Understanding Principal Stresses
Understanding Principal Stresses
(OP)
Hello everyone,
I have an issue with evaluating principal stresses and quite confused and needed your priceless comments.
Normally what we assuming is; max. principal stress (s1) is stress which generally tensile,
and minimum principal (s3) is compressive.
With this assumptions i am trying to comment results of my fea case in ansys workbench. (for a brittle material)
What is confusing me is in the results of loadstep which i am looking for maximum value of maximum principal stress is negative.
Normally i am looking max value of maximum principal stress which is positive and tensile direction, and min value of minimum principal stress which i assuming compressive direction.
So how to evaluate that negative value? What does it mean? I am waiting for your priceless comments. Thanks!!!
I have an issue with evaluating principal stresses and quite confused and needed your priceless comments.
Normally what we assuming is; max. principal stress (s1) is stress which generally tensile,
and minimum principal (s3) is compressive.
With this assumptions i am trying to comment results of my fea case in ansys workbench. (for a brittle material)
What is confusing me is in the results of loadstep which i am looking for maximum value of maximum principal stress is negative.
Normally i am looking max value of maximum principal stress which is positive and tensile direction, and min value of minimum principal stress which i assuming compressive direction.
So how to evaluate that negative value? What does it mean? I am waiting for your priceless comments. Thanks!!!





RE: Understanding Principal Stresses
Rick Fischer
Principal Engineer
Argonne National Laboratory
RE: Understanding Principal Stresses
RE: Understanding Principal Stresses
RE: Understanding Principal Stresses
This is probably easier in 2D.
You have three stresses: sigma_x, sigma_y and tau_xy. Now imagine a line in the plane, you can find an orientation for that line so there will be no shear in that coordinate system.
Now you have three new values: sigma_1, sigma_2, angle. Sigma_1 and sigma_2 are the principal stresses and the angle describes their orientation. They can be both tensile (+) and compressive (-) depending on the loading.
For more detailed info (if you need it): https://en.wikipedia.org/wiki/Cauchy_stress_tensor...
Best Regards
Thomas
RE: Understanding Principal Stresses
Aerospace Stress Analysis and FEA Courses
http://www.stressebook.com
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