Browsing by Author "Koti, V."

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Al/Graphene/CNT Hybrid Composites: Hardness and Sliding Wear Studies
(Belgrade University, 2021) Manjunath Naik, H.R.; Manjunatha, L.H.; Koti, V.; Avinash, A.; Koppad, P.G.; P, S.K.
Graphene and carbon nanotubes are two carbon based materials known for their unique wear and friction properties. It would be quite interesting to understand the wear behavior of aluminium hybrid composites when these two nanosize reinforcements are incorporated into it. The hybrid composites with varying weight fractions of graphene (1, 2, 3 and 5 wt.%) and fixed CNT content of 2 wt.% were produced using powder metallurgy technique. The effect of varying graphene content on hardness and sliding wear of hybrid composites was studied. The wear tests were done as per ASTM G-99 standard with fixed sliding velocity (2 m/s) and sliding distance (1200 m) but varying applied load (10 - 30 N). Worn surface analysis was conducted using scanning electron microscope to arrive at wear mechanisms responsible for wear of aluminium and its hybrid composites. Increase in graphene content led to increase in bulk hardness with highest value of 61 RHN for hybrid composite with 3 wt.% graphene content. The wear rate of hybrid composites was found to be decreasing with enhancement in graphene content. Lower wear rate in hybrid composites was due to the formation of lubricating layer on the worn surface. © Faculty of Mechanical Engineering, Belgrade. All rights reserved
Effect of Variations in Mn Content on Mechanical and Corrosion Characteristics of Cu-Al-Mn Shape Memory Alloys; УТИЦАЈ ВАРИЈАЦИЈА У САДРЖАЈУ МН НА МЕХАНИЧКЕ И КОРОЗИОНЕ КАРАКТЕРИСТИКЕ Cu-Аl-Мn ЛЕГУРА СА МЕМОРИЈОМ ОБЛИКА
(Belgrade University, 2024) Mamatha, K.M.; Mallik, U.S.; Koti, V.; Murthy, K.V.S.; Koppad, P.G.
In this work, the role of Mn on the shape memory effect and mechanical and corrosion behavior of Cu-Al-Mn shape memory alloys was studied. The composition of Al was fixed to 10 wt% while that of Mn was varied from 2 to 10 wt%. The strain recovery by SME was evaluated using the bend test, while the yield and ultimate tensile strength were obtained using the tension test. The corrosion behavior was studied using three different solutions: freshwater, substitute ocean water, and Hank’s solution. The yield and ultimate tensile strength of Cu-Al-Mn alloys increased with Mn content up to 6%, which was attributed to grain refinement and precipitation hardening, while the fracture analysis showed mixed mode failure for all alloys. The corrosion behavior of Cu-Al-Mn alloys was modified due to the addition of Mn. With the increase in Mn content, the alloys displayed better corrosion resistance and lower corrosion rates. The corroded surface analysis tested in freshwater showed pitting corrosion, while Cu-Al-Mn alloy with low Mn content was tested in substitute ocean water. Hank’s solution showed surface damage with an unstable surface layer. © Faculty of Mechanical Engineering, Belgrade. All rights reserved
Hardness and electrical conductivity of uncoated and silver coated carbon nanotubes reinforced copper nanocomposites
(Springer, 2022) Koti, V.; Mahesh, n.; Murthy, K.V.S.; Koppad, P.G.; Sethuram, D.
In the present study, carbon nanotube reinforced copper nanocomposites were fabricated using the powder metallurgy technique which includes ball milling and hot pressing. The carbon nanotube weight percentage in the nanocomposite was varied from 0.25 to 1.50% in the steps of 0.25%. Further, to improve the interfacial bonding between the carbon nanotubes and copper matrix, the carbon nanotubes were coated with silver using the electroless deposition method. The sintered and hot pressed copper nanocomposites with uncoated and silver-coated carbon nanotubes were subjected to optical and scanning electron microscope studies to understand the dispersion of nanotubes. The density, microhardness and electrical conductivity of developed nanocomposites were studied. The dispersion of nanotubes was found to be uniform throughout the copper matrix resulting in the improvement in microhardness. Especially when compared with sintered samples, the hot-pressed nanocomposites with silver-coated carbon nanotubes showed significant improvement in microhardness however beyond 0.75% content the microhardness for samples was found to drop. The electrical conductivity of nanocomposites was found to decrease with the increase in the MWCNT content which was attributed to the clustering of MWCNTs due to strong van der Waal forces and the increase in the number of interfaces between MWCNTs and copper matrix. © 2022, Indian Academy of Sciences.