Effects of electromagnetic vibration on the structure and mechanical properties of AI-6%Si alloy during directional solidification

The effects of electromagnetic vibration on the grain refinement in directional solid- ification were investigated. It was found that the electromagnetic vibration applied in the melt not only can refine grains remarkably but also can enhance both tensile strength and ductility values of AI-6%Si alloy. SEM graphs show that coarse dendrite structure was broken up into a somewhat globular structure, and the morphology of eutectic silicon was changed from flaky to fibrous under electromagnetic vibration treatment. The refine mechanism under electromagnetic vibration was discussed.     

粉料除铁机原理及振动参数设计

针对玻璃、冶金、铸造、陶瓷等行业中普遍使用的粉料中含铁杂质问题,设计了一种除铁机。该机利用双电机驱动自同步惯性振动过筛,电磁除铁,生产效率高、操作简便。基本参数为振幅λ=1.3×10^-3m,抛掷指数D=2.75,选用20目筛处理颗粒尺寸为d=0.07～0.05mm的粒料时,生产率Q=600kg/h。为电磁系统及振动系统、结构设计提供了理论依据。     

Solidification structure of eutectic Al-Si alloy under a high magnetic field-aid-electromagnetic vibration

An electromagnetic vibration was generated by simultaneously imposing a strong static magnetic field (up to 10 T) and an alternative electricity current to the metal. Its effects on the solidification structure of eutectic Al-Si alloy have been investigated experimentally. It is found that the eutectic structure has been refined by solely imposing high magnetic field while it is coarsened under the electromagnetic vibration. Furthermore, polyhedral Si grains and non-dendritic α-Al appeared when the electrom...     

电磁振荡对铝合金半连铸坯微观组织及溶质元素晶内含量的影响

研究了电磁振荡作用下7075铝合金半连铸坯微观组织及溶质元素的晶内分布，对其细化、非枝晶组织形成及溶质元素晶内含量的影响机制进行了探讨。认为在电磁振荡作用下，熔体中结晶核心增加，游离晶粒的枝晶生长方式得到抑制是形成均匀细小的近球形和蔷薇形非枝晶组织的原因，并从电磁场改变7075铝合金凝固过程中的溶质分配系数、结晶间隔、液穴内部温度场、流动场以及微观组织形貌等方面出发，分析了电磁振荡对溶质元素晶内含量的影响。     

被动式电磁阻尼器用于转子振动控制的实验研究

提出了一种无需控制的被动式电磁阻尼器．其采用直流电工作．用于实验转子系统并取得了良好的减振效果。该阻尼器结构简单．性能可靠．有推广应用前景。     

Refinement mechanism of low voltage pulsed magnetic field on solidification structure of silicon steel

The grain refinement of a silicon steel solidified with a low voltage pulsed magnetic field (LVPMF) was investigated by experiments and modeling. The experiment results show that complete fine equiaxed grains are acquired by applying the LVPMF. The effects of process parameters, such as the melt cooling rate and superheating on the solidification structure, were also studied. Complete fine equiaxed grains can be obtained under a larger range of cooling rate or superheating when the LVPMF is applied. The magnetic force and the melt flow during solidification were modeled and simulated to reveal the grain refinement mechanism. The simulation results show that the LVPMF has a double role in electromagnetic convection and electromagnetic vibration on the alloy melt. We propose the refining mechanism: The melt vibration and convection can promote nucleus multiplication, which contributes to heterogeneous nucleation enhancement and leads to a high nucleation rate and grain refinement.     

粉料除铁机电磁系统及结构设计

应用电磁理论和振动机械理论，针对玻璃、冶金、铸造、陶瓷等行业普遍使用的除铁机，设计了电磁系统及结构。主要部件的结构尺寸为：激磁线圈，采用双玻璃丝包扁铝线，截面积为19mm^2共600匝，轭铁尺寸为δ=110mm，每根弹簧刚度为41．25kg／cm，两台JW08B-4-M2型0．18kW激振电机。     

电磁振荡强度对半连铸7075铝合金微观组织的影响

在 70 75铝合金半连铸过程中 ,通过同时施加一个稳恒磁场和一个交变磁场 ,使金属熔体产生受迫振荡的方法。实验研究了电磁振荡强度对晶粒细化的影响规律。结果表明 :电磁振荡法获得的铝合金晶粒尺寸较CREM法的小 ,且随着电磁振荡强度的增加 ,铸锭微观组织变得更加细小和均匀。对在电磁振荡作用下 ,合金凝固组织的细化机理进行了探讨。     

热镀锌电磁封流技术的研究综述

热镀锌是镀锌板生产过程中必不可少的步骤,而热镀锌电磁封流技术相对于传统热镀锌技术具有带钢表面无划伤、沉没辊和稳定辊不被腐蚀、维修频率低和工作效率高的优势,具有重要的工程应用价值。首先,介绍了热镀锌电磁封流技术的特点和意义。其次,分别介绍了电磁泵热镀锌电磁封流技术、CVGL热镀锌电磁封流技术、直流磁场热镀锌电磁封流锌技术和永磁感应密封热镀锌电磁封流技术的工作原理、研究现状、技术组成及其优缺点。再次,分析了热镀锌电磁封流锌工作过程中,温度场、流场、固体结构力学场和电磁场之间复杂耦合的特点,并且依据热镀锌电磁封流过程的技术特点,指出了热镀锌电磁封流过程中带钢振动的抑振技术、锌液不稳定流动抑制技术、温度稳定性控制技术、张力控制等关键技术。最后,提出了电磁装置结构参数优化、带钢振动抑制技术和基于大数据的过程控制技术是提高热镀锌电磁封流锌工作过程的关键技术。     

电磁振荡下半连铸Al合金凝固组织的细化机制

在半连铸7075铝合金过程中, 通过同时施加稳恒磁场和交变磁场的方法, 使凝固熔体产生受迫振荡, 研究了电磁振荡的强度和频率对晶粒细化的影响规律. 对电磁振荡作用下, 合金凝固组织的细化机理进行了探讨. 结果表明 电磁振荡法获得的晶粒尺寸要较CREM法所获得的小, 且随着电磁振荡强度增加及频率降低, 铸锭整体组织变得更加细小和均匀.     

Progress on Numerical Simulation of Vibration in the Metal SolidificationEI北大核心CSCD

The application of vibration technology to the metal solidification process can not only effectively improve the solidified structure and the performance of castings, but also have the advantages of low cost, energy saving and environmental protection. Therefore, the application of vibration technology in metal solidification has been extensively studied in experiments. However, due to the high temperature and opacity of the metal melt, hindering its measurement and observation, the mechanism how the vibration affects the solidification is not fully understood. Numerical simulation can provide the variation law of various parameters such as flow field, temperature field and stress field under vibration condition, which helps us understand the mechanism of vibration more thoroughly. Meanwhile, the numerical simulation of the influence of vibration on the solidification of metal melt has been much less systematically studied. This paper introduces the research progress of numerical simulation of vibration applied in metal solidification. The main vibration modes include ultrasonic vibration, mechanical vibration and pulsed electromagnetic vibration. The application mainly includes melt processing, filling, solidification, purification and ageing process of numerical simulation. The current research status of numerical simulation theory and technology of vibration applied in all aspects of casting was summarized systematically. Furthermore, the future research directions of numerical simulation of vibration in metal solidification process were prospected.     

电磁动态塑化挤出机性能的模拟计算与分析

介绍了聚合物电磁动态塑化挤出机的结构特点，采用ANSYS有限元软件对其模头的流场和温度场进行了模拟计算，通过对结果的分析表明，振动力场对提高挤出机的性能和挤出制品的质量具有显著效应。     

CSP轧机主传动系统致振因素的分析

对CSP轧机主传动系统异常振动现象进行分析,为了确定引起振动的原因,分析了主传动系统机械间隙的存在对振动产生的影响,以及轧制界面因轧制力矩的变化对振动产生影响。通过MATLAB的Simulink软件对轧制力矩进行仿真发现,轧制力矩的波动对主传动系统振动的产生有直接影响;摩擦系数的波动对主传动系统振动产生的影响,是对主传动系统产生稳态的自激扭转振动;在对变频器控制的电气参数与主传动系统扭振的影响分析得出,由电磁谐波产生的谐波转矩,使主传动系统产生相应的扭振响应。最后在理论上提出了一系列抑制振动的措施。     

磁声波对金属凝固组织的影响

提出了运用强磁场和交流电流的共同作用直接在金属液中产生声波（磁声波）的新方法，并研究了所生成的磁声波在细化合金凝固组织晶粒的效果，该方法可以从根本上解决机械声波无法在高温生产领域应用的难题，理论解析表明，运用交变电磁力在液体金属内生成的磁声波的强度和所施加的静磁场的磁感应强度和交流电流的电流密度的乘积成正比；电磁力的频率越大，生成的磁声波越接近于由机械振动产生的声波，实验中测定的磁声波压力和理论解析结果基本一致，这种方法产生的磁声波具有促进金属凝固组织晶粒细化的作用。     

超声波振动在铸造生产中的应用

介绍了超声波振动对结晶的影响:在熔融金属内,超声波除了起到振动作用外,还能引起强烈的空化现象以及因超声场的不均匀而造成熔融金属的强烈移动现象,进而形成了均匀的细小晶粒;随着超声波功率的增大,凝固后组织中的共晶团数量明显增多。总结认为,与铸造生产常用的冶金方法(如变质处理、孕育处理)相比,物理方法(超声波处理、电磁搅拌、脉冲电场处理)更环保和节约。     

Vibration suppression device using permanent-electromagnet and MRF shear damper

A vibration isolation and vibration suppression device is presented. The device consists of an electromagnetic actuator and a magneto rheological fluid (MRF) rotary shear damper. In the device, the MRF damper supports a vibrating body. Since the body is connected to the base with large rigidity using the MR damper, vibrations are small when an exciting force acts on the body directly. When base vibrations occur, the electromagnetic actuator under the disturbance force cancellation control isolates vibrations, where the shear force of the damper is controlled to be small. This device can control both vibrations due to exciting force acting on the body and base vibrations without using a heavy vibration table. To validate the system, experimental tests have been performed, and it is clarified that this device works well. Especially, the transmissibility in low frequency region can be suppressed within one.     

低压电磁铆接放电电流分析

线圈放电电流对铆接力起决定作用,铆接力是顺利实现铆接的关键因素。放电电流可采用幅值和频率等参数描述。该文在放电回路分析的基础上,通过电阻分流器法测量成形线圈放电电流,分析低压电磁铆接系统参数对线圈放电电流的影响。研究结果表明,在低压电磁铆接下,线圈放电电流为一衰减震荡波形,幅值在kA级,周期为ms级,能顺利实现直径4mmTA1铆钉的成形。同时线圈匝数、导线截面尺寸、放电电容和驱动片厚度等参数,对低压电磁铆接放电电流的幅值和周期均产生较大的影响。在成形中需优化电阻、电感和电容三者的匹配关系,以满足不同工艺放电电流的要求。     

应用时间序列双谱分析的电磁换向阀故障诊断法

提出一种利用时间序列双谱分析实现电磁换向阀的故障诊断的新方法。通过将实验采集到的换向阀正常工作和出现故障时的振动信号进行双谱分析,可以观察到振动信号双谱幅值图存在明显差异。由此可知,时间序列双谱分析可以诊断出换向阀的不同类型故障,是一种实现液压元件故障检测的有效方法。     

Three-dimensional characteristics analysis of the wire-tool vibration considering spatial temperature field and electromagnetic field in WEDM

In this paper, a three-dimensional multi-physics coupling model (thermal model, electromagnetic field model and structural model) is proposed for analyzing and controlling the vibration of wire electrode in cutting thin plate process. Firstly, a three-dimensional thermal model is developed to evaluate temperature distribution of wire electrode considering heat convection and heat conduction, and the numerical solutions of wire temperature increment are performed under different process parameters. Secondly, the mechanism of electromagnetic force acting on wire tool is clarified in detail, and a spacial finite element method (FEM) program is designed to analyze the electromagnetic field considering electromagnetic induction. Then, combining thermal model with electromagnetic field model, and conventional structural model, a multi-physics coupling model is established to acquire the frequency and amplitude of wire vibration under random multiple-spark discharges. Furthermore, the simulational results of multi-physics coupling model on wire vibration show a good agreement with experimental data, and the influencing rules of processing parameters on wire vibration are also illustrated to seek the best parameter combination. Eventually, three practical methods are presented to restrain wire vibration performance, and the significant effects on suppressing the wire vibration and improving geometric accuracy have been obtained.     

Microstructure formation and grain refinement of Mg-based alloys by electromagnetic vibration technique

The microstructure formation and grains refinement of two Mg-based alloys, i.e. AZ31 and AZ91D, were reported using an electromagnetic vibration （EMV） technique. These two alloys were solidified at various vibration frequencies and the microstructures were observed. The average size of grains was quantitatively measured as a function of vibration frequencies. Moreover, the grain size distribution was outlined versus number fraction. A novel model was proposed to account for the microstructure formation and grain refinement when considering the significant difference of the electrical resistivity properties of the solid and the liquid during EMV processing in the semisolid state. The remarkable difference originates uncoupled movement between the mobile solid and the sluggish liquid, which can activate melt flow. The microstructure evolution can be well explained when the fluid flow intensity versus vibration frequency is taken into account. Moreover, the influence of the static magnetic field on texture formation is also considered, which plays an important role at higher vibration frequencies.