The Numerical Simulation of Casting Process for Making Metal Matrix Composites

In this paper,a numerical simulation of the casting process for making the MMC.using the PEM, is studied.The convection of liquid metal and the release of latent heat of solidification are taken into account.The algorithm and program for axisymmetric casting model are developed to the problem of coupling between flow and heat transfer,as well as phase change.The variational curves of temperature,the position of flow front and the distrsbutions of volume fraction of solid metal in matrix and their variation with time are obtained.The influences of technological paarmeters to casting are discussed.     

Present Statue and Future of the In-situ Reaction Synthesis Technology for Metal Matrix Composites Fabricated

Among the methods of fabrication of ceramic particles reinforced Metal Matrix Composites, the in-situ reaction synthesis technology has obvious technical and economical advantages over other traditional methods. The in-situ reactive technology has become the leading direction in composites research area in the past decade. The main in-situ reaction synthesis methods include XD, VLS, SHS, DIMOX, PRIMEX, RSD, CR, MA, etc. The principles, properties and prospective application of the main in-situ reaction synthesis methods are reviewed. The Metal Matrix Composites, prepared by in-situ reaction composite technology, can normally achieve higher mechanical properties than other traditionally prepared composites under the same condition. The in-situ reaction synthesis technology, with its wide raw material resources, low price, relatively simple processes, low cost preparation and application feasibility in large-scale industry process, is of great future.     

Numerical Simulation of Temperature Field during the Dissolution-Diffusion Bonding Process to Mending Iron Casting Defects

The common finite element method microcomputer software for simulation of the temperature field is developed by authors. It is used for calculating the temperature field duringthe mending process of iron casting defects by means of the dissolution-diffusion bonding technology. The correctness has been proved by testing results. This software has been used to analyse thecaused of hardness rising in heat effecting zone,and also find out the approach for solving the problem.     

Recent Development of Solid/Liquid Reaction Synthesis Technology for Metal Matrix Composites

TheSolid/liquidReactionSynthesisTechnologyforMetalMatrixCompositeshasattractedanincreasinginterest, andalotofimportantprogresseshavebeenmadeinrecentyears.Fivetypicalprocesses ,exothermicdispersion ,coatingtech nologybycontactreaction ,liquidcontactreaction ,meltinfiltrationandreactivespraydeposition ,havebeenreviewed .More attentionhasbeenpaidtorecentdevelopmentoftheresearchworkontheexothermicdispersion ,coatingtechnologybycontact reactionandliquidcontactreaction .Thecharacteristicsoftheseprocessesareanalysed ,andtheexistedproblemsonthereac tionsynthesistechnologiesarediscussed .     

Numerical Simulation of the Solidification Process Under the Effect of Nature Convection

The process of solidification is numerically simulated with control volume method. The authors study the nature convection in the liquid phase and flow pattern of nature convection during the process of solidification. The result of simulation shows that there are the global flow cells inside the liquid phase, and the local circumfluence exists in the global cells. Especially, the authors analyze transformation of the interface between phases under the effect of free convection on the process of solidification.     

Influence of Interface and Meso-structure on Elastic Modulus of Particulate Reinforced Aluminium Matrix Composite

Taking SiCp/6066Al composite as an example,calculate and analyse influence of interface performance parameters(interface/matrix modulus ratio,interface Poisson ratio and interface volume fraction) and meso-structural parameters(particulate shape,arrangement pattern and dimensional variance mode) on elastic modulus of particulate reinforced aluminium matrix composite.It is proven: Components' performances and interface performances influence elastic modulus of the composite remarkably,meso-structure does not influence obviously.In engineering practice,effect of meso-structure can be negligible.Under the precondition of guaranteeing specific elongation of the composite,the approach that can enhance elastic modulus of the composite at maximum efficiency is to improve interfacial bonding situation of composite.The satisfying result can be obtainable when interface modulus is 20% ~ 30% of matrix modulus.     

Numerical Simulation on Drying Characteristics of a Combined Microwave-convection Process

Combined microwave-convection drying characteristics are investigated by numerical simulation. Combined microwave-convection drying has advantage of swift drying and sterilization. Based on qualitative analyses on the mechanism of combined microwave-convection drying, the differential equations are established and the numerical simulation method is described. The humidity, vapor pressure and temperature, along the radius in a spherical pill, are calculated by the numerical simulation during drying process. The calculation results show the relationship between humidity, vapor pressure, temperature and drying time, and that drying process is greatly influenced by input microwave power. The calculation results are good consistent with the experimental datum.     

Numerical simulation of influence for the process parameters on multi-roll flexible stretch forming

Multi-roll stretch forming (MRSF) process is a new flexible process. Through extensive numerical simulations of the MRSF process, it is found that the smaller the distance between die and rollers is, the more easily the shape can be formed, and the better the quality of formed part can be. However, the distance between clamps and rollers has little effect on the formed parts. The corresponding stretch forming experiment has been done and the results show that the simulation trend is consistent with the experimental results.     

不同熔化速率下的电渣重熔过程数值模拟分析

电渣重熔能提高钢锭的质量,从而满足特种行业的需要,其过程伴随着复杂的物理现象,存在着磁流体流动、传热和传质以及电化学等多方面的影响。通过耦合电磁以及流动和温度方程对电渣重熔过程的三维瞬态进行了数学模拟,研究了熔化速率对重熔过程的影响。结果表明：电流密度、焦耳热和电磁力都随着熔化速率的增大而增大,当熔化速率由14.4 kg/h增加到27.0kg/h,电流密度、焦耳热和电磁力最大值的增大比例超过100%。随着熔化速率的增大,温度最大值有小幅的增加,而且速度最大值的增大幅度接近50%;金属熔池深度则由27 mm增大到38 mm,不利于保证铸坯的质量。     

The Numerical Simulation Commercial Software for Secondary Cooling Process in Billet Continuous Casting

A numerical simulation commercial software has been developed by the object-oriented Visual Basic programming language on the basis of the 2D mathematical model of secondary cooling Process in billet continuous casting. Thereby an effective experimenting tool for computer simulation of continuous casting process is gained. By simulation with the software, the caster structures and operating parameters in continuous casting can be designed and optimized. The simulating calculation examples on several casters and its production applications indicate that the commercial software developed has more accuracy, practicability and commonality, as also as simpler operating capability. The simulated results have been successfully applied to the design and production of the high-efficiency modification for several billet casters interiorly.     

固液混合油辣椒多相流灌装的数值模拟

以固液混合油辣椒多相流的灌装过程为主要研究对象,采用流体力学计算软件Fluent对其灌装过程进行数值模拟,分别对直径为36、48、60 mm的计量缸在灌装过程中的密度场、各相体积分数的分布状况进行研究。数值模拟结果表明:随着灌装机构计量缸直径的增大,灌装流场的密度均匀性变好,高密度和低密度区域明显减少,直径为60 mm的计量缸其固液混合油辣椒多相流流体的各相体积分数和密度分布比其他两种较好,体积分数与初始设定基本吻合,研究结果为灌装装置的结构设计和灌装工艺提供了理论依据。     

Analysis on the Bioleaching Mechanism of Heavy Metal in Sludge by Composite Thiobacillus

The variation of heavy metal speciation during the bioleaching of sludge were carried out. By virtue of heavy metal speciation transformation pattern, the transformation mechanism of heavy metal speciation during the bioleaching could be judged indirectly. The test results show that the bioleaching process of Cu, Ni, Cd are mainly dominated by direct mechanism, the bioleaching process of Zn is mainly dominated by indirect mechanism, and bioleaching process of Cr, Pb are mainly dominated by combined mechanism, while the chemical principle between Cr and Pb are different.     

Numerical Analysis on Mechanism of the Metal Pushing Type Continuously Variable Transmission

Continuously variable transmissions have attracted a great deal of interest in recent years because they shift with very little shock and offer significant advantages of acceleration performance and fuel economy for automobile.The slide angle is very important physical parameter in belt study. It's magnitude expresses the changing of direction of friction force's and makes the distribution of force very complicated. In this paper,the reason of the slide angle has been discussed. The formulae of wrapping angle relation with slide angle is put forward. The magnitude of slide angle is computed by used the Runge Kutta method in different speed ratios. On the basis of study a new descrete numerical analyse approach is proposed to analysis and calculate the tension and thrust of the key work piece's the metal rings and the metal blocks of the metal pushing type continuously variable transmission respectively under different speed ratios and torque ratios. The research result in this paper can be used to analyse the strength of the metal rings and the metal blocks and improve the load capability of the CVT gearbox. [WT5HZ]     

Numerical Simulation on Whole Construction Process of High-Rise CFST Structures

The time-changing analysis model for concrete filled steel tubes was established based on the time-changing concrete model of CEB-FIP MC90, in which the interaction between steel tube and concrete core was considered by the restraint conditions of master and slave nodes. The numerical simulation method was developed for analyzing the whole construction process of high-rise CFST structures. A real structure was taken as numerical example, in which the influence of concrete creep and shrinkage as well as construction process was considered. The results of numerical simulation are compared with those obtained from on-site monitoring. It is shown that the concrete creep and shrinkage as well as construction process have big influence on high-rise CFST structures, which should be taken into account in designs and constructions.     

Numerical Analysis of Drained undrained Triaxial Tests for Overconsolidated Clays

In the framework of critical state soil mechanics, a simplified hardening law is proposed to describe the change between subloading surface and the normal consolidation surface with plastic deformation based on subloading surface concept proposed by Hashiguchi. The characteristics of overconsolidated clays, such as stress strain relationship, strain hardening and softening and stress dilatancy are simulated, and the results are in accordance with the data from triaxial drained compression test. Numerical model is also used to predict the stress strain relationship in the isotropic consolidation condition and the stress paths in the undrained triaxial compression tests.