Powder Granular Modeling for Metal Injection Molding in Future

研究和发展了二维和三维粉末颗粒模型，以定量描述粉末-粘结剂化合物在金属注射成型中的非牛顿流动和固结过程。通过两年的项目，我们开发了新的程序系统Grande(颗粒离散单元)，用于直接模拟粉末-粘结剂化合物。通过各种分析和模拟，我们得到了以下结果：1)我们开发的颗粒模型使我们能够预测绿色化合物流动过程中粘弹性性质的变化。只有粉末的机械性能和聚合物的粘弹性模型才是用作粘结剂的必要属性。即使是局部的流变行为也可以被精确地分析，因此这种颗粒模型应该定量地再现实验测量的表观粘度系数。2)通过本模拟可以直接评估实际金属注射成型中细槽和浇口中二维和三维非牛顿流动的粉末固有的基本行为，如团聚、动量传递和分离过程。3)颗粒建模和热分析的耦合分析使我们能够对粉末-热塑性粘结剂的固结或凝固行为以及粉末-热固性粘结剂的重熔和流动行为做出定量评估。

Two and three dimensional powder granular modelings have been investigated and developed to make quantitative description of non-newtonian flow and consolidation processes of powder-binder compound in the metal injection molding. Through two year project, we have newly developed new program system "GRANDE" (GRANular Distinct Element) for direct simulation of powder-binder compound. BY various analyzes and simulations, we have obtained the following results.1) Our developed granular modeling enables us to predict change of visco-elastic properties of green compound flow in process. Only necessary properties are mechanical properties of powders together with visco-elastic model of polymers to be used as a binder. Even local rheological behaviors are accurately analyzed, so that experimentally measured apparent viscosity coefficient should be quantitaitively reproduced by this granular modeling.2) Fundamental behaviors such as agglomeration, momentum transfer and separation processes intrinsic to powders can be directly assessed by the present simulation for two and three dimensional non-newtonian flow in thin channel and a gate in the actual metal injection molding.3) Coupling analysis of granular modeling with thermal analysis even in three dimensional situation enables us to make quantitative evaluation on consolidation or solidification behaviors of powder-thermoplastic binder and on re-melting and flow bahaviors of powder-thermoset binders.