THE EFFECTS OF RATE SENSITIVITY AND PLASTIC POTENTIAL SURFACE CURVATURE ON PLASTIC-FLOW LOCALIZATION IN POROUS SOLIDS

Plastic flow localization in porous elastic-viscoplastic solids is analyzed with an emphasis on the effects of material rate sensitivity and plastic potential surface curvature. The effect of rate sensitivity is included in a material model that accounts for a change of yield surface curvature in a rate-insensitive porous ductile solid. Shear band formation under plane strain and axisymmetric tension, and localized necking in biaxially stretched sheets are analyzed by using the present material model. The results illustrate the interactions of the effects of void nucleation and growth, material rate sensitivity and plastic potential surface curvature on plastic flow localization. The effects of nonproportional straining paths on localized necking in thin sheets are also demonstrated.