Establishment of Particle-micromechanics -Road to Net-shaping-

本研究项目的目标是首先建立描述粉末颗粒力学行为的颗粒微观力学的基本理论。;其次，在此基础上，研究粉末压实行为的模拟方法，以期实现近净形状生产。;第三，建立永磁体等磁性器件磁特性分析的理论与仿真方法。磁铁通常由各向异性磁粉在磁场中压实制成；在压实过程中易磁化轴的旋转或对准决定了磁铁的特性；在生产中，没有采取科学的方法，因此对这些产品的磁特性进行优化是非常重要的。试图建立一种控制和优化磁体功能的理论和方法。结果表明：1)在颗粒模型的模拟中，在易于处理的圆形或球形模型的基础上，建立了非圆形或非球形模型。2)虽然在模拟中加入了粒子间摩擦，但作为相对运动的阻力还不够。我们开发了一个新的摩擦模型，描述了真实的阻力，因此，我们将能够评估粉末压实过程不仅定性而且定量。3)在连续介质方法中，实验研究了粉末压实材料的弹性特性，并将杨氏模量表示为相对密度。结合粉末压实的塑性理论，建立了弹塑性有限元公式。通过应用这一点，我们将能够模拟生产复杂形状的压实过程。我们发展了一种新的描述局部旋转的磁Cosserat理论。建立了一种有限元模拟方法，能够分析在外加磁场作用下，易磁化轴在压实过程中的旋转或对中情况。结果表明，磁场强度和磁场施加方式对取向起决定性作用。该理论包括几个材料参数；这些在本项目中尚未确定。这应该为今后的工作做准备。少

The objective of this research project it first to establish fundamental theory for particle micro-mechanics that describes mechanical behavior of powder particles. ; second, based on this, to develop simulation method for investigating powder compaction behavior with a view to performing near net shape production. ; third, to develop a theory and simulation method for analyzing magnetic characteristics of magnetic devices such as permanent magnet. Magnet is usually made from anisotropic magnetic powders by compacting them in magnetic field ; rotation or alignment of the easy axs of magnetization during compaction determines the characteristics of the magnet ; in the production, scientific approach has not been undertaken, thus optimization of magnetic characteristics of these products is of geat importance. An attempt is made to develop a theory and method for controlling and optimizing the function of the magnet. The results obtained are as follows :1)In simulation by particulate mod … More eling, we developed non-circular or non-spherical model, on top of circular or spherical model, that are easily treated.2)Although inter-particle friction was incorporated in this simulation, it was not sufficient as resistant against relative movement. We developed a new model for friction that describes real resistant, and therefore, we shall be able to evaluate powder compaction process not only qualitatively but also quantitatively.3)In the continuum approach, elastic properties of powder compacts were investigated experimentally, and we expressed the Young modulus in terms of relative density. Elasto-plastic finite element formulation was carried out combining plasticity theory for powder compaction. By applying this, we shall be able to simulate compaction processes for producing complicated shapes.4)We developed a new magnetic Cosserat theory that describes local rotation. A finite element simulation was developed that is capable of analyzing rotation or alignment of easy axs of magnetization during compaction in applied magnetic field. It was thus shown that the strength of magnetic field and application pattern of magnetic field gave a decisive role to the alignment. The theory includes a few material parameters ; these were not yet determined in this project. This should be done for future work. Less