Articles written in Sadhana

    • Selection of coating material for magnesium alloy using Fuzzy AHP-TOPSIS


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      Magnesium alloys are inherently negative electrochemical potential and are very reactive compared to other engineering metals. They are prone to galvanic corrosion and micro cracks. Various coating materials or Alternatives and the required criteria and sub-criteria for the selection of Alternatives for AZ31B magnesium alloy substrate are identified by means of literature review. Criteria weight and the rank of the alternatives are usually vague and hence uncertainty prevails. The best Alternative from several potential ‘‘Candidates’’, subjectto several criteria and sub-criteria, needs to get decided. In such cases, multi criteria decision making (MCDM) techniques help in determining the MOST suitable coating material. This paper concentrates on the selection ofcoating material for the magnesium alloy substrate. The problem is subjective, uncertain and equivocal in nature. Hence in this study, fuzzy analytic hierarchy process (AHP) is applied to obtain the weights of criteria and technique for order performance by similarity to ideal solutions (TOPSIS) is utilised for ranking theAlternatives.

    • Sensitivity analysis and optimisation of HVOF process inputs to reduce porosity and maximise hardness of WC-10Co-4Cr coatings


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      This paper aims at developing an empirical relation to predict the porosity and micro-hardness, by means of High Velocity Oxy Fuel (HVOF) sprayed WC-10Co-4Cr coatings. For determining the coating performance, process parameters such as flow rate of LPG fuel, flow rate of oxygen, spray distance, flow rate ofcarrier gas and feed rate of the coating powder play a significant role. Five-factors, five-level central composite rotatable design (CCD) was employed in this analysis to reduce the number of experiments by covering all possible combinations of the process variables. A mathematical model was established to assess the porosity and microhardness of the coatings including HVOF process parameters and the appropriateness of the model was examined using analysis of variance. Using RSM, process parameter optimizations were conducted. Thecoatings produced using optimized process variables had a minimum porosity level of 0.2 Vol. percentage and a maximum hardness of 1325.26 HVx compared to other coatings. This has been confirmed by the developing response graphs and also by plotting contours. The optimization of HVOF parameters using RSM, as well as the correlation of spray variables with properties of the coating, enables the recognition of the framework of the characteristics to attain the preferred consistency of WC-10Co-4Cr coatings. Analysis of Sensitivity is alsoperformed to determine the most significant process parameter for the HVOF operation.

    • A PID control scheme with enhanced non-dominated sorting genetic algorithm applied to a non-inverting buck-boost converter


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      The non-inverting buck-boost converter is designed to regulate the output voltage of the non-linear converter in real-time applications. Numerous studies have been carried out in recent years to improve the dynamic behavior of converters using intelligent control techniques; still, the occurrence of large overshoots in transient and reduction of ripple over voltage has not been effectively discussed. This can be efficiently handled by selecting filter capacitance values effectively. This article proposes a design of a Proportional-integralderivative controller optimized by a non-dominated sorting genetic algorithm (NSGA) and enhanced nondominated sorting genetic algorithm (ENSGA) to choose the filter capacitance value and to maintain the converter output voltage at the desired level. A dynamic crowding distance-based ENSGA has been employed to attain the homogenous distribution of non-dominated solutions. The stability of the buck-boost mode is analyzed using frequency response. Based on the simulation results obtained for various load conditions, the ENSGA controller outperformed the NSGA controller in terms of better output voltage regulation, lesser transients, and minimizing the ripple voltage.

    • Multi response optimization of HVOF process parameters in low carbon steels


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      To fabricate the high-grade coating, HVOF is commonly used because of its potential to form dense deposits with low porosity and low oxide content. Due to higher kinetic power, a shorter dwell time, and lower flame temperatures, HVOF spraying provides a more desirable composition for dense coatings and regulates the phase transitions of the powder particles than plasma spraying. Because of the proper balance of hard-phase WC particles and the strong and durable metallic matrix cobalt chromium, WC–Co–Cr is an effective coatingmaterial for minimizing abrasive wear (Co Cr). Process variables such as liquefied petroleum gas flow rate, oxy flow rate, spray distance, carrier gas rate of flow, and feed rate of the deposition powder material all have a role in coating performance. In this work, a five-element central composite design (CCD) was utilised to reduce the number of trials by encompassing all possible combinations of process variables. A mathematical model was used to determine the porosity and micro hardness of the coatings, as well as the high velocity oxy fuelprocessing variables, and the model’s appropriateness was assessed using an analytical variable. The response surface methodology has been used to optimize process parameters (RSM).

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