>>14379532Calculus takes delta x to zero, to get dx.
This unit stress takes the area to zero. It does this so you can have an absolute accurate model of parts under stress without worrying about location.
There are two types of stresses. Normal stress, like if you have a bolt and pulling on it in tension. That's the sigma. There's also shear. That's the tau. That's using a length to transmit stress parallel to the shear area. Shear can't be single plane. It's always two plane to stop a torsional moment.
It's a tensor in the idea of an array of vectors, like a page with an arrow over each letter. It's not a tensor in the sense of a vector of arrays of scalars. The vectors are rather locked in, but they still have direction. The tensor math makes a lot of things easier.
Later on you can use Mohr's Circle for load conditions that are at 90 degrees of your unit stress.
Tensors are also used in relativity, the energy stress tensor. Don't really know if they relate or were influenced by this. That has to do with electromagnetism and brownian motion of photoelectric interaction, not stress through materials which is Newtonian.
