Blue is compression, red is tension. Load a beam and watch the shear and moment diagrams draw themselves, spin Mohr’s circle, and push a column until it buckles.
Drag the load along the beam. The color inside the beam is the bending stress σ = My/I, the curve is the real (exaggerated) deflected shape, and the V and M diagrams below update live.
Set the stresses on the element, then rotate it. The point on the circle moves twice as fast as the element. Where the circle crosses the σ axis are the principal stresses (no shear).
Euler’s critical load P_cr = π²EI/(KL)² depends on how the ends are held. Increase the load and watch the column bow out in its buckling mode shape.