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Sampath V
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Sampath V
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Sampath V
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Sampath, Vedamanickam
Vedamanichkam, Sampath
Sampath, V.
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66 results
Now showing 1 - 10 of 66
- PublicationInfluence of quaternary alloying additions on transformation temperatures and shape memory properties of Cu-Al-Mn shape memory alloy(05-02-2009)
;Mallik, U. S.The transformation temperatures, shape memory effect and superelasticity of Cu-Al-Mn shape memory alloys are highly sensitive to variations in composition. A ternary shape memory alloy Cu-12.5 wt.% Al-5 wt.% Mn was chosen for the present study and different amounts (1, 2 and 3 wt.%) of quaternary elements Zn, Si, Fe, Pb, Ni, Mg, Cr and Ti were added to the ternary (base) alloy. The influence of quaternary additions on shape memory characteristics of these alloys was studied by differential scanning calorimetry, bend and tensile test. Zn and Ni as quaternary additions were found to increase the transformation temperatures, whereas Fe, Cr, Ti, Si and Mg decrease them. These additions were found to increase the extent of strain recovery by shape memory effect, whereas decrease the superelasticity of the alloys. © 2008 Elsevier B.V. All rights reserved. - PublicationMicrostructural and Thermal Investigations of Cu-Al-Mn-Ni Shape Memory Alloys(01-01-2017)
;Aksu Canbay, CananShape memory alloys manifest two distinct characteristics, namely shape memory effect and superelastic effect. They are used in a wide variety of engineering, medical and commercial applications. The use of shape memory alloys in a particular application depends on the shape memory characteristics, viz., shape recovery strain and transformation temperatures. The martensitic transformation and its reversibility form the basis of these functional properties. The transformation temperatures are much influenced by alloying addition, grain-refinement, thermomechanical treatment, etc. In this work, the effect of composition, in general, and that of nickel, in particular, on the microstructure and transformation temperatures and thermodynamic parameters have been explored. The microstructural and phase analyses were carried out by optical microscopy and X-ray diffraction, respectively. The thermodynamic quantities/parameters, such as enthalpy and entropy associated with the transformations as well as the transformation temperatures, were determined by differential scanning calorimetry. The phase analyses were also carried out by thermogravimetry and differential thermal analysis. The results have been analysed and discussed in this paper. - PublicationMetallurgical and shape memory characteristics of grain-refined Cu-Zn-Al shape memory alloys(01-12-2002)
; ; Sivakumar, M. S.Copper-based shape memory alloys (SMAs) are prone for grain growth during thermomechanical and betatising treatments. The grain growth of the alloy leads to intergranular cracking on quenching to form martensite in the alloy, which in turn leads to poor mechanical properties including corrosion resistance of the alloy. In the present work, grain refinement of a CuZnAl shape memory alloy was done by adding 0.2 to 0.4 wt.% of zirconium, titanium and boron as grain refiners. The effect of these additions on the microstructure and shape memory properties of the alloys were studied. The results show that the Zr and Ti additions reduce the grain size from 1.5 mm to 200 μm and 500 μm respectively. The Zr-added alloy shows good strain recovery and corrosion resistance compared with the alloy in the other conditions. - PublicationInfluence of microstructure on mechanical and magnetic properties of an Fe-Ni-Co-Al-Ta-B shape memory alloy(03-04-2019)
;Adarsh, S. H.Ni-Ti shape memory alloys are the only shape memory alloys that are commercially available on the market and are also used in diverse medical and engineering applications. However, they still have some limitations associated with them, such as the use of expensive raw materials, sophisticated equipment for production and lack of easy cold formability when compared with iron-based and copper-based SMAs. Researchers have therefore been looking for viable alternatives to Ni-Ti SMAs, such as iron- and copper-based SMAs, that are cheaper and easier to produce and process. Fe-28Ni-17Co-11.5Al-2.5Ta-0.05B (at%) (abbreviated NCATB) shape memory alloy shows huge superelasticity (>13%) and high tensile strength at room temperature. NCATB alloy has therefore attracted the attention of researchers and engineers to exploit its advantages in different fields. In the current work, an NCATB shape memory alloy was prepared by two different techniques, namely vacuum induction melting under an argon atmosphere and vacuum arc remelting followed by suction casting technique. The cast alloys were subsequently thermally treated and characterized by optical microscopy (OM), differential scanning calorimetry (DSC), x-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). Vickers hardness test and carbon and sulphur analyses were also carried out on the alloys. The major objective of the present work is to evaluate the influence of aging on microstructure and, in turn, on mechanical and magnetic properties of an NCATB shape memory alloy. Aging at 600 °C up to 48 h was found to be the optimum heat treatment to achieve enhanced mechanical properties in both NCATB1 and NCATB2 alloys. Ferromagnetic (Ni,Fe,Co)3(Al,Ta) γ′ ordered precipitate particles and paramagnetic NiAl (β) phases were found to be critical for using the alloy for magnetic applications. - PublicationOn the feasibility of the application of electroslag refining to an aluminium alloy(01-01-1992)
; Dwarakadasa, E. S.Electroslag refining (ESR) is a process already well established for ferrous materials. In view of its obvious potential for improving material behaviour for critical applications, an attempt has been made to study the possibility of using ESR for a selected aluminium alloy (corresponding to the Indian Specification IS:7670). This paper outlines the difficulties involved in applying ESR to aluminium alloys and highlights the need for careful selection of slag composition. The mode of solidification and features of the macrostructure of the material refined with a halide slag are then correlated with the slag characteristics. - PublicationHot deformation behavior of Fe–28Ni–17Co-11.5Al-2.5Ta-0.05B (at.%) shape memory alloy by isothermal compression(01-12-2019)
;Adarsh, S. H.A Gleeble-3800 thermomechanical simulator was used to conduct experiments at deformation temperatures varying between 1050 and 1200 °C and strain rates varying between 0.01 and 10 s−1 with the maximum strain of 0.6. Processing maps incorporating efficiency map and instability map were generated using the dynamic material model (DMM). Deformation mechanisms were investigated using true stress-true strain curves, processing maps, kinetic analysis, and microstructural analysis. A constitutive equation was established in the form of an Arrhenius hyperbolic sine function, which yielded an activation energy of ~ 412 kJ/mol for deforming the alloy at elevated temperature. Based on the process map, optimum process parameters for the formation of recrystallized grains during the hot deformation of the sample were predicted to be T = 1100 °C and ε˙ = 0.01s−1, which were also verified by microstructural analysis. Based on an analysis of the work-hardening characteristics, the critical conditions for the deformation were found to be, σs = 0.88 σp, σc = 0.95 σp, and εs = 0.24 εp. Cingara-Queen model was used to determine the flow curve until the peak value of flow stress. This model is highly compatible with the experimental findings as validated by the high correlation coefficient (Adj. R2 = 0.9851). - PublicationGiant reversible adiabatic temperature change and isothermal heat transfer of MnAs single crystals studied by direct method in high magnetic fields(25-08-2019)
;Koshkid'ko, Yu S. ;Dilmieva, E. T. ;Cwik, J. ;Rogacki, K. ;Kowalska, D. ;Kamantsev, A. P. ;Koledov, V. V. ;Mashirov, A. V. ;Shavrov, V. G. ;Valkov, V. I. ;Golovchan, A. V. ;Sivachenko, A. P. ;Shevyrtalov, S. N. ;Rodionova, V. V. ;Shchetinin, I. V.The magnetocaloric effect (MCE) in single crystals of MnAs compound was studied both experimentally and theoretically. Direct measurement of MCE showed that the adiabatic temperature change (ΔTad) in a magnetic field of 10 T was 15 K. But direct measurement of the quasi-adiabatic heat transfer (ΔQ) of the sample yielded a value of 9500 J/kg in a magnetic field of 10 T. To date, it is the highest experimentally recorded value for ΔQ by direct measurement. Phenomenological considerations that take into account the interaction of magnetic and structural order parameters explain a number of anomalies in the magnetic and magnetocaloric properties of MnAs that were observed during the experiments. - PublicationFabrication of carbon and silver nanomaterials incorporated hydroxyapatite nanocomposites: Enhanced biological and mechanical performances for biomedical applications(01-09-2021)
;Balu, Satheesh Kumar; ;Andra, Swetha ;Alagar, SrinivasanManisha Vidyavathy, S.Hydroxyapatite is widely utilized for different biomedical applications because of its outstanding biocompatibility and bioactivity. Cuttlefish bones, which are available aplenty, are both inexpensive and eco-friendly sources for calcium carbonate. In the present study, cuttlefish bones-derived HAp nanorods have been utilized to fabricate HAp nanocomposites incorporating 1, 3 and 5 wt% each of GO, MWCNTs, GONRs and Ag NPs. Characterization using such techniques as XRD, FTIR, HRSEM and EDS was performed to analyze the physicochemical properties of nanocomposites, and MTT assay, hemolysis, bioactivity and drug release to evaluate the biological properties. The XRD and HRSEM results reveal that crystallite and particle size increase with increasing wt% of carbon nanomaterials and Ag NPs. However, the addition of nanomaterials did not modify the shape of HAp. The MTT assay and hemolysis results suggest GONRs possess better biocompatibility than GO and CNTs due to their smooth edge structure. While adding carbon materials up to 3 wt% caused an increase in the hardness, adding up to 5 wt% of them caused a decrease in the hardness due to the agglomeration of the particles. Biocompatibility and Vicker's hardness studies show that adding carbon nanomaterials up to 3 wt% caused significant improvement in biocompatibility and mechanical properties. Antibacterial activity test was performed to analyze the ability to preclude the formation of biofilms. The results showed better activity for silver-incorporated nanocomposites in the presence of E. coli and S. aureus bacteria. Drug release studies were performed using lidocaine drug and the results showed nearly similar drug release profile for all the samples except HAg3. Finally, nanocomposite HRA3 could be a suitable candidate for biomedical applications since it shows better biological and mechanical properties than GO and MWCNTs nanocomposites. - PublicationEffect of thermal processing on microstructure and shape-memory characteristics of a copper-zinc-aluminum shape-memory alloy(01-01-2007)Although Cu-based shape-memory alloys possess higher transformation temperatures compared with Ni-Ti shape-memory alloys and a higher magnitude of strain recovery, they are still not used extensively in commercial applications since they suffer from some inherent drawbacks, such as a lack of ductility and stabilization of martensite. Cu-Zn-Al alloys in particular are more prone to stabilization. In the present work, therefore, a Cu-Zn-Al alloy with a low Al content (<3 wt%) prepared by ingot metallurgy was thermally processed by subjecting it to different quenching treatments, such as direct quenching, up-quenching and step-quenching using water, oil and brine solution as the quenchants. The effect of different methods of quenching as well as the quenchants themselves on the microstructure, transformation temperatures and shape-memory characteristics of the alloy was investigated and the results obtained have been interpreted. The study reveals that quenching in a brine solution results in 100% martensite, thereby getting rid of the deleterious effects of aging. The characteristic transformation temperatures are also modified by variations in the rate of quenching.
- PublicationNano-Manipulation, Nano-Manufacturing, Nano-Measurements by New Smart Material-Based Mechanical Nanotools(28-11-2018)
;Koledov, Victor ;Shavrov, Vladimir ;Lega, Peter ;Von Gratowski, Svetlana ;Shelyakov, Alexander ;Orlov, Andrey ;Irzhak, Artemy; Mashirov, AlexeyRecent progress in the study of new functional materials, such as Ti(NiCu) intermetallic with shape memory effect (SME), opens up exciting possibilities for the design reconfigurable micro- and nano-structures and for operating mechanical nanotools controlled by external fields or heat. This report gives an overview of physical effects, in particular, solid state phase transitions and accompanying phenomena in alloys and composites exhibiting SME. The limitations pertaining to the minimum size of the nanomechanical devices exhibiting shape memory effect that arise due to the solid state phase transitions are now under discussion and have not been completely understood yet. The modern nanotechnologies allow designing of the mechanical micro- and nanotools, such as nanotweezers, nanopinchers etc., with an active layer thickness of about several tenths of nm, and whose overall size is below 1 μm. The nanotools with SME can be controlled by heating as well as by magnetic field activation in ferromagnetic alloys exhibiting SME, such as Ni 2 MnGa. 3D nanomanipulation is demonstrated by composite nanotweezers with SME in different nanoobjects, such as CNTs, nanowires, nanowhiskers, bionanoobjects, DNA, etc. In these devices, the surface interactions and Casimir and van der Waals forces affect the process of nanomanipulation. The prospects of nanorobotics and manufacturing on nanoscale adapting the principle of mechanical bottom-up nanoassembly are discussed. In addition, nanoscale measurements can take advantage of 3D mechanical nanomanipulation, including transportation of analytes to nanosensors, elasticity measurements by nanotools with calibrated force, etc.