Modeling of damage evolution during upsetting of porous metalceramic composites

Abstract

Article is devoted to finite element analysis of the pore nucleation contribution into consolidation of porous metal-ceramic composites during upsetting. This process is modeled in 2D plane strain approach by loading the porous metal matrix containing cylindrical rigid ceramic inclusions of the same size. At the initial time the rigid inclusions are located at the equal distance from each other in both horizontal and vertical directions. It is assumed that the matrix and rigid inclusions interact through contact forces without adhesion. To simulate the flow of the porous matrix material, plastic yield condition in Gurson―Tvergaard form is used. Finite element analysis shows matrix surface separation from the inclusion surfaces at the initial period of loading. Then external loading suppresses pores in the form of self-contacted zones on the inner matrix surfaces. The higher initial matrix density corresponds to the faster growth of empty space near rigid inclusions during upsetting. Modeling demonstrates non-monotonous increase in relative density and normal stresses at punches due to metal matrix detachment from ceramic inclusions and pore nucleation. It was found that residual porosity during upsetting increased with increase of concentration of rigid inclusions and could reach 0,1―3% for large strain. It should also be noted that the reduction of material’s strength is confirmed by the dependence of the punch stresses on the upset height. With an increase in volume fraction of inclusions, pore formation near rigid inclusions in-creases and the material reaction weakens.