Nonlinear viscoelastic behavior of flexible cellular plastics refined rod model

A new technique of modelling nonlinear viscoelastic behavior of low-density flexible foams including cellular plastics used in advanced implants, namely, artificial analogs of periodont of the dental system and trabecular bones of the skeletal system has been developed. The material microstructure is modeled by a rod structure with chaotically oriented cubic cells. Young's modulus and critical strain (i.e., the case of stability loosing) dependence on the solid state phase fraction of flexible cellular plastics has been investigated. The dependences of tangential stress on shear strain, hydrostatic pressure on volume strain and axial stress on longitudinal deformation with taking into account solid phase viscosity at a given strain rate have been obtained for the simulated materials. The numerical results led to the conclusion that at a certain compression rate the transversal strain factor of a material becomes negative.