Phase Behaviors in Bi-phase Simulation of Powder Segregation in Metal Injection Molding

Powder segregation induced by mold filling is an important phenomenon that affects the final quality of metal injection molding （MIM）. The prediction of segregation in MIM requires a bi-phase flow model to describe distinctly the flows of metallic powder and polymer binder. Viscous behaviors for the flows of each phase should hence be determined. The coefficient of interaction between the flows of two phases should also be evaluated. However, only viscosity of the mixed feedstock is measurable by capillary tests. Wall sticking is supposed in the traditional model for capillary tests, while the wall slip is important to be taken into account in MIM injection. Objective of the present paper is to introduce the slip effect in bi-phase simulation, and search the suitable way to determine the viscous behaviors for each phase with the consideration of wall slip in capillary tests. Analytical and numerical methods were proposed to realize such a specific purpose. The proposed method is based on the mass conservation between the capillary flows in mono-phase model for the mixed feedstock and in bi-phase model for the flows of two phases. Examples of the bi-phase simulation in MIM were realized with the software developed by research team. The results show evident segregation, which is valuable for improving the mould designs.     

A New Explicit Algorithm for Bi-Phasic Mixture Flow in MIM

Metal injection moulding (MIM) is a new technology to manufacture small intricate parts in large quantity. Numerical simulation plays an important role in its development. To predict the specific segregation effect in MIM injection, mixture theory is adopted to model the injection flow by a bi-phasic model. This model conducts to the solution of two-coupled Stokes equations. It is an extremely computational consuming solution in the scope of the traditional algorithms, which induce a serious challenge to cost-effectivity of the MIM simulation. Referred to some methods proposed by Lewis in mono-phasic simulation and the implicit algorithms in MIM simulation, a new explicit algorithm is proposed and realized to perform efficiently this type of bi-phasic flow. Numerically this algorithm is devised to perform the simulation in a fully uncoupled manner except for a global solution of the pressure field in each time step. The physical coupling is taken into account in a sequential pattern by fractional steps. This special algorithm does not need any iteration, so it is straightforward and robust, suitable for MIM simulation and other sorts of simulations for multi-phasic flow.     

金属板件冲压过程的数值模拟

本文介绍以大时间增量方法求解金属板件冲压成形数值模拟的原理及实施方式。讨论了与之相关具有接触和摩擦几何非线性问题的描述方法，并给出二维问题的算例。     

金属切削加工切屑形成过程仿真技术

分析金属切削加工切屑形成过程,计算切屑位置参数,由屑型判别框图确定切屑类型,并完成各类型切屑特征造型,实现切削加工过程中切屑形成过程仿真。     

基于技术进步的观点,对金属材料成型中数值模拟的讨论

基于技术进步的观点,本文分析了在金属材料成型数值模拟软件开发中,可应用的新技术—即面向对象的程序设计方法,友好的输出界面和数值模拟软件与CAD／CAM软件的集成。     

金属再结晶组织模拟及实验对比研究

金属再结晶过程计算机组织模拟,可以仿真实验中观测不到的组织演变细节,得到定量的特征参数,预报退火后的材料性能,指导热处理工艺设计。构建一个新的静态再结晶MC Potts模拟模型,并以1060铝合金为研究对象,进行再结晶模拟与实验对比研究。结果表明,1060铝合金表现出明显的再结晶特征,得到了近似等轴晶组织;新模型模拟的再结晶形核位置、组织形貌与实验结果一致,组织演变过程也与实验结果基本一致,但模拟的再结晶等轴晶与实验近似等轴晶不完全一致,模拟的再结晶速度也低于实验结果。     

柴油机燃油电控喷射用快速电磁阀的研究

阐述了快速电磁铁实现快速动作的机理,建立了快速电磁铁优化设计的数学模型,并用计算机对其结构进行了最佳化设计。在确定快速电磁铁最佳结构参数的基础上,建立了其动态特性计算机仿真的教学模型,对其动态特性进行了计算机仿真,并对不同能量输入方式和不同线圈参数的仿真结果进行了比较。     

Numerical Simulation Research on Laser Shock Forming of Thin Metal Sheet

Laser shock forming (LSF) of sheet metal is a new technique realized by applying an impulsive pressure generated by laser-induced shock wave on the surface of metal sheet.LSF of brass sheet metal was investigated using a Q-switched Nd:YAG laser with an energy per pulse of 15～50 joules.ABAQUS software was used to simulate laser shock forming process.The central displacement of the shocked region is measured and compared with the simulation.The higher pulse energy, the higher central displacement of the shocked region were obtained.The deformation of the simulation matches the experiment quite well.     

土石混填路堤基底坡度效应的数值模拟研究

在山区高速公路建设中,路堤多采用土石混合料填筑。结合西部某高速公路工程项目,对其红色碎屑岩类无粘性土石混填路堤进行数值模拟,着重研究路堤基底角度从0o变化到20o时路堤及基底附近的应力形变场特征及其变化规律。结果表明路堤内的最大沉降值和最大水平位移值随基底坡度的增大而减小,其位置逐渐升高,并逐渐向坡面靠近,而路堤内应力的分布受坡度的影响不明显。     

基于Marc金属正交切削过程仿真的参数化建模

对金属正交切削过程的仿真,方便和快捷地对刀具—工件系统进行造型是必要的。本文通过建立刀具、工件的参数化模型并选用了合适的造型方式,应用数据库技术,采用C++Builder软件完成了接口设计;给定刀具的结构尺寸、几何角度和工件的几何尺寸以及刀具与工件的相对位置,即可生成二维造型的的过程文件,并在Marc软件环境中完成刀具—工件的建模。最后介绍了刀具—工件的参数化造型的关键技术及其过程。从而为正交切削过程的数值模拟奠定了基础。