Why Does Mild Steel Only Have One Yield Point?

In summary, the speaker had conducted an experiment on Young's Modulus using mild steel as the specimen. However, after plotting the graph, they noticed that there was only one yield point instead of the expected two (upper and lower). The data was recorded by a computer, but the speaker is unsure if there was a mistake. They then asked for an explanation on how it is possible to get a single yield point for mild steel. The equations used in the experiment were also provided. Another person in the conversation suggested that the equipment used may not have been sensitive enough to measure the second yield point. Ultimately, the speaker concludes that there must have been a mistake in the experiment.
  • #1
Mattheo
12
0

Homework Statement


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.


Homework Equations



E = (ΔL/L)/(F/A)


The Attempt at a Solution

 
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  • #2
Mattheo said:

Homework Statement


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.


Homework Equations



E = (ΔL/L)/(F/A)


The Attempt at a Solution

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
Chestermiller said:
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)?

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
Mattheo said:
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?
I don't know what to say. It's hard to argue with the data. I always tend to believe the data.

Chet
 
  • #5
Chestermiller said:
I don't know what to say. It's hard to argue with the data. I always tend to believe the data.

Chet

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

Cheers.
 

FAQ: Why Does Mild Steel Only Have One Yield Point?

What is Young's Modulus?

Young's Modulus, also known as the modulus of elasticity, is a measure of a material's stiffness or resistance to deformation when subjected to external forces. It is a material property that is used to describe the relationship between stress and strain in a material.

How is Young's Modulus calculated?

Young's Modulus is calculated by taking the ratio of stress to strain in a material. The formula for calculating Young's Modulus is E = σ/ε, where E is Young's Modulus, σ is stress, and ε is strain.

What is the significance of Young's Modulus?

Young's Modulus is an important material property as it helps engineers and scientists understand and predict how a material will behave under different types of stress. It is also used in the design and testing of materials for various applications, such as in construction, manufacturing, and medical devices.

What are yield points?

Yield points are specific points on a stress-strain curve where a material begins to exhibit permanent deformation or plastic behavior. This means that the material will not return to its original shape once the stress is removed. Yield points are used to determine a material's yield strength, which is the maximum stress a material can withstand before it starts to permanently deform.

How is Young's Modulus related to yield points?

Young's Modulus is closely related to yield points as it is used to calculate the yield strength of a material. The slope of the stress-strain curve in the elastic region, which is represented by Young's Modulus, can also indicate the material's stiffness and its resistance to yielding. A higher Young's Modulus generally correlates with a higher yield strength.

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