Browsing by Author "M.r, R."

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Active layer damping of bi-directionally tapered functionally graded sandwich plates with 1-3 piezoelectric composites
(Taylor and Francis Ltd., 2024) Shada, S.K.; Kattimani, S.; M.r, R.
This article investigates the effect of smart damping on bi-directionally tapered functionally graded sandwich plates. The substrate comprises FG material on both sides of the core of either soft herex or ceramic material. The viscoelastic layer of ALD is restrained, while the compelling layer consists of 1-3PZC. The finite element formulation developed incorporates layer-wise and first-order-shear-deformation theory. The plate’s damping is actively controlled using velocity feedback control incorporating piezoelectric patches. The effects of various parameters of taper ratio and patch positions on vibration control are investigated. The efficacy of the ALD in improving the structural performance of plates is investigated. © 2024 Taylor & Francis Group, LLC.
Degradation, wettability and surface characteristics of laser surface modified Mg–Zn–Gd–Nd alloy
(Springer, 2020) K.r, R.; Bontha, S.; M.r, R.; Das, M.; Balla, V.K.
This work evaluates the effects of laser surface modification on Mg–Zn–Gd–Nd alloy which is a potential biodegradable material for temporary bone implant applications. The laser surface melted (LSM) samples were investigated for microstructure, wettability, surface hardness and in vitro degradation. The microstructural study was carried out using scanning and transmission electron microscopes (SEM, TEM) and the phases present were analyzed using X-ray diffraction. The in vitro degradation behaviour was assessed in hank’s balanced salt solution (HBSS) by immersion corrosion technique and the effect of LSM process parameters on the wettability was analyzed through contact angle measurements. The microstructural examination showed remarkable grain refinement as well as uniform redistribution of intermetallic phases throughout the matrix after LSM. These microstructural changes increased the hardness of LSM samples with an increase in energy density. The wetting behaviour of processed samples showed hydrophilic nature when processed at lower (12.5 and 17.5 J/mm2) and intermediate energy density (22.5 and 25 J/mm2), which can potentially improve cell-materials interaction. The corrosion rate of as cast Mg–Zn–Gd–Nd alloy decreased by ~83% due to LSM. [Figure not available: see fulltext.]. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
Effect of dilution on the microstructure and high-temperature wear resistance of self-lubricating nickel alloy claddings
(SAGE Publications Inc., 2024) Gudala, S.; Rokkala, U.; Rao Medabalimi, S.; M.r, R.; Konovalov, K.S.
In this study, the impact of substrate dilution on the microstructure and tribological properties of tungsten inert gas (TIG)-deposited self-lubricating claddings was investigated. The dilution of Ti content on cladding increased as the TIG current increased, and the microhardness of the cladding decreased. The content of intermetallic phases such as TiNi and TiC increased with the increase in TIG current. The tribological studies revealed that coating dilution at higher TIG currents has prominent effects on wear behaviour at elevated temperatures. In both clads, the percentage decrease in hardness from higher TIG current to lower TIG current was noted as 31%. The higher dilution of Ti content in the cladding was found to be beneficial in tribological studies performed, especially at higher temperatures (≥400). Also, solid lubricants such as MoS2 and BaF2 encapsulation in the nickel alloy were found to be beneficial at both low and high temperatures. © The Author(s) 2024.
Laser surface melting of Mg-Zn-Dy alloy for better wettability and corrosion resistance for biodegradable implant applications
(Elsevier B.V., 2019) K.r, R.; Bontha, S.; M.r, R.; Das, M.; Balla, V.K.
In order to improve the performance of magnesium (Mg) for resorbable implant applications, Mg-1Zn-2Dy alloy was developed and the surface of the alloy has been modified by melting using lasers. Laser melted samples, at different laser energy density, were then subjected to microstructural, hardness, wettability and in-vitro degradation assessment. The microstructure of the Mg-Zn-Dy alloy mainly consisted of ?-Mg and eutectic phase (Mg 8 ZnDy). The melted region of the alloy surface evolved with fine grain microstructure at the near surface region and columnar grains near to the liquid solid substrate. The degree of grain size refinement obtained at the melted zone in the order of 1–2 ?m. The cross sectional microhardness of the modified zone was measured by Vickers microhardness tester. Due to these microstructural refinements and solid solution strengthening the surface hardness of laser treated alloy increased by two-fold. It was found that as the energy density increased the surface roughness along with the surface energy also increased. The wetting behaviour of the surface was estimated through measuring the contact angle by dropping the polar and non-polar liquid. Results showed that the surface energy is also found to change with LSM due to changes in the surface morphology, microstructure and chemical composition of the material. The detailed degradation study was carried out by immersing the samples in hanks balances salt solution (HBSS).The improvement in the degradation behaviour followed by laser surface melting is related to the microstructural refinement as a result of rapid heating and cooling of the melted zone. © 2019 Elsevier B.V.