In this note precise definitions of the concepts of elastic and permanent deformation are used to establish non-uniqueness of elastic rotations for deformations of materials with elastic range. Introduction. A feature common to theories of elastic-plastic materials is a representation of deformations in terms of elastic and inelastic parts. The question of the uniqueness of such a representation has been commented upon by many authors. In [1], [2], and [3], the inherent non-uniqueness of such

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... presentations has been asserted. On the other hand, some writers (see [4] , for example) have assumed uniqueness of such representations. The purpose of this note is to state precise conditions under which non-uniqueness (in the form of non-uniqueness of elastic rotations) arises in a mechanical theory proposed by the present author [1], Roughly speaking, I show that, in a material with elastic range, the larger the symmetry group the larger the number of possibilities for the elastic rotation. In particular, the elastic rotation is shown to be arbitrary for isotropic materials.