Constitutive behavior of thin sheet metal in micro forming

Size effect makes most know-how of traditional macro-forming not suitable for the micro forming process. On the basis of the micro tension experiment of the CuZn36 sheet, the influence of t/d (thickness/grain size) to yield stress and tangent modulus is investigated in this paper, and the constitutive relation considered of the size effect is obtained by revising the double-linear elastic-plastic constitutive relation. Combined the incremental stress-strain relation in macro plastic mechanics and the results of micro tension, the elastic-plastic incremental constitutive equation suitable for the micro forming is established using Mises yield criterion and kinematic hardening model. The incremental method flow chart is presented which can be used for finite element analysis and practical application.