电火花加工小电流放电的统计分析

研究小电流维持放电条件，通过不同电流下，放电维持时间的统计分析，首次将电流－放电时间平面划分为熄火，随机过渡和稳定放电三个区，从而确定了电流控制策略的作用范围。     

静电放电模拟器放电回路的设计

由于分布参数的影响，按集总参数设计的静电放电模拟器难以产生IEC61000—4—2标准规定的静电放电电流通过对标准电流波形及给定参数的分析，设计了易于实现的人体-金属模型放电回路．通过模拟仿真，确定了放电回路的具体元件参数．针对分布参数的影响，给出了集总电路元件参数与标准规定的放电电流参数的相对误差灵敏度设计曲线，利用该设计曲线通过时集总元件参数的调整，可获得完全符合标准要求的放电电流．     

铅酸蓄电池放电特性研究与运行分析

提出了一种简单的电池放电特性建模方法,建立了放电曲线数学模型,并通过年度蓄电池放电数据对其进行验证,利用此方法可以估计出任意放电电流下的电压曲线,并据此估算出电池的剩余放电时间。     

微机在蓄电池起动性能测试仪中的应用

<正> 一、概述起动性能测试仪是测试铅酸蓄电池大电流放电性能的一种仪器,要求在恒流放电的条件下读出放电电流及电流随时间的变化值。目前各厂家一般采用人工调节碳质变阻器的办法维持电流恒定。多人同时读取电流、电压及时     

电火花加工中电极间放电状态对加工稳定性的影响

分析了对电火花加工中的放电脉冲波形,讨论了各种的脉冲波形及其放电状态对加工稳定性的影响。由实测的放电电压看出,理想的火花放电维持时间很短,由于各种不利因素的存在,大部分时间内,加工是火花放电、过渡放电、电弧放电交替地概率性地出现。一般情况下,过渡放电和电弧放电约占整个脉冲数量20％-50％,当非火花脉冲数大于50％时,加工将不能正常进行,最终导致不能加工。     

射频气体放电激励电压电流及相位传感器的研制

由于分布电容的存在而造成对仪器的干扰，使得对射频放电电压电流及相位的测量，到目前为止仍然是比较困难和昂贵的；使用简单的电压电流探头而无干扰地精确地测量出电压、电流和相位角，从而计算出复合阻抗几乎是不可能的。这里介绍一种自行研制的传感器，结合网络分析理论，采用数字与计算机技术实现对射频放电电压、电流及相位角精确的测量，经实际使用精度高，抗干扰能力强，价格低廉。     

一种用于飞行时间质谱仪的脉冲辉光放电离子源

介绍了一种用于飞行时间质谱仪的新型辉光放电离子源。该离子源在微秒级脉冲（瞬短脉冲）模式下工作。实验结果表明，瞬短脉冲辉光放电的电流比直流辉光放电有数量级的提高。对瞬短脉冲辉光放电离子源与质谱仪的接口的结构要求相当苛刻，必须用一块可加工陶瓷片屏蔽采样板，把采样板与辉光放电的阳极隔开，才能达到良好的真空及溅射。以黄铜为样品，瞬短脉冲辉光放电的瞬时溅射率达到２４．４μｇ／ｓ·ｍｍ＾２。就黄铜样品的典型谱     

多信息融合技术驱动的电加工控制优化研究

针对电火花微孔加工放电过程出现畸变,导致检测电路难于获取放电间隙状态的现象,提出了一种采用放电电流和放电电压双特征信息多重检测的方法,基于计算机信息融合技术,完成Matlab模糊神经网络训练模型的构建,提取放电状态特征,得到进行电火花加工电极的伺服控制策略,实验测试结果表明,采用该控制策略方法比某传统单一电路检测控制策略加工效果明显好转,获得相同微小孔深加工时间明显缩短,电极的损耗明显降低。     

脉冲大电流放电储能试验研究

为研究适合脉冲大电流放电的储能方式,利用静电放电模拟器分别对陶瓷电容器、薄膜电容器和电解电容器进行了静电放电储能试验。根据静电放电模拟测试系统测得的数据分别计算出每种电容器的储能效率,并进行了具体分析。结果表明陶瓷电容器最适合静电放电储能,其次是薄膜电容器,而电解电容器则不能满足高压脉冲大电流的储能要求。     

LabVIEW控制汤生放电电流信号的实时采集

针对汤生放电下微弱电流信号，在LabVIEW平台下通过RS-232串口实时控制Keithley 6517A型静电计并对其进行实时数据采集。     

New fault detection method based on reduced kernel principal component analysis (RKPCA)

Remanufacturing is the only way for sustainable development of mechanical equipment manufacturing. For remanufacturing blanks containing cracks, the primary task is the prevention of crack propagation to ensure effectiveness of the manufacturing processes to follow. When pulsed current passes through a specimen, due to the existence of crack, the temperature around the crack tips rises sharply and may even climb above the fusion point of the material, which causes the crack tip to become blunt. In this work, with compressor rotor blade material FV520B as a specimen, the distributions of current density, temperature field, and stress field are calculated at the instant of discharge based on the thermo-electro-structure coupled theory. The crack arrest experiment is performed on high pulsed current discharge device of type HCPD-I. By making comparisons of morphology, microstructure, and size of fusion zone and heat-affected zone (HAZ) around the crack tip before and after energizing, the relationships between the sizes of fusion zone and the HAZ and the discharge energy and the current path are derived. The obvious partition and refined grains around the crack tip are prominent because of violent temperature change. The experimental and simulation results are found in fine agreement. The high current pulsed discharge can be used effectively to prevent a crack to further expand and show substantial potentials for application in remanufacturing domain.     

Influence of discharge energy on machining characteristics in EDM

The machining characteristics of electrical discharge machining (EDM) directly depend on the discharge energy which is transformed into thermal energy in the discharge zone. The generated heat leads to high temperature, resulting in local melting and evaporation of workpiece material. However, the high temperature also impacts various physical and chemical properties of the tool and workpiece. This is why extensive knowledge of development and transformation of electrical energy into heat is of key importance in EDM. Based on the previous investigations, analytical dependence was established between the discharge energy parameters and the heat source characteristics in this paper. In addition, the thermal properties of the discharged energy were experimentally investigated and their influence on material removal rate, gap distance, surface roughness and recast layer was established. The experiments were conducted using copper electrode while varying discharge current and pulse duration. Analysis and experimental research conducted in this paper allow efficient selection of relevant parameters of discharge energy for the selection of most favorable EDM machining conditions.     

Numerical calculation and experimental research on crack arrest by detour effect and joule heating of high pulsed current in remanufacturing

The remanufacturing blanks with cracks were considered as irreparable. With utilization of detour effect and Joule heating of pulsed current, a technique to arrest the crack in martensitic stainless steel FV520B is developed. According to finite element theory, the finite element（FE） model of the cracked rectangular specimen is established firstly. Then, based on electro-thermo-structure coupled theory, the distributions of current density, temperature field, and stress field are calculated for the instant of energizing. Furthermore, the simulation results are verified by some corresponding experiments performed on high pulsed current discharge device of type HCPD-I. Morphology and microstructure around the crack tip before and after electro pulsing treatment are observed by optical microscope（OM） and scanning electron microscope（SEM）, and then the diameters of fusion zone and heat affected zone（HAZ） are measured in order to contrast with numerical calculation results. Element distribution, nano-indentation hardness and residual stress in the vicinity of the crack tip are surveyed by energy dispersive spectrometer（EDS）, scanning probe microscopy（SPM） and X-ray stress gauge, respectively. The results show that the obvious partition and refined grain around the crack tip can be observed due to the violent temperature change. The contents of carbon and oxygen in fusion zone and HAZ are higher than those in matrix, and however the hardness around the crack tip decreases. Large residual compressive stress is induced in the vicinity of the crack tip and it has the same order of magnitude for measured results and numerical calculation results that is 100 MPa. The relational curves between discharge energies and diameters of the fusion zone and HAZ are obtained by experiments. The difference of diameter of fusion zone between measured and calculated results is less than 18.3%. Numerical calculation is very useful to define the experimental parameters. An effective method to prevent further extensi     

Experimental investigation and 3D finite element prediction of the white layer thickness, heat affected zone, and surface roughness in EDM process

An axisymmetric three-dimensional model for temperature distribution in the electrical discharge machining process has been developed using the finite element method to estimate the surface integrity characteristics of AISI H13 tool steel as workpiece. White layer thickness, depth of heat affected zone, and arithmetical mean roughness consisting of the studied surface integrity features on which the effect of process parameters, including pulse on-time and pulse current were investigated. Additionally, the experiments were carried out under the designed full factorial procedure to validate the numerical results. Both numerical and experimental results show that increasing the pulse on-time leads to a higher white layer thickness, depth of heat affected zone, and the surface roughness. On the other hand, an increase in the pulse current results in a slight decrease of the white layer thickness and depth of heat affected zone, but a coarser surface roughness. Generally, there is a good agreement between the experimental and the numerical results.     

ELECTRICAL DISCHARGE DIAMOND GRINDING OF HIGH SPEED STEEL

A combination of two machining processes (i.e., a hybrid process) has a potential to improve process performance. This paper reports on experimental investigation of the electrical discharge diamond grinding process that combines mechanical grinding with electrical discharge machining. In this process, the workpiece is simultaneously subjected to heating, by electrical sparks bridging the gap between the metallic wheel bonding material and the work, and abrasion by diamond grains. The effect of current, voltage, pulse-on-time and duty factor on the grinding forces and the material removal rate while machining high speed steel workpiece, are investigated. The spark discharges facilitate grinding by thermally softening the work material in the grinding zone, and consequently decreasing the nromal force. It is observed that the material removal rate increases with an increase in current and pulse on-time, while it decreases with an increase in voltage and duty factor. These independent parameters are also found to significantly influence the grinding forces.     

The dependence of extracted current on discharge gas pressure in neutral beam ion sources on HL-2A tokamak

The discharge gas pressure is a key factor to influence the extracted current of ion source. In this paper, the dependence of extracted current on discharge gas pressure was investigated in detail at different arc discharge currents. The discharge gas pressure with a very broad range (0.1 Pa-2.7 Pa) was scanned for the first time. It is turned out that, with the increasing of discharge gas pressure, the extracted current increases and the arc voltage decreases at different arc currents; however, when the discharge gas pressure exceeds a certain value, the extracted current decreases. For the same discharge gas pressure, the higher the arc current, the higher the arc voltage and the extracted current are. The arc efficiency was also calculated, and its dependence on gas pressure was almost the same with the dependence of extracted current on gas pressure, but at the same discharge gas pressure, the lower the arc current, the higher the arc efficiency is and the lower the extracted current is.     

Study of the current signal and material removal during ultrasonic-assisted electrochemical discharge machining

Electrochemical discharge machining (ECDM) is a cost-effective machining process used to shape non-conductive materials such as glass and ceramics. The process can overcome poor machinability of hard and brittle materials. Different types of physical phenomena can be added to the ECDM components to improve the machining efficiency. As the main target of this paper, ultrasonic vibration was integrated to the cathode of the ECDM process (UAECDM), which resulted in vibration concentration only to the machining zone. In order to design the experimental configuration, modal analysis was used. Machining speed was the main output of this investigation. Gas film and electric discharge were two main physical phenomena during ECDM. The thickness of gas film, location, and pattern of discharges were determined, experimentally. Also, current signal was a useful tool that could record significant details of involved mechanisms and phenomena during machining. Images of gas film showed that the application of ultrasonic vibration decreased the thickness of gas film by 65%. In addition, the vibration amplitude of 10 μm created the most uniform current signal, which had a considerable effect on the material removal rate (MRR). Results showed that all levels of vibration amplitude increased the machining speed during discharge and hydrodynamic regimes of the machining process.     

The hydraulics of parallel sluice gates under low flow delivery condition

In this paper the flow through parallel sluice gates under low flow conditions and with some of the gates closed resulting in symmetrical or asymmetrical gate installations was studied experimentally. The current stage–discharge formula for single sluice gates cannot be used for either free flowing or submerged parallel sluice gates. Then, on the basis of experimental observations, the effect of the closed gates was considered to develop a submergence distinguishing condition curve formula. For both free and submerged regimes, the Π-theorem along with the incomplete self-similarity concept was used to develop head–discharge formulas for symmetrical and asymmetrical gate installations. The proposed formulas were then calibrated using the compiled experimental data. The new approach is shown to be applicable within the entire range of operation, i.e. from free to submerged flow regimes as well as the transition zone.     

Design and evaluation of a unipolar aerosol particle charger with built-in electrostatic precipitator

A new unipolar charger of aerosol particle has been designed and evaluated. The free ion and particle trajectories have been simulated. Four parameters, including electrical characteristics, particle loss, charging efficiency and the average charges, were varied to evaluate the charger. The experimental results show that the average discharge current was stable at 5?µA with 2.6?kV applied on the needle. The standard deviation is 0.0016 when clean air is entered in the discharging zone, as compared to the deviation of 0.024 with unfiltered ambient air which indicates that discharge current is more stable when clean air is entered. The electrostatic loss, diffusion loss and total particle loss were below about 4, 7 and 9% for all particles (sizes of 20–1000?nm), respectively. The intrinsic and extrinsic charging efficiency increased with the particle diameter. The intrinsic efficiency is practically 100% for particle diameters above 50?nm. Compared to the intrinsic efficiency, the extrinsic charging efficiency decreased by 5% given the fact that some of particles may be deposited inside the charger. As for the average particle charge number, the maximum relative error between the results of experiment and theory was less than 15%.     

电流型电火花加工脉冲电源的研究

分析了传统独立电火花加工脉冲电源和逆变式电火花加工脉冲电源的不足,论述了电源型电火花加工脉冲电源的工作原理,大量的样机和独立式脉冲电源的对比工艺试验表明,电流型脉冲电源不仅满足了电火花加工多项性能指标的要求,而且达到了高效节能的效果。