Theoretical and experimental study of vibrational behaviour of laminated stators of electrical machines

An accurate determination of the resonant frequencies and vibrational characteristics of a stator is essential in the design of quiet electrical machines. This paper presents both a fundamental theoretical and an experimental study of the vibrational behaviour of long and short laminated stators of electrical machines. The paper describes briefly the method of analysis, based on the three-dimensional theory of elasticity, for free vibrations of stators with encased construction. To prove the general validity of the analysis and to study the effect of windings, frame, and impregnation upon the resonant frequencies and vibrational behaviour of the stators of electrical machines, extensive experimental investigations were conducted on a number of stator models which include a solid model, long laminated, and short laminated models with and without windings, frame and impregnation. The paper compares the experimental and analytical results for some of these models which prove the general validity of the analysis. Finally, the paper also includes the important findings of these extensive investigations.     

Study on effects of electrode material and dielectric medium on arc plasma in electrical discharge machining

In this paper, the arc plasma of electrical discharge machining (EDM) was simulated by coupling the flow field, the heat transfer field, and the electromag     

电熔爆等离子体电弧的多场耦合仿真与试验分析

针对电熔爆加工过程中等离子体电弧分布研究量化程度不足的现状,运用磁流体动力学理论,建立了包含阴极-等离子体电弧-阳极表面的二维数学模型,采用Comsol有限元仿真软件求解出不同加工电流等离子体电弧温度场、压力场、电势场及阳极表面电流密度分布特性,并根据电熔爆等离子体电弧的加工需求搭建了试验系统,对仿真结果进行验证。研究结果表明:增大加工电流可提高电弧最高温度,使电熔爆放电通道内温度和压力梯度增大,造成放电通道不稳定;增大电流使电弧受到指向电弧中心的电磁力增加,导致电弧收缩明显,加工能量过于集中,使加工表面质量降低;在电流100～175 A之间,加工后表面粗糙度可控制在Ra 6.3μm以下,试验结果与仿真结论具有较好的一致性。     

A control system for uniform bead in fillet arc welding on tack welds

Positioning a workpiece accurately and preventing weld distortion, tack welding is often adopted before main welding in the construction of welded structures. However, this tack weld deteriorates the final weld bead profile, so that the grinding process is usually performed for a uniform weld bead profile. In this study, a control system for uniform weld bead is proposed for the fillet arc welding on tack welds. The system consists of GMA welding machine, torch manipulator, laser vision sensor for measuring the tack weld size and the database for optimal welding conditions. Experiments have been performed for constructing the database and for evaluating the control capability of the system. It has been shown that the system has the capability to smooth the bead at the high level of quality.     

建筑电气工程施工中的质量通病分析

对电气工程施工中一些质量通病产生的原因、危害以及解决办法进行分析和探讨。     

Heat input in full penetration welds in gas metal arc welding (GMAW)

Weld bead characteristics are metallurgically controlled by heat input, which depends on the welding parameters. However, for numerous welding specialists, an accurate measurement of the current, voltage, and welding speed is enough for preventing unambiguous process specifications. But a comprehensive knowledge of the effect of others parameters, such as plate thickness and the type of pass to be performed (full penetration, root pass, or filler pass), is also required if a less conservative welding procedure is aimed. The goal of the present paper is to increase the ability to control the quality of the welding processes used in production by considering the effect of heat losses through the back side of the weld by radiation for full penetration welding, when developing welding procedure specifications. It is concluded that the thermal efficiency factor and, consequently, the heat input need to be differentiated in the welding specifications for full penetration welding.     

基于电信号与高速摄像的弧焊过程测试分析系统研究

文章针对弧焊过程复杂、非线性的特点,研制了弧焊过程测试分析系统。系统由传感器、数据采集卡、高速摄像机等硬件检测设备、光学设备和控制软件构成。该系统具有电信号采集、瞬时分析、统计分析、同步高速摄影、图像处理等功能。利用该系统对弧焊过程信号进行了测试与分析,实验表明：该系统稳定可靠,功能完善,能有效地对弧焊过程进行监测分析与质量评定。     

基于MSC.NASTRAN的点焊模型及其比较分析

点焊是汽车车身结构常用的一种连接方式,为对这种结构进行有限元分析必须建立相应的点焊模型。本文介绍了MSC.NASTRAN中常用的3种点焊模型,并用一个例子说明了不同的点焊模型对分析结果的影响。     

Electromagnetic arc path control in robot plasma welding

Arc welding has always presented a challenge to robot operation. Variations in joint fit-up, positional welding requirements and the high levels of welder skill demanded by transient changes in operating conditions are just some of the variables with which any arc welding robot must cope. The article examines how an inertia-less high-frequency weaving technique using a novel deflector system can solve many of these problems even for high speed seam tracking.     

Characteristic of a triple-cathode vacuum arc plasma source

In order to generate a better ion beam, a triple-cathode vacuum arc plasma source has been developed. Three plasma generators in the vacuum arc plasma source are equally located on a circle. Each generator initiated by means of a high-voltage breakdown between the cathode and the anode could be operated separately or simultaneously. The arc plasma expands from the cathode spot region in vacuum. In order to study the behaviors of expanding plasma plume generated in the vacuum arc plasma source, a Langmuir probe array is employed to measure the saturated ion current of the vacuum arc plasma source. The time-dependence profiles of the saturated current density of the triple vacuum arc plasma source operated separately and simultaneously are given. Furthermore, the plasma characteristic of this vacuum arc plasma source is also presented in the paper.     

An arc generator of a broad plasma stream

The design and basic parameters of an arc plasma generator based on a combined cathode are described. The cathode consists of a hot tungsten filament located in the hollow cathode. A plasma stream with a cross section of 150×10 cm² and a density of ∼10¹⁰ cm⁻³ at a pressure of 0.1–1 Pa is generated at a discharge current of up to 60 A without a cathode spot. The plasma generator can be utilized for final cleaning and activation of surfaces of materials and articles before depositing functional coatings on them and in plasma-assisted deposition by using either vacuum arc or magnetron discharges.     

Angular distribution of plasma in the vacuum arc ion source

This paper presents measurements of the angular distribution of the plasma components and different charge states of metal ions generated by a MEVVA-type ion source and measured by a time-of-flight mass-spectrometer. The experiments were performed for different cathode materials (Al, Cu, and Ti) and for different parameters of the vacuum arc discharge. The results are compared with prior results reported by other authors. The influence of different discharge parameters on the angular distribution in a vacuum arc source is discussed.     

Determination of the mechanical thermostat electrical contacts switching quality with sound and vibration analysis

A mechanical thermostat is a device that switches heating or cooling appliances on or off based on temperature. For this kind of use, electronic or mechanical switching concepts are applied. During the production of electrical contacts, several irregularities can occur leading to improper switching events of the thermostat electrical contacts. This paper presents a non-obstructive method based on the fact that when the switching event occurs it can be heard and felt by human senses. We performed several laboratory tests with two different methods. The first method includes thermostat switch sound signal analysis during the switching event. The second method is based on sampling of the accelerometer signal during the switching event. The results show that the sound analysis approach has great potential. The approach enables an accurate determination of the switching event even if the sampled signal carries also the switching event of the neighbour thermostat.     

三偏心蝶阀蝶板等离子喷焊过程PLC控制系统研究

介绍了三偏心蝶阀自动跟踪等离子喷焊设备。控制系统采用CPM2A-60CDT—D型PLC（可编程控制器）为控制核心，实现喷焊工艺过程控制及喷焊面实时跟踪控制。给出了PLC控制系统的硬件实现及软件设计。     

An algorithm for the estimation of the quality of the spot welds

Spot welds are widely used in industry, especially in automotive, so welds must be reliable. One of the approaches to estimate the quality of spot welds is to use ultrasonic testing. Spot welding is used in the automotive repair industry as well. However, a spot weld testing device, dedicated for the automotive repair industry, is not available. The objective of this work was to develop an algorithm for estimation of the quality of spot welds, to be used in a simple device in the automotive repair industry. The algorithm developed identifies the peaks in the acquired signal and separates the main peaks (ultrasonic signal reflected from the backwall of the weld) from intermediate peaks (which identify the defects in the weld or undersized weld). Then, according to the peak distribution and peak amplitude variations in the signal, the quality of the weld is determined and an automatic pass or fail indication given. The algorithm was verified using a finite element model of a good weld, an undersized weld and a weld with a pore.     

Weld seam tracking and panorama image generation for on-line quality assurance

Traditionally, automated quality inspection of welding tasks relies on nonvisual information and is mainly done off-line. In this work, we introduce an image acquisition system which is capable of monitoring the welding process on-line, resulting in high-quality image information during an ongoing welding process. We show how to further exploit this image information by automatically tracking the weld seam position in the image, even under heavy smoke and gas disturbances. We exploit the high information redundancy between subsequent frames given by large overlap to generate a seamless image of the entire weld seam and effectively suppress adverse optical effects caused by, e.g., smoke and sparks.     

Interaction between laser-induced plasma/vapor and arc plasma during fiber laser-MIG hybrid welding

Hybrid plasma is an important physical phenomenon in fiber laser-MIG hybrid welding. It greatly affects the stability of the process, the quality of the weld, and the efficiency of energy coupling. In this paper, clear and direct proofs of these characteristics are presented through high-speed video images. Spectroscopic analysis is used to describe the characterization of hybrid plasma. The hybrid plasma forms a curved channel between the welding wire and the keyhole during the fiber laser-MIG hybrid welding process. The curved channel is composed of two parts. The laser-induced plasma/vapor expands due to the combined effect of the laser and the MIG arc, forming an ionization duct, which is one part of the curved channel. The resistance of the duct is smaller than that of other locations because of the rise in electrical conductivity. Consequently, the electrical arc is guided through the duct to the surface of the material, which is the other part of the curved channel. The spectral intensities of metal elements in laser-MIG hybrid welding are much stronger than those in MIG-only welding, whereas the spectral intensities of shielding gas element in laser-MIG hybrid welding are much weaker.