Analysis of Powder Segregation in Powder Injection Molding

2011 ◽  
Vol 217-218 ◽  
pp. 1372-1379
Author(s):  
Yu Hui Wang ◽  
Xuan Hui Qu ◽  
Wang Feng Zhang ◽  
Yan Li
Keyword(s):  
Fluid Flow ◽  
Injection Molding ◽  
Volume Fraction ◽  
Fluid Model ◽  
Powder Injection Molding ◽  
Powder Injection ◽  
Exchange Term ◽  
Mixture Density ◽  
Two Fluid Model ◽  
Two Fluid

The powder injection molding (PIM) combines the thermoplastic and powder metallurgy technologies to manufacture intricate parts to nearly shape. The powder segregation is a special effect arising in PIM different from than the pure polymer injection. The two-fluid flow model is used to describe the flows of binder and powder so as to realize the prediction of powder segregation effect in PIM injection. To take into account binder–powder interaction, the mixture model of inter-phase exchange term is introduced in the two-fluid model. The two-fluid equations largely resemble those for single-fluid flow but are represented in terms of the mixture density and velocity. The volume fraction for each dispersed phase is solved from a phase continuity equation. As the key to calculate the phase exchange term, the drag coefficient is defined as a function of mixture viscosity. The effective viscosity of binder and powder are agreed with the additive principle. The volume fractions of binder and powder give directly the evolution of segregation during the injection course. Segregation during PIM injection was simulated by software CFX and results were compared with experimental data with good agreement. The basic reasons that caused segregation are identified as boundary effect, differences in density and viscosity of binder and powder. The segregation zones are well predicted. This showed that the two-fluid model is valid and efficient for the prediction of the segregation effects in PIM injection.

Filling of Microarray Fabricated by Micro Powder Injection Molding

2017 ◽  
Vol 898 ◽  
pp. 1171-1176 ◽  
Author(s):  
Lin Liu ◽  
M.X. Qi ◽  
Z.Q. Xie ◽  
Z.Y. He ◽  
F. Ming
Keyword(s):  
Injection Molding ◽  
Volume Fraction ◽  
Fluid Model ◽  
Flow Analysis ◽  
Mold Temperature ◽  
Powder Injection Molding ◽  
Powder Injection ◽  
Two Fluid Model ◽  
Micro Pillars ◽  
Micro Cavity

Flow analysis during injection molding is crucial for dimensional control in micro powder injection molding. Numerical simulation of injection molding of ZrO2 microarray based on in-house feedstock was conducted. A powder-binder two fluid model was developed to analyze temperature, viscosity and powder volume fraction of the feedstock for micro pillars of different dimensions with diameters of 0.2, 0.5 and 1 mm, respectively. In general the binder temperature decreased with size reduction of the micro cavity caved on the silicon wafer and increased with mold temperature. The micro pillars of φ0.2 mm exhibited the highest viscosity, which indicated difficulty for filling during injection molding. An increase in mold temperature facilitated the decrease of the feedstock viscosity, which improved the filling of the micro cavities. Powder-binder segregation became evident as the size of the micro cavities reduced to 0.2 mm.

scholarly journals Computational investigation of liquid-solid slurry flow through an expansion in a rectangular duct

2014 ◽  
Vol 62 (3) ◽  
pp. 234-240 ◽  
Author(s):  
Gianandrea Vittorio Messa ◽  
Stefano Malavasi
Keyword(s):  
Volume Fraction ◽  
Particle Density ◽  
Fluid Model ◽  
Solid Volume Fraction ◽  
Solid Particles ◽  
Rectangular Duct ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Two Fluid Model ◽  
Two Fluid

Abstract The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery

scholarly journals Behaviour and Stability of the Two-Fluid Model for Fine-Scale Simulations of Bubbly Flow in Nuclear Reactors

2015 ◽  
Vol 13 (4) ◽  
pp. 449-459 ◽  
Author(s):  
Henrik Ström ◽  
Srdjan Sasic ◽  
Klas Jareteg ◽  
Christophe Demazière
Keyword(s):  
Volume Fraction ◽  
Nuclear Reactors ◽  
Fluid Model ◽  
Bubbly Flow ◽  
Domain Size ◽  
Fuel Assemblies ◽  
Two Fluid Model ◽  
Liquid Flows ◽  
Two Fluid ◽  
Meso Scale

Abstract In the present work, we formulate a simplistic two-fluid model for bubbly steam-water flow existing between fuel pins in nuclear fuel assemblies. Numerical simulations are performed in periodic 2D domains of varying sizes. The appearance of a non-uniform volume fraction field in the form of meso-scales is investigated and shown to be varying with the bubble loading and the domain size, as well as with the numerical algorithm employed. These findings highlight the difficulties involved in interpreting the occurrence of instabilities in two-fluid simulations of gas-liquid flows, where physical and unphysical instabilities are prone to be confounded. The results obtained in this work therefore contribute to a rigorous foundation in on-going efforts to derive a consistent meso-scale formulation of the traditional two-fluid model for multiphase flows in nuclear reactors.

scholarly journals Effects of Cr and B Contents on Volume Fraction of (Cr,Fe)2B and Hardness in Fe-Based Alloys Used for Powder Injection Molding

2012 ◽  
Vol 43 (7) ◽  
pp. 2237-2250 ◽  
Author(s):  
Jeonghyeon Do ◽  
Hyuk-Joong Lee ◽  
Changwoo Jeon ◽  
Dae Jin Ha ◽  
Choongnyun Paul Kim ◽  
...  
Keyword(s):  
Injection Molding ◽  
Volume Fraction ◽  
Powder Injection Molding ◽  
Powder Injection

scholarly journals On the use of α-shapes for the measurement of 3D bubbles in fluidized beds from Two-Fluid Model simulations

1970 ◽  
Vol 3 ◽  
pp. 26-27
Author(s):  
Ignacio Julián ◽  
David González ◽  
Javier Herguido ◽  
Miguel Menéndez
Keyword(s):  
Delaunay Triangulation ◽  
Fluidized Beds ◽  
Volume Fraction ◽  
Fluid Model ◽  
Accurate Description ◽  
Model Simulations ◽  
Two Fluid Model ◽  
Cloud Of Points ◽  
Two Fluid

A geometrical technique based on shape construction was employed to reconstruct the simulated domain of 3D bubbles in gas-solid fluidized beds from Two-Fluid Model simulations. The Delaunay triangulation of the cloud of points that represent volume fraction iso-surfaces was filtered using α-shapes, allowing a topologically accurate description of the bubbles.

scholarly journals Investigation on Bubble Diameter Distribution in Upward Flow by the Two-Fluid and Multi-Fluid Models

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5776
Author(s):  
Yongzhong Zeng ◽  
Weilin Xu
Keyword(s):  
Experimental Data ◽  
Volume Fraction ◽  
Fluid Model ◽  
Bubble Diameter ◽  
Diameter Distribution ◽  
Bubble Flow ◽  
Calculation Results ◽  
Two Fluid Model ◽  
Gas Volume ◽  
Two Fluid

Bubble flow can be simulated by the two-fluid model and the multi-fluid model based on the Eulerian method. In this paper, the gas phase was further divided into several groups of dispersed phases according to the diameter by using the Eulerian-Eulerian (E-E) multi-fluid model. The diameters of bubbles in each group were considered to be the same, and their distributions were reorganized according to a specific probability density function. The experimental data of two kinds of bubble flow with different characteristics were used to verify the model. With the help of the open-source CFD software, OpenFOAM-7.x (OpenFOAM-7.0, produced by OpenFOAM foundation, Reading, England), the influences of the group number, the probability distribution function, and the parameters of different bubble diameters on the calculation results were studied. Meanwhile, the numerical simulation results were compared with the two-fluid model and the experimental data. The results show that for the bubble flow with the unimodal distribution, both the multi-fluid model and the two-fluid model can obtain the distribution of gas volume fraction along the pipe radius. The calculation results of the multi-fluid model agree with the experimental data, while those of the two-fluid model differ greatly from the experimental data, which verifies the advantage of the multi-fluid model in calculating the distribution of gas volume fraction in the polydisperse bubble flow. Meanwhile, the multi-fluid model can be used to accurately predict the distribution of the parameters of each phase of the bubble flow if the reasonable bubble diameter distribution is provided and the appropriate interphase force calculation model is determined.

Fabrication and Bending Strength of Al/SiC Composites with High Volume Fraction of Reinforcement by Combining Powder Injection Molding and Pressure Infiltration

2011 ◽  
Vol 189-193 ◽  
pp. 2945-2948
Author(s):  
Liang Xiong ◽  
Hao He ◽  
Yi Min Li
Keyword(s):  
Particle Size ◽  
Injection Molding ◽  
Bending Strength ◽  
Volume Fraction ◽  
High Volume ◽  
Powder Injection Molding ◽  
High Volume Fraction ◽  
Powder Injection ◽  
Pressure Infiltration ◽  
Sic Composites

The paper presents the result of an experimental investigation on the fabrication of Al/SiC composites with high volume fraction of SiC particles by pressure infiltration of liquid aluminum into preforms prepared by powder injection molding (PIM). To obtain the required high particle volume fraction, SiC powders with a bimodal particle size distribution were used. The influence of powder loading and particle size on the bending strength of the prepared composites has been investigated. It is demonstrated that pressure infiltration permits to achieve high relative densities for the composites (i.e. 98.8%). The microstructure studies revealed a uniform distribution of SiC particles in the composites without interface reactions between the particles and the aluminum matrix. The bending strength increases with increasing powder loading and decreasing particle size of the coarse powders in the bimodal powder system.

A Two-Fluid Model of Mixing in a Two-Dimensional Enclosure

1998 ◽  
Vol 120 (1) ◽  
pp. 115-126 ◽  
Author(s):  
O. J. Ilegbusi ◽  
M. D. Mat
Keyword(s):  
Potential Energy ◽  
Buoyancy Force ◽  
Volume Fraction ◽  
Fluid Model ◽  
Two Dimensional ◽  
Material Interface ◽  
Thermal Buoyancy ◽  
Two Fluid Model ◽  
Nonisothermal Conditions ◽  
Two Fluid

Mixing of fluids in a cavity under isothermal and nonisothermal conditions is studied with a two-fluid model. This model involves the solution of separate transport equations for zone-averaged variables of each fluid with allowance for interface transport of momentum and energy. The effects of thermal and potential energy driven convection as well as Prandtl number are investigated. The material interface is represented by the contour of the volume fraction separating the fluids. The effect of the buoyancy force due to the initial potential energy of the fluids is found to predominate over thermal buoyancy for comparable Grashof numbers.

Numerical Study of Two-Phase Flow in a Horizontal Pipeline Using an Unconditionally Hyperbolic Two-Fluid Model

2018 ◽  
Author(s):  
Raphael V. N. de Freitas ◽  
Carina N. Sondermann ◽  
Rodrigo A. C. Patricio ◽  
Aline B. Figueiredo ◽  
Gustavo C. R. Bodstein ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Fluid Model ◽  
Momentum Conservation ◽  
Design Stage ◽  
Two Phase Flows ◽  
Two Phase ◽  
Efficient Manner ◽  
Two Fluid Model ◽  
Two Fluid

Numerical simulation is a very useful tool for the prediction of physical quantities in two-phase flows. One important application is the study of oil-gas flows in pipelines, which is necessary for the proper selection of the equipment connected to the line during the pipeline design stage and also during the pipeline operation stage. The understanding of the phenomena present in this type of flow is more crucial under the occurrence of undesired effects in the duct, such as hydrate formation, fluid leakage, PIG passage, and valve shutdown. An efficient manner to model two-phase flows in long pipelines regarding a compromise between numerical accuracy and cost is the use of a one-dimensional two-fluid model, discretized with an appropriate numerical method. A two-fluid model consists of a system of non-linear partial differential equations that represent the mass, momentum and energy conservation principles, written for each phase. Depending on the two-fluid model employed, the system of equations may lose hyperbolicity and render the initial-boundary-value problem illposed. This paper uses an unconditionally hyperbolic two-fluid model for solving two-phase flows in pipelines in order to guarantee that the solution presents physical consistency. The mathematical model here referred to as the 5E2P (five equations and two pressures) comprises two equations of continuity and two momentum conservation equations, one for each phase, and one equation for the transport of the volume fraction. A priori this model considers two distinct pressures, one for each phase, and correlates them through a pressure relaxation procedure. This paper presents simulation cases for stratified two-phase flows in horizontal pipelines solved with the 5E2P coupled with the flux corrected transport method. The objective is to evaluate the numerical model capacity to adequately describe the velocities, pressures and volume fraction distributions along the duct.

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