电磁场作用下半固态合金熔体流动行为对凝固组织的影响

电磁场技术在半固态合金加工中的应用促进了制备工艺的开发和创新,也为获得高质量的半固态合金制品提供了保障。电磁场引起的半固态合金熔体流动状态和性质对合金元素传输、晶粒长大、温度场分布、凝固组织等均有重要影响。主要综述了电磁场对半固态合金流动行为的影响、数值模拟技术在解析半固态合金流动行为中的应用等方面的研究进展,并结合笔者的研究经历介绍了电磁场搅拌技术在半固态合金浆料制备中的应用、熔体流动对半固态合金凝固组织的影响,以及在半固态合金熔体流动特性研究中的新发现。在这些研究工作的基础上,着重综述了应用商业软件和数学建模对半固态合金熔体中电磁场作用引起的流动行为进行模拟、仿真所做的工作和取得的成果。最后,对电磁场技术在半固态合金加工中的应用以及电磁场作用下半固态合金熔体流动特性对半固态合金凝固组织影响的研究进展进行了总结,并对其发展前景和主要发展方向进行了展望。     

Density and Thermal Conductivity Measurements for Silicon Melt by Electromagnetic Levitation under a Static Magnetic Field

The density and thermal conductivity of a high-purity silicon melt were measured over a wide temperature range including the undercooled regime by non-contact techniques accompanied with electromagnetic levitation (EML) under a homogeneous and static magnetic field. The maximum undercooling of 320 K for silicon was controlled by the residual impurity in the specimen, not by the melt motion or by contamination of the material. The temperature dependence of the measured density showed a linear relation for temperature as: ρ(T) = 2.51 × 10³−0.271(T−T _m) kg · m⁻³ for 1367 K < T < 1767 K, where T _m is the melting point of silicon. A periodic heating method with a CO₂ laser was adopted for the thermal conductivity measurement of the silicon melt. The measured thermal conductivity of the melt agreed roughly with values estimated by a Wiedemann–Franz law.     

微波炉电磁场仿真匹配

以典型的M20L微波炉为代表,采用计算机仿真技术,研究微波炉腔体的匹配问题。对微波炉实体建模和设置腔体内介质材料电特性参数,并进行了仿真研究,得到的结果与实际测试数据一致,验证了建模的准确性。在此基础上研究了微波炉腔体结构参数对匹配性能的影响,找到了影响匹配的主要参数(炉腔顶板高度、波导位置、耦合窗和转环滚轮高度等)。通过对主要参数的优化设计解决了M20L微波炉的打火、熔轴等问题,并提高了输出效率,进一步的实验研究证实该微波炉各项性能满足要求。     

小麦气力输送流场颗粒流化特性数值模拟

目的 探索仓泵式气力输送小麦颗粒时不同输送压力下罐体及引出管内颗粒的流化特性,从而得出最佳操作压力。方法 利用Solidworks建立简易的等比例发送装置三维模型,采用模拟仿真软件Fluent对0.25、0.3、0.35 MPa等3种不同输送压力进行数值模拟,并利用CFD–Post进行数据后处理。结果 当进气口压力为0.35 MPa时物料最先输送完毕,用时为10 s。整体发料过程从引出管入口至出口处三者压力分别降低了97.1%、96.8%、98.1%,其中当进气口压力为0.3 MPa时,压力降低最小,能量利用率最高。结论 输送压力越大输送速度越快,其压降也最大。考虑经济性与高效性可得,最佳进气口压力为0.3 MPa。     

Physical Simulation of Mold-Filling Processing of Thin-Walled Castings under Traveling Magnetic Field

Mold-filling process of thin-walled castings under the condition of traveling magnetic field has been studied by physical simulation method using gallium melt and fast speed photography. Flow morphology and its formation mechanism were obtained and discussed for thin-walled casting. The influences of magnetic field density on the filling ability, filling velocity and mold filling time have been studied. The differences in filling capability between gravity casting and casting under the traveling magnetic field have been compared. The results indicate that the mold filling ability of the gallium melt increases greatly under the condition of traveling magnetic field; the filling time is shortened from 18 s under gravity field to 3 s under the traveling magnetic field and average flow rate of the melt increases from 1.6 to 8.68 cm3/s; the change law of the cross-section morphology of the gallium melt during the mold filling is that at first, the cross-section area does not change, then it decreases gradual     

变化电磁场中带电超微粒子的精确量子论

利用SU(1,1)Lie代数和SO(3)Lie代数 ,得到变化电磁场中带电超微粒子的精确量子论     

金属熔体在超声场中凝固的研究

本文综述了超声场对金属凝固过程的影响，着重总结了声空化、声流所起的作用，同时介绍了超声在新材料制备中的应用。     

熔融聚合物中气泡的运动分析与实验研究

文中求出了CO2气泡注入到熔融聚合物流场后的计算模型,利用熔体流变学理论与两相流理论对气泡的头部、尾部、速度进行分析,计算了气泡在聚合物熔体中的速度表达。结果表明,其头部速度Un,尾部速度Ut等不仅与熔体的性质、流场条件有关,同时还与此气泡在流道中位置、气泡内的压力变化等诸多因素有关。为此引入综合系数C以修正上述理论计算模型,通过一系列实验,得出影响CO2在熔融聚合物中运动的综合系数C,利用其对上述理论运动模型加以有效的实验修正,进一步得到符合实际的气泡在熔融聚合物流场中运动计算模型。     

再论变化电磁场中带电超微粒子的精确量子论

利用创新的SU(1 ,1 )Lie代数理论及SO(3)Lie代数理论 ,得到变化电磁场中带电超微粒子的精确量子论 ,由此进一步明确微观领域中的时空概念     

高速粒子冲击仪中粒子的运动分析

高速粒子冲击仪是用来检测护目镜片强度的仪器,它对于保证在工作条件恶劣的环境下的正常工作非常必要.文章在对高速粒子冲击试验仪中粒子运动状态分析的基础上,结合有关的国内外标准,对两种不同标准要求下的冲击仪发射装置进行了研究,完成了发射装置的参数设计.     

SiC颗粒粒度对熔铝氧化渗透合成SiCp/Al2O3-Al复合材料微观断裂机制的影响

首次采用Ｘ光电子谱仪（ＸＰＳ）对熔铝氧化渗透合成的ＳｉＣｐ／Ａｌ２Ｏ３０－Ａｌ事材料断口表面进行定量相分析,并通过与金相分析所确定的材料中各夺应相含量一一进行对比,进而确定出裂纹穿过各组成相的优选程度,实现了该多元复合材料微观断裂机制的定量表重。研究结果证实：ＳｉＣ颗粒粒度对该材料的微观断裂机制有着至关重要的影响,室温及高温的力学性能测试结果表明,根据微观断裂机制优化出的ＳｉＣ颗粒粒度为１０μｍ的Ａｌ２Ｏ３－Ａｌ基复合材料,其力学性能总体水平优于国外同类产品。     

四电极电磁流量计磁场分布特性数值模拟

文章开展了四电极电磁流量计磁场分布数值模拟研究工作.采用有限元分析方法计算了四电极电磁流量计磁场分布特性,考察了四电极电磁流量计权重函数分布.分析了仪器偏心、流体磁导率对磁场分布影响.为正确理解注聚井中四电极电磁流量计测量响应特性提供了理论分析基础,指出了采用有限元技术是分析电磁流量计测量特性的较好途径.     

振动挤出过程中毛细管内聚合物熔体的剪切应力分析

不依赖现有的任何本构关系，并考虑惯性项的影响，建立了平行叠加振动条件下毛细管内聚合物熔体剪切应力的计算公式；实验测量一定振动频率和振幅下毛细管瞬时入口压力、瞬时体积流量、以及体积流量与入口压力波形的相位差，通过上述公式即可求得振动力场下毛细管内聚合物熔体的剪切应力分布。     

旋转电磁场作用下金属凝固补缩机理探讨

研究了金属熔体在旋转电磁场作用下的凝固过程。据金属凝固理论和磁流体力学分析,电磁搅拌力引起的动量对流对补缩的促进作用并不大。旋转电磁场阻碍中心疏松、缩孔形成的机制为：电磁力引起的动量对流增强了熔体的热、质传输过程,使熔体温度分布更趋均匀,温度梯度减小,使心部熔体的固相率更趋一致且在短时内增至特征固相分数,且凝固末期熔体的凝固速率增大,使心部熔体在短时内凝固,从而避免了中心疏松、缩孔的形成。     

Physical Properties of Basalt and Numerical Simulation of the Melting Process in Basalt Particle Beds

The physical properties of basalt, such as density, viscosity, permeability, and heat conductivity, were studied experimentally. By introducing the measured parameters into the governing equations of the finite differential method (FDM), the melting processes of basalt, in relation to the thermal boundary conditions and particle sizes, were simulated for the purpose of designing a melting furnace for basalt. The governing equations were discretized in a tri-diagonal matrix form and were solved using the tridiagonal matrix algorithm (TDMA) and the alternative direction implicit (ADI) solver. The temperature distribution, position of the two-dimensional phase-change boundary, and melting time were calculated during the numerical simulation. These provide the basis for determining the heating procedure, for controlling the furnace temperature, and for predicting basalt melting states. In the experiment, an electrical furnace was designed based on the computations. It is demonstrated that the simulation results are reasonably consistent with the observed data.     

电磁流量计矩形与鞍状线圈感应磁场的数值仿真

讨论了电磁流量计矩形和鞍状线圈所产生磁感应强度的分布情况。运用毕奥-萨伐尔定律和叠加原理,通过数值仿真得到励磁线圈在测量管道内电极横截面上的磁场分布情况。提出磁感应强度的方向平行程度和大小均匀程度2个指标,并用其来判别感应磁场分布的均匀程度。依据以上2个指标,分别对不同尺寸的矩形和鞍状励磁线圈所产生的感应磁场进行计算分析和优化。     

Experiment and Simulation of Breakage of Particle Compounds under Compressive Loading

Two-dimensional finite element (FE) compressive stress analyses were carried out on the particle compound material to understand the stress pattern distributions before cracking. FE analysis was followed by discrete element (DE) simulation. A study of the crack propagating mechanism in a particle was represented by a model material that typifies pellets of high-strength pressed agglomerate building materials. For this, concrete spheres of strength category B35 (compressive strength 35 N/mm²) were used. It was observed that the ring tensile stress is responsible for the crack initiation in the spherical particle compounds.