I gave what you said a thought, starting with a simpler case of 2D. I realized that the same question I asked is valid for 2D too! Why 2 planes/square at a point is considered instead of one line.
I am, in some sense, confusing shear stress and normal stress. I will give it some more thinking...
Thank you Sir. I had a look at the reference and the closest thing I could find is this sentence "(In physical problems we often work with quantities that require the simultaneous specification of two directions. For example, the flux of x-momentum across a unit area of surface perpendicular to...
Can you link me to a good source? I have tried many videos, websites but they all go like ' we need 3 planes to define stress at a point' or 'consider a infinitesimal cube at a point and its faces' assuming it as an axiom.
Equilibrium renders the matrix symmetric reducing the need for 9 to 6 dependants right? But mathematically didn't we need 9 quantities to define stress and be able to express stresses in any plane/direction?
Can u please elaborate what you mean by "their directions"? I understand the principle...
My question is simple. Why do we need 9 different quantities, ie 1 normal stress and 2 shear stresses on 3 different planes, to define stress at a point?
example: http://www.geosci.usyd.edu.au/users/prey/Teaching/Geol-3101/Strain/stress.html
I think it should be enough to define the 3 stresses...