A shallow arch under central load exhibits a subcritical bifurcation: the structure snaps discontinuously to an inverted state. The energy landscape has two wells; snap-through occurs when the load exceeds the saddle-node point.
Parameters
Snap-through is a first-order elastic instability. Critical load: F_cr = 2k·h (linear estimate). Bistability enables mechanical logic gates, energy harvesters, and deployable structures.