How Do You Calculate Elastic Modulus and Strengths from a Stress-Strain Curve?

[Name:riley]

Hello I'm having trouble wrapping my head around finding things from stress strain curvesI need to find:
Elastic modulus (Young’s modulus)
•Yield strength
•Tensile strength
•Uniform and total elongation (ductility)

elastic modulus I think is 1240/0.02 = 62000

but I'm unsure of how to find the others.

Thank you to anyone who helps out.

 

[billy_joule]

No, that is not the Youngs modulus.

Can you define any of the terms in your own words? i.e. do you know what you are looking for?

 

[Name:riley]

Thank you for your response

I am OK with yield and tensile strength it turns out.

I know what the elongation is and understand the formula Lf - Lo/Lo I just don't understand where to get the lengths from in the curve, I believe the strain is the elongation of the material but don't know where to get the original an final lengths from. Either from uniform at the 0.2% point or the total elongation.

The elastic modulus is the measure of the elasticity of the material, I know that is measured form 0 to 0.02 ( the 2% rule) of the strain as this is the beginning of the plastic region. As E= stress/strain I thought but it seems that's not the case.

I hope these explanations are satisfactory, I understand why you asked for them I guess I should have showed more of an effort to find the answers.

 

[SteamKing]

Thank you for your response

I am OK with yield and tensile strength it turns out.

I know what the elongation is and understand the formula Lf - Lo/Lo I just don't understand where to get the lengths from in the curve, I believe the strain is the elongation of the material but don't know where to get the original an final lengths from. Either from uniform at the 0.2% point or the total elongation.

You need to review the definition of 'engineering strain':

http://www.engineeringtoolbox.com/stress-strain-d_950.html

Scroll down until your reach the section titled 'Strain'.

The elastic modulus is the measure of the elasticity of the material, I know that is measured form 0 to 0.02 ( the 2% rule) of the strain as this is the beginning of the plastic region. As E= stress/strain I thought but it seems that's not the case.

This rule only applies to materials for which there is no region where Hooke's law applies, i.e., the stress is not a linear function of the strain anywhere on the stress-strain curve. Steel, for example, has a well-defined region where the stress-strain curve is linear; aluminum does not, and therefore the 2% rule is used to estimate Young's modulus for aluminum and aluminum alloys.

 

[rezeew]

Dear fellow scientist,

I understand that you are having trouble finding certain values from a stress-strain curve. Let me provide some guidance to help you out.

Firstly, the elastic modulus or Young's modulus can be calculated by taking the slope of the linear portion of the stress-strain curve. This is the region where the material behaves elastically, meaning it can return to its original shape after being subjected to stress. As you correctly mentioned, the elastic modulus can be calculated by dividing the stress (measured in MPa or psi) by the strain (measured in % or mm/mm).

Moving on to yield strength, this is the point on the stress-strain curve where the material begins to deform plastically. In other words, it has reached its limit of being able to return to its original shape. To find the yield strength, you can draw a line parallel to the linear portion of the curve until it intersects with the curve. The stress value at this point is the yield strength.

Tensile strength, on the other hand, is the maximum stress that a material can withstand before it fractures. This can be found by identifying the peak point on the stress-strain curve.

Uniform and total elongation, also known as ductility, refers to the ability of a material to deform or stretch before it fractures. This can be calculated by measuring the change in length of the material after it has reached its maximum stress (tensile strength) and dividing it by its original length. The uniform elongation is the percentage of elongation before the material starts to neck, while the total elongation is the overall percentage of elongation before fracture.

I hope this explanation helps you in finding these values from a stress-strain curve. If you have any further questions, please do not hesitate to reach out.

Best regards,