A modified plasticity theory for sintered powder materials, taking into acc
ount the real complex state of porosity and micro-defects (cracks, non-meta
llic inclusions, etc.) is proposed. Equations for plastic flow were develop
ed and methods for calculating the true mechanical properties are suggested
. The yield criterion derived, in conjuction with simple uniaxial compressi
on tests conducted on specimens of the porous material, may evaluate the re
al state of the material porosity related to micro-defects which may consti
tute the sources for the initiation and propagation of cracks, even in high
compressive stress fields such as those developed in most manufacturing pr
ocesses, as well as the formation of new pores during plastic deformation.
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