Contribution to the Experimentation, the Modeling and the Numerical Simulation of Metal Injection Molding Process

摘要

注射是金属粉末注射成型的重要工艺步骤之一。通过数值模拟以预测充填模腔，是选择注射工艺参数及模具设计的关键因素。本论文主要研究与注射模拟相关的不同方面：进行原料实验以获得某些重要特性，供数值模拟研究之用；充填典型腔模具的流动扩展计算模拟；和以聚合物与金属粉末为基础的原料分子动力学研究。
　　注射于模腔内的原料特性由实验和解析方法获得。所选原料由粘结剂(以聚丙烯，石蜡与硬脂酸为基础)和316L不锈钢粉末以一定比例组成。该原料被论文作者定义，以应用于注塑机器和注射与分子动力学的计算模拟。
　　在定义原料的某些重要特性后，论文作者致力于316L不锈钢粉末恒定粘度流动注射的二维数值模拟研究。在建立分解Navier-Stokes方程和支配充填模腔的输运方程的解法后，该解法在典型情况的应用中得以验证。双向注入模具的充填注射数值模拟，即两个阵面在一个模腔内流动填充，通过显式有限元法研究。本项研究侧重于输运方程算法的研究与实施，主要以上风法(具体即Streamline Upwind Petrov-Galerkin(SUPG))为研究方法，该方法证实Petrov-Galerkin常规算法的稳定性。单注射问题以创新方法处理：以单独正常网为基础，联合使用近似Navier-Stokes方程的有限元法及有限差分法分解输运方程。收敛流量和发散流量由论文作者通过Matlab自编程的数值模拟求解。有限元/有限差分联结算法与SUPG上风法在单注射数值模拟中就以下几项关键标准进行对比：填充的阵面形状和状态根据时间，速度剖面和尽显决议解算时间。在参照原料具体参数的前提下，当量粘度表达式被定义并在FEM解算器上使用。当量粘度表达式用以建模，可更准确地表达模具中的流动过程。
　　明确原料粘度表达式的重要性后，通过应用耗散粒子动力学方法(简称DPD)，论文作者进行了分子动力学研究，以模拟计算原料的介观尺度。原料模拟过程使用ESPResSo软件包，在数值模拟过程中特意侧重粒子间的相互作用，DPD的温控器和整合方法。原料的Poiseuille流在一个方形截面上以非平衡分子动力学(简称NEMD)方法进行模拟。温度，负荷率和粘结剂/粉末比例对流体剪切粘度产生的影响因此得以证明。

目录

文摘

英文文摘

INTRODUCTION

CHAPTER 1 THEORETICAL FOUNDATIONS

1.1 METAL POWDER INJECTION MOLDING PROCESS

1.1.1 Principle of the Process

1.1.2 Metal Powders for PIM

1.1.3 Binder Systems for MicroPIM

1.1.4 Compounding Feedstocks for MicroPIM

1.1.5 Rheology Measurements of PIM Feedstocks

1.1.6 Patterning Process for PIM Microparts

1.2 MIXTURE THEORY AND NUMERICAL SIMULATIONS OF INJECTION MOULDING PROCESS

1.2.1 Mixture Theory in Injection Moulding

1.2.2 Main Physical and Numerical Aspects

1.3 MICRO POWDER INJECTION MOLDING：PROCESS CHARACTERISATION

1.4 STATISTICAL MECHANICS，THERMODYNAMICS AND HYDRODYNAMICS

1.5 COMPUTER SIMULATIONS

1.5.1 Molecular Dynamics

1.5.2 Langevin Dynamics

1.6 COARSE-GRAINING AND LEVELS OF DESCRIPTION

CHAPTER 2 PHYSICS OF BINDER AND METALLIC PARTICLES

2.1 CHARACTERISTICS OF METAL POWDER AND BINDER USED IN THE STUDY

2.1.1316L Stainless Steel Powder

2.2 BINDER

2.2.1 Feedstock

2.3 FEEDSTOCK VISCOSITY MODEL

2.3.1 Theoretical Overview

2.3.2 Proposition of a New Viscosity Formulation

2.4 METALLIC PARTICLES AND BINDER COMPOUNDS INTERACTIONS

2.4.1 Particle Mass Determination

2.4.2 Bonded and Non-bonded Interactions

2.4.3 Lennard-Jones Units

2.4.4 Determination of Lennard-Jones Parameters

2.4.5 Van der Waals Interactions

2.5 EXPERIMENTAL MEASUREMENT AND THEORETICAL APPROACH OF BINDER COMPOUNDS CHARACTERISTICS

2.5.1 Experimental Protocol for Determination of Degree of Polymerisation-SEC Analysis

2.5.2 Number of Monomers per Polymeric Chain

2.5.3 Summary of Binder Compounds Characteristics

2.6 CONCLUSIONS AND REMARKS

CHAPTER 3 SIMULATION OF MICRO INJECTION MOULDING

3.1 DEVELOPMENT OF THE EXPLICIT FINITE ELEMENT SCHEME

3.1.0 Variables and Notations

3.1.1 Overview of the Problem

3.1.2 Governing Equations

3.1.3 Description of the Numerical Model

3.1.4 Phase Interaction

3.1.5 Viscous Diffusion

3.1.6 Incompressibility

3.1.7 Evolution of the Phase Volume Fractions

3.1.8 Determination of the Filling State

3.1.9 Boundary Conditions Applied in Solution

3.1.10 Time Step Control

3.1.11 Summarize of the Solving Scheme of Explicit Algorithm

3.2 A STREAMLINE-UPWIND MODEL FOR FILLING FRONT ADVECTION

3.2.1 Introduction

3.2.2 Petrov-Galerkin Formulation

3.2.3 Weighting the Modification：Stabilization Parameter τ

3.3 NUMERICAL SIMULATION OF THE FILLING STAGE IN THE CASE OF BI-INJECTION MOULDING

3.3.1 Comparative Results

3.3.2 Comparison with Experiments

3.3.3 Concluding Remarks

3.4 A COUPLED FINITE ELEMENT/FINITE DIFFERENCE APPROACH FOR FILLINO FRONT TRACKING IN POWDER INJECTION MOULDING

3.4.0 Variables and Notations

3.4.1 Overview of the Problem

3.4.2 Formulation of the Biphasic FluidFlow Problem

3.4.3 Solution Procedure for the Transport Equation in 2D

3.4.4 Solving Method for Navier-Stokes Equations

3.4.5 Solution Procedure Algorithms

3.4.6 Comparison with an Analytical Solution

3.4.7 Comparison with FEM/SUPG Method

3.4.8 Comparison with Experiments

3.5 CONCLUSIONS

CHAPTER 4 MOLECULAR DYNAMICS SIMULATION OF METAL POWDER INJECTION MOLDING FEEDSTOCK

4.1 VARIABLES AND NOTATIONS

4.2 INTRODUCTION-MESOSCALE SIMULATION TECHNIQUES

4.2.1 Complex fluids

4.2.2 Macroscale and Microscale Simulation Approaches

4.2.3 Mesoscale Simulation Techniques

4.2.4 Molecular Dynamics Ensembles

4.3 THEORETICAL DEVELOPMENTS IN DISSIPATIVE PARTICLE DYNAMICS：A THOROUGH LITERATURE REVIEW

4.3.1 A Short History of Dissipative Particle Dynamics

4.3.2 Applications of Dissipative Particle Dynamics

4.3.3 Dissipative Particle Dynamics

4.3.4 Stochastic Differential Equations and Fokker-Planck Equations for DPD

4.3.5 Dynamics of the Particles-Multi-Body Dissipative Particle Dynamics

4.3.6 Matching the Equation Of State(EOS)

4.3.7 Hydrodyynamics for DPD

4.3.8 Concluding Remarks

4.4 THE ESPRESSO PACKAGE

4.4.1 ESPResSo-Extensible Software Package for Research on Soft Matter

4.4.2 Simulation Setup

4.4.3 Concluding Remarks

4.5 MOLECULAR DYNAMICS OF POLYMERIC CHAINS

4.5.1 Introduction

4.5.2 Simulation of Metallic Particle Charged Polymer Melt

4.5.3 Concluding Remarks

4.6 NON-EQUILIBRIUM MOLECULAR DYNAMICS FOR THE DETERMINATION OF SHEAR VISCOSITY OF MULTI-BODY FLUID

4.6.1 Introduction

4.6.2 Molecular System Modeling

4.6.3 Development of the Model for Shear Viscosity Determination

4.6.4 Concluding Remarks

SUMMARY AND OUTLOOK

ACKNOWLEDGEMENTS

REFERENCES

LIST OF PUBLICATIONS