CroninProjects.org/ Vince/ Course/ IntroStructGeol/ 3445-Lect-Stress.html

John Logan looking at the Large Sample Rig in the rock-deformation lab at the Center for Tectonophysics, Texas A&M University, on the occasion of the 50th anniversary of the Center in 2018. Dr. Logan designed the LSR and joined countless students and colleagues in conducting great scientific investigations using this tool.

John Logan looking at the Large Sample Rig in the rock-deformation lab at the Center for Tectonophysics, Texas A&M University, on the occasion of the 50th anniversary of the Center in 2018. Dr. Logan designed the LSR and joined countless students and colleagues in conducting great scientific investigations using this tool. Photo by Vince Cronin.

Introductory Structural Geology — Stress


This page is under construction!

Refer to Ben van der Pluijm and Steve Marshak, Processes in Structural Geology and Tectonics ( psgt.earth.lsa.umich.edu ), chapter 2, pages 41-60.

Terms you should work to understand and use properly

anisotropic anisotropic stress bar Cartesian coordinate system compression (compressive)
continuum deformation differential stress dilation displacement
distortion eigen value eigen vector ellipse ellipsoid
force heterogeneous homogeneous hydrostatic stress inhomogeneous
isotropic (isotropy) isotropic stress linear anisotropy lithostatic stress material discontinuity
mean stress newton normal (direction) normal stress pascal
planar anisotropy principal plane principal stress σ 1 σ 2
σ 3 shear shear stress strain strength
stress stress ellipsoid stress matrix stress tensor tension (tensile)
traction vector — — —

Pronunciations of some important terms from the table above are available from the Cronin-Structure-Ed channel on YouTube at https://youtu.be/lVyK2Yufsmg.

Videos available

These and other tidbits are available on the YouTube channel Cronin-Structure-Ed (https://www.youtube.com/channel/UCZJu-OKjQ29vJiUbmmDMMBQ?view_as=subscriber

  1. Stress part 1: https://youtu.be/FtQ8UAYioTw
  2. Stress part 2: https://youtu.be/6FZtfmij4qA
  3. Stress part 3: https://youtu.be/q26W7SPbz1w
  4. Stress part 4: https://youtu.be/0IjWsn3v9_w

Other notes

I asserted that the Mohr diagram is a very clever graphical computer, but that it was devised at a time when electronic calculators did not exist. We now have access to powerful electronic computers, so it is reasonable to ask how one might solve for the principal stresses given the tractions on a randomly oriented cube within an anisotropic stress field. The Mathematica notebook EigenDecomposition3D.nb is one example of how this problem might be solved. That notebook is accessible online via http://CroninProjects.org/Vince/Course/IntroStructGeol/EigenDecomposition3D.nb and a non-executable PDF of that notebook is available via http://CroninProjects.org/Vince/Course/IntroStructGeol/EigenDecomposition3D.pdf .

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