Formal definition of wedging and conditions for its possibility in systems with coulomb friction

In some mechanical systems a phenomenon referred to as wedging can occur. Although this phenomenon has been known as long as about forty years, its generally accepted formal definition is still lacking, to say nothing of its coherent theory.In this paper, definitions of wedging and conditions for its possibility in systems with Coulomb friction are analyzed. The equivalence of two different definitions of wedging for systems with different numbers of frictional contacts is demonstrated. Clear geometrical wedging conditions for two-dimensional systems with three frictional contacts and analytical wedging conditions for three-dimensional systems with an arbitrary number of frictional contacts are obtained. The efficiency of these conditions is illustrated by a number of examples.