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Structure and wettability of pulsed electrodeposited Ni-W-Cu-(α-alumina) nanocomposite

SURFACE & COATINGS TECHNOLOGY 2016年 307卷 525-533页

作者： Allahyarzadeh, M. H. Aliofkhazraei, M. Rouhaghdam, A. R. Sabour Torabinejad, V. Tarbiat Modares Univ Dept Mat Engn Fac Engn POB 14115-143 Tehran Iran

The Ni-W-Cu-(alpha-alumina) nanocomposite layers were formed on carbon-steel substrate using pulse current electrodeposition. The effects of pulse frequency and duty cycle on structural characteristics and wettability of coatings were investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to study the microstructure and chemical compositions, respectively. Structural analysis was also carried out using the X-ray diffraction (XRD) method. To investigate wettability features, contact angle measurements were performed. Results revealed that pulse plating parameters could significantly influence the structure, composition, morphology, and wettability of nanocomposite coatings. The atomic force microscopy (AFM) and profilometry results showed that coatings with rough surfaces are obtained at lower pulse frequency. The EDS analysis indicated that the lower duty cycle results in deposition of more amounts of copper and alumina. The larger hydrophobic surfaces can be obtained at higher duty cycles, where the lower duty cycles lead to fabrication of hydrophilic surfaces. (C) 2016 Elsevier B.V. All rights reserved.

关键词： pulse parameters Electrodeposition Wettability Ni-W-Cu-(alpha-Al2O3)

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pulsed-DC Discharge for Plasma CVD of Carbon Thin Films

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IEEE TRANSACTIONS ON PLASMA SCIENCE 2019年第1期47卷 22-31页

作者： Al Mamun, Md Abdullah Furuta, Hiroshi Hatta, Akimitsu Kochi Univ Technol Grad Sch Engn Kochi 7828502 Japan Kochi Univ Technol Ctr Nanotechnol Kochi 7828502 Japan

A pulsed-dc discharge method for plasma chemical vapor deposition (CVD) was developed using a constructed versatile pulsed-dc generator and a vacuum discharge chamber. Argon (Ar) gas discharge experiments were performed under a variety of discharge conditions, and plasma conditions were evaluated using optical emission spectroscopy. The developed system can perform glow discharge by employing nearly rectangular, unipolar, and high-voltage negative pulses with a wide variation of voltage amplitudes and a set discharge current, pulse repetition rate, and duty cycle. Plasma conditions could also be tuned by varying the pulse parameters. A preliminary test of the deposition of diamond-like carbon (DLC) films on silicon (Si) substrates and ultrathin pyrolytic carbon (PyC) films on nanothickness metal-catalyzed glass substrates was performed with acetylene (C2H2) by selecting some typical deposition conditions based on the gas discharge experiments. The deposited films were characterized via Raman spectroscopy. The characteristic properties of DLC and PyC films were achieved. The DLC films demonstrated conventional hard insulating properties while the ultrathin PyC films exhibited conductive and semitransparent properties. These results revealed that the developed pulsed-dc discharge system for plasma CVD is applicable for the synthesis of insulating hard as well as soft conducting carbon thin films.

关键词： Capacitively coupled plasma (CCP) chemical vapor deposition (CVD) diamond-like carbon (DLC) high-voltage pulsed-dc generator pulse parameters pulsed-dc discharge pyrolytic carbon (PyC)

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Assembling of thick-section HSLA steel with one seam per layer multi-pass PC-GMA welding producing superior quality

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JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING 2017年第12期39卷 5205-5218页

作者： Agrawal, B. P. Ghosh, P. K. Galgotias Univ Sch Mech Engn Yamuna Expressway Greater Noida 201308 Uttar Pradesh India Indian Inst Technol Roorkee Roorkee 247667 Uttarakhand India

Assembling of 25-mm-thick HSLA steel plate with extra narrow gap between the plates is done with the help of multi-pass one seam per layer pulse current gas metal arc welding process maintaining vertical weld deposition. Assembling of thick plates is also made using conventional groove with commonly used procedure of multi-pass multi-seam per layer weld deposition. Distortion and shrinkage that developed in the weld joints have been suitably determined. The effects of welding parameters in reference to weld thermal behavior on shrinkage stress and bending stress have been studied. The observations show that the use of one seam per layer technique allowing extra narrow gap welding with properly selected parameters can improve quality of weld joint with respect to distortion and stresses. The effect of pulse parameters on weld quality is studied, correlated and discussed. Cost benefits of applying such a welding technique have been justified with respect to consumption of less filler material and time for preparation of weld joint.

关键词： PC-GMAW pulse parameters HSLA steel Extra narrow gap weld Shrinkage stress Bending stress

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A discussion of the IEEE standard on transition and pulse waveforms, Std-181-2003

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MEASUREMENT 2005年第1期37卷 31-38页

作者： Paulter, NG Larson, DR Blair, JJ NIST Elect & Elect Engn Lab Dept Commerce Div Elect Gaithersburg MD 20899 USA Bechtel Nevada Las Vegas NV 89193 USA

The IEEE Std-181-2003, which is a new standard on pulse techniques and definitions, has been recently published. This standard was written to replace the withdrawn IEEE standards, Std-181-1977 and Std-194-1977. The Std-181-2003 combines information from both of the withdrawn standards. The new standard has incorporated new definitions not contained in the withdrawn standards and deleted and clarified definitions contained in the withdrawn standards. The new standard also provides examples of different waveform types and incorporates algorithms for computing waveform parameters, both of which were not contained in the withdrawn standard. This paper introduces the Std-181-2003 by describing its contents and changes relative to the withdrawn standards. Published by Elsevier Ltd.

关键词： aberrations algorithms IEEE standard overshoot pulse parameters pulse standard state levels transition duration transition settling error undershoot waveform parameters waveform terms

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A Modified Algorithm to identify the strongest velocity pulse in three orthogonal components of ground motions

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SOIL DYNAMICS AND EARTHQUAKE ENGINEERING 2021年 146卷

作者： Zhao, Tianci Zhao, Boming Beijing Jiaotong Univ Key Lab Urban Underground Engn Minist Educ Beijing Peoples R China Beijing Jiaotong Univ Sch Civil Engn Beijing Peoples R China

An algorithm for the identification of the strongest velocity pulse is proposed based on wavelet analysis, which considers three orthogonal components of the ground motion. According to the NGA-West2 database, 6288 strong motion records were analyzed, and further, the classification results were compared with those obtained from the existing identification method of Shahi and Baker (2014) [1]. Among the results, our algorithm classified more records as pulse-like ground motion and has expanded the pulse identifications. In other words, the proposed algorithm can reflect the three orthogonal characteristics of the original ground motion records. Besides, the relationships of pulse amplitude, period with magnitude and fault distance were analyzed. Based on the analysis of near-fault ground motions containing velocity pulses, the following conclusions can be made: (1) The peak of the strongest velocity pulse gradually reduces with the increase of the fault distance, while gradually rises with the increase of the magnitude. Comparing with the fault normal or fault parallel orientation component, the strongest velocity pulse component has larger energy and smaller peak velocity. (2) For the relationship between the velocity pulse period and magnitude, results show that when Mw < 7, the predicted value of our model is larger than that of the Shahi and Baker (2014) [1] model;however when Mw >= 7, the prediction results from these two models are fairly close. The difference between the two models decreases as magnitude increases. That is because the strongest velocity pulses occupied more in the horizontal direction under a large magnitude.

关键词： Ground motion Velocity pulse Wavelet Strongest pulse orientation component Near-fault pulse parameters

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Microstructure and hardness of Al-Mg-Si weldments produced by pulse GTA welding

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2008年第3-4期36卷 263-269页

作者： Manti, Rajesh Dwivedi, D. K. Agarwal, A. Indian Inst Technol Dept Mech & Ind Engn Roorkee 247667 Uttar Pradesh India

This paper describes the effects of pulsed TIG welding process parameters (pulse duration, peak current, and pulse frequency) on the microstructure and microhardness of Al-0.8%Mg-0.5%Si (6061) alloys. It was observed that pulse TIG welding produced finer grain structure of weld metal than conventional TIG welding (without arc pulsation). An increase in the pulse frequency has been found to refine the aluminium and eutectic grain structure of weld metal especially when welding is done using short pulse duration. Long pulse duration lowers the pulse frequency up to which refinement of constituents in weld metal takes place. Effect of the pulse frequency on the grain structure was found to be determined by pulse duration. For a given pulse frequency, long pulse duration produced a coarser structure than short pulse duration. An increase in the peak current coarsened the grain structure.

关键词： Al-Mg-Si alloy microstructure microhardness pulse parameters TIG welding liquation

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Experimental study on uniformity of copper layer with microstructure arrays by electroforming

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2021年第7-8期114卷 2019-2030页

作者： Zhao, Yongfei Qian, Shuangqing Zhang, Yong Wan, Xiaofeng Zhang, Hua Nantong Univ Sch Mech Engn Nantong 226019 Peoples R China Shazhou Profess Inst Technol Dept Mech & Elect Engn Zhangjiagang 215600 Peoples R China

Metal microstructures have a high potential to meet high application requirement of a variety of new industries because they can make components obtain optical, thermal, bionic, and other functional properties. Electroforming is one of the most efficient technologies for large-scale fabrication of micromachined devices with microstructures due to its good repeatability and reproducibility. However, the thickness nonuniformity of the electroformed layer is a bottleneck problem in the preparation of microstructures, which leads to quality defects such as voids in the microstructures. In order to fabricate the void-free microstructures, pulse electrodeposition of copper was proposed in this paper. The effects of pulse electrodeposition parameters on the surface morphology and thickness uniformity of copper deposits were investigated. In this paper, copper was electrodeposited by direct current and pulse current respectively on the microgroove arrays with an aspect ratio of 2.5:1. The experimental results revealed that the pulse parameters can effectively improve the quality of the electroformed layer and enhance the uniformity of the microgrooves. It was determined that the pulse average current density 2 A/dm(2), the duty cycle 20%, and the frequency 2000 Hz were the optimum parameters for copper electroforming. Under these conditions, the void-free microstructures were successfully prepared.

关键词： Microstructures Electroforming Copper pulse parameters Uniformity

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Effects of pulse duration and overlapping factor on melting ratio in preplaced pulsed Nd:YAG laser cladding

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OPTICS AND LASERS IN ENGINEERING 2013年第1期51卷 69-76页

作者： Farnia, Amirreza Ghaini, Farshid Malek Sabbaghzadeh, Jamshid Tarbiat Modares Univ Dept Mat Sci & Engn Fac Engn Tehran 14115143 Iran Iranian Natl Ctr Laser Sci & Technol INLC Tehran Iran

Melting ratio is known as a suitable factor to illustrate the effects of process parameters on the clad profile in order to provide a proper process design. However, the definition of melting ratio based on continuous irradiation of energy does not accommodate for pulse parameters. Hence, in order to study the effects of pulse parameters, such as pulse duration and overlapping factor, the definition of melting ratio is restated for pulsed laser process based on energy density concept. Carbon steel was cladded with Stellite 6 by scanning a 400 W pulsed Nd:YAG laser over a preplaced layer of powder paste. The results show that the trends of clad profiles variations can be explained using the restated definition. The results also show two different ranges for the effects of pulse duration and overlapping factor on melting ratio. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： pulse parameters Melting ratio Preplaced Laser cladding Stellite 6

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NIST-NPL interlaboratory pulse measurement comparison

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2003年第6期52卷 1825-1833页

作者： Paulter, NG Smith, AJA Larson, DR Souders, TM Roddie, AG Natl Inst Stand & Technol Div Elect Gaithersburg MD 20899 USA NIST Div Elect Gaithersburg MD 20899 USA

A comparison of the pulse parameter values obtained from the pulse measurement services of the National Institute of Standards and Technology, USA, and the National Physical Laboratory, U.K., was performed. The comparison was based on the pulse parameters of amplitude, transition duration, overshoot, and undershoot (preshoot). The parameter comparison was applied to raw (measured) waveforms, corrected waveforms (if applicable), and reconstructed waveforms. The results of the comparison show that the pulse parameter values for both national laboratories are within published uncertainties.

关键词： interlaboratory comparison overshoot pulse amplitude pulse parameters pulse waveforms transition duration undershoot

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Modeling and simulation of wire feed rate for steady current and pulsed current gas metal arc welding using 317L flux cored wire

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2007年第11-12期34卷 1111-1119页

作者： Palani, P. K. Murugan, N. Gov Coll Technol Fac Mech Engn Coimbatore 641013 Tamil Nadu India Coimbatore Inst Technol Coimbatore 641014 Tamil Nadu India

Wire feed rate plays a vital role in determining the weld characteristics in gas metal arc welding (GMAW). The wire feed rate is affected by any change in welding current in the case of steady current GMA welding and by any change in frequency, peak current, base current and duration of peak and base currents in the case of pulsed GMA welding. To predict the wire feed rate for any set of these parameters, a mathematical model was developed from the results obtained by conducting experiments. Electrode resistance heating constant and arc resistance heating constant were also determined by fitting a regression model. The above parametric constants have been used to simulate the wire feed rates for pulsed GMA welding for different pulse parameters using MATLAB. The effects of pulse parameters on the burnoff factor and burnoff rates were also analysed. The investigation was carried out using AWS 5.22-95 filler wire of size 1.2 mm diameter and the base metal used was IS:2062 structural steel plate of 20 mm thickness. An argon and 5% CO2 gas mixture at a flow rate of 16 l/min was used for shielding throughout the welding.

关键词： welding current wire feed rate regression analysis pulse parameters arc resistance heating constant wire resistance heating constant

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