Can Mohr's Circle be Constructed with Only xx and yy Strain Values?

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SUMMARY

This discussion centers on the construction of Mohr's Circle using strain values obtained from a strain rosette with two gauges positioned at 0 and 90 degrees on a beam. The user has successfully measured the xx and yy strain but is uncertain about determining the xy strain required for plotting the circle. It is established that the gauges are aligned with the principal directions of strain, which simplifies the process of identifying principal strains from the readings.

PREREQUISITES
  • Understanding of strain measurement techniques, specifically using strain gauges.
  • Familiarity with Mohr's Circle and its applications in stress analysis.
  • Knowledge of kinematics of bending in structural analysis.
  • Basic principles of uniaxial stress and strain relationships.
NEXT STEPS
  • Research how to calculate shear strain (xy) from principal strains (xx and yy).
  • Study the derivation and application of Mohr's Circle in two-dimensional stress analysis.
  • Explore the effects of gauge orientation on strain readings in different loading conditions.
  • Learn about advanced strain measurement techniques, such as digital image correlation (DIC).
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Mechanical engineers, structural analysts, and students studying material mechanics who are involved in strain measurement and stress analysis using Mohr's Circle.

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Homework Statement


I have used a strain rosette with two gauges at 0 and 90 degrees to find strain on a beam under force and an trying to plot Mohr's circle for the problem. As the gauges are at right angles finding the xx and yy strain is easy but I am lost about how to find the xy strain, which I need to plot the circle. How can I find xy from the xx and yy strain values?

Homework Equations

The Attempt at a Solution



I have got xx and yy but I honestly have no idea how to find xy[/B]
 
Last edited:
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How does the orientation of these gages relate to the principal axes of strain for this particular deformation? Do you know?

Chet
 
Chestermiller said:
How does the orientation of these gages relate to the principal axes of strain for this particular deformation? Do you know?

Chet

Hi Chet, I'm not sure how to tell to be honest! All I know is that the gauges are put on a long beam, one parallel to the edge of the beam and the other perpendicular and then the beam was forced downwards on the unsupported end.

I'm also told to think of it has a simple, uniaxial stress in x direction if that makes any difference.
 
Your gages are aligned with the principal directions. If you understand the kinematics of bending, then you will know why.

Chet
 
Oh OK. Does that mean that the readings on the gauges are the principle strains?
 
GBA13 said:
Oh OK. Does that mean that the readings on the gauges are the principle strains?
Sure..
 

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