Browsing by Author "Narayanasamy, R"

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    Effect of temperature and strain rate on compressive response of extruded magnesium nano-composite
    (National Engg. Reaserch Center for Magnesium Alloys, 2015-10-01) Selvam, B; Marimuthu, P; Narayanasamy, R; Senthilkumar, V; Tun, K.S.; Gupta, M
    The hot deformation behaviour of extruded magnesium-zinc oxide nano composite has been studied using hot compression test. The test was conducted in the temperature range of 250-400 °C and in the strain rate range of 0.01 to 1.5 s-1.The processing map was obtained using the power dissipation efficiency with the functions of temperature and strain rate. The workability and instability domains were observed in the processing map for a nano composite. The optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images were used to confirm the formation of dynamic recrystallization (DRX), dynamic recovery (DRY) and instability regions. The workability region of the composite was identified at a working temperature of 400 °C and the strain rate of 0.01 s-1 from the processing map. The instability regions were observed at higher strain rates (>0.1 s-1) and temperatures (250-400 °C).
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    Hot deformation response of AL 6061-MWCNTs alloy composites
    (Blue Eyes Intelligence Engineering and Sciences Publication, 2019-10-10) Jeyasimman, D; Senthilkumar V; Narayanasamy, R
    In this investigation, the effect of multi walled carbon nanotubes (MWCNTs) on compressive response with Al 6061 alloy nanocomposites prepared by mechanical alloying has been investigated. Hot deformation tests required to develop processing map were conducted at three temperatures such as 250, 350 and 450°C and in the three strain rates of 0.01, 0.1 and 1.0 s-1. The development of geometric dynamic recrystallization (DRX), dynamic recovery (DRV), instability regions and shear bands were confirmed by characterization study of prepared nanocomposites after hot Compression tests. The average activation energies for hot compression response was calculated as 153.00 KJ/mole for 2 wt.% MWCNTs reinforced Al 6061 alloy (AA 6061) nanocomposites. The most favorable key processing parameters for hot deformation was identified as temperature between 370-450°C and the range of strain rate was 0.1-0.01s-1. The region which are prone to shear localization, cracks and other instability were identified using the processing map and the same was verified with microstructural images obtained using optical and SEM images. © BEIESP.
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    Investigation on dry sliding wear behavior of Mg/BN nanocomposites
    (National Engg. Reaserch Center for Magnesium Alloys, 2018-05-30) Kaviti, R. Vara Prasad.; Jeyasimman, D; Parande, Gururaj; Gupta, Manoj; Narayanasamy, R
    The present research objective is to investigate the effect of boron nitride nanoparticles reinforcement on dry sliding wear behavior of pure Magnesium and magnesium nanocomposites. The fabricated nanocomposites contains varied percentages of boron nitride such as 0% (pure Mg), 0.5%, 1.5% and 2.5% were synthesized by using powder metallurgy technique and followed by a hot working process called hot extrusion. The pin on disk equipment was used for conducting the wear tests for traditional loads of 5 N, 7 N and 10 N at different sliding speeds of 0.6, 0.9 and 1.2 m/s against the steel disk at room temperature. For all traditional loads and sliding speeds, the changes in wear rate and friction co-efficient (µ) with respect to sliding distances were observed and analyzed. The wear characteristics are observed with the help of scanning electron microscopy under given test conditions. To investigate dominant wear mechanisms for various test conditions, the morphologies of all worn composites surfaces were analyzed. Final results show that, for all nanocomposites the wear level raises with respect to the sliding speeds and loads. Magnesium reinforced with 0.5% boron nitride shows lower wear rates and low friction coefficient values compare with magnesium reinforced with 1.5% boron nitride and 2.5% boron nitride nanocomposites
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    Sintered eutectoid P/M steel behaviour during cold upsetting
    (ABM, ABC, ABPol, 2008-01-03) Kannan, A. Rajesh; Pandey, K.S.; Shanmugam, S; Narayanasamy, R
    Cold upsetting experiments were carried out on sintered Fe-0.8%C steel preforms in order to evaluate the technical relationship that exist between the applied stresses against continuous deformation and densification. Powder preforms of 86% theoretical density and 0.40 of initial aspect ratio were subjected to incremental compressive loading of 0.04 MN under three different friction conditions such as dry, graphite and zinc stearate employed during deformation until fracture appears at free surfaces. Experimental results revealed that the response of applied stresses with induced strain and attained densification exhibits a continuous enhancement but with three different stages. Irrespective of friction conditions the first and third stage shows steep rise. which offers high resistance to deformation, whereas the second stage shows virtually steady state; deformation needed gradual increase in applied stresses but with high rate of densification. Further. preform deformed under without lubricant exhibited maximum strain hardening as well as an enhanced rate of strain hardening through out the deformation in comparison with lubricants employed conditions.
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    The dependence of the strain path on the microstructure, texture and mechanical properties of cryogenic rolled Al-Cu alloy
    (Institute of Physics Publishing, 2020-03-23) Selvan, C. Chinthanai; Narayana, C. Sathiya; Ravisankar, B; Narayanasamy, R; Valliammai, C. Thillaiyadi
    An investigation was conducted on Al-4%Cu alloy sheets to study the role of deformation path on the strength properties, evolution of microstructure and crystallographic texture during cryogenic rolling. Samples were rolled to two distinct thickness strains (50% and 75%) by unidirectional and cross rolling (bidirectional) routes. The strength and hardness properties were found to be more efficient in the cross rolled samples at 50% reduction than their counterparts rolled unidirectionally. Dynamic recovery was observed at higher rolling reductions on cross rolling. Microscopic features observed by EBSD revealed the occurrence of significant grain refinement on the samples rolled with a change of strain path. Also, the alteration of the rolling route resulted in distinct deformation textures and microstructures. TEM studies pointed out the scattered diffusion of the disintegrated dislocation cores and the redistribution of the second phase particles on higher rolling reductions with the change of strain path. Furthermore, the texture results showed a threefold increase on the Goss/Brass ratio which indicated the good fracture toughness behaviour of the cross rolled samples at lower reductions. © 2020 The Author(s). Published by IOP Publishing Ltd.