Large deformation character of two kinds of models for rubber

A new elastic law that contains strain invariants I-2 and I-1 is proposed. In order to reveal the inherent character of the new elastic law, it is examined by some typical but simple deformation of an element. For comparison, the elastic law given by J.K. Knowles, E. Sternberg (An asymptotic finite-deformation analysis of the elastostatic field near the tip of a crack, J. Elasticity 3 (2) (1973) 67-107) is also examined by the same typical deformations of an element. The restriction on material parameters for the new elastic law and that given by Knowles and Sternberg (loc. cit.) is derived. (C) 2000 Elsevier Science Ltd. All rights reserved.