Isotropy postulate for finite deformations

We present a new formulation of the isotropy postulate for finite deformations that covers a wider class of deformation or loading trajectories, as distinct from its formulations in the literature [11–13], and provide an experimental foundation for this new formulation of the isotropy postulate. S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Priknadnaya Mekhanika, Vol. 35, No. 1, pp. 17–27, January, 1999.