the plastic region). I was calculating these properties for a fea model.

 

[RPstress]

16% is very plastic. About the only materials capable of 16% elastic strain are elastomers.

For a linear FE analysis generic properties as suggested by CoryPad are probably adequate (depends a bit on what the analysis is for). This is as long as it is a steel; cast iron might be rather different.

 

[israelkk]

vtmike

Yield strength is usually taken at 0.2% strain (0.002). Therefore, according to your data E=130000/0.002=65e6. However, for steels E=30E6. Therefore, I assume that your manufacturer takes the yield strength at ~ 0.43% or something is wrong with the value of the yield strength.

 

[CoryPad]

Yield is taken at 0.2 % OFFSET strain.