锻造铝合金轮毂动态淬火过程的数值模拟

使用计算流体力学(Computational fluid dynamic,CFD)方法,考虑沸腾传热及两相流动,采用三维动网格技术对锻造6061铝合金轮毂入水淬火冷却处理的动态过程进行了多物理场耦合模拟。模拟得到了淬火水槽内流体的流场与系统整体温度场,在此基础上分析了侧边与底部冷却喷管对轮毂淬火温度分布均匀性的影响及轮毂在淬火过程中的温度变化。结果表明:该模拟方法能够反应淬火过程的流场与温度场变化,侧边与底部冷却喷口能够对轮毂均匀降温,该工况下多轮毂同时冷却过程中各轮毂间的温度差异较小,轮毂温度变化曲线符合工艺要求。     

因瓦合金TIG焊接温度场模拟分析

根据因瓦合金和45钢TIG焊接特点,建立几何模型并确定双椭球热源模式,利用ANSYS软件模拟不同板厚焊接过程中温度场变化,实现温度场与应力场的弱耦合,模拟焊接温度场分布再现温度场的大小及分布情况;利用不同的焊接工艺参数和被焊材料厚度进行了焊接试验,测定焊接过程中特定位置的变形情况,对比分析数值模拟与试验结果.结果表明,在电流132 A,电弧电压17.1 V,焊接速度4 mm/s,板厚1.88 mm的焊接工艺参数条件下可以实现因瓦合金的熔透性焊接,获得良好的焊接接头;利用有限元数值分析方法模拟了焊接工艺参数条件下的焊件温度场分布和熔透性,模拟结果与试验结果一致.     

多晶硅定向生长的数值模拟研究

利用多物理场有限元软件COMSOL Multiphysics3.5(a)对多晶硅定向凝固过程进行数值模拟,获得了定向凝固过程中加热熔化和结晶过程的温度场分布.通过对模拟结果的分析,得到了多晶硅熔化过程温度分布和结晶时固液界面形状,为后续生产实践中工艺方案的优化及缺陷分析等提供重要的理论依据.     

基于数值模拟的复杂铸件粉末注射成形问题研究

采用流体力学计算软件CFX对钳口铸件注射成形工艺的充模过程进行了三维模拟分析,得到了充模过程中各位置的瞬时温度场分布和瞬时压力场分布,并分析了充模过程中不同时刻模腔中各位置的压力和温度变化。通过研究铸件钳口熔体充模流动过程中不同时刻流体粉末的体积分数变化,指出数值模拟过程中固体粉末的体积分数变化和分布,可以得到成形精致坯的密度分布,以分析成形精致坯出现密度分布不均以及成形坯缺陷的原因,寻找控制成形缺陷和零件质量的方法。     

铝合金轮毂砂型重力铸造过程的数值模拟

对电动车铝合金轮毂在砂型重力铸造凝固过程中的温度场和速度场进行数值模拟。运用有限元模拟软件Procast,模拟了电动车轮毂砂型重力铸造过程,研究了不同组成与浇注工艺对温度场和速度场分布的影响规律。结果表明:数值模拟结果反映了材料组成与浇注工艺对温度场和速度场分布的影响规律。     

ForceArc双面焊熔池流场与温度场的数值模拟

基于超威弧(ForceArc)焊接时电弧的形态特征,及超短电弧下实现强制熔滴喷射过渡的特点,采用双椭圆分布热源模型及峰值指数熔滴热焓衰减分布模型. 通过分析工件坡口形貌对ForceArc焊接物理过程的影响,建立贴体坐标系下的ForceArc焊接过程三维瞬态数值分析模型. 模拟了不同预热温度及层间温度对焊接过程的影响,分析了工件上下坡口形貌对熔池传热、传质的影响,并与试验结果进行了对比. 结果表明,文中所建模型能够较好地模拟ForceArc焊接过程,对优化其焊接工艺参数具有一定的指导意义.     

感应淬火工艺参数优化和组织硬度分布预测

基于ANSYS模拟S45C轴的感应淬火过程,提出了感应淬火工艺的电流密度J8、电流频率f、加热时间t和一定水压下喷水冷却时间t1等参数的确定方法,在其工艺参数优化基础上预测了感应淬火的组织和硬度分布,并将模拟结果与采用Carsi组织预测修正模型的计算结果及实测组织硬度结果对比分析,结果表明预测工艺参数、组织和硬度的方法可行;同时考虑感应淬火冷却过程的换热系数h变化对计算组织和硬度分布影响.     

中厚板弯曲过程中减薄量的数值模拟

对3种材质的铝合金中厚板在一系列条件下进行了弯曲实验,并对实验过程进行了有限元数值模拟分析,弯曲减薄量的模拟结果与实验数据吻合良好,各试样减薄率约0.5%～4.5%不等.通过模拟获得了板料弯曲过程中的瞬态应力场分布,能够从中了解应力中性层的移动规律.结果表明,有限元数值模拟能够对中厚板弯曲过程的理论研究和工艺编排起到一定帮助和指导作用.     

线性摩擦焊接头通电热处理的温度场模拟

基于电流生热理论,使用ABAQUS软件对TC4钛合金线性摩擦焊接头的直接通电热处理过程进行了模拟,得出了不同电流下温度场的分布云图以及特征点的温度变化曲线。为验证模拟的准确性,在电阻点焊机电源下对线性摩擦焊接头进行了通电热处理,并运用红外设备对热处理过程中接头表面温度场进行了测量。通过模拟与试验对比,发现二者吻合性较好,说明该模型可正确预测通电热处理温度场,为合理选取通电热处理参数提供理论依据。     

无缝钢管连轧过程有限元数值模拟研究

针对MINI-MPM少机架连轧管机组,应用有限元模拟软件MARC模拟实现了3种工艺条件下三机架限动芯棒轧管过程,分析了轧制过程中不同工艺对金属流动、各机架变形区内摩擦分布规律以及轧制力的变化规律.     

大面积聚晶金刚石复合片电火花加工温度场及应力场的数值模拟

在研究电火花加工机理的基础上,基于有限元原理,建立了电火花连续脉冲放电磨削聚晶金刚石复合片时的物理模型,对磨削过程工件表面的温度场、应力场分布及工件材料的变形规律进行了模拟分析.研究了脉冲宽度及峰值电流对温度场、应力场分布及复合片变形量的影响规律.结果表明,有限元法是分析大面积聚晶金刚石复合片电火花磨削过程中温度场、应力场及变形的一种有效方法,其计算结果可用来指导制定合理的加工工艺参数以提高加工质量和加工效率.     

Influence of Joint EMSFN and M-EMS on Fluid Flow in the Mold During Continuous Casting

Homogenization of physical properties and the chemical composition through the control of liquid metal flow is essential during the continuous casting production of billets. This work was aimed at obtaining improved finished products via continuous casting that implements two magnetic fields. These fields were realized via two electromagnetic stirring processes implemented in a single process: one in the nozzle and one in the mold. The qualitative effects of applying double electromagnetic stirring (EMS) were verified through numerical simulation of 178 mm?×?178 mm square billets exposed to double electromagnetic fields during the continuous casting process. The accuracy of the numerical calculations was verified via physical experiments. In addition, the final simulation results were compared with the intermediate results, to determine the true effects of different EMS on the metal flow in the mold. The results revealed that casting using EMS with different directions of magnetic field in the mold and the nozzle has the best effect on the distribution of the fluid flow and minimal influence on the stability of the meniscus and yields the minimum metal-jet penetration into the mold.     

Temperature field simulation of laser-TIG hybrid welding

The three-dimensional transient temperature distribution of laser-TlG hybrid welding was analyzed and simulated numerically. Calculations were based on a finite element model, in which the physical process of hybrid welding was studied and the coupling effect of the laser and arc in the hybrid process was fully considered. The temperature fields and weld crosssections of the typical welding parameters are obtained using present model. The calculation results shou that the model can indicate the relationship of energy match between laser and arc to joints cross-sections objectively, and the simulation results are well agreed with the experimental results.     

Coupled computation method of physics fields in aluminum reduction cells

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摩擦焊接过程数值模拟技术研究进展

根据摩擦焊接过程数值模拟存在的主要难点,重点介绍了摩擦焊接热输入、焊合区金属塑性变形、以及焊接过程主要参量场,如温度场、应力应变场有限元热力耦合分析的几种模型及其研究进展。文献研究表明,目前摩擦焊接过程物理参量场的数值模拟主要采用二维、非稳态、变物性模型。一般忽视辐射及对流换热。焊接界面上热流量可以根据扭矩曲线或摩擦系数分布曲线计算,热流分布采用均布或线性假设,近年来有关学者直接根据焊接材料的性能数据和设定的焊接规范参数进行摩擦焊接过程特征参量及相应物理参量场的模拟研究工作,并模拟了摩擦焊接过程的两种产热模型及其转化规律（摩擦初期的摩擦产热与摩擦后期的塑性变形产热）。     

Numerical calculation and industrial measurements of metal pad velocities in Hall-Heroult cells

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横向磁通连续感应加热过程中带材涡流场和温度场的仿真分析

基于新型磁-热耦合仿真计算方法,在考虑带材材料物性参数随温度变化的前提下,以45钢带材为例对横向磁通连续感应加热过程中带材表面涡流和温度的分布情况进行了模拟和计算,并与不考虑材料物性参数随温度变化及15MnV钢带材在相同条件下连续感应加热这两种情况进行了对比。结果表明:带材材料物性参数随温度产生的变化对感应加热结果影响较大,且45钢和15MnV钢计算得到的感应加热工艺参数存在较大差异。      

基于主成分-贝叶斯分类模型的除草机器人杂草识别方法

计算机应用技术的不断发展加快了各领域人工智能系统的步伐,在农业方面,机器视觉自动除草设备已逐渐成为研究热点。计算机视觉技术是以图像处理为前提,在土壤背景下,准确的识别出农作物与杂草的分布情况,进行有目标性的除草作业,为实现精细农业做出贡献。针对玉米地视觉识草问题,采用颜色、形状、纹理多特征融合技术,利用主成分分析方法进行特征降维,再结合贝叶斯分类算法进行玉米与杂草的识别分类。仿真实验结果表明:此种方法能够实现杂草的有效分类。     

Progress and Application of Microstructure Simulation of Alloy SolidificationEI北大核心CSCD

Solidification structures are the interaction links between the alloy components and their mechanical properties. Scientifically comprehending about the formation mechanisms, dominant factors and control methods in alloy solidification has a significant effect on the structure control and optimization. Dendritic structure is the most frequently observed solidification microstructure of alloys and controlled by heat, solute, melt flow, capillary and many other factors. Modelling and simulating can accurately quantify various phenomena and evolution rules in the process of solidification, thus play an increasingly important role in the design, preparation, processing and performance optimization of alloy materials. Over the past two decades, remarkable progress has been made and various models have been proposed in microstructure simulation during alloy solidification process, such as deterministic method, phase field (PF), Monte Carlo (MC) and cellular automaton (CA). With the advantages of clear physical meaning, easily programming and high calculation efficiency, CA method has been widely applied in the study of solidification structure simulation and exhibits great advantages. Considering the current development level of computer hardware, numerical model and calculation method, microstructure simulation of large components mainly adopts macro-microscopic coupling calculation method, such as CA-FD/FE model. The heat transfer and other multi-physical fields are calculated at the level of coarse mesh, where-as nucleation and dendritic growth are simulated at a much finer grid level. This paper reviews the main models and development of CA method used for nucleation simulation. The key aspects in the simulation of dendritic growth including mean solid-interface interface curvature, growth kinetics and the algorithm for eliminating "pseudo anisotropy" are discussed. Based on this, the development and application status of macro-micro coupling model during casting, directional solidification and other manufacturing fields are summarized. Finally, the existing problems and future tendency for simulation of solidification structures are analyzed.     

基于双磁介质层复合的超材料低频吸波体研究

本研究将磁性吸波涂层融入至超材料的结构设计中,得到了一种新型低频复合超材料吸波体,吸波体由环形电阻膜、双层磁性吸波涂层和金属背板组成。采用CST仿真软件计算了超材料吸波体的吸收性能,研究了吸波体各个结构参数对吸收性能的影响。仿真结果表明,设计的超材料吸波体厚度为2.5 mm时,在1.9和4 GHz处存在2个吸收峰,在1.59～6.59GHz频率范围内反射损耗低于-8dB,吸收带宽达到5GHz。通过吸波体电磁场分布对吸波机理进行了讨论。结果表明,吸波体低频吸收带宽的增加是由于表面的电阻膜图案改变了超材料吸波体的电场分布和磁场分布,促进了磁介质层的损耗。最后制备了吸波体样品并进行了反射率测试,实物测试结果与仿真结果基本一致,说明设计制备的吸波体具有优异的低频吸波性能,吸波带宽相比磁性吸波涂层大幅提高。