Calculating Young's Modulus, Yield Stress, etc. from Force-Elongation Graph

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SUMMARY

The discussion focuses on deriving mechanical properties such as Young's Modulus, Yield Stress, Yield Strain, and Ultimate Tensile Strength (UTS) from a Force-Elongation graph of an Aluminium specimen. The user initially calculated UTS as 695.7 MPa using a maximum force of 53.5 kN and an initial cross-sectional area of 76.9 mm², which is significantly lower than the expected value of approximately 400 MPa for Aluminium. Additionally, the calculated Young's Modulus was reported as 13 GPa, which is also below the typical range of 69 GPa for Aluminium. The discrepancies indicate potential errors in the calculations or assumptions made during the analysis.

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  • Understanding of mechanical properties of materials, specifically Aluminium.
  • Familiarity with stress and strain calculations.
  • Knowledge of Force-Elongation graphs and their interpretation.
  • Basic proficiency in using formulas for UTS and Young's Modulus.
NEXT STEPS
  • Review the calculation methods for Ultimate Tensile Strength (UTS) in materials science.
  • Study the principles of Young's Modulus and its significance in material properties.
  • Learn about the correct interpretation of Force-Elongation graphs for accurate data extraction.
  • Investigate common errors in mechanical property calculations for Aluminium and other metals.
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Materials scientists, mechanical engineers, and students studying material properties who are involved in analyzing stress-strain relationships in metals, particularly Aluminium.

DuncanBain
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Evening all,

I have a Force vs. Elongation graph of a specimen (Aluminium). From this I need to derive the values of Young's Modulus, Yield Stress, Yield Strain, Ultimate Tensile Strength and so forth.

I assumed this was fairly straight forward, but when I tried calculating the UTS, my answer was way way off of what it should roughly be.

The calculation I tried is as follows:

The maxima of the curve was 53.5kN and the A0 of the specimen was 76.9mm2.

UTS = F/A0 = 53500 / 76.9x10-6 = 695.7MPa

The answer should be around the 69GPa mark.

Any ideas where I'm going wrong? I get similar results when trying to calculate any other values from the graph.

Many thanks.
 
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695.7MPa (~100 ksi) is about right for Al. That's pretty strong for Al.

69 GPa would be about right for the elastic (Young's) modulus.
 
Thanks for the reply. Made a mistake in my post in saying Young's Modulus should be around 69GPa rather than say that the UTS should be around 400MPa? So I guess it's really not that far off.

I also calculated Youngs Modulus but got around 13GPa which seems very low.
 

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