Abstract
In the present paper, V-bending of polypropylene (PP) is analyzed by the finite element method using a plastic constitutive equation for hydrostatic-pressure-dependent polymers proposed by one of the present authors. The yield surface is expressed by the first and second invariants of stress to describe the hydrostatic-pressure dependence. A plastic potential that is different from the yield surface is employed to describe the incompressibility of polymeric materials. Isotropic hardening is assumed. The proposed constitutive equations are implemented in the finite element code MSC.Marc with user subroutines. The calculated load-stroke curves appropriately describe the effect of introducing the hydrostatic-pressure dependence of PP. Moreover, the calculated results agree with the experimental ones for various thicknesses of specimens. Finally, the calculated distributions of bending stress and bending strain in the specimen also show the effects of hydrostatic-pressure dependence.
