Strain rosette, Mohr's circle

1. Jan 15, 2015

GBA13

1. The problem statement, all variables and given/known data
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?

2. Relevant equations

3. The attempt at a solution

I have got xx and yy but I honestly have no idea how to find xy

Last edited: Jan 15, 2015
2. Jan 15, 2015

Staff: Mentor

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

Chet

3. Jan 15, 2015

GBA13

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.

4. Jan 15, 2015

Staff: Mentor

Your gages are aligned with the principal directions. If you understand the kinematics of bending, then you will know why.

Chet

5. Jan 15, 2015

GBA13

Oh OK. Does that mean that the readings on the gauges are the principle strains?

6. Jan 15, 2015

Sure..