How Do You Calculate Young's Modulus from Tensile Stress and Strain Data?

In summary, the young's modulus for the material can be calculated by dividing the stress of 280MN/m^2 by the strain of 0.0035, which represents the increase in length of the alloy bar by 0.35%. This calculation assumes that the original length of the bar was L and that the stress and strain are proportional according to Hooke's law.
  • #1
anthonyk2013
125
0
A light alloy bar is observed to increase in length by .35% when subjected to a tenstile stress of 280MN/m^2.
Calculate youngs modulus for the material.

σ=280MN/M^2
x=.35%
ε=?
E=?
L=?

I have too many unknowns where do I start?
 
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  • #2
What's the definition of Young's modulus? How is it calculated?
 
  • #3
SteamKing said:
What's the definition of Young's modulus? How is it calculated?

E=σ/ε

to find ε=x/L so think I might have to work of .35% but not sure how.
 
  • #4
What does the 0.35% represent?
 
  • #5
The length of the alloy has increased by .35%
 
Last edited:
  • #6
And how would this increase be related to the strain?
 
  • #7
Is strain not increase in length/original length ?
 
  • #8
Yes.
 
  • #9
I have the increase in length I don't have strain and I don't have original length.
Is it possible to work out length using only .35%?
 
  • #10
Well, let's start with the basics. Assume the original length of the test specimen was L. After the stress was applied, what is the length of the test specimen? What is the strain due to the applied stress?
 
  • #11
Strain=.35/L
 
  • #12
anthonyk2013 said:
Strain=.35/L

From the OP:

"A light alloy bar is observed to increase in length by .35% when subjected to a tenstile stress of 280MN/m^2."

Would you like to revise your answer?
 
  • #13
Sorry SK but I'm lost now.
 
  • #14
Stress and strain are proportional according to hooks law?
 
  • #15
Yes, but you are avoiding the question about the strain of the test piece after it has the stress applied.

If the length of the test piece increases by 0.35%, what is its new length in terms of its original length?
 
  • #16
Sorry SK but I'm still lost. Do I need to convert .35 from a % to measurement by dividing by 100.
 
  • #17
Look, if something increases in length by 25%, what is its new length compared to its original length?
 
  • #18
If you have D dollars in your account to start with, and you earn 0.35% per year interest (compounded annually), how much money do you have in your account after 1 year? How much has the account value increased?
 
  • #19
D+.35%?
 
  • #20
anthonyk2013 said:
D+.35%?

.35% is not an amount of money. To verify this, try spending .35% at your local store.

The amount of money you would have after 1 year would be (D+0.0035D), and the amount of money you would have earned would be 0.0035D dollars.
 
  • #21
Divide by 100 to get the value. I won't forget that too soon. Sorry guys elementary stuff.

So X=.0035
 
  • #22
anthonyk2013 said:
Divide by 100 to get the value. I won't forget that too soon. Sorry guys elementary stuff.

So X=.0035
Actually, the bar getting larger by 0.35% means that ε = 0.0035.
 
  • #23
E=280/.0035

So if you multiply strain by 100 you get the percentage it increases by?
 
  • #24
Yes. The strain is the fraction it increases by. To get the % increase in length, you multiply the strain by 100%.
 

Related to How Do You Calculate Young's Modulus from Tensile Stress and Strain Data?

1. What is direct stress?

Direct stress refers to the force per unit area that is applied to a material in a direction perpendicular to its cross-sectional area. It is typically measured in units of newtons per square meter (N/m^2) or pounds per square inch (psi).

2. What is the formula for direct stress?

The formula for direct stress is stress = force/area. This means that the stress on a material is equal to the force applied to it divided by its cross-sectional area.

3. How is direct stress different from shear stress?

Direct stress and shear stress are both types of stress that act on materials, but they differ in the direction of force. Direct stress is applied perpendicular to the surface of a material, while shear stress is applied parallel to the surface.

4. What is the relationship between direct stress and strain?

Direct stress and strain have a linear relationship, meaning that as stress increases, strain also increases proportionally. This relationship is described by Hooke's Law, which states that stress is equal to the material's elastic modulus multiplied by its strain.

5. How is direct stress measured?

Direct stress can be measured using various instruments, such as a strain gauge or a load cell. These devices can accurately measure the amount of force being applied to a material, which can then be used to calculate the stress using the material's cross-sectional area.

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