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Rajiv Shekhar

Bio: Rajiv Shekhar is an academic researcher from Indian Institute of Technology Kanpur. The author has contributed to research in topics: Heat transfer & Anode. The author has an hindex of 14, co-authored 56 publications receiving 605 citations. Previous affiliations of Rajiv Shekhar include Indian Institute of Technology, Jodhpur & Indian Institutes of Technology.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the need for dummy workpieces above and below the workpiece for obtaining uniform hole diameter, specifically at the ends, has been pointed out, and the results also point to the need to use dummy work pieces above and above the work piece for obtaining a uniform hole.
Abstract: _1 , respectively. Results also point to the need for using dummy workpieces above and below the workpiece for obtaining uniform hole diameter, specifically at the ends.

70 citations

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TL;DR: In this article, the influence of alloying and thermomechanical processing on the microstructure and texture evolution on the two Mg-Li-Al based alloys was elicited.
Abstract: In the present study, the influence of alloying and thermomechanical processing on the microstructure and texture evolution on the two Mg–Li–Al based alloys, namely Mg–9 wt% Li–7 wt% Al–1 wt% Sn (LAT971) and Mg–9 wt% Li–5 wt% Al–3 wt% Sn–1 wt% Zn (LATZ9531) has been elicited. Novel Mg–Li–Al based alloys were cast (induction melting under protective atmosphere) followed by hot rolling at ∼573 K with a cumulative reduction of five. A contrary dual phase dendritic microstructure rich in α-Mg, instead of β-Li phase predicted by equilibrium phase diagram of Mg–Li binary alloy was observed. Preferential presence of Mg–Li–Sn primary precipitates (size 4–10 μm) within α-Mg phase and Mg–Li–Al secondary precipitates ( ( 1 0 1 ¯ 0 ) slip planes. The quantification of the grain average misorientation (less than 2°) using electron backscattered diffraction confirmed the presence of strain free grains in majority of the grains (fraction >0.75) after hot-rolling of Mg–Li–Al based alloys. Role of alloying in rendering distribution of dual-phase structure has strongly influenced dynamic-recrystallization and grain-growth in the hot-rolled Mg–Li–Al based alloys.

68 citations

Journal ArticleDOI
TL;DR: In this paper, a parametric study of electrochemical (DC mode) deep hole drilling in which acidified salt solution replaces acid electrolyte is performed, and the results show that the best hole is obtained at a voltage of 9.V, tool feed rate of 0.9mm/min, bare tip length of 4.128mm, with an electrolyte composition of 12.5% NaCl and 2.5 % HCl.

57 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of five process variables (voltage, tool feed rate, pulse on-time, duty cycle, and bare tip length of tool) on the responses of pulse-current shaped-tube electrochemical deep hole drilling (PC-STED) of nickel-based superalloy have been discussed.
Abstract: This paper presents the experimental investigation of pulse-current shaped-tube electrochemical deep hole drilling (PC-STED) of nickel-based superalloy. Influence of five process variables (voltage, tool feed rate, pulse on-time, duty cycle, and bare tip length of tool) on the responses, namely, depth-averaged radial overcut (DAROC), mass metal removal rate (MRRg) and linear metal removal rate (MRRl) have been discussed. Mathematical models have been developed to express the effects of the process parameters on DAROC, MRRg and MRRl. The proposed model permits quantitative evaluation of the hole quality and process performance simultaneously. The results have been confirmed for the profile of the drilled hole and MRRl obtained experimentally. In all the experiments, through holes of 26 mm depth and diameters ranging from 2.205 mm to 3.279 mm were drilled. The results have been explained by the interelectrode gap dynamics prevailing during pulse electrochemical deep hole drilling. Optimum parameters determined from these experiments can be used to efficiently drill high-quality deep holes of high aspect ratio in nickel-based superalloys.

50 citations

Journal ArticleDOI
TL;DR: In this paper, a mathematical model that uses STEM operating parameters (voltage, tool diameter and feed rate, bare tip length and electrolyte composition) as inputs to predict radial overcut has been developed.
Abstract: Shaped tube electrolytic machining (STEM) is a versatile and relatively low cost process for drilling deep, high aspect ratio holes. Since the radius of a drilled hole is the sum of the tool radius and radial overcut, one crucial aspect of dimensional accuracy is radial overcut. However, models of overcut in the literature are scarce and have primarily been restricted to shallow holes. Moreover these models were purely empirical and therefore restricted in scope. A fundamental mathematical model that uses STEM operating parameters (voltage, tool diameter and feed rate, bare tip length and electrolyte composition) as inputs to predict radial overcut has been developed. Predictions from the proposed radial overcut model are much closer to experimental data compared to those from the models available in the literature. A novel contribution of this study has been the formulation of a methodology to determine the magnitude of current flowing out radially from the bare tip length using experimentally measured total current values.

33 citations


Cited by
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Journal ArticleDOI
TL;DR: A novel image encryption algorithm based on a hybrid model of deoxyribonucleic acid (DNA) masking, a genetic algorithm (GA) and a logistic map is proposed that demonstrates excellent encryption and resists various typical attacks.

343 citations

Journal ArticleDOI
TL;DR: An overview of the current technological and economical capabilities of electrochemical (ECM)-based, electro-physical (EDM-based) and photonic (Laser/EBM)-based additive and removal processes for turbomachinery component manufacture is presented in this paper.
Abstract: This paper presents an overview of the current technological and economical capabilities of electrochemical (ECM-based), electro-physical (EDM-based) and photonic (Laser-/EBM-based) additive and removal processes for turbomachinery component manufacture. Starting with the industrial demands and challenges of today, the technologies are reviewed in detail regarding achievable geometrical precision and surface integrity as well as material removal and deposition rates for conventionally difficult-to-cut Ti- and Ni-based alloys and dedicated steels. Past, existing and future areas of technology application of these advanced non-mechanical manufacturing processes are discussed. The paper focusses on the description of shaping processes therefore excludes pure welding or coating applications.

315 citations

Journal ArticleDOI
TL;DR: In this paper, the developing history and recent progress of superlight magnesium-lithium base alloys are reviewed, and future research directions are suggested based on the current research progress.
Abstract: Magnesium–lithium base alloy is one of the lightest metallic engineering materials with a density of 1·35–1·65 g cm−3, which is referred to as superlight materials. It has become an attractive material in the fields of aerospace, automobiles, portable electronics, etc. In this paper, the developing history and recent progress of superlight magnesium–lithium base alloys are reviewed. The progress on molten electrolysis preparation, processing technologies and surface processing technologies are introduced, and future research directions are suggested based on the current research progress.

245 citations

Journal ArticleDOI
TL;DR: Promising research points include the development of more appropriate techniques of experiments both in vitro and in vivo to detect and analyze the biocompatibility and cytotoxicity of MNPs and understand the possible influencing mechanism of the two properties.
Abstract: It is generally recognized that nanoparticles possess unique physicochemical properties that are largely different from those of conventional materials, specifically the electromagnetic properties of magnetic nanoparticles (MNPs). These properties have attracted many researchers to launch investigations into their potential biomedical applications, which have been reviewed in this article. First, common types of MNPs were briefly introduced. Then, the biomedical applications of MNPs were reviewed in seven parts: magnetic resonance imaging (MRI), cancer therapy, the delivery of drugs and genes, bone and dental repair, tissue engineering, biosensors, and in other aspects, which indicated that MNPs possess great potentials for many kinds of biomedical applications due to their unique properties. Although lots of achievements have been obtained, there is still a lot of work to do. New synthesis techniques and methods are still needed to develop the MNPs with satisfactory biocompatibility. More effective methods need to be exploited to prepare MNPs-based composites with fine microstructures and high biomedical performances. Other promising research points include the development of more appropriate techniques of experiments both in vitro and in vivo to detect and analyze the biocompatibility and cytotoxicity of MNPs and understand the possible influencing mechanism of the two properties. More comprehensive investigations into the diagnostic and therapeutic applications of composites containing MNPs with "core-shell" structure and deeper understanding and further study into the properties of MNPs to reveal their new biomedical applications, are also described in the conclusion and perspectives part.

234 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the progress achieved over the last one and a half decades on ED multilayer films with GMR effect and to critically evaluate the GMR results reported for various element combinations accessible to the electrodeposition (ED) technique for the preparation of FM/NM multi-layer films (ED multilayered nanowires will be treated very briefly only).

218 citations