CONSTITUTIVE MODELS FOR POWDER MATERIALS

Constitutive models to describe the mechanical material behaviour of hardmetal powders are studied. Three classes of constitutive relationships are examined, described as cap plasticity, multisurface plasticity and endochronic plasticity. A representative model of each class is studied in detail. An optimization technique is used to fit the constitutive parameters to empirical test data on multiaxially loaded hardmetal powder specimens. Of all models tested, an endochronic model proposed by Bazant shows the best agreement with the empirical test data. Different phenomena can be simulated with the model by adding certain constitutive functions. It is, however, difficult to fit the model to test data because of the large number of model parameters, most of which have no physical meaning.