Which Formulation Allows Using a Constant Shear Modulus for Small-Strain Buckling of Soft-Core

Although the stability theories energetically associated with dif-ferent finite strain measures are mutually equivalent if the tangen-tial moduli are properly transformed as a function of stress, only one theory can allow the use of a constant shear modulus G if the strains are small and the material defonns in the linear elastic range. Recently it was shown that, in the case of heterogeneous orthotropic structures very sofi in shear, the choice of theory to use is related to the problem of proper homogenization and de-pends on the type of structure. An example is the difference be-tween Engesser:S and Haringx: ~ formulas for critical load of col-umns with shear, which were shown to be energetically associated with Green:\ ' and AlmallSi's Lagrangian finite strain tensors. In a previous brief paper of the authors in a conference special issue, it was concluded on the basis of energy arguments that, for con-stant G, Engesser:S formula is correct for sandwich columns and Haringx's formula for elastomeric bearings, but no supporting experimental results were presented. To present them. is the mail! purpose of this technical brief [001: 10.111511.1979516