高冲击下电流变阻尼器多物理场建模与仿真

针对将电流变阻尼器应用于冲击载荷下的火炮反后坐装置,阻尼器采用固定电极板式结构,利用COMSOL Multiphysics多物理场软件,建立电流变阻尼器的二维轴对称几何模型,根据计算流体动力学模块,得到不可压缩的电流变流体层流仿真。分析高速冲击下电流变流体在环形间隙的流动情况,并且在变化的电场耦合作用下,仿真计算出电流变阻尼器输出阻尼力的大小,同时也研究阻尼器结构参数对输出阻尼力的影响。仿真结果表明:在1~5 k V范围内增加极板电压,环形通道流体速度降低1.03 m/s,总输出阻尼力提高375.9 N;在电场强度为5 k V/mm情况下,阻尼通道有效长度增加25mm,阻尼力由828.2 N增大至1 950.8 N;保持阻尼通道长度不变,环形间隙增大1.5 mm,阻尼力下降至113.3 N。     

以环氧树脂为母液的悬浮液的电流变效应

研究了以淀粉，二氧化锡和三氧化铝为分散相颗粒，以非油类的环氧树脂为母液的悬浮液，在交流电场作用下的电流变效应及其影响因素，如电场强度，悬浮液浓度，颗粒粒径等，还研究了漏电流密度及其影响因素，实验表明，以环氧树脂为母液的悬浮液具有明显的电流变效应，非油类的环氧树脂可作为电流变液的母液。     

低电场强度下非均相含钛冶金熔渣的流变特性

研究1500℃下低强度电场对含Ti C非均相含钛冶金熔渣流变特性的影响,借助SEM-EDS检测手段对渣样进行表征分析,揭示含钛熔渣流变响应机理。结果表明:随电场强度的增加,含钛熔渣在不同剪切速率下表观黏度增大,表现出正电致流变效应;在电场作用下,Ti C固相质点由分散状态变为呈链状或簇状分布,钙钛矿由分散状逐渐聚集,且晶粒随电场强度增大逐渐粗化;Ti C固相质点的规律性变化以及高温下形成的钙钛矿在电场作用下的结构演变行为共同影响非均相含钛熔渣的流变特性。     

外加电场对细粒散体浸堆渗透性的影响

基于电渗理论,提出利用外加直流电场强化细粒散体浸堆中溶浸液渗流的方法,通过实验研究与机理分析探讨电场作用对细粒散体渗透特性的影响。结果表明:电场作用能够降低双电层厚度,使渗流通道的截面积增加,溶液渗流阻力降低,溶浸液的渗流速度增大;其次,电场对颗粒微孔隙间及渗流盲区的毛细水起到电渗驱动作用,促进不动液的流动;浸堆的渗透系数随着电场强度的增大先增加后降低,高电场强度下容易发生电解现象及电渗固结现象,存在能够使渗流系数达到极值的最优电场强度;颗粒粒径越小,最优电场强度越低,浸堆的导电能力就越好,电场作用对浸堆的渗透性影响越明显,渗透系数的增加幅度随着颗粒粒径的减小呈指数增加趋势。     

电脉冲作用下铝铜熔体内电场分布规律研究

采用数值模拟与实验验证相结合的方法,对电脉冲作用下铝铜熔体内电场分布规律进行了探讨。结果表明,脉冲电场在熔体表层附近较强,随着熔体深度的增加,电场强度逐渐减弱;电极电导率越小,电脉冲作用范围越大,电极电导率越大,电脉冲作用范围越小;两电极间距越大,电场强度越弱,越有利于电场强度的均匀分布;对于电极电导率与熔体电导率相近的情况,电极的插入深度对电场的分布影响不大。     

电流变阻尼器辅控的位移补偿装置构架设计

介绍了电流变液及评价参数,分析了电流变阻尼器数学模型,提出了利用电流变效应辅助控制液压元件的构架设计思路,用于系统的位移补偿,为构造新型机电液智能控制元件或伺服系统提供技术储备.     

磁流变液在阻尼通道处的流变特性分析

研究了磁流变液在阻尼通道处的流变特性,利用COMSOL、Fluent软件对阻尼通道进行了流体仿真,分析了阻尼通道处磁流变液的速度、压力分布情况。结果表明:环形槽可以有效提高阻尼器的阻尼力,当深度为0.55 mm、宽度为2.2 mm,间隙为1.4 mm时,可使阻尼器的阻尼力达到最大,同时也证明了该理论模型的正确性。     

交流电场对45钢粉末法铝硅共渗的影响

通过一对平行电极对45钢试样与渗剂施加交流电场,进行交流电场增强粉末法铝硅共渗。通过分析对比电场增强粉末法铝硅共渗与常规铝硅共渗渗层的厚度、组织、微区成分、相结构及抗氧化性能,研究电场对45钢粉末法铝硅共渗的作用特性。结果表明:交流电场能够显著促进粉末法铝硅共渗,渗层厚度和硅含量随电场强度增加而增加,渗层相结构也发生相应变化,当渗扩温度≥650℃、电场电流≥0.5 A时,富铝相消失;常规工艺700℃共渗4 h的渗层厚度仅约24μm,但在电流为0.7 A的电场作用下,可获得约100μm厚渗层;900℃循环氧化试验表明,电场铝硅共渗试样的抗氧化性能远高于常规铝硅共渗试样。     

1.6%C超高碳钢的电致超塑性压缩行为及其与40Cr钢的电致超塑性焊接

以热机械处理获得的超细晶1.6%C超高碳钢为研究对象,借助电致超塑性压缩试验研究了电场强度和初始应变速率对超高碳钢超塑性的影响,并探讨了其与40Cr钢电致超塑性焊接的可行性.实验结果表明,在压缩温度780℃、初始应变速率(0.5-5.0)×10-4 s-1,试样接正极环状电极接负极条件下,超高碳钢的应力应变曲线呈现出明显的超塑性压缩流变特征,其应变速率敏感性指数为0.46;当电场强度为3 kV/cm时,其超塑稳态流变应力降低10%以上.在焊接温度780℃、初始应变速率1.5×10-4 s-1、预压应力56.6MPa、电场强度3 kV/cm条件下,超高碳钢与40Cr钢实现了电致超塑性焊接,其接头拉伸强度达到533 MPa,比不加电场时增加15%.     

并联式磁流变阻尼器磁场分布分析

为了更好地利用长行程磁流变阻尼器阻尼通道内磁场有效面积及控制的灵活性,实现对冲击力和位移的平稳控制,对阻尼器进行了磁场有限元仿真与分析,给出了4个线圈输入电流不同时阻尼通道内有效长度上的磁感应强度分布的非参数化模型。结合冲击载荷下控制目标,为控制算法的设计奠定了基础。     

The electromechanical principle of electrorheological fluid-assisted polishing

An up-to-date abrasive polishing process using electrorheological (ER) fluid, known as ER fluid assisted polishing, is potentially useful in the surface finish of three dimensional micro or meso-scale devices. For a more detailed understanding of this process, the electrostatic principle of how an ER fluid functions on the polishing is described. Dielectric particles suspended in a dielectric fluid are polarized with the application of an electric field, and they experience the dipolar interaction force each other and the translational force along the field, defined as dielectrophoresis due to the non-uniform electric field. As a result of the calculations of the exerted forces on the ER and abrasive particle suspended in silicone oil, ER particles strongly attract the abrasive particles as well as each other when they are aligned with the electric field. Because this attraction force is much higher than the dielectrophoretic force, abrasive particles adhere to ER particles which concentrate on a tool along the field lines. The behavior of particles is observed by the CCD camera, and borosilicate glass is polished to evaluate machining performance.     

电流变技术与应用

电流变效应是一种奇特的效应。电流变液在外加电场的作用下产生粘度的连续变化，可以在液体和固体间快速并可逆地转化。这种特性预示着其潜在的广泛应用，因而引起了人们极大重视，本文介绍了电流变效应、电流变材料和电流变的式程应用。     

An investigation of effective area in electrorheological fluid-assisted polishing of tungsten carbide

Electrorheological (ER) fluid-assisted polishing is a novel polishing method for the finishing of micro-aspheric lens, dies and mirror. This paper investigates the effective area in the ER fluid-assisted polishing of tungsten carbide, which is used as the die material for the mass production of micro-aspheric glass lens. The effective area is defined as the area in which the abrasive particles concentrated in the vicinity of the tool tip makes the effective material removal from the workpiece. The electric field strength applied between the tool and the workpiece is analysed. The interacting forces between particles suspended in the electrorheological fluid are calculated. An approach is proposed to predict the effective area and the experiments are conducted to confirm the validity of the proposed method.     

Investigation into electrorheological fluid-assisted polishing

Electrorheological fluid (ER fluid) is a functional fluid with the property that its viscosity can vary with the applied electric field strength. This paper investigates a polishing method using the electrorheological fluid, known as ER fluid-assisted polishing, for the finishing of micro dies of tungsten carbide alloy, which are used for the mass production of micro aspheric glass lens. The machining principle of the ER fluid-assisted polishing is introduced. By proper design of experiments based on a Taguchi orthogonal array and by multi-variable linear regression, empirical models are developed for evaluation of the effect of the process parameters on the material removal depth and surface roughness obtained in the ER fluid-assisted polishing. Further experiments are conducted to confirm the validity of the developed statistical model by comparing the model predictions with the experimental results and meanwhile the influences of the process parameters on the polishing performance are revealed.     

电流变技术在车辆减振装置中的应用研究

电流变技术应用于车辆减振控制具有响应速度快、阻尼无级可调、能耗低等特点,可以通过适当的控制规律实现对结构振动的最优控制。本文通过对充气式电流变减振器原理进行分析,讨论了减振器阻尼力计算公式,它包括电流变液基础粘度引起的本底阻尼力、由电场作用引起的电致阻尼力和气室气体引起的压力三部分。开发了一种结构简单的充气式电流变液体减振器,对影响减振器性能的主要结构参数进行了分析讨论,给出了减振器设计中参数选择的一般原则和应注意的问题。通过台架实验,对所设计的电流变液体减振器性能进行了考察,得到了较好的示功图和速度特性曲线,为车辆路试奠定了基础。     

整体叶轮电火花加工电极的成形电铸

电火花加工是整体叶轮的主要加工工艺方法之一,其中工具电极的制造是关键.研究了采用电铸技术制备电火花加工工具电极.由于电极结构复杂,电沉积时电场发生畸变,导致阴极表面的电场分布极不均匀,侧壁与底部结合处的电流密度远小于阴极表面其他地方的电流密度,针对这种情况,通过增加辅助阳极、屏蔽侧面等改善措施,成功制备了工具电极.     

Chatter suppression based on nonlinear vibration characteristic of electrorheological fluids

Self-excited chatter is a serious problem in machining shops and its frequency is always near the resonant frequency of the machining system. This paper proposes a novel design method for a tunable-stiffness boring bar containing an electrorheological (ER) fluid to suppress chatter in boring. The ER fluid undergoes a phase change when subjected to an external electrical field and serves as a complex spring behaving nonlinearly in the structure. The deformation modes of the ER fluid are dependent on the applied electric field and the strain amplitude. As a result, the global stiffness and energy dissipation properties of the boring bar under an electric field change drastically at different amplitudes of vibration. It is found that the amplitude of chatter can be prevented from increasing by using the nonlinear vibration characteristic of the ER fluid. It is shown experimentally that the chatter can be suppressed under a certain range of the electric field related to the cutting conditions.     

Microstructure and Properties of Lap Joint Between Aluminum Alloy and Galvanized Steel by CMT

Lap joining of 1-mm-thick Novelist AC 170 PX aluminum alloy to 1.2-mm-thick ST06 Z galvanized steel sheets for automotive applications was conducted by cold metal transfer advanced welding process with ER4043 and ER4047 filler wires. Under the optimized welding parameters with ER4043 filler wire, the tensile shear strength of joint was 189 MPa, reaching 89% of the aluminum alloy base metal. Microstructure and elemental distribution were characterized by optical metalloscope and electron probe microanalysis. The lap joints with ER4043 filler wire had smaller wetting angle and longer bonded line length with better wettability than with ER4047 filler wire during welding with same parameters. The needle-like Al-Fe-Si intermetallic compounds (IMCs) were spalled into the weld and brought negative effect to the tensile strength of joints. With increasing welding current, the needle-like IMCs grew longer and spread further into the weld, which would deteriorate the tensile shear strength.     

Microstructure and Functional Mechanism of Friction Layer in Ni<Subscript>3</Subscript>Al Matrix Composites with Graphene Nanoplatelets

Microstructure and functional mechanism of friction layer need to be further researched. In the present work, the friction coefficients and wear rates are analyzed through response surface methodology to obtain an empirical model for the best response. Fitting results show that the tribological performance of Ni₃Al matrix composites (NMCs) with graphene nanoplatelets (GNPs) is better than that of NMCs without GNPs, especially at high sliding velocities and high loads. Further research suggests that the formation of integrated friction layer, which consists of a soft microfilm on a hard coating, is the major reason to cause the differences. Of which, the wear debris layer (WDL) with a low shear strength can reduce the shear force. The ultrafine layer (UL), which is much harder and finer, can effectively avoid fracture and improve the load support capacity. Moreover, the GNPs in WDL and UL can be easily sheared and help to withstand the loads, trending to be parallel to the direction of shear force.