Abstract
The consideration of different shapes of the yield surface during the compaction of porous materials indicates that an ellipsoid should be recommended due to its simple mathematical form and close description of the actual behaviour of powdered metal (PM) materials during forming processes. Such a yield surface described by a new yield function is discussed for the 7XXX series PM rapidly solidified aluminum alloy. The function is applied to derivation of upper bound theory for porous metals. This paper emphasizes the experimental approach to the determination of the coefficients for this function, relating them to the properties of porous materials (density) and forming conditions (pressure, temperature, strain rate). The yield function and flow rules are verified by cold isostatic pressing and simple hot uniaxial compaction with a satisfactory level of correlation between the experimental and estimated results. The assumption in the upper bound approach that the porous body may be characterized by the existence of displacement rate discontinuities is judged by microstructures, hardness, and density throughout the deformation zone during extrusion.
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Duszczyk, J. Plasticity theory for working of porous metals. J. Materials Shaping Technology 9, 103–115 (1991). https://doi.org/10.1007/BF02833640
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DOI: https://doi.org/10.1007/BF02833640