Frank-Read Dislocation Source

A dislocation segment pinned at two fixed points is the smallest engine of crystal plasticity: under a resolved shear stress it bows outward, resisted by its own line tension, and settles into a stable arc — until the stress crosses a sharp threshold, τ꜀ = Gb/L, past which no stable shape exists and the segment spirals, sheds an expanding dislocation loop, and reforms to do it again. This simulator integrates the real curvature-driven force balance at every point along the line rather than animating a canned shape, so the stable-arc regime, the critical-stress transition, and the repeated loop emission all emerge from the same physics that governs work hardening in real metals.