>>14410639That's a component stress tensor. What calculus does to functions, taking the delta x and delta y of the slope to zero, the unit stress cube does for the area under load. The part becomes a set of dots with a stress value instead of a bunch of other parts glued together.
It's a cube because of shear. Shear is transmitting force through an inconsequential length. It's the cross sectional area that matters. It's always two planes to keep it from slipping off, like you're skinning a chicken.
Tensors come in for the calculations. It simplifies things. The normal and shear stresses are vectors. You create a matrix of vectors. That makes the sum of forces and stress/strain equations easier.
A matrix of vectors is a tensor. But those vectors are locked in position wise. The first row is always going to be normal stress x,y,z. It's not a tensor in the sense of tensor flow, that those directions vary. A matrix of vectors is a tensor. A vector of matrix is a much more complicated tensor but not this.
