Development of Simulation Method for Predicting Compact Shape in HIP and CIP

本研究的主要目的是建立粉末等静压成形过程中压坯形状和密度分布的模拟方法。对于热等静压，粘塑性有限元法，而对于CIP的刚塑性有限元分析公式的开发，也试图进行分析的弹塑性有限元方法。传统的vonsticity方程似乎不适用于氧化铝粉末测试。提出了一个新的本构方程。根据陶瓷粉末的变形是由于颗粒间的相对滑动，即存在内摩擦，提出了一种非关联流动法则，建立了刚塑性本构方程，并与实验结果进行了比较。非关联流动规则比关联流动规则与实验结果吻合得更好。然而，非关联流动规则还需要进一步研究，并尝试通过三维压实来检验本构方程。同时，设计并建造了一台可在压制过程中改变应力比的平面应变压制装置。结果表明，尽管传统的和新发展的本构方程都是各向同性的，但在压实过程中，粉末中明显地产生了各向异性.本文将进一步推广包含各向异性的本构方程，并对颗粒材料力学进行系统的研究.

The main objiective of this study is to develop simulating methods to predict the shape of compacts and sensity distribution in the compacts in isostatic pressing of powders. For HIP, a visco-plastic finite element method was developed, whereas for cip a formulation was developed for rigid-plastic finite element analysis; an attempt was also made to analyze by an elastoplastic finite element method.The conventional vonstitutive equation appeared not to apply to alumina powders tested. A new constitutive equation was therefore presented. Further, a non-associated flow rule was also proposed, since the deformation of the ceramic powders is attributed to the relative sliding between particles, which means that internal friction exists.The rigid-plastic finite formulation was developed based on the newly developed constitutive equations, and the results were compared with experimental ones. It appeared that the non-associated flow rule provided better agreement with that of expermental compared with the associated one. Howeber, the non-associated flow rule should be investigated further.An attempt was also made to examine the constitutive equation by the three-dimensional compaction. Also a plane-strain compacting device on which stress ration can be varied during a compacting process was newly designed and built. It was thus found that anisotyopy was apparently induced in the powder during compaction, althoug the constitutive equations, both conventional and newly developed, are isotropic.Generalization of the constitutive equations including anisotropy is a further woek and a systematic study of the mechanics of granular matreials will be pursued.