A direct method for calculating M-eigenvalues of an elasticity tensor

The strong ellipticity condition (abbr. SE-condition) of the displacement equations of equilibrium for general nonlinearly elastic materials plays an important role in nonlinear elasticity and materials. Existing literature shows that it can be equivalently transformed into the SE-condition of an elasticity tensor, and that the SE-condition of an elasticity tensor holds if and only if all of its M-eigenvalues are positive. In order to judge the strong ellipticity of an elasticity tensor, we in this paper propose a direct method for calculating all M-eigenvalues of an elasticity tensor and show that the direct method is workable by a numerical example.