Determining Young's Modulus of Aluminium from Tensile Test

In summary: The linear portion of the stress-strain curve (engineering) is a vertical line when i plot it with excel.This does not let me calculate the slope."If the value of Young's Modulus calculated from the data doesn't match the value given online, is there a reason for this discrepancy?Yes, there could potentially be a discrepancy due to factors such as defects in the material, incorrect calculation of stress or strain, or a difference in the test methodologies.
  • #1
storm
4
0
My Aim is to determine the youngs modulus of aluminium from the data we get from tensile strength test.
The attached excel sheet contains all the data i am using such as elongation,load value(which is in kN i have converted to N for calculating Stress)
For stress,
I am using the formula
Stress(ε)=Force/Area
For strain,
I am using the formula
Strain(σ)=ΔL/L
My issue's are,
  1. The linear portion of the stress-strain curve(engineering) is a vertical line when i plot it with excel.This does not let me calculate the slope.
  2. When i have attempted to calculate Youngs modulus with the formula ε/σ,I am getting a value of
    758681.8 N/mm2 which is approximately 10x the value which is given online.
My question is whether the values have potentially increased due to various factors/defects or am i making a simple error in calculating stress and strain?

P.S:This is my first post in the forums so do forgive me for making errors/not following protocol.If I did make such errors please tell me how to fix them :)
 

Attachments

  • Aluminium.xlsx
    1.2 MB · Views: 598
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  • #2
I can't open the attachment . Please upload file again in a different format or just paste relevant sections .
 
  • #3
Nidum said:
I can't open the attachment . Please upload file again in a different format or just paste relevant sections .
I can't paste relevant section since the excel sheet has 2400 or so rows for the values of load and elongation.(unless its possible to do so?)
Can you suggest a different file type?
 
  • #4
One of the ODF formats like .ods would probably be ok if available .

If not mentioned specifically see if there is an 'Open Office' format option .
 
  • #5
Site says OpenDocument Spreadsheet format is not permitted.
The attached file type is'Strict OPEN XML spreadsheet'.
 

Attachments

  • Aluminium2.xlsx
    156.1 KB · Views: 343
  • #6
The latest version does not open either but no matter as I've now found some software that was able open the original file .

Please explain exactly what you did in this experiment , why there are so many duplicated test results yet so few actual changes of load and measured extension and what the units are for the values in the tables ?
 
  • #7
Nidum said:
The latest version does not open either but no matter as I've now found some software that was able open the original file .

Please explain exactly what you did in this experiment , why there are so many duplicated test results yet so few actual changes of load and measured extension and what the units are for the values in the tables ?
The test was pretty straight forward,I planted the specimen on the Universal Testing Machine for tensile strength testing.
The 'duplicated' values of load and elongation are the values the the universal tester recorded during the test from start till point of rupture.
The initial units are in kN and in mm,
I've converted kN to N for calculating stress(x1000) divided by area.
 
  • #8
The basic method for determining young's modulus is to determine the slope of a line parallel the linear region (<0.2% yield) of a stress-strain curve. MIL-HDBK-5J, page 1-10 has a pretty good overview, or of course Wikipedia does as well. The data provided doesn't seem to follow the general shape I would expect for a tensile test on aluminum, are you sure you've processed it correctly?

See here for "typical" stress-strain curve for Aluminum 6061-T6 (and many other metals): Assist Docs, MIL-HDBK-5J

MIL-HDBK-5J, Page 3-279:
upload_2017-5-9_17-38-32.png
 

1. What is Young's Modulus of Aluminium?

Young's Modulus, also known as the elastic modulus, is a measure of the stiffness of a material. It represents the relationship between stress (force per unit area) and strain (deformation) in a material. In other words, it measures how much a material will stretch or compress under a given amount of force.

2. What is a tensile test?

A tensile test is a type of mechanical test used to determine the strength and ductility of a material. It involves pulling a test specimen, such as a piece of metal, to its breaking point while measuring the amount of force applied and the resulting deformation. This information can then be used to calculate properties such as Young's Modulus.

3. How is Young's Modulus of Aluminium determined from a tensile test?

To determine Young's Modulus of Aluminium from a tensile test, a sample of the material is subjected to gradually increasing amounts of tensile stress until it reaches its breaking point. During this process, the amount of strain (deformation) is measured at different points and plotted on a stress-strain curve. The slope of this curve at the elastic region is equal to Young's Modulus.

4. What factors can affect the accuracy of Young's Modulus determination from a tensile test?

There are several factors that can affect the accuracy of Young's Modulus determination from a tensile test. These include the quality and preparation of the test specimen, the speed at which the test is conducted, and external factors such as temperature and humidity. It is important to carefully control these variables to obtain accurate results.

5. Why is Young's Modulus important?

Young's Modulus is an important material property that is used in engineering and design. It helps engineers understand how a material will behave under different types of stress, which is crucial for designing safe and efficient structures and products. It also allows for the comparison of different materials and helps in selecting the right material for a specific application.

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