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RISS 인기검색어
- 검색키워드
- 저자 : S. Narayanan (검색결과 65 건)
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Fretting-corrosion mapping of tin-plated copper alloy contacts
Narayanan, T.S.N.S.,Park, Y.W.,Lee, K.Y. Elsevier Sequoia [etc.] 2007 Wear: An international journal on the science and Vol.262 No.1
The fretting corrosion of tin-plated contacts is influenced by several factors including frequency, amplitude, temperature, humidity, normal load, current load, etc. The present paper aims to develop fretting-corrosion maps to assess the fretting corrosion behaviour of tin-plated copper alloy contacts under varying experimental conditions. The extent of change in contact resistance up to 20000 fretting cycles and the nature of changes, such as, the extent of fretting wear and oxidation, assessed by surface analytical techniques, are used to develop the fretting-corrosion maps. The fretting-corrosion maps are segmented into various zones depending on the predominant processes that occur under a given set of conditions. The proposed fretting-corrosion maps are not quantitative to predict the exact life-time of the contact. However, they will be useful to draw some guidelines about the performance of the tin-plated copper alloy contacts under various conditions.
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Fretting corrosion of lubricated tin-plated contacts
Narayanan, T.S.N. Sankara,Park, Young Woo,Lee, Kang Yong Emerald Group Publishing Limited 2008 Industrial lubrication and tribology Vol.60 No.5
<B>Purpose</B> - The objective of this paper is to study the effect of a commercial lubricant, which contains a 50-50 mixture of zinc diamyldithiocarbamate and petroleum oil, on the fretting corrosion of tin-plated copper alloy contacts. <B>Design/methodology/approach</B> - The change in contact resistance as a function of fretting cycles was used to assess the effectiveness of the lubricant in preventing the fretting corrosion of tin-plated contacts. The surface profile, surface roughness, extent of fretting damage and extent of oxidation of the contact zone were assessed by a laser scanning microscope and surface analytical techniques to correlate the change in contact resistance with fretting cycles. <B>Findings</B> - The lubricant film provides a surface coverage of 6.76±1?mg/cm<SUP>2</SUP> and it easily establishes metallic asperity contact between the mated tin-plated contacts. The contact resistance of lubricated contacts remains stable for several thousand fretting cycles. Lubricated contacts reach a threshold value of 0.1?O around 100,000 cycles, whereas unlubricated contact reaches this value around 13,500 cycles itself. For lubricated contacts, the extent of mechanical wear of the tin coating is significantly reduced. As a result, they experience a lesser damage at the contact zone and exhibit a smoother profile. The formation of tin oxide is not appreciable and there is no oxide accumulation at the contact zone even at 380,000 cycles. The lubricant is very effective in delaying the fretting wear during the initial stages and in preventing the oxidation and accumulation of oxidation products at the contact zone in the later stages. <B>Originality/value</B> - Metallic dialkyldithiocarbamates are useful anti-wear and extreme pressure additives for lubricating oils. Dithiocarbamates improve the antioxidant properties of the lubricants and are effective in reducing the wear and increasing the friction-reducing and load-carrying ability of the base stock. The use of molybdenum dithiocarbamate as a grease additive is found to be effective in reducing fretting corrosion of ball bearings under random rotary vibrating conditions. The effect of dithiocarbamate containing lubricant oils or greases on the fretting corrosion of electrical contacts has not far been studied. The paper explores the effect of a lubricant that contains a 50-50 mixture of petroleum oil and zinc diamyldithiocarbamate on the fretting corrosion of tin-plated contact.
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Modeling of Single-Pulse Operated Switched Reluctance Generator and its Verification
S. S. Ahmad,G. Narayanan 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a mathematical model for a switched reluctance (SR) generator feeding a dc link through a power electronic converter. SR machines are operated in singlepulse mode at close to and above base speed. The SR generator is modeled as a current source, controllable with dc-link voltage Vdc and switching angles (αon and αoff ) of the converter. This current source model is used to predict the dc-link dynamics for constant resistance, constant current and constant power loads. This is further utilized to derive the voltage build-up condition for an SR generator. The generator model, dc-link dynamics and voltage build-up conditions are validated through simulations and experiments.
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Evaluation of DC-link Capacitor RMS Current in Switched Reluctance Motor Drive
S. S. Ahmad,G. Narayanan 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In this paper a method to evaluate the DC-link capacitor RMS current of a switched reluctance machine (SRM) drive under different operating conditions is presented. Square current reference is considered. Methods are developed for both soft chopping and hard chopping method of current control. A newly proposed simplified flux linkage model is used to evaluate converter switching functions and phase currents which are then used to evaluate the capacitor current stress. The capacitor current is found to be lower for soft chopping than for hard chopping. While the capacitor current is maximum at lowest operating speed with hard chopping, the maximum occurs at an intermediate speed for soft chopping for a given magnitude of current reference. The proposed method is useful to size the DC-link capacitor during the design of SRM drive.
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Fuzzy logic based yaw stability control for active front steering of a vehicle
S. Krishna,S. Narayanan,S. Denis Ashok 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.12
Yaw stability control is an important consideration for improving the stability and handling behavior of a vehicle during extreme steeringmaneuvers. This paper proposes a fuzzy logic based yaw stability controller for an active front steering of a four-wheeled road vehicleby using steer-by-wire system. The proposed control system takes the yaw rate error, the steering angle given by the driver and thevehicle body side slip angle as inputs, for calculating the additional steering angle as output for stabilizing the yaw moment of the vehicle. A three degrees-of-freedom vehicle model is considered. Performance of the proposed system is simulated for sinusoidal, step maneuverusing Matlab/Simulink tool, and the results are compared with the existing fuzzy control system which uses two inputs such steeringangle and yaw rate. The simulation results show better performance of the proposed fuzzy based yaw controller as compared with theexisting control system.
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Adenomatoid odontogenic tumor of the mandible with unusual radiographic features: A case report
Narayanan, Veena S.,Naidu, Giridhar,Ragavendra, Raju,Mhaske-Jedhe, Shubangi,Haldar, Maya Korean Academy of Oral and Maxillofacial Radiology 2013 Imaging Science in Dentistry Vol.43 No.2
Adenomatoid odontogenic tumor (AOT) usually presents as a unilocular, pericoronal radiolucency in the maxillary anterior region in adolescent females. Very few conditions occur in such a narrow age range and at such a restrictive site. Rarely, these tumors present with varied clinical features. A case of AOT of the mandible is reported with unusual features such as large size, multilocular appearance, and aggressive behavior. The role of radiology in diagnosis of atypical AOT is extremely important. The unique radiological manifestations of the lesion helped in the diagnosis, and it was managed conservatively with no evidence of recurrence.
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Narayanan, K.B.,Han, S.S. Applied Science Publishers ; Elsevier Science Ltd 2017 Carbohydrate polymers Vol.160 No.-
The natural algal polysaccharide carrageenan was used for the greener synthesis of silver/silver chloride nanoparticles (Carr-Ag/AgCl NPs) without any toxic chemicals. We report the robust, highly selective, and sensitive colorimetric sensing of Hg<SUP>2+</SUP> ions using Carr-Ag/AgCl NPs without any further surface modification. The dark-brown color of a solution of Carr-Ag/AgCl NPs turned to white in a concentration-dependent manner with the addition of Hg<SUP>2+</SUP> ions, confirming the interaction of Carr-Ag/AgCl NPs with Hg<SUP>2+</SUP> ions. The plot of the extinction ratio of absorbance at 350nm to 450nm (A<SUB>350</SUB>/A<SUB>450</SUB>) for Carr-Ag/AgCl NPs against the concentration of [Hg<SUP>2+</SUP>] ions was linear, and the calibration curve was A<SUB>350</SUB>/A<SUB>450</SUB>=1.05254+0.00318xC<SUB>Hg</SUB> with a lower detection limit of 1μM. This portable and cost-effective method for mercury(II) ion sensing is widely applicable in on-field qualitative and quantitative measurements of [Hg<SUP>2+</SUP>] ions in environmental or biological samples.
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Narayanan, T.S.N. Sankara,Lee, Min-Ho ELSEVIER SCIENCE 2016 JOURNAL OF ALLOYS AND COMPOUNDS Vol.687 No.-
<P><B>Abstract</B></P> <P>Microarc oxidation (MAO) of magnesium is performed in a single stage using an alkaline silicate electrolyte and acidic zirconate electrolyte as well as in two stages, sequentially using the alkaline silicate followed by the acidic zirconate electrolyte. The morphological characteristics, surface roughness, phase content, corrosion behaviour and bioactivity were compared. The surface morphology, thickness, average surface roughness (R<SUB>a</SUB>), and phase composition of the MAO coatings show a strong dependence on the type of electrolytes used and the methodology employed for deposition. Based on the corrosion protective ability in Hank’s balanced salt solution, the uncoated and MAO coated Mg are ranked as follows: Uncoated Mg < MAO coated Mg prepared using alkaline silicate electrolyte < MAO coated Mg prepared using acidic zirconate electrolyte < MAO coated Mg prepared in two stages, sequentially using the alkaline silicate followed by the acidic zirconate electrolyte. Poorly crystalline calcium deficient apatite is formed on all samples after immersion in SBF at 37 °C for 240 h.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Characteristics of MAO coating depend on electrolyte type and deposition methodology </LI> <LI> MAO coating by dual electrolytes in two stages offered better corrosion resistance. </LI> <LI> Poorly crystalline calcium deficient apatite is formed after immersion in SBF. </LI> </UL> </P>
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