Powder Granular Modeling for Metal Injection Molding in Future

为了定量描述金属注射成形过程中粉末-粘结剂复合材料的非牛顿流动和固结过程，研究并建立了二维和三维粉末-颗粒模型。通过两年的项目，我们新开发了新的程序系统“GRANDE”（颗粒离散元），用于直接模拟粉末粘合剂复合材料。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过程中的绿色化合物流的粘弹性性质的变化。唯一必要的性能是粉末的机械性能以及用作粘合剂的聚合物的粘弹性模型。即使是局部流变行为的准确分析，使实验测量的表观粘度系数应定量再现这种颗粒模型。2）基本行为，如团聚，通过对实际金属注射成形中的细通道和浇口中的二维和三维非牛顿流动的模拟，可以直接评估粉末固有的动量传递和分离过程。即使在三维情况下，颗粒模拟与热分析的耦合分析也使我们能够对粉末-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进行定量评估。

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.