Y. Wang et M. Aron, A REFORMULATION OF THE STRONG ELLIPTICITY CONDITIONS FOR UNCONSTRAINED HYPERELASTIC MEDIA, Journal of elasticity, 44(1), 1996, pp. 89-96
The conditions for the strong ellipticity of the equilibrium equations
of compressible, isotropic, nonlinearly elastic solids (established b
y Simpson and Spector [1]) are expressed in terms of the stored-energy
function regarded as a function of the principal stretches. The appli
cability of this reformulation is illustrated with the help of two spe
cific examples.