M12.1 The Amazing Stress Camera

Of course, there is not really an amazing stress camera that can see the internal stresses in a solid. This analogy is used to convey one central notion: stresses within a material vary with orientation.

Stress transformation equations are used to compute stresses at any orientation. Knowing stresses at a point in a solid in two orthogonal directions (such as the $x$ and $y$ directions), we can compute the state of stress at that same point in any other orientation. We can also consider all possible orientations to determine the largest stresses at the point — both the principal stresses and the maximum shear stress state.