Near Net Shape Manufacturing of CuCr Vacuum Switching Contacts ...

WS 15/12 17th Plansee Seminar 2009, Vol. 3 Feist, Oberbreyer et al.
Summary
A mathematical model dedicated to numerically resolve the traditional PM process-chain – consisting of
die-compaction and sintering – by means of the finite element method (FEM) was presented. The model
relies on the concepts of continuum mechanics and describes the constitutive response using a combined
DRUCKER-PRAGER-cap plasticity model and an anisotropic visco-elastic model for the compaction- and
sintering-stage, respectively. Development and application of the model is motivated by the demands for
near net shape (NNS) manufacturing of parts reducing or making subsequent mechanical treatment almost
obsolete. The numerical model allows for fast and relatively cheap evaluation of different processplans
and optimization to achieve the demands of NNS-products.
The mathematical model was outlined with an emphasis on the employed constitutive models. Determination
of the relevant constitutive properties in the framework of powder-characterization was covered
subsequently. In order to determine appropriate initial guesses for the relevant process-parameters based
on the identified material behavior an analytical procedure was presented. Its results can be used both for
subsequent experimental as well as virtually conducted compaction-tests.
Application of the numerical model and the analytical procedure was finally given by means of a switching
contact part made of CuCr-alloy as used in the power-generation industry. For the sake of simplicity,
application of the model was restricted to a first step within an iterative numerical procedure with the objective
both to obtain almost uniform density-distributions and to minimize geometrical deviations from the
desired final geometry.
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