Abstract
In this work, powder compaction process was investigated by using a numerical material model, which involves Mohr-Coulomb theory and an elliptical surface plasticity model. An effective algorithm was developed and implemented in the ANSYS finite element (FEM) code by using the subroutine USERMAT. Some simulations were performed to validate the proposed metal powder material model. The interaction between metal powder and die walls was considered by means of contact elements. In addition to the analysis of metal powder behaviour during compaction, the actions transmitted to die were also investigated, by considering different friction coefficients. This information is particularly useful for a correct die design.
Highlights
A deep knowledge of metal powder behaviour during compaction stage is necessary to predict the final shape and density distribution of formed products, and to avoid damages and breakages, which may occur during the subsequent sintering phase
Material model was implemented in ANSYS finite element (FEM) code by subroutine USERMAT
Several numerical simulations were performed considering a simple 2D axialsymmetric geometry to evaluate the forces acting on the die walls, in addition to metal powder behaviour analysis
Summary
A deep knowledge of metal powder behaviour during compaction stage is necessary to predict the final shape and density distribution of formed products, and to avoid damages and breakages, which may occur during the subsequent sintering phase. The material model used in this study consists of two limit surfaces [21] F1 and F2: the former, F1(σ), θ is related to the Mohr-Coulomb criterion (cone surface); the latter, F2(σ, σc), is related to a yield elliptical surface (cap surface) where σc represents a hardening parameter, function of volumetric plastic strain. Such a formulation is suitable for modelling metal powders with extremely different relative density (from r 0.2 to r 1.0 ). The proposed model allows calculating bulk modulus K with the following relationship:
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