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The thin plastic sheet rests on a wooden kitchen table. The presence of a local buckle is revealed by the locally buckled plastc sheet’s relfection of a seemingly seriously deformed patio door. The reflection is distorted by an upward “pimple” (local upward buckle) in the thin plastic sheet. (See the next image.) The local buckle occurred after a very hot saucepan was set on the plastic sheet-covered kitchen table for a few seconds, then removed. Before the hot saucepan was removed the circular portion of the plastic sheet directly under the hot saucepan was in a state of uniform in-plane compression because it’s radial expansion was constrained by friction and by the unheated material not under the saucepan. When the hot saucepan was removed this uniformly and irreversibly compressed region was free to buckle upward. The local buckle remains to this day because there occurred irreversible local nonlinear deformation of the plastic sheet during its traumatic experience.
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