Experimental apparatus for the elastic-to-plastic bending of beams and the formation of plastic hinges

A beam mounted on a fixed-and-floating support pair is loaded, at a chosen position, by a high-force loading screw that drives it continuously from the elastic range into permanent plastic deformation. A dial gauge records the deflection while the load increases; unloading then reveals the residual deformation. The resulting load–extension curves make the three regimes — linear elastic, nonlinear transition, plastic flow — directly observable, and allow the student to confirm that the superposition principle, which holds in the elastic range, fails once yielding begins.