In the field of powder metallurgy (PM), complex components with complicated shapes can be manufactured. One important step in the PM process is the powder pressing process, where powder is consolidated during a forming operation into a desired shape, normally by applying pressure. During powder pressing, the mechanical properties of powder materials change dramatically. PM manufacturers tend to produce components with shapes of increasing complexity, requiring improved pressing equipment and methods. The most crucial aspect is to control the powder flow during die filling and the final powder density distribution after the filling stage, which has been shown to affect the strength of the final component significantly [1].
To investigate the non-homogeneity of the density of PM components, experimental studies combined with numerical simulations of the die filling stage are exploited.
This work covers the numerical modelling and simulation of die filling. The discrete element method (DEM) [2] was used to model the powder, and computational fluid dynamics (CFD) to model the air. To study the effect of air on powder flow, the DEM was coupled to the CFD using a two-way coupling approach. Experimental measurements with digital speckle photography (DSP) from a previous study [3] were used for comparison with the numerical simulations.
The comparison of the DSP measurements and the numerical simulations showed similar macroscopic flow characteristics. Thus, the adequacy of the proposed DEM-CFD model has been demonstrated in a metal powder die filling operation. The DEM-CFD method has been shown to be an effective method for the numerical simulation of the interaction between powder and air.
References
[1] Zenger, D. & Cai, H. (1997). Handbook of the Common Cracks in Green P/M Compacts. Metal Powder Industries Federation, MPIF. Worcester, USA.
[2] Cundall, P. A., & Strack, O. D. (1979). A discrete numerical model for granular assemblies. geotechnique, 29(1), 47-65.
[3] Larsson, S., Gustafsson, G., Jonsén, P. & Häggblad, H.-Å. (2016). Study of Powder Filling Using Experimental and Numerical Methods. In: World PM2016 Congress & Exhibition, Hamburg, October 9-13, 2016.
IACM , 2018. p. 1695-1695
13th World Congress on Computational Mechanics (WCCM XIII), July 22-27, 2018, New York, NY, USA