Basic issues concerning finite strain measures and isotropic stress-deformation relations

It is indicated that the commonly-used Rivlin-Ericksen representation formula for isotropic tensor functions exhibits some properties that might be undesirable for its reasonable and effective applications. Towards clarification and improvement, a set of three mutually orthogonal tensor generators is introduced to achieve an alternative representation formula for isotropic symmetric tensor-valued functions of a symmetric tensor. This representation formula enables us to express the unknown representative coefficients in terms of simple, explicit tensorial inner products of the argument tensor and the value tensor without involving their eigenvalues. In particular, the tensorial interpolation expressions thus obtained assume a unified form for the three different cases of coalescence of the eigenvalues of the argument tensor. Moreover, each summand in the alternative representation formula is shown to inherit the continuity and differentiability properties of the represented isotropic tensor function. These results are used to study some basic issues concerning finite strain measures and stress-deformation relations of isotropic materials, such as continuity and differentiability properties of the representation, determination of the representative coefficients in terms of experimental data for stress and deformation tensors, and computations of finite strain measures.