Browsing by Author "Rajendra Udupa, K."

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Characterization of DC Magnetron Sputtered Copper Thin Film on Aluminium Touch Surface
(Springer, 2019) Augustin, A.; Rajendra Udupa, K.; Udaya Bhat, K.
Hospital care-assisted infections introduce problems like prolonged hospital stay, additional financial burden and higher death rate. Since copper is registered by US Environmental Protection Agency as the only solid antimicrobial metal, it could be used in hospital touch surfaces. In the present work, copper has been deposited on the aluminium substrate by DC magnetron sputtering method with different target power. Prior to the coating, the substrate has undergone double zincation process. The coating has been characterized by XRD, SEM, TEM, scratch hardness test and microhardness test. From the TEM micrographs, the grain size has been found to decrease from 49 to 18 nm on increasing the deposition power from 50 to 150 W. Along with the decrease in the grain size, the mechanical properties like scratch hardness and microhardness of the coating have been increased. The preferred growth along [111] direction observed in XRD analysis is responsible for the increase in the hardness of the coating apart from the presence of the nano-grains. The SEM image of the coating shows nodular morphology which enhances the surface area. © 2019, The Indian Institute of Metals - IIM.
Comparison of creep rates of AA 5356 alloy based aluminium silicon carbide composite and AISI 316L stainless steel by indentation creep test method
(2012) Udaya Prasanna, H.U.; Rajendra Udupa, K.; Hegde, S.
[No abstract available]
Crystallite size measurement and micro-strain analysis of electrodeposited copper thin film using Williamson-Hall method
(American Institute of Physics Inc. subs@aip.org, 2016) Augustin, A.; Rajendra Udupa, K.; Bhat, K.U.
The improvement in hydrophilicity of copper coating on aluminium for better antimicrobial activity can be achieved by increase in surface energy. The surface energy depends on the micro-strain of the coating. Micro-strain in the coatingincreases with reduction in crystallite size. In this investigation, the crystallite size in the electrodeposited copper coating was varied by varying deposition current density. Crystallite size and micro-strain in the coating were estimated using Williamson-Hall method. Values of crystallite sizes using TEM micrographs were in agreement with that using Williamson-Hall method. Also, presence of nano-Twins in the coating contributed for micro-strain in copper coating. Â© 2016 Author(s).
Dynamic strain ageing in AISI 316L type stainless steel as revealed by indentation creep studies
(Elsevier Ltd, 2013) Udaya Prasanna, H.; Rajendra Udupa, K.
The phenomenon of dynamic strain ageing (DSA) is known to be prevalent in many of the iron and nickel based alloys which are mainly used as materials for nuclear power plant parts. This behaviour of the material is revealed as a jerky flow phenomenon in the tensile test results, when tests are performed at particular strain rate ranges. Authors probe into this aspect of the behaviour of AISI 316L stainless steel through the indentation creep test route so as to find out the implication of DSA on indentation creep test results. The occurrence of DSA is confirmed by the authors by compression tests carried out on samples of 316L with different loads at set strain rates. The authors attempt to find the evidence for DSA through creep data obtained from the indentation creep tests. Their findings reinforce the theory that there is a limiting stress above which the applied stress should pull the dislocations away from the solute atmosphere. Â© 2013 The Authors.
Effect of multi directional forging on impression creep behavior of Zn-24Al-2Cu alloy
(Elsevier Ltd, 2018) Sharath, P.C.; Rajendra Udupa, K.; Preetham Kumar, G.V.
Multi directional forging (MDF) of Zn-24Al-2Cu alloy were carried at 100Â°C and 200Â°C with total equivalent strain of 0.6 and 1.2 respectively. The average grain size was reduced from 30 to 1 Î¼m after MDF processing. Impression creep behavior of MDF processed samples was studied at 2 kg and 2.5 kg load with temperatures 30, 50, 100 and 150Â°C. Microstructural characterizations were carried out using optical microscope, transmission electron microscope and X-Ray diffractometer. Steady state creep rate values were recorded in the range of 1.2x10-5 to 5.2x10-7. The four phase transformation occurred in the structure after MDF process and during the impression creep test. Initial stress exponent (n) values are in the range of 2.5 to greater than 5. High values of 'n' showed due to the existence of threshold stress. The true activation energy values calculated are in the range of 22-129 kJ/mol. Changes in creep properties of MDF processed samples seem to be more sensitive to change in temperature compared to microstructural differences. Lattice diffusion controlled by dislocation climb is the dominant creep mechanism. Â© 2018 Elsevier Ltd. All rights reserved.
Experimental optimization of volumetric wear behavioural study of as cast and 1hr homogenized Al-25Mg2Si2Cu4Ni alloy at constant speed based on Taguchi method
(Elsevier Ltd, 2018) Harlapur, M.D.; Mallapur, D.G.; Rajendra Udupa, K.
In the current study, an experimental optimization study on the volumetric wear behaviour of Aluminium (Al-25Mg2Si2Cu4Ni) alloy in as cast and 1Hr homogenized with T6 heat treatment is carried out at constant speed. The Pin-on-disc apparatus was used to carry out sliding wear test. Taguchi method based on L-16 orthogonal array was employed to analyze the data on the wear behaviour. Signal-to-noise ratio with the objective of smaller the better and mean of means results were used. General regression model is obtained by correlation. Lastly confirmation test was completed to make a comparison between the experimental results foreseen from the mentioned correlation. The mathematical model reveals the load has maximum contribution on the wear rate compared to speed. Scanning Electron Microscope was used to analyze the worn-out wear surfaces. Wear results show that 1Hr homogenized Al-25Mg2Si2Cu4Ni alloy samples with T6 treated had better volumetric wear resistance as compared to as cast samples. Â© 2017 Elsevier Ltd.
Formation of microstructural features in hot-dip aluminized AISI 321 stainless steel
(University of Science and Technology Beijing, 2018) Huilgol, P.; Rajendra Udupa, K.; Udaya Bhat, K.
Hot-dip aluminizing (HDA) is a proven surface coating technique for improving the oxidation and corrosion resistance of ferrous substrates. Although extensive studies on the HDA of plain carbon steels have been reported, studies on the HDA of stainless steels are limited. Because of the technological importance of stainless steels in high-temperature applications, studies of their microstructural development during HDA are needed. In the present investigation, the HDA of AISI 321 stainless steel was carried out in a pure Al bath. The microstructural features of the coating were studied using scanning electron microscopy and transmission electron microscopy. These studies revealed that the coating consists of two regions: an Al top coat and an aluminide layer at the interface between the steel and Al. The Al top coat was found to consist of intermetallic phases such as Al7Cr and Al3Fe dispersed in an Al matrix. Twinning was observed in both the Al7Cr and the Al3Fe phases. Furthermore, the aluminide layer comprised a mixture of nanocrystalline Fe2Al5, Al7Cr, and Al. Details of the microstructural features are presented, and their formation mechanisms are discussed. © 2018, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.
Mechanical Properties and Microstructural Characterization of Multi Directional Forged and Heat Treated Zn-24al-2cu Alloy
(National Institute of Technology Karnataka, Surathkal, 2018) P. C, Sharath; G. V, Preetham Kumar; Rajendra Udupa, K.
Multi directional forging (MDF) is one of the techniques to achieve severe plastic deformation (SPD) which yields ultrafine grained metallic materials. In this technique, the material is compressed in a channel die to a fixed strain, retaining its shape by appropriately rotating it over the three axis. In the present investigation, the MDF process was carried out on selected Zn-24Al-2Cu alloy at two different temperatures, viz., 100 °C for three passes and 200 °C for six passes. Further, the MDF process was subjected to age hardening treatment by following the sequence of solutionizing, MDF processing and post aging. The aging studies were carried out by the choice of aging temperature between 100 to 250 °C and aging curves were generated. Further, all mechanical characterizations of the material were carried out on the test samples which had been aged at 100 °C for one hour as this combination of parameters yielded highest hardness in all the categories of sample. Techniques like optical microscopy, electron microscopy and X-Ray diffractometry were used to characterize and analyze the microstructure of MDF processed and age hardened materials. Microstructural analysis revealed that the MDF processing reduces the grain size, yielding fine grained materials, apart from well-distributed phases. The microstructure is observed to be consisting of three phases, viz., Al-rich α phase, Zn-rich η phase and CuZn4 ε phase. Mechanical characterization of the materials revealed an important fact that strength and hardness increased along with the ductility. It was attributed to fineness of grain and evolution of phases in a favorable manner because of MDF and aging treatment meted out to the material. The creep behavior of the material is investigated by conducting the indentation creep test with 2 kg and 2.5 kg load at different temperatures from 30 to 150 °C. The MDF processed material is found to lose its creep resistance substantially mainly because of microstructural refinement. It was possible to infer from the determination of value ofactivation energy that creep occurred by various mechanisms at different temperature regimes. Those mechanisms include dislocation creep and diffusional creep. Wear behavior of the materials was assessed by conducting the test on pin on disc machine resorting optimization of parameters using Taguchi method. It was proved that processing the materials by MDF followed by post-aging improved the wear resistance of the materials. Wear mechanism was observed to be abrasive type in the case of solutionized samples and adhesive type in MDF-processed samples as revealed by SEM investigations on worn surface.
Rotating bending fatigue tests were carried out on austempered ductile iron containing 1.5 wt% nickel and 0.3 wt% molybdenum. The ductile iron was austenitized at 900 or 1050 °C and then austempered at 280 or 400 °C for different lengths of time to obtain different microstructures. The fatigue strength was correlated with the amount of retained austenite and its carbon content, which were both determined by X-ray diffraction technique. While the tensile strength decreased with increasing retained austenite content, the fatigue strength was found to increase. Carbide precipitation was found to be detrimental to fatigue strength. Lower austenitizing temperature resulted in better fatigue strength. © 1994 Chapman & Hall.
(Kluwer Academic Publishers, Effect of microstructure on the fatigue strength of an austempered ductile iron) Shanmugam, P.; Prasad Rao, P.; Rajendra Udupa, K.; Venkataraman, N.
1994