Mechanical Engineering

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Shiv Nadar University

Metallic glasses show a unique combination of high strength, excellent corrosion, and wear resistances because of their amorphous structure having a short-range order. In spite of excellent properties, the application of metallic glasses is restricted because of their inherent limitations in the bulk form, including limited tensile ductility. Using metallic glasses as the coatings for structural applications is an attractive way of taking advantage of their superior properties. Additionally, metallic glass-based composites having crystalline phases embedded in a amorphous matrix have also shown improved properties. Thus, metallic glasses can be synthesized as the coatings or subjected to surface modification to provide functionally superior surfaces. This article is a review of metallic glass-based coatings and surface modification of metallic glasses to achieve functionally superior surfaces for structural applications. Essential theoretical concepts were discussed which influence the processing. Common ways of processing along with the influence of various processing parameters were explored. Some non-conventional techniques which emerged as a result of continued efforts were also taken into account. Corrosion and wear properties of these materials along with the underlying mechanisms were discussed in detail. Focus was given to the recent product level applications explored in the open literature. Current challenges in the field were reviewed and guidelines for the future developments were provided. Copyright © Taylor & Francis Group, LLC.

World University root node

(SoE) School of Engineering

Critical Reviews in Solid State and Materials Sciences

Amorphous Coatings and Surfaces on Structural Materials

This book explores the domain of reliability engineering in the context of machine tools. Failures of machine tools not only jeopardize users' ability to meet their due date commitments but also lead to poor quality of products, slower production, down time losses etc. Poor reliability and improper maintenance of a machine tool greatly increases the life cycle cost to the user. Thus, the application area of the present book, i.e. machine tools, will be equally appealing to machine tool designers, production engineers and maintenance managers. The book will serve as a consolidated volume on various dimensions of machine tool reliability and its implications from manufacturers and users point of view. From the manufacturers' point of view, it discusses various approaches for reliability and maintenance based design of machine tools. In specific, it discusses simultaneous selection of optimal reliability configuration and maintenance schedules, maintenance optimization under various maintenance scenarios and cost based FMEA. From the users' point of view, it explores the role of machine tool reliability in shop floor level decision- making. In specific, it shows how to model the interactions of machine tool reliability with production scheduling, maintenance scheduling and process quality control. © 2016 Scrivener Publishing LLC. All rights reserved.

Machine Tool Reliability

Recent wind tunnel studies have shown that an aeroelastic system, prior to losing stability through flutter, goes through a regime where the response is characterized by intermittent bursts of periodic oscillations. The focus of this study is to investigate the reasons for this intermittent behavior through a numerical model. The studies indicate that the intermittency is observed only when the flow is accompanied by small random fluctuations. A stochastic bifurcation analysis is carried out to gain an understanding for this phenomenological interesting behavior. © 2016 The Authors.

Fulltext

Procedia Engineering

Numerical Investigations on Intermittency Route to Aeroelastic Flutter

Nanoscale patterns have dimensions that are comparable to the length scales affected by intermolecular and surface forces. In this study, we systematically investigated the individual roles of curvature, surface energy, lateral stiffness, material, and pattern density in the adhesion and friction of nanopatterns. We fabricated cylindrical and mushroom-shaped polymer pattern geometries containing flat- and round-topped morphologies using capillary force lithography and nanodrawing techniques. We showed that the curvature, surface energy, and density of the patterns predominantly influenced the adhesive interactions, whereas lateral stiffness dominated friction by controlling the geometrical interaction between the indenter and pillar during sliding. Interestingly, in contrast to previous studies, cylindrical and mushroom-shaped pillars showed similar adhesion characteristics but very different frictional properties. Using fracture mechanics analysis, we showed that this phenomenon is due to a larger ratio of the mushroom flange thickness (t) to the radius of the pillar stem and we proposed a design criterion for mushroom patterns to exhibit a geckolike effect. The most important result of our work is the discovery of a linear master curve in the graph of adhesion versus friction for pillars with similar lateral stiffness values that is independent of curvature, material, surface energy, and pattern density. These results will aid in the identification of simple pattern parameters that can be scaled to tune adhesion and friction and will help broaden the understanding of nanoscale topographical interactions. © 2016 American Chemical Society.

ACS Applied Materials and Interfaces

Individual Role of the Physicochemical Characteristics of Nanopatterns on Tribological Surfaces

In this paper, the design and fabrication of photovoltaic thermal integrated greenhouse system (PVTIGS) for biogas heating has been done for climatic condition of IIT Delhi, India. PVTIGS can also be used for a number of applications like generating electricity, space heating, enhancing production of biogas, crop cultivation and crop drying, etc. Thermal modelling of proposed system (PVTIGS) without load has been developed based on energy balance equations. Further, with the help of thermal modelling the solar cell temperature, room temperature and solar cell efficiency have been calculated for a typical clear day of May. Experimental validation have been done on the basis of correlation coefficient (r) and root mean square percentage deviation (e) and found to be in fair agreement between theoretical and experimental values. Effect of packing factor, mass flow rate of air below module, absorptivity (degradation effect) and transmittivity (dusting effect) on thermal load levelling have been discussed. Electrical energy has been calculated and validated with experimental values. Further, thermal energy and overall thermal energy have been evaluated and found to be 11.18 kW h and 12.76 kW h respectively for a clear day without load. © 2016 Elsevier Ltd

Solar Energy

Thermal modelling of photovoltaic thermal (PVT) integrated greenhouse system for biogas heating

A hybrid photovoltaic-thermal (PVT) greenhouse solar dryer under forced mode has been proposed and different parameters have been evaluated for different climatic condition of Indian Institute of Technology, New Delhi (28_350 N, 77_120E, 216 m above MSL), India. In the present study, radiation data and ambient air temperature have been taken from IMD (Indian Meteorological Department) Pune. Further, thermal modelling has been done for the PVT greenhouse dryer and different parameter such as crop temperature, greenhouse temperature, outlet air temperature and cell temperature have been calculated by the help of program made on MATLAB 2013a. Fair agreement has been found between theoretical and experimental data with correlation coefficient value (r) and root mean square percentage deviation (e) are 0.92 and 4.64, 0.99 and 0.97, 0.99 and 0.96 for solar cell, greenhouse room and crop temperature respectively. Further, on yearly basis useful thermal energy, useful electrical energy, useful equivalent thermal energy, thermal exergy and overall thermal efficiency have been calculated. Further, embodied energy, energy payback time, CO2 mitigation and carbon credit earn have also been calculated. It was found that payback time for system is 1.23 and 10 years on the basis of overall thermal energy and overall exergy basis respectively. © 2016 Elsevier Ltd

Energy

Exergoeconomic analysis of photovoltaic-thermal (PVT) mixed mode greenhouse solar dryer

A hybrid photovoltaic-thermal (PVT) greenhouse solar dryer under mixed mode has been proposed and different parameters have been evaluated for climatic condition of Indian Institute of Technology, New Delhi (28_350N, 77_120E, 216 m above MSL), India. Further thermal modelling has been developed for the PVT greenhouse dryer by considering different parameter namely crop, greenhouse and solar cell temperatures, etc. Numerical computations have been done with the help of program made on MATLAB 2013a and the results are validated with experimental values. Characteristic curves have been developed for drying and system efficiency with experimental validation. Further, an overall thermal energy and exergy have been calculated. Theoretical and experimental values of overall thermal energy found to be 1.92 kW h and 2.03 kW h respectively. It can be seen that there is good agreement between theoretical and experimental value with r = 0.98 and e = 10.76. Further validation has also been done for energy and exergy of PVT dryer. © 2016 Elsevier Ltd.

Performance analysis of photovoltaic-thermal (PVT) mixed mode greenhouse solar dryer

Present study is an attempt to study of different heat storage methods and their application for sustainable development. Solar energy is a prime source of energy which is responsible for other renewable sources directly or indirectly. The major drawback of solar energy is its availability in day time only. Thermal storage devices can overcome this drawback as they can store the energy in day time that can be utilized in off sunshine hours. In the present study classification of thermal storage methods has been done. Further different application of phase change material (PCM) has been discussed. Study shows that PCM can be successfully integrated nearly with all the solar thermal devices. This study will also help to understand to store maximum thermal energy that reduce the requirement of conventional fuels like coal, oil etc. Further, it will help in reducing greenhouse gasses and climatic changes. © 2016 IEEE.

International Conference on Emerging Trends in Electrical, Electronics and Sustainable Energy Systems, ICETEESES 2016

Importance of phase change material (PCM) in solar thermal applications: A review

The aeroelastic response of a NACA 0012 airfoil in the flow regimes prior to flutter is investigated in a wind tunnel. We observe intermittent bursts of periodic oscillations in the pitch and plunge response, that appear in an irregular manner from a background of relatively lower amplitude aperiodic fluctuations. As the flow speed is increased, the intermittent bursts last longer in time until eventually transitioning to a fully developed periodic response, indicating the onset of flutter. The repeating patterns in the measured response are visualized using recurrence plots. We show that statistics of the recurrence states extracted from these plots can be used to develop model-free precursors that forewarn an impending transition to flutter, well before its onset. © 2015 Elsevier Ltd.

Journal of Fluids and Structures

Precursors to flutter instability by an intermittency route: A model free approach

In the present study, an attempt has been made to evaluate the effect of packing factor of photovoltaic (PV) module on the performance of hybrid photovoltaic-thermal (PVT) greenhouse solar dryer. Different parameters have been evaluated for climatic condition of Indian Institute of Technology, New Delhi (28-350N, 77-120E, 216 m above MSL), India. For the analysis solar radiation and ambient air temperature have been taken from IMD (Indian Meteorological Department) Pune. Further thermal modelling has been done for the PVT greenhouse dryer and different parameter like crop temperature, greenhouse temperature, outlet air temperature and cell temperature have been calculated with variation of packing factor of PV module by the help of MATLAB program. Further effect of packing factor on thermal energy, electrical energy, overall thermal energy, cell efficiency have been evaluated. Variation in thermal energy, electrical energy, and overall thermal energy with respect to packing factor found to be 3.66-2.05, 0-0.92 and 3.66-4.47 kWh respectively for a typical day of June. © 2016 IEEE.