Analysis of particles in magnetorheological polishing fluid for finishing of ferromagnetic cylindrical workpiece

Magnetorheological honing process is developed for nanofinishing of internal surfaces of ferromagnetic and non-ferromagnetic cylindrical objects. The process makes use of smart fluid called magnetorheological (MR) polishing fluid for finishing which has a property to become stiff in the existence of magnetic field. The smart MR polishing fluid is made with the ingredients of carbonyl iron (CI) particles, abrasive particles, and base fluid. Direct current given to the electromagnet coil engenders magnetic field on finishing tool surface. Magnetic force acts on magnetic CI particles which further exert the repulsive force on nonmagnetic silicon carbide (SiC) abrasive particles and performs finishing when tool rotates as well as reciprocates inside the cylindrical workpiece. The CI and SiC particles present in MR polishing fluid are magnetically simulated and analyzed using finite element (FE) analysis. The distribution of magnetic flux density and magnitude of magnetic force acting on CI particles are analyzed through FE analysis. It is found that the CI particles which are available adjacent to the active abrasives are major responsible for indenting the active abrasive particles into workpiece surface. Also, the effect of finishing tool surface areas and particles size on the strength of chains of CI particles in MR polishing fluid have been analyzed.     

管坯电磁成形时线圈受力的研究

成形线圈设计是电磁成形工艺的关键技术之一,为了有针对性地进行防破设计,提高线圈的使用寿命,采用数值模拟的方法研究了螺线管线圈和阶梯形线圈电磁胀形时的磁场,得到了成形瞬间的磁力线分布和线圈受到的磁压力分布.结果表明:线圈、工件的结构参数和相对安装位置对线圈的磁压力分布影响很大;将受力分布引入成形线圈设计,有效地提高了工艺实验中线圈的使用寿命.     

Thermodynamic multifield modeling of electromagnetic metal forming

The purpose of this work is the formulation of a thermo-magneto-mechanical multifield model and presentation of the numerical strategies applied. In particular, this model is used to simulate electromagnetic sheet metal forming processes (EMF). In this process, deformation of the workpiece is driven by the interaction of a current generated in the workpiece with a magnetic field generated by a coil adjacent to the workpiece. The interaction of these two fields results in a material body force known as Lorentz force. Up to now, modeling approaches found in literature for EMF are restricted to the axisymmetric case. For real industrial applications however, the modeling of three-dimensional forming operations becomes crucial for an effective process design.The development and application of such a 3D model is the subject of the work at hand.     

Initial experiment for embossing a 3-D microstructure on the inside wall of a wound tube by an electromagnetic compression process

The purpose of this study is to discuss the feasibility of an economical electromagnetic forming (EMF) process to fast manufacture microstructure on the inside well of a wound thin tube. To form the three-dimensional (3-D) microstructure on the inside wall, a copper film is wound onto the forming mandrel and then inserted into the forming coil that provides external compressive force on the tube surface using the EMF process. This study proposes an inexpensive method that uses a reverse electro-discharge machining process with a homocentric path to manufacture the forming mandrel. The thickness effects of the single tube on the formed microstructure are investigated by an economical EMF device with low voltage and high capacitance. In addition, a composite tube is proposed to prevent electromagnetic field loss, reduce the gap, and provide good contact force. By using a composite tube in an EMF process, the forming depth and the profile completeness of the microstructure are improved.     

利用高速振动降低零件回弹及蒙皮件制造——电磁成形技术的新应用

目的 为了解决传统大型蒙皮成形需要大型装备及零件回弹大的问题,提出带弹性垫的蒙皮件电磁渐进成形新方法.方法 通过电磁线圈放电,材料在磁压力和弹性垫的反弹力作用下出现高速振动,消除零件回弹.采用ANSYS和ABAQUS有限元分析软件分别进行电磁场和结构场模拟,分析有无弹性垫、线圈结构和放电位置对蒙皮成形质量的影响规律.结果 在无弹性垫的条件下对板料进行冲击,板料上的塑性应变几乎没有变化.如果采用螺旋方形线圈和带弹性垫的成形工艺,虽然板料上的塑性应变增加,但是线圈正对板料区域出现1.5 mm的鼓包.采用电磁屏蔽方法调整板料上的电磁力分布和材料流动,当线圈在6个位置多次放电后,板料回弹明显减低,并且零件表面光滑.结论 在模拟得到的最佳工艺参数下,建立了实验装置,实验结果与模拟一致.     

管件长度对电磁成形线圈放电电流的影响

为研究电磁成形过程线圈放电电流的变化规律,在放电回路分析的基础上,采用试验分析与代数解析相结合的方法研究了管件长度对线圈放电电流的影响.试验结果表明:随着管件长度的增加,线圈放电电流的幅值和频率均增加.通过解析方法定性分析管件长度对线圈放电电流的影响,其结果与试验结果一致.管件长度不同时,放电回路的等效电感不同,管件长度与等效电感成反比.将管件和成形线圈等效为圆柱线圈可定性分析电磁成形系统的电感和互感.     

管件电磁成形数值模拟方法及缩径变形分析

随着电磁成形工艺应用的发展,需要强有力的数值模拟方法来预测成形过程,并用来指导成形系统设计.归纳了现有的电磁成形模拟方法及各自的特点,讨论了模拟中存在的问题和面临的挑战.应用FEM软件ANSYS对铝合金管件电磁缩径成形进行了数值模拟,研究了管件均匀缩径变形规律.变形管坯轮廓验证了电磁缩径成形的模拟结果.     

大口径铝合金波纹管电磁胀形数值模拟

目的研究大口径铝合金波纹管电磁成形过程及工艺参数对成形效果的影响规律。方法针对波纹管现有制造工艺——压弯和焊接复合成形存在压痕严重、焊缝多和可靠性不高等问题,提出采用电磁成形波纹管的方法,并基于ANSYS建立了波纹管电磁胀形的三维有限元分析模型。结果揭示了波纹管电磁胀形过程中的应力应变分布规律,发现波纹区域和过渡圆角区域是应力和应变集中区。采用单因素实验方法,获得了放电电压和线圈匝数对成形质量的影响规律。结论在波纹管电磁胀形过程中,波纹区域的应力和应变均呈圆环带状分布,波纹管的壁厚在波纹的波峰处达到最小,最大减薄率为10.67%。放电电压和线圈匝数都存在一个最佳值。放电电压过小时,成形不足,放电电压过大时,工件高速碰撞模具,引起较大反弹,导致最终贴模性较差;线圈匝数也对成形质量有一定的影响,在本次模拟实验中,11匝线圈作用下的工件贴模性最佳。     

盘件辗轧成形技术研究进展

辗轧成形作为一种先进的连续局部塑性回转成形工艺,具有成形载荷小、生产过程自动化、近净精确成形等显著的技术经济优点。盘类零件作为重要的承载基本零件类型之一,采用辗轧技术成形盘件是机械行业的重大技术创新。介绍了采用辗轮的盘件辗轧机成形盘件的工艺原理和研究现状,叙述了利用技术改造的数控径轴向环轧机辗轧盘件的工艺原理及研究进展,结果表明盘件辗轧成形技术作为一种先进的零件柔性近净制造技术,具有十分诱人的应用前景,是未来制造业的发展方向。     

铝合金双曲率薄壁件电磁渐进辅助拉伸成形工艺方案设计与开发

目的 针对铝合金双曲率薄壁件传统拉伸成形工艺成形均匀性差的问题,提出一种采用电磁渐进辅助拉伸成形的高精度成形工艺。方法 设计电磁渐进辅助拉伸成形工艺方案,基于有限元仿真软件LS-DYNA R13.0,建立拉伸成形和电磁成形有限元模型。通过数值仿真研究线圈移动路径和放电电压组合对成形质量的影响以及薄壁件的整体贴模成形过程和等效塑性应变。结果 与单程放电相比,双程放电能够大幅度提高板材变形均匀性。与以中间值电压连续放电以及先大电压后小电压的放电电压组合相比,在先小电压后大电压的放电电压组合下,板材的成形质量更高。选择线圈双程顺序移动路径和7 kV-10 kV放电电压组合,通过10次拉伸和9层54次放电,得到了减薄率仅为3%的贴模性良好的双曲率薄壁件。变形量基本呈现随着放电层数的增加而不断降低的趋势。电磁放电仅扩展更大的塑性应变区域,不改变已贴模区板材的塑性应变值。结论 与拉伸成形相比,电磁渐进辅助拉伸成形工艺有效提高了板材的塑性变形程度并极大控制了回弹的发生。     

铝合金车门把手磁脉冲成形工艺中贴模性能研究

目的 研究铝合金在磁脉冲成形后零件轮廓的形状偏差与工艺参数之间的关系,分析形状偏差形成原因.方法 开展螺旋线圈不同放电能量下的汽车车门把手零件的成形实验,并采用光子多普勒测速系统(Photonic doppler velocimeter,PDV)测速,利用Dyna/EM模块建立的数值模型,主要从电磁力的分布、应力波的传...     

Numerical simulations of an electromagnetic acoustictransducer-receiver system for NDT applications

The development of a multistage numerical model of an electromagnetic acoustic transducer (EMAT), with particular emphasis on an EMAT receiver, is presented. The model includes five separate modeling states: static magnetic field simulation of an electromagnet; pulsed eddy current distribution of a generic meander-line coil suspended over a conducting specimen; Lorentz force distribution due to the interaction of the static magnetic field with the eddy current distributions; acoustic wave generation and propagation based on the dynamic Lorentz forces; and acoustic wave detection by an EMAT receiver. In particular, it is shown how the transient particle displacement fields are converted into an induced voltage response as part of the EMAT receiver system. Numerical simulations show that the voltage response is dependent on the wire spacing of the receiver coil     

Optimum Location of Tube Blank in Electromagnetic Bulging

Using analytical method, this paper gets 'the mutual inductance between coil and workpiece in tube blank electromagnetic bulging. According to this, we obtain the optimum locations of tube blank with different length of coil and workpiece. There is a good agreement between results calculated and the experimental data.     

Algorithmic formulation and numerical implementation of coupled electromagnetic‐inelastic continuum models for electromagnetic metal forming

The purpose of this work is the algorithmic formulation and implementation of a recent coupled electromagnetic‐inelastic continuum field model (Continuum Mech. Thermodyn. 2005; 17 :1–16) for a class of engineering materials, which can be dynamically formed using strong magnetic fields. Although in general relevant, temperature effects are for the applications of interest here minimal and are neglected for simplicity. In this case, the coupling is due, on the one hand, to the Lorentz force acting as an additional body force in the material. On the other hand, the spatio‐temporal development of the magnetic field is very sensitive to changes in the shape of the workpiece, resulting in additional coupling. The algorithmic formulation and numerical implementation of this coupled model is based on mixed‐element discretization of the deformation and electromagnetic fields combined with an implicit, staggered numerical solution scheme on two meshes. In particular, the mechanical degrees of freedom are solved on a Lagrangian mesh and the electromagnetic ones on an Eulerian one. The issues of the convergence behaviour of the staggered algorithm and the influence of data transfer between the meshes on the solution is discussed in detail. Finally, the numerical implementation of the model is applied to the modelling and simulation of electromagnetic sheet forming. Copyright © 2006 John Wiley & Sons, Ltd.     

Forming tubular hexahedral screws—Process development by means of a combined finite element-boundary element approach

The aim of the present paper is twofold: first, to propose a new forming process that is capable of producing hexahedral heads with washers in tubular screws and, second, to present a numerical approach to solve the plastic deformation of the tubular preforms and the elastic deformation of the dies.The methodology draws from independent determination of mechanical properties and fabrication of prototypes with a forming tool designed and fabricated by the authors to the development of a direct boundary integral element formulation for solving the elastic deformation of the dies inside an existing in-house finite element computer program.The performance of the proposed forming process is assessed by experimentation and results and observations are explained in the light of the proposed numerical approach based on the combination of the finite element (FE) with the boundary element (BE) methods.Because project and design of tooling is often only dependent on boundary solutions for the elastic deformation of dies and for the contact between the workpiece and the dies, the proposed FE-BE approach seems as a cost-effective methodology that avoids discretization of dies by finite elements, reduces the overall size and improves the performance of the resulting computer models.     

热金属气压成型电磁感应加热有限元模拟

应用感应加热理论,利用麦克斯韦方程组和温度微分方程,建立了电磁场与温度场耦合的有限元数学模型,使用有限元分析软件ANSYS对热金属气压成型工艺中的电磁感应加热过程进行了模拟与分析。模拟结果表明:随着电磁感应线圈电流频率的提高,在相等的加热时间内,金属钢管的升温速度不断增加,且最终达到的温度也进一步升高。随着电磁感应线圈电流密度的增加,在相等的加热时间内、相同的电磁感应线圈电流频率下,金属钢管的升温速度不断增加,加热效率得到有效提高,且最终达到的温度也逐步升高。随着金属钢管与线圈的间隔增加,金属钢管内、外表面的温度均逐渐降低;外表面温度的降低趋势越来越平缓,而内表面温度的降低趋势则不断加剧。     

Research on deformation characteristics of JCOE forming in large diameter welding pipe

In the present work, the JCOE forming is investigated using the finite element (FE) method. A twodimensional FE model is established for the plane strain condition by FE code ABAQUS, and the FE model is validated by experiments. The aim of this research is to investigate forming quality states in the JCOE forming process; in particular, the effects of technological parameters on forming quality are evaluated. Taking the JCOE forming process of X80 steel φ1 219 mm×22 mm×12 000 mm welding pipe for instance, the deformation characteristics of JCOE forming are analyzed, in which the geometry of the formed pipe, residual stress distributions and effects of process parameters on JCOE forming quality can be obtained. Thus, the presented results of this research provide an effective approach to improve welding pipe forming quality.     

板料电磁成形磁场力分布研究

为研究平板电磁成形中板料上磁场力的分布规律,基于 Ansys 软件建立了 3 D 电磁场有限元模型,分析了在一定放电脉冲作用下,当板料的平面尺寸小于或等于线圈的几何尺寸时,板料上感应电流和磁场力的分布规律。 结果表明,板料的几何尺寸小于或等于对应线圈尺寸会影响板料上感应电流和磁场力的分布,其中圆形线圈对称放置影响最大,矩形线圈单边放置影响较小,匀压力线圈影响最小。     

喷射成形锭材传热过程的数值模拟

通过把喷射沉积形状预测模型的计算结果实时传递到二维传热方程中 ,建立起喷射沉积锭材的计算机传热模型 ,可对不同工艺条件、不同时刻的沉积锭传热行为进行计算 ,可得到任何喷射工艺条件下、任何时刻沉积坯的温度分布及任何点的冷却曲线 .并得出以下结论 :沉积衬底预热有利于减少沉积坯初始阶段的不致密区 ;改变喷射沉积工艺时 ,沉积坯的温度分布随沉积坯形状的不同发生变化 .