On the influence from punch geometry on the stress distribution at powder compaction

A numerical analysis, using the finite element method, of the mechanical behavior at powder compaction at higher densities was performed. In this investigation the material behavior is modeled using an advanced macroscopic constitutive description initially presented by Brandt and Nilsson [1]. This material model, like many other models describing powder compaction at higher densities, includes a large number of constitutive parameters and as a result, a complete material characterization is a difficult task to perform or at least requires a large number of different experiments. A remedy to this problem is to apply inverse modeling, i.e. optimization, for determination of relevant material properties from comparatively simple experiments. It is then of course important, in order to achieve high accuracy results from the optimization procedure, that the stress fields produced during the experiments involves high gradients of stress. Adhering to simple uniaxial die compaction experiments the main parameter that can be used in order to achieve such a feature is the geometry of the punch used for load application. In the present investigation a number of punch profiles are studied and it is found that a skewed punch geometry is the most appropriate one to be used for experimental die compaction aiming at a constitutive description of the powder material based on inverse modeling. The main efforts are devoted towards an analysis based on the previously mentioned material model by Brandt and Nilsson [1] but also relevant results for another type of constitutive model will be presented.

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