Description of the elasto-plastic material routine SGDI

The report describes the FORTRAN subroutine SGDI for rate-independent deviatoric plasticity with von Mises yield criterion and isotropic hardening, which corresponds to the VM23 material type in the EUROPLEXUS code (abbreviated as EPX in the following). EPX is a Finite Element code for the numerical simulation of fast transient dynamic events in fluid-structural system, jointly developed by the French Commissariat a l'Energie Atomique et aux Energies Alternatives (CEA Saclay) and by the Joint Research Centre of the European Commission (JRC Ispra). The subroutine I part of the FORTRAN90 module M_MATERIAL_VM23. In order to simplify the description of the routine and of the material model, the parts dealing with Gauss point failure and element erosion have been neglected