Model of Viscoplasticity for Transversely Isotropic Inelastically Compressible Solids

A transversely isotropic, viscoplasticity model is formulated as an extension of Bodner's model. Account is made of inelastic deformation that can occur in strongly anisotropic materials under hydrostatic stress. The extended model retains the simplicity of the Bodner model, particularly in the ease with which the material constants are determined. Although the proposed model is based on a scalar state variable, it is capable of representing material anisotropy under the assertion that history-induced anisotropy can be ignored relative to strong initial anisotropy. Physical limitations on the material parameters are identified and discussed. The model is applied to a W∕Cu metal matrix composite; characterization is made using off-axis tensile data generated at NASA Glenn Research Center.