Browsing by Author "SannaYellappa, N."

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    An experimental study of influence of wire electro discharge machining parameters on surface integrity of TiNiCo shape memory alloy
    (Cambridge University Press, 2017) Soni, H.; SannaYellappa, N.; Ramesh, M.R.
    Shape memory alloys (SMAs) are unique class of smart materials with excellent physical, mechanical and biomedical properties, which have wide applications in several fields such as aerospace, robotics, biomedical, and dental etc. These alloys are well known for exhibiting shape memory effect (SME) and pseudoelasticity (PE), it is a well-established fact that they are required to be processed into functioning parts. The conventional machining affects the internal properties of shape memory alloys and hence, it is reported that nonconventional machining techniques are more suitable. Wire electro discharge machining (WEDM) is one of the nonconventional machining processes for machining complicated shapes without hampering the internal properties of such type of materials. In the present experimental investigation, wire electro discharge machining of Ti50Ni40Co10 shape memory alloy (SMA) has been carried out and machining performances such as surface roughness (SR), and material removal rate (MRR) have been evaluated. Experimental results exposed that pulse on time, pulse off time and servo voltages are most influential process parameters on the responses. The machined surface has been characterised with respect to microstructure, microhardness, and phases formed. © Materials Research Society 2017.
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    Computer aided cooling curve analysis to calculate the thermophysical properties of zinc aluminium 12
    (American Institute of Physics Inc. subs@aip.org, 2019) Dey, K.; SannaYellappa, N.
    Computer Aided Cooling Curve Analysis (CA-CCA) is the utilization of time-Temperature graph to reveal several processing and material parameters. Its application ranges from prediction of transition temperatures, amount of different phases, latent heat and dendrite coherency point among various others. In the current paper, both Newtonian and Fourier methods were used and solidification parameters such as phase change temperature, latent heat and thermal diffusivity of zinc-12% aluminium alloy (ZA 12) were determined. The phase transition temperatures were observed at 440 +C and 370 +C for liquidus and solidus respectively. The value of latent heat obtained by Fourier technique was 130.7âJ/g which is closer to the theoretical value of 118âJ/g when compared to Newtonian technique. It can be mainly attributed to the fact that the effect of temperature gradient within the solidifying sample is taken into consideration in Fourier technique. Also thermal diffusivity was calculated as a temperature dependent function for the mushy zone (440-370 +C) using the Fourier method ranging from 5.04 × 10-5m2/s and 3.04 × 10-5m2/s. © 2019 Author(s).
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    Corrosion of ECAPed magnesium alloys and its background: A Review
    (Chulalognkorn University, 2019) Naik, G.M.; SannaYellappa, N.; Kumar, S.S.S.
    The aim of this review article is to provide a brief mechanistic overview of magnesium alloys, equal channel angular pressing and corrosion behavior of un-ECAPed and ECAPed Mg alloys. The considerate of the corrosion processes of ECAPed Mg alloys builds upon interpretation of the corrosion of fine-grain magnesium alloys. This provides an understanding of the effect of grain size on corrosion of Mg alloys. This deep understanding is essential as a foundation if we are to produce corrosion-resistant magnesium alloys. Considerable has previously been accomplished, but there is enormous scope for development. This present concise review can provide a foundation for further, much desirable research. © 2019 Chulalognkorn University.
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    Numerical simulation and characterization of zinc aluminium 12 alloy for latent heat thermal energy storage application
    (American Institute of Physics Inc. claims@aip.org, 2020) Dey, K.; SannaYellappa, N.
    Thermal Energy Storage (TES) has gained popularity in recent times as it provides an efficient and economical approach to limit the discrepancy between supply and demand for energy. In the current paper, the thermal performance of a hypereutectic zinc-12% aluminium (ZA 12) alloy has been studied and is proposed as a potential metallic phase change material to be used for the purpose of Latent Heat Thermal Energy Storage (LHTES) application operating at a temperature range of 300 °C to 500°C. Characterization of the alloy is performed using Fourier technique to determine relevant properties. The change in enthalpy is calculated to be 296.33?J/g-K, while the measured value of mean specific heat and latent heat were 0.531?J/g-K and 130.68?J/g respectively. Both solid fraction and thermal diffusivity were determined as a function of temperature for the mushy region. A numerically validated transient model based on the enthalpy -porosity formulation is employed to analyze the solidification/melting performance of ZA 12 alloy. Contour of liquid fraction and velocity streamline during phase transformation is obtained revealing various details about the process mechanism. © 2020 Author(s).
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    Performance of profile characteristics at different machining parameters during wire electric discharge slant type taper profiling on Nicrofer 4722
    (Inderscience Publishers, 2024) Manoj, I.V.; SannaYellappa, N.
    In the present study, a slant type taper fixture is employed to achieve taper machining by wire electric discharge machining. Machining parameters like wire distance between the guides (WD), wire offset (WO), corner-dwell time (CT) and cutting-speed override (CO) is used to produce tapered components at 0°, 15°, and 30° angles. It is observed that as the WD, CO and WO increases the profile roughness also increases. The profiling error (PE) increases with increasing WD and CO parameters due to the increase in wire lag phenomenon. However, the WO and CT parameters showed a decreasing effect on PE. There is a reduction observed in the recast layer thickness, as the taper angle increased. The apex of the triangular profile always tends to be shifted opposite to the wire direction of travel at 15° and 30° tapered components due to the electromagnetic force and decreased strength of the tapered corners. © © 2024 Inderscience Enterprises Ltd.