Journal Articles
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Item Friction-free permanent magnet bearings for rotating shafts: A comprehensive review(Electromagnetics Academy, 2020) Bekinal, S.I.; Doddamani, M.This article presents a comprehensive review of modeling, analysis, and development of permanent magnet bearings (PMB) for rotating shafts. The different configurations of PMB are highlighted with relevant approaches to estimate their features. The progress in mathematical approaches adopted and optimization of the static and dynamic bearing characteristics in terms of accuracy are discussed in depth. Further, key developments on instability issues and their realization in combination with other bearings for rotors stability in low and high-speed applications are reviewed. Finally, concluding remarks on key aspects to be followed in the design and development of PMB are presented. © 2020, Electromagnetics Academy. All rights reserved.Item 3D printing of highly pure copper(MDPI AG membranes@mdpi.com, 2019) Tran, T.Q.; Chinnappan, A.; Lee, J.K.Y.; Loc, N.H.; Tran, L.T.; Wang, G.; Vijay Kumar, V.V.; Jayathilaka, W.A.D.M.; Ji, D.; Doddamani, M.; Ramakrishna, S.Copper has been widely used in many applications due to its outstanding properties such as malleability, high corrosion resistance, and excellent electrical and thermal conductivities. While 3D printing can offer many advantages from layer-by-layer fabrication, the 3D printing of highly pure copper is still challenging due to the thermal issues caused by copper’s high conductivity. This paper presents a comprehensive review of recent work on 3D printing technology of highly pure copper over the past few years. The advantages and current issues of 3D printing methods are compared while different properties of copper parts printed by these methods are summarized. Finally, we provide several potential applications of the 3D printed copper parts and an overview of current developments that could lead to new improvements in this advanced manufacturing field. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Item Mechanical behavior of 3D printed syntactic foam composites(Elsevier Ltd, 2020) Bharath, H.S.; Sawardekar, A.; Waddar, S.; Jeyaraj, J.; Doddamani, M.A three-dimensional printed (3DP), polymer based syntactic foams are developed using hollow glass micro balloons (GMB) dispersed in high density polyethylene (HDPE). This work presents the buckling and vibration response of 3D printed foams subjected to axial compression. The buckling load is estimated using Modified Budiansky Criteria (MBC) and Double Tangent Method (DTM) through the load–deflection plots. The first three natural frequencies and their mode shapes are computed as a function of axial compressive load. It is noted that the natural frequency reduces with an increase in axial compressive load. It is also observed that with an increase in GMB %, the natural frequencies and critical buckling load increases. In mode-1, the natural frequency decreases in pre-buckling regimes and increases exponentially in post-critical loading conditions. Analytical solutions obtained from the Euler-Bernoulli-beam theory are compared with experimental results. It is noted that the fundamental frequency approaches zero when the axial load is equal to the critical load. The critical buckling load is estimated through the vibration correlation technique and compared with the results obtained using DTM and MBC methods. The property map is plotted for buckling load against the density of various composites. © 2020 Elsevier LtdItem A Review of Superconducting Magnetic Bearings and Their Application(Institute of Electrical and Electronics Engineers Inc., 2022) Supreeth, D.K.; Bekinal, S.I.; Shivamurthy, S.R.; Doddamani, M.Magnetic bearings are being researched for high-speed applications, such as flywheel energy storage devices, to eliminate friction losses. As per Earnshaw's theorem, stable levitation cannot be achieved for a static passive magnetic bearing system. Fully passive stable levitation can be achieved with the help of superconducting magnetic bearings (SMB). This article provides an in-depth review of the modeling, analysis, and development of SMB. The different SMB configurations are highlighted, together with essential methodologies for estimating and improving their performance. The advancements in mathematical models used and the optimization of bearing characteristics are thoroughly discussed. Further, key developments in the application of SMB in flywheel energy storage systems are also reviewed. © 2002-2011 IEEE.Item A comprehensive review on 3D printing advancements in polymer composites: technologies, materials, and applications(Springer Science and Business Media Deutschland GmbH, 2022) Jagadeesh, P.; Madhu, M.; Rangappa, S.M.; Karfidov, K.; Gorbatyuk, S.; Khan, A.; Doddamani, M.; Siengchin, S.3D printing is a constantly expanding technology that represents one of the most exciting and disruptive production possibilities available today. This technology has gained global recognition and garnered considerable attention in recent years. However, technological breakthroughs, particularly in the field of material science, continue to be the focus of research, particularly in terms of future advancements. The 3D printing techniques are employed for the manufacturing of advanced multifunctional polymer composites due to their mass customization, freedom of design, capability to print complex 3D structures, and rapid prototyping. The advantages of 3D printing with multipurpose materials enable solutions in challenging locations such as outer space and extreme weather conditions where human involvement is not possible. Each year, numerous research papers are published on the subject of imbuing composites with various capabilities such as magnetic, sensing, thermal, embedded circuitry, self-healing, and conductive qualities by the use of innovative materials and printing technologies. This review article discusses the various 3D printing techniques used in the manufacture of polymer composites, the various types of reinforced polymer composites (fibers, nanomaterials, and particles reinforcements), the characterization of 3D printed parts, and their applications in a various industries. Additionally, this review discussed the limitations of 3D printing processes, which may assist future researchers in increasing the utility of their works and overcoming the shortcomings of previous works. Additionally, this paper discusses processing difficulties, anisotropic behavior, stimuli-responsive characteristics (shape memory and self-healing materials), CAD constraints, layer-by-layer appearance, and void formation in printed composites. Eventually, the promise of maturing technology is discussed, along with recommendations for research activities that are desperately required to realize the immense potential of operational 3D printing. © 2022, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.Item Synthesis and application of sustainable vegetable oil-based polymers in 3D printing(Royal Society of Chemistry, 2024) Saraswat, R.; Shagun, N.; Dhir, A.; Balan, A.A.S.; Powar, S.; Doddamani, M.In the past ten years, there has been significant growth in the global 3D printing market, particularly in the development of natural and bio-based polymers. However, a major challenge is the limited availability of sustainable 3D printable resins capable of matching the performance of synthetic materials. This underscores the urgent need for the development of innovative and environmentally friendly resin materials. Herein, we introduce bio-based polymers, highlighting their recent advancements and offering a comprehensive overview of their diverse applications across various fields, including 3D printing. An area that has received less attention in this domain is polymers derived from vegetable oil (VO) or plant-based oil. Specifically, we thoroughly investigate the acrylation of epoxidized VOs and the subsequent formation of resins from these acrylates, which are essential materials for digital light processing (DLP), stereolithography (SLA), and extrusion-based 3D printing. The chemical modification of VOs, such as epoxidation and acrylation, is extensively explored, together with their respective types and applications. Furthermore, we delve deeply into the suitability of acrylate resins for 3D printing purposes. In conclusion, this review offers insights into the potential applications of 3D printed products utilizing materials derived from VOs. © 2024 The Author(s).Item Compressive and flexural properties of functionally graded fly ash cenosphere-epoxy resin syntactic foams(John Wiley and Sons Inc, 2015) Doddamani, M.; Kishore; Shunmugasamy, V.C.; Gupta, N.; Vijayakumar, H.B.The present study focuses on developing functionally graded syntactic foams (FGSFs) based on a layered co-curing technique. The FGSFs were characterized for compressive and flexural properties and compared with plain syntactic foams. The results showed that the specific compressive modulus was 3-67% higher in FGSFs compared to plain syntactic foams. FGSF exhibited 5-34% and 34-87% higher specific modulus and strength, respectively in flexural mode. The microscopic examinations of comparative responses of the filler and matrix to deformation suggest that the failure is dominated by the matrix. The gradient in the composition of syntactic foams helps in effectively distributing the stress throughout the microstructure and results in improved mechanical performance of syntactic foams. From the microscopy studies, it is evident that, the failure mechanism in the FGSF under flexural loading is governed by a crack that initiated on the tensile side of the specimen and propagated through the thickness to cause complete fracture. The microscopic observations further clearly demonstrate the existence of seamless interfaces between the layers and a clear difference in the cenosphere concentration across the interface, affirming the gradation in the prepared samples. The results show that appropriate compositions of FGSFs can be selected to develop materials with improved mechanical performance. © 2014 Society of Plastics Engineers.Item Dry sliding wear of epoxy/cenosphere syntactic foams(Elsevier Ltd, 2015) Manakari, V.; Parande, G.; Doddamani, M.; Gaitonde, V.N.; Siddhalingeshwar, I.G.; Kishore; Shunmugasamy, V.C.; Gupta, N.Abstract Dry sliding wear behavior of epoxy matrix syntactic foams filled with 20, 40 and 60 wt% fly ash cenosphere is reported based on response surface methodology. Empirical models are constructed and validated based on analysis of variance. Results show that syntactic foams have higher wear resistance than the matrix resin. Among the parameters studied, the applied normal load (F) had a prominent effect on wear rate, specific wear rate (ws) and coefficient of friction (?). With increasing F, the wear rate increased, whereas ws and ? decreased. With increase in filler content, the wear rate and ws decreased, while the ? increased. With increase in sliding velocity as well as sliding distance, the wear rate and ws show decreasing trends. Microscopy revealed broken cenospheres forming debris and extensive deformation marks on the wear surface. © 2015 Elsevier Ltd.Item Wear response of walnut-shell-reinforced epoxy composites(ASTM International, 2017) Doddamani, M.; Parande, G.; Manakari, V.; Siddhalingeshwar, I.G.; Gaitonde, V.N.; Gupta, N.Present work utilizes agricultural by-product, walnut shell, as reinforcing filler in epoxy matrix for investigating dry sliding wear behavior using a pin-on disc wear-testing machine. Effects of sliding velocity (0.5-1.5 m/s), normal load (10-50 N), sliding distance (1000-3000 m) and filler content (10-30 wt. %) on wear rate (Wt), specific wear rate (Ws) and coefficient of friction (?) are investigated. The experiments were planned as per design of the experiments scheme and the wear characteristics were analyzed through response surface modeling (RSM) method. The lowest Wt of 1.1 mm3/km was noted for 1.5 m/s sliding velocity with 30-wt. % filler content. Sliding distance did not have a significant influence on Ws above a critical load of 40 N. The minimum ? was observed at 1-m/s sliding velocity, 40-N load, 1000-m sliding distance, and 30-wt. % filler. Lower values of Wt and ? at higher walnut-shell loadings support feasibility of using such composites in wear-prone applications. The wear mechanism was determined in the composites using extensive scanning electron microscopic observations. © © 2017 by ASTM International.Item Utilization of low computational cost two dimensional analytical equations in optimization of multi rings permanent magnet thrust bearings(Electromagnetics Academy chew@jpier.org Suite 207777 Concord Avenue Cambridge, MA 02138, USA 02138 Massachusetts, 2017) Bekinal, S.I.; Doddamani, M.; Dravid, N.D.Replacement of conventional bearings by passive magnetic bearings for high-speed applications, in terms of their performance will be effective, if the design is carried out by optimizing the geometrical dimensions in the given control volume. Present work deals with modification and utilization of two-dimensional (2D) analytical equations in optimization of multi rings permanent magnet (PM) thrust bearing configurations. Conventional and rotational magnetized direction (RMD) configurations are selected in optimizing the design variables for maximum bearing characteristics in a given volume with a constant aspect ratio. The design variables chosen for optimization are axial offset of rotor, number of rings, radial air thickness and inner diameter of the rotor and stator PM rings. MATLAB codes for solving 2D equations are developed in optimizing configuration variables. Further, optimized parameter values of the two configurations are compared. Finally, optimized results obtained using 2D and three-dimensional (3D) equations for the conventional configuration with same aspect ratio are compared, and conclusions are presented. © 2017, Electromagnetics Academy. All rights reserved.