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在金属或陶瓷粉末注射成形中,由于粉末与粘结剂的密度差异,二者在高速充模的过程中会产生局部比例变化,即偏析现象。针对偏析现象,采用两相流注射模型,将注射喂料视为由粉末相和粘结剂相组成的混合流体,预测注射成形坯件中粉末相和粘结剂相的分布。将结果引入到后续的烧结模拟中,宏观烧结模型采用基于热弹粘塑性的本构关系。据此模拟产品在烧结过程中发生的收缩和变形以及预测产品在烧结过程中现场强度(In-situ strength)。模拟结果说明注射坯件的非匀质性导致产品的烧结过程中产生非均匀收缩和内部应力的大幅度上升,影响产品的精度和性能。这种从注射到烧结的模拟体系可用于优化粉末注射成形工艺的喂料设计、模具设计以及注射和烧结工艺参数的选取。
In the metal or ceramic powder injection molding, due to the density of the powder and binder differences, the two in the process of high-speed filling will have a local proportion change, that segregation phenomenon. Aiming at the segregation phenomenon, a two-phase injection model was adopted. The injection feed was regarded as a mixed fluid composed of powder phase and binder phase, and the distribution of powder phase and binder phase in injection-molded blanks was predicted. The results are introduced into the subsequent sintering simulation. The macroscopic sintering model uses the constitutive relation based on thermo-visco-plasticity. According to this simulation product shrinkage and deformation occurred in the sintering process and predict the product during sintering in-situ strength (In-situ strength). The simulation results show that the inhomogeneity of the injection blank leads to the non-uniform shrinkage and the significant increase of the internal stress in the sintering process, which affects the accuracy and performance of the product. This injection to sinter simulation system can be used to optimize powder injection molding process feeding design, mold design and injection and sintering process parameters.