Harish Hirani - Academia.edu (original) (raw)

Papers by Harish Hirani

Research paper thumbnail of Stimuli-responsive discriminative detection of Cu2+ and Hg2+ with concurrent sensing of S2- from aqueous medium and bio-fluids by C N fused azophenine functionalized “smart” hydrogel assay @A potential biomarker sensor for Wilson’s disease

Sensors and Actuators B: Chemical, 2021

Abstract A multi-functional azophenine based colorimetric chemosensor, CN-1 has been reported by ... more Abstract A multi-functional azophenine based colorimetric chemosensor, CN-1 has been reported by catalytic FeCl3 mediated facile oxidative C-N bond fusion of o-anisidine. The chemosensor, characterized by single crystal X-ray crystallography, can be exploited towards ‘naked-eye’ discriminative detection of Cu2+ and Hg2+ (LOD = 30 and 480 ppb respectively) from purely aqueous medium through colorimetric and electrochemical (CV) readouts. It is equally responsive towards intoxicated real water specimen, like river water, industrial sewage water, demonstrating its practical applicability. Along with detection, CN-1 exhibited metal ion sequestration capability, leading to the removal of ∼74% and ∼40% removal of Cu2+ and Hg2+ respectively from contaminated water bodies. Moreover, the unprecedented uniqueness of the synthesized azophenine based chemosensor levies in its capability towards ppb level Cu2+ detection colorimetrically from target-specific bio-fluids to monitor aberrant unbound copper levels, thereby highlighting it as a potential biomarker sensor as well as a pathological non-invasive diagnostic tool of Wilson’s disease, which has been explored for the first time in the domain of azophenine based host-guest chemistry. The reversible spectrochemical response in presence of aqueous S2- could efficiently formulate “Write-Read-Erase-Read” nature of a memory element and four-input complex logic circuitry for molecular level information storage, which is also hitherto unexplored in the azophenine family. One step ahead, fabrication of functionalized “smart” hydrogel assay escalates the reliability and practical applicability of the present work through simple ‘naked eye’ colorimetric-optical readouts.

Research paper thumbnail of Development of a magnetorheological brake with a slotted disc

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2015

A conventional disc wears out and the brake pollutes the environment. Brake pad dust is reported ... more A conventional disc wears out and the brake pollutes the environment. Brake pad dust is reported to be the largest source of environment pollution1. The particles emanating because of wear of the brake pad pollute the environment2,3,4. In addition to pollution caused by wear particles, the friction-induced noise between the brake pad and the disc is also a major concern5. Also, localized heating occurs in a conventional disc brake. To tackle both of these problems, conventional disc brakes can be replaced with manetorheological fluid brakes. Magnetorheological fluids are materials having a shear yield stress which is a function of the magnetic field. On the application of a magnetic field, magnetorheological particles become aligned and increase the shear resistance between relatively moving surfaces. The friction between the stator and the rotor increases and fulfils the braking function, which means that magnetorheological fluids can be used as brake friction materials. A magnetor...

Research paper thumbnail of Control on wear of journal bearing operating in mixed lubrication regime using grooving arrangements

Industrial Lubrication and Tribology, 2016

Purpose The journal bearings subjected to heavy load and slow speed operate in mixed lubrication ... more Purpose The journal bearings subjected to heavy load and slow speed operate in mixed lubrication regime causing contact between the interacting surfaces and resulting in wear. Complexity of wear behavior and lack of unifying theory/model make wear-control very challenging. Design/methodology/approach In the present research work, theoretical and experimental investigations have been conducted to explore the effect of grooving arrangements on the wear behavior of journal bearing operating in mixed lubrication regime. The theoretical model of Hirani (2005) that uses mass conserving cavitation algorithm has been used to determine the bearing eccentricity for different groove arrangements (with varying groove location and extent) for identifying a groove arrangement that minimizes the wear. The wear tests on the grooved bearings were conducted after suitable running-in of the new bearings on a fully automated journal bearing test set-up. A load and speed combination required to operate ...

Research paper thumbnail of Effect of Particle Size on Shear Stress of Magnetorheological Fluids

Research paper thumbnail of Particle Dynamics of Polydisperse Magnetorheological Fluids

Smart Science, 2015

In the present research work, three dimensional simulations of magnetorheological fluids, contain... more In the present research work, three dimensional simulations of magnetorheological fluids, containing soft magnetic polydisperse particles in silicone oil, has been presented. The computer simulation helps to visualize and analyze the formed transient microstructures. The initial positions of particle-centres were decided based on random distribution. The particle positions were updated considering magnetic, hydrodynamic and repulsions forces on each particle along with explicit time marching scheme. Finally the particle's positions at 10 ms have been plotted. The yield behaviors of MRFXXS (small sized: 2 to 33 µm) and MRFXXL (large sized: 45 to 212 µm) have been estimated using particle dynamic simulations and the predicted results have been compared with the results obtained from experiments. Due to large number of particles and limitations of computer hardware, the yield behavior of MRFXXM1 i.e. mixed (2 to 212 µm) sized magnetic particles could not be simulated. However, experiments were performed to investigate the yield behavior of MRFXXM1. The results show that MRFXXM1 is better than MRFXXS and MRFXXL.

Research paper thumbnail of Development of Analytical Equations for Design and Optimization of Axially Polarized Radial Passive Magnetic Bearing

Journal of Tribology, 2014

In the present research work, analytical equations have been developed for design and optimizatio... more In the present research work, analytical equations have been developed for design and optimization of radial axial polarized passive magnetic bearing (PMB) with single layer for facilitating easy and quick solution, obviating the need of costly software. Seven design variables: eccentricity, rotor width, stator width, rotor length, stator length, clearance, and mean radius were identified as the main factors affecting the design and were thus considered in the development of analytical equations. The results obtained from the developed analytical equations have been validated with the published results. The optimization of the bearing design, with minimization of magnet volume as the objective function, was carried out to demonstrate the accuracy and usefulness of the developed equations.

Research paper thumbnail of Design of eight pole radial active magnetic bearing using monotonicity

2014 9th International Conference on Industrial and Information Systems (ICIIS), 2014

In the present research, studies have been carried out to design an eight-pole electromagnetic be... more In the present research, studies have been carried out to design an eight-pole electromagnetic bearing considering copper- and iron- losses. The magnetic lévitation force was maximized for the given geometric constraints using (i) numerical optimization and (ii) monotonicity analysis. The dimensions of the electromagnet using both the methods has been presented and compared.

Research paper thumbnail of Synthesis and characterization of low cost magnetorheological (MR) fluids

Behavior and Mechanics of Multifunctional and Composite Materials 2007, 2007

ABSTRACT Magnetorheological fluids have great potential for engineering applications due to their... more ABSTRACT Magnetorheological fluids have great potential for engineering applications due to their variable rheological behavior. These fluids find applications in dampers, brakes, shock absorbers, and engine mounts. However their relatively high cost (approximately US$600 per liter) limits their wide usage. Most commonly used magnetic material "Carbonyl iron" cost more than 90% of the MR fluid cost. Therefore for commercial viability of these fluids there is need of alternative economical magnetic material. In the present work synthesis of MR fluid has been attempted with objective to produce low cost MR fluid with high sedimentation stability and greater yield stress. In order to reduce the cost, economical electrolytic Iron powder (US$ 10 per Kg) has been used. Iron powder of relatively larger size (300 Mesh) has been ball milled to reduce their size to few microns (1 to 10 microns). Three different compositions have been prepared and compared for MR effect produced and stability. All have same base fluid (Synthetic oil) and same magnetic phase i.e. Iron particles but they have different additives. First preparation involves organic additives Polydimethylsiloxane (PDMS) and Stearic acid. Other two preparations involve use of two environmental friendly low-priced green additives guar gum (US$ 2 per Kg) and xanthan gum (US$ 12 per Kg) respectively. Magnetic properties of Iron particles have been measured by Vibrating Sample Magnetometer (VSM). Morphology of Iron particles and additives guar gum and xanthan gum has been examined by Scanning Electron Microscopy (SEM) and Particles Size Distribution (PSD) has been determined using Particle size analyzer. Microscopic images of particles, MH plots and stability of synthesized MR fluids have been reported. The prepared low cost MR fluids showed promising performance and can be effectively used for engineering applications demanding controllability in operations.

Research paper thumbnail of Effect of cylindricity on the tribological performance of heavily loaded slow-speed journal bearing

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2014

Theoretical and experimental studies have been conducted to analyze the effect of cylindricity on... more Theoretical and experimental studies have been conducted to analyze the effect of cylindricity on performance of a heavily loaded slow-speed journal bearing. The design of experiments has been employed to quantify the effect of bearing clearance and cylindricity on the wear. Since the initial experimental results did not establish any definitive trend, the effect of running-in was considered and the sliding distance required for reaching steady wear was estimated by conducting tests on lubricity tester employing conformal block and disc configuration. Further experiments incorporating the running-in were then conducted on journal bearing test rig. The wear coefficient was determined using the steady wear data obtained experimentally on the lubricity tester. A mathematical model was formulated to estimate wear of the bearing incorporating the actual cylindricity. The theoretical and experimental results corresponded well indicating a strong dependence of wear on the bearing cylindric...

Research paper thumbnail of Tribological study of elastomeric bearings for marine propeller shaft system

Tribology International, 2009

Elastomeric compounds, due to their favourable properties like sufficient hardness, toughness and... more Elastomeric compounds, due to their favourable properties like sufficient hardness, toughness and natural resistance to abrasion and corrosion, are commonly used as bearing material for propeller shaft system of Indian Coast Guard Ships. Recently unequal and non-uniform wear of these bearings has resulted in unscheduled lay off of the Coast Guard Ships. To solve this problem of bearing wear, a mixed lubrication analysis of seawater lubricated journal bearing has been attempted in the present study. A computer code was written to estimate lubricating film thickness for a given set of load and speed condition, and to predict the lubrication regime for the specified surface roughness parameters. To validate the theoretical analysis performed in the present study, the results obtained from the computer simulation have been compared with the established studies on the water lubricated bearing. To understand the uneven wear of marine bearings, actual geometric clearances of new and worn out bearings recorded by the ship maintenance team, and the operational data (load, speed and operating hours), obtained from the log books of ICGS Sangram (AOPV) of Indian Coast Guard, are listed in the present paper. The dynamic viscosity of sea water, surface roughness of propeller shaft and bearings, and particulate contamination has been measured. Finally, the suggestions have been enlisted for proper operation of shaft-bearing system so as to maintain the wear within the permissible limits during ship's operational cycle.

Research paper thumbnail of Design and Development of a Test Setup for Online Wear Monitoring of Mechanical Face Seals Using a Torque Sensor

Tribology Transactions, 2008

Online condition monitoring technique helps to detect the root cause of failure of any machine. T... more Online condition monitoring technique helps to detect the root cause of failure of any machine. The present article describes a design of the online failure monitoring facility for mechanical face seals. The experimental test facility is to operate the seal (i.e., carbon-graphite) in real conditions of fluid pressure, temperature, and misalignment, which occur in an industrial environment. The developed test setup consists of two proximity displacement sensors (accuracy 2 µm), one fiber-optic sensor (accuracy 10 µm), one accelerometer (3.97 mV/ms −2), and one non-contact torque sensor (accuracy 0.05 N.m). To validate the test facility, a typical conical carbon graphite (C = 59.195%, O = 4.625%, and Sb = 36.18%.) mechanical face seal (outer dia = 82 mm and inner dia = 63 mm) for a rotary joint used in steam/hot water was selected. The root cause of failure of such seals has been identified. Finally, recommendations have been made that provide some assistance to design the mechanical face seal.

Research paper thumbnail of Root Cause Failure Analysis of Outer Ring Fracture of Four-Row Cylindrical Roller Bearing

Tribology Transactions, 2009

ABSTRACT Four-row cylindrical roller bearings having pin-type steel cage and pronged machined sol... more ABSTRACT Four-row cylindrical roller bearings having pin-type steel cage and pronged machined solid brass cage are commonly used in the back-up roll assembly of cold rolling mills. The present article briefs about these bearings and investigates the root cause failure of such gigantic (inner ring ID = 865 mm, inner ring OD = 945 mm; outer ring ID = 1073.0 mm, outer ring OD = 1180 mm) four-row cylindrical roller bearings. In the present study, a visual examination of failed rolling surfaces has been emphasized. An analytical approach has been utilized to determine the maximum load on the roller and the outer ring raceway interface. The maximum principal normal and shear stresses have been evaluated for coefficients of friction equal to 0.001, 0.1, 0.2, and 0.3. A three-dimensional static finite element analysis has been performed to explain the cracking of the outer ring of the bearing. Condition monitoring based on oil analysis is adopted to validate the conclusions drawn from the finite element analysis of roller bearings.

Research paper thumbnail of Lubricant Shear Thinning Analysis of Engine Journal Bearings

Tribology Transactions, 2001

The high shearing stresses encountered in the modern engine bearing lubricant film lead to signif... more The high shearing stresses encountered in the modern engine bearing lubricant film lead to significant drop in viscosity of multigrade oils and affect the values of film thickness, power loss and oil flow significantly in the engine bearings. The popular mobility method is incapable to incorporate shear thinning, and time-consuming numerical schemes are not readily acceptable in industry. The present

Research paper thumbnail of Rapid performance evaluation of journal bearings

Tribology International, 1997

This paper describes a rapid method for evaluating the significant design parameters such as load... more This paper describes a rapid method for evaluating the significant design parameters such as load capacity, maximum pressure, flow, power loss, and maximum temperature in the oil film. The proposed analytical pressure expression is a modification of that given by Reason and Narang. An analytical expression for maximum pressure is presented. The accuracy of the proposed modification is validated up to an eccentricity ratio of 0.99. The effective temperature rise, which depends on the fraction of heat generation carried away by lubricant, is chosen to be a function of the eccentricity ratio. An expression for maximum temperature, based on existing experimental findings, is given. A journal bearing design table is provided to help the designer without the involvement of numerical and mathematical complexities.

Research paper thumbnail of Parametric study on balance ratio of mechanical face seal in steam environment

Tribology International, 2010

... An experimental parametric study on four balance ratio conditions with constant speed and var... more ... An experimental parametric study on four balance ratio conditions with constant speed and variable steam pressures has been performed, which has ... loading arising from the intimate contact in between the mating surfaces of seal and shaft, and seal and housing during running ...

Research paper thumbnail of Design, development, and performance evaluation of high-speed magnetorheological brakes

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2008

Magnetorheological (MR) fluids change their flow resistance on the application of magnetic field.... more Magnetorheological (MR) fluids change their flow resistance on the application of magnetic field. This variation in resistance to shear, offered by MR fluid, is rapid and almost completely reversible (no hysteresis). This unique feature has motivated authors to design a variable resistance brake using MR fluid. The present paper describes the design procedure of MR brake and discusses the effect of MR gap on its braking torque. Two brakes, Brake 1 with MR gap 1 mm and Brake 2 with MR gap 2 mm have been designed and fabricated. To generate magnetic field one central electro-magnet and two side electromagnets have been suggested. To validate the theoretical design and its findings, prototyping, and experimental study of MR brake have been performed. Vibrating sample magnetometer test has been carried out to obtain magnetic properties of the MR fluid and its magnetic phase. An experimental test setup has been developed to measure the braking torque under various operating speeds (200 t...

Research paper thumbnail of Multiobjective optimization of a journal bearing using the Pareto optimality concept

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2004

This paper deals with multiobjective optimization (minimization of temperature rise, minimization... more This paper deals with multiobjective optimization (minimization of temperature rise, minimization of oil feed flow, minimization of power loss) and discrete design variables (lubricant viscosity, radial clearance, length-diameter ratio) related to the design of a journal bearing. The aim of this paper is to show the sensitivity of radial clearance, oil viscosity and length-diameter ratio on bearing power loss and oil flow. The paper attempts to remove the difficulty of selecting the weighting factor in multiobjective journal bearing optimization problems. The optimization model is based on a hybrid solution scheme for journal bearings. The objective of bearing optimization is to minimize a linear combination (weighted sum) of power loss and oil flow. Constraints are imposed on the maximum fluid film pressure, minimum film thickness, maximum temperature rise and critical speed. A generic algorithm is used as the optimization tool with a penalty to those solutions that violate constra...

Research paper thumbnail of Performance evaluation of a magnetorheological fluid variable valve

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2007

Magnetorheological (MR) fluids which can exhibit substantial reversible rheological changes under... more Magnetorheological (MR) fluids which can exhibit substantial reversible rheological changes under the excitation of external magnetic fields, have enabled the construction of many novel and robust electromechanical devices in recent years. Generally, Bingham plastic model is utilized for the estimation of the characteristics of MR fluids. However, when the geometry and design of the MR device as well as the rheological conditions of the fluid itself become complicated due to the engineering application requirements, the accuracy of Bingham plastic model, which simplifies the relation between the fluid shear stress, and shear rate into a linear function, is degraded. In this paper, a multi-degree-of-freedom (MDOF) magnetorheological fluid damper with a novel ball-and-socket structure was developed, which was aimed to enhance the human shoulder rehabilitation treatment. The performance of the proposed smart device with its complex design was estimated numerically using a finite element method (FEM) with a Herschel-Bulkley model and theoretically with a model that is based on a Bingham plastic fluid characteristics. The performance of the developed damper was validated experimentally using a dedicated testing facility for various input conditions. It was found that the FEM simulations with the Herschel-Bulkley model showed a better agreement with the experimental results in comparison with the theoretical predictions which were somewhat degraded with the employed Bingham plastic model.

Research paper thumbnail of A Hybrid Solution Scheme for Performance Evaluation of Crankshaft Bearings

Journal of Tribology, 2000

In the past few decades the research efforts towards efficient solutions of crankshaft bearing us... more In the past few decades the research efforts towards efficient solutions of crankshaft bearing using both rapid (e.g., analytical, semi-analytical, curve fits) and rigorous numerical approaches have made sufficient progress. Analytical solutions compromise on accuracy. In contrast numerical methods require very high computational time and facilities with large memory requirements. These features make it very difficult to obtain a solution that is optimal with respect to memory requirements, computational speed and accuracy. Therefore, here a hybrid procedure for thermal analysis of crankshaft bearings is attempted, which uses a combination of both the analytical and numerical solution techniques. Operational parameters such as journal velocity and effective viscosity are calculated with reasonable accuracy using analytical method. Other parameters such as maximum pressure, oil-flow, and power loss are evaluated by numerical technique. Experiments to validate the proposed hybrid proc...

Research paper thumbnail of Magnetic Bearing Configurations: Theoretical and Experimental Studies

IEEE Transactions on Magnetics, 2008

A radial magnetic bearing, consisting of two permanent magnets, is an attractive choice because o... more A radial magnetic bearing, consisting of two permanent magnets, is an attractive choice because of its zero wear, negligible friction, and low cost, but it suffers from low load capacity, low radial stiffness, lack of damping, and high axial instability. To enhance the radial load and radial stiffness, and reduce the axial thrust, we have made a theoretical and experimental study of various radial configurations, including hydrodynamic lubrication to improve dynamic performance of the magnetic bearing. We developed an experimental setup to investigate the performance of bearing configurations under different operating conditions. The motion of a rotating shaft is mapped by two displacement sensors with a data acquisition system and personal computer. The first critical speed of each configuration is determined experimentally and verified through frequency analysis. We present a polar plot of displacement data.

Research paper thumbnail of Stimuli-responsive discriminative detection of Cu2+ and Hg2+ with concurrent sensing of S2- from aqueous medium and bio-fluids by C N fused azophenine functionalized “smart” hydrogel assay @A potential biomarker sensor for Wilson’s disease

Sensors and Actuators B: Chemical, 2021

Abstract A multi-functional azophenine based colorimetric chemosensor, CN-1 has been reported by ... more Abstract A multi-functional azophenine based colorimetric chemosensor, CN-1 has been reported by catalytic FeCl3 mediated facile oxidative C-N bond fusion of o-anisidine. The chemosensor, characterized by single crystal X-ray crystallography, can be exploited towards ‘naked-eye’ discriminative detection of Cu2+ and Hg2+ (LOD = 30 and 480 ppb respectively) from purely aqueous medium through colorimetric and electrochemical (CV) readouts. It is equally responsive towards intoxicated real water specimen, like river water, industrial sewage water, demonstrating its practical applicability. Along with detection, CN-1 exhibited metal ion sequestration capability, leading to the removal of ∼74% and ∼40% removal of Cu2+ and Hg2+ respectively from contaminated water bodies. Moreover, the unprecedented uniqueness of the synthesized azophenine based chemosensor levies in its capability towards ppb level Cu2+ detection colorimetrically from target-specific bio-fluids to monitor aberrant unbound copper levels, thereby highlighting it as a potential biomarker sensor as well as a pathological non-invasive diagnostic tool of Wilson’s disease, which has been explored for the first time in the domain of azophenine based host-guest chemistry. The reversible spectrochemical response in presence of aqueous S2- could efficiently formulate “Write-Read-Erase-Read” nature of a memory element and four-input complex logic circuitry for molecular level information storage, which is also hitherto unexplored in the azophenine family. One step ahead, fabrication of functionalized “smart” hydrogel assay escalates the reliability and practical applicability of the present work through simple ‘naked eye’ colorimetric-optical readouts.

Research paper thumbnail of Development of a magnetorheological brake with a slotted disc

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2015

A conventional disc wears out and the brake pollutes the environment. Brake pad dust is reported ... more A conventional disc wears out and the brake pollutes the environment. Brake pad dust is reported to be the largest source of environment pollution1. The particles emanating because of wear of the brake pad pollute the environment2,3,4. In addition to pollution caused by wear particles, the friction-induced noise between the brake pad and the disc is also a major concern5. Also, localized heating occurs in a conventional disc brake. To tackle both of these problems, conventional disc brakes can be replaced with manetorheological fluid brakes. Magnetorheological fluids are materials having a shear yield stress which is a function of the magnetic field. On the application of a magnetic field, magnetorheological particles become aligned and increase the shear resistance between relatively moving surfaces. The friction between the stator and the rotor increases and fulfils the braking function, which means that magnetorheological fluids can be used as brake friction materials. A magnetor...

Research paper thumbnail of Control on wear of journal bearing operating in mixed lubrication regime using grooving arrangements

Industrial Lubrication and Tribology, 2016

Purpose The journal bearings subjected to heavy load and slow speed operate in mixed lubrication ... more Purpose The journal bearings subjected to heavy load and slow speed operate in mixed lubrication regime causing contact between the interacting surfaces and resulting in wear. Complexity of wear behavior and lack of unifying theory/model make wear-control very challenging. Design/methodology/approach In the present research work, theoretical and experimental investigations have been conducted to explore the effect of grooving arrangements on the wear behavior of journal bearing operating in mixed lubrication regime. The theoretical model of Hirani (2005) that uses mass conserving cavitation algorithm has been used to determine the bearing eccentricity for different groove arrangements (with varying groove location and extent) for identifying a groove arrangement that minimizes the wear. The wear tests on the grooved bearings were conducted after suitable running-in of the new bearings on a fully automated journal bearing test set-up. A load and speed combination required to operate ...

Research paper thumbnail of Effect of Particle Size on Shear Stress of Magnetorheological Fluids

Research paper thumbnail of Particle Dynamics of Polydisperse Magnetorheological Fluids

Smart Science, 2015

In the present research work, three dimensional simulations of magnetorheological fluids, contain... more In the present research work, three dimensional simulations of magnetorheological fluids, containing soft magnetic polydisperse particles in silicone oil, has been presented. The computer simulation helps to visualize and analyze the formed transient microstructures. The initial positions of particle-centres were decided based on random distribution. The particle positions were updated considering magnetic, hydrodynamic and repulsions forces on each particle along with explicit time marching scheme. Finally the particle's positions at 10 ms have been plotted. The yield behaviors of MRFXXS (small sized: 2 to 33 µm) and MRFXXL (large sized: 45 to 212 µm) have been estimated using particle dynamic simulations and the predicted results have been compared with the results obtained from experiments. Due to large number of particles and limitations of computer hardware, the yield behavior of MRFXXM1 i.e. mixed (2 to 212 µm) sized magnetic particles could not be simulated. However, experiments were performed to investigate the yield behavior of MRFXXM1. The results show that MRFXXM1 is better than MRFXXS and MRFXXL.

Research paper thumbnail of Development of Analytical Equations for Design and Optimization of Axially Polarized Radial Passive Magnetic Bearing

Journal of Tribology, 2014

In the present research work, analytical equations have been developed for design and optimizatio... more In the present research work, analytical equations have been developed for design and optimization of radial axial polarized passive magnetic bearing (PMB) with single layer for facilitating easy and quick solution, obviating the need of costly software. Seven design variables: eccentricity, rotor width, stator width, rotor length, stator length, clearance, and mean radius were identified as the main factors affecting the design and were thus considered in the development of analytical equations. The results obtained from the developed analytical equations have been validated with the published results. The optimization of the bearing design, with minimization of magnet volume as the objective function, was carried out to demonstrate the accuracy and usefulness of the developed equations.

Research paper thumbnail of Design of eight pole radial active magnetic bearing using monotonicity

2014 9th International Conference on Industrial and Information Systems (ICIIS), 2014

In the present research, studies have been carried out to design an eight-pole electromagnetic be... more In the present research, studies have been carried out to design an eight-pole electromagnetic bearing considering copper- and iron- losses. The magnetic lévitation force was maximized for the given geometric constraints using (i) numerical optimization and (ii) monotonicity analysis. The dimensions of the electromagnet using both the methods has been presented and compared.

Research paper thumbnail of Synthesis and characterization of low cost magnetorheological (MR) fluids

Behavior and Mechanics of Multifunctional and Composite Materials 2007, 2007

ABSTRACT Magnetorheological fluids have great potential for engineering applications due to their... more ABSTRACT Magnetorheological fluids have great potential for engineering applications due to their variable rheological behavior. These fluids find applications in dampers, brakes, shock absorbers, and engine mounts. However their relatively high cost (approximately US$600 per liter) limits their wide usage. Most commonly used magnetic material "Carbonyl iron" cost more than 90% of the MR fluid cost. Therefore for commercial viability of these fluids there is need of alternative economical magnetic material. In the present work synthesis of MR fluid has been attempted with objective to produce low cost MR fluid with high sedimentation stability and greater yield stress. In order to reduce the cost, economical electrolytic Iron powder (US$ 10 per Kg) has been used. Iron powder of relatively larger size (300 Mesh) has been ball milled to reduce their size to few microns (1 to 10 microns). Three different compositions have been prepared and compared for MR effect produced and stability. All have same base fluid (Synthetic oil) and same magnetic phase i.e. Iron particles but they have different additives. First preparation involves organic additives Polydimethylsiloxane (PDMS) and Stearic acid. Other two preparations involve use of two environmental friendly low-priced green additives guar gum (US$ 2 per Kg) and xanthan gum (US$ 12 per Kg) respectively. Magnetic properties of Iron particles have been measured by Vibrating Sample Magnetometer (VSM). Morphology of Iron particles and additives guar gum and xanthan gum has been examined by Scanning Electron Microscopy (SEM) and Particles Size Distribution (PSD) has been determined using Particle size analyzer. Microscopic images of particles, MH plots and stability of synthesized MR fluids have been reported. The prepared low cost MR fluids showed promising performance and can be effectively used for engineering applications demanding controllability in operations.

Research paper thumbnail of Effect of cylindricity on the tribological performance of heavily loaded slow-speed journal bearing

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2014

Theoretical and experimental studies have been conducted to analyze the effect of cylindricity on... more Theoretical and experimental studies have been conducted to analyze the effect of cylindricity on performance of a heavily loaded slow-speed journal bearing. The design of experiments has been employed to quantify the effect of bearing clearance and cylindricity on the wear. Since the initial experimental results did not establish any definitive trend, the effect of running-in was considered and the sliding distance required for reaching steady wear was estimated by conducting tests on lubricity tester employing conformal block and disc configuration. Further experiments incorporating the running-in were then conducted on journal bearing test rig. The wear coefficient was determined using the steady wear data obtained experimentally on the lubricity tester. A mathematical model was formulated to estimate wear of the bearing incorporating the actual cylindricity. The theoretical and experimental results corresponded well indicating a strong dependence of wear on the bearing cylindric...

Research paper thumbnail of Tribological study of elastomeric bearings for marine propeller shaft system

Tribology International, 2009

Elastomeric compounds, due to their favourable properties like sufficient hardness, toughness and... more Elastomeric compounds, due to their favourable properties like sufficient hardness, toughness and natural resistance to abrasion and corrosion, are commonly used as bearing material for propeller shaft system of Indian Coast Guard Ships. Recently unequal and non-uniform wear of these bearings has resulted in unscheduled lay off of the Coast Guard Ships. To solve this problem of bearing wear, a mixed lubrication analysis of seawater lubricated journal bearing has been attempted in the present study. A computer code was written to estimate lubricating film thickness for a given set of load and speed condition, and to predict the lubrication regime for the specified surface roughness parameters. To validate the theoretical analysis performed in the present study, the results obtained from the computer simulation have been compared with the established studies on the water lubricated bearing. To understand the uneven wear of marine bearings, actual geometric clearances of new and worn out bearings recorded by the ship maintenance team, and the operational data (load, speed and operating hours), obtained from the log books of ICGS Sangram (AOPV) of Indian Coast Guard, are listed in the present paper. The dynamic viscosity of sea water, surface roughness of propeller shaft and bearings, and particulate contamination has been measured. Finally, the suggestions have been enlisted for proper operation of shaft-bearing system so as to maintain the wear within the permissible limits during ship's operational cycle.

Research paper thumbnail of Design and Development of a Test Setup for Online Wear Monitoring of Mechanical Face Seals Using a Torque Sensor

Tribology Transactions, 2008

Online condition monitoring technique helps to detect the root cause of failure of any machine. T... more Online condition monitoring technique helps to detect the root cause of failure of any machine. The present article describes a design of the online failure monitoring facility for mechanical face seals. The experimental test facility is to operate the seal (i.e., carbon-graphite) in real conditions of fluid pressure, temperature, and misalignment, which occur in an industrial environment. The developed test setup consists of two proximity displacement sensors (accuracy 2 µm), one fiber-optic sensor (accuracy 10 µm), one accelerometer (3.97 mV/ms −2), and one non-contact torque sensor (accuracy 0.05 N.m). To validate the test facility, a typical conical carbon graphite (C = 59.195%, O = 4.625%, and Sb = 36.18%.) mechanical face seal (outer dia = 82 mm and inner dia = 63 mm) for a rotary joint used in steam/hot water was selected. The root cause of failure of such seals has been identified. Finally, recommendations have been made that provide some assistance to design the mechanical face seal.

Research paper thumbnail of Root Cause Failure Analysis of Outer Ring Fracture of Four-Row Cylindrical Roller Bearing

Tribology Transactions, 2009

ABSTRACT Four-row cylindrical roller bearings having pin-type steel cage and pronged machined sol... more ABSTRACT Four-row cylindrical roller bearings having pin-type steel cage and pronged machined solid brass cage are commonly used in the back-up roll assembly of cold rolling mills. The present article briefs about these bearings and investigates the root cause failure of such gigantic (inner ring ID = 865 mm, inner ring OD = 945 mm; outer ring ID = 1073.0 mm, outer ring OD = 1180 mm) four-row cylindrical roller bearings. In the present study, a visual examination of failed rolling surfaces has been emphasized. An analytical approach has been utilized to determine the maximum load on the roller and the outer ring raceway interface. The maximum principal normal and shear stresses have been evaluated for coefficients of friction equal to 0.001, 0.1, 0.2, and 0.3. A three-dimensional static finite element analysis has been performed to explain the cracking of the outer ring of the bearing. Condition monitoring based on oil analysis is adopted to validate the conclusions drawn from the finite element analysis of roller bearings.

Research paper thumbnail of Lubricant Shear Thinning Analysis of Engine Journal Bearings

Tribology Transactions, 2001

The high shearing stresses encountered in the modern engine bearing lubricant film lead to signif... more The high shearing stresses encountered in the modern engine bearing lubricant film lead to significant drop in viscosity of multigrade oils and affect the values of film thickness, power loss and oil flow significantly in the engine bearings. The popular mobility method is incapable to incorporate shear thinning, and time-consuming numerical schemes are not readily acceptable in industry. The present

Research paper thumbnail of Rapid performance evaluation of journal bearings

Tribology International, 1997

This paper describes a rapid method for evaluating the significant design parameters such as load... more This paper describes a rapid method for evaluating the significant design parameters such as load capacity, maximum pressure, flow, power loss, and maximum temperature in the oil film. The proposed analytical pressure expression is a modification of that given by Reason and Narang. An analytical expression for maximum pressure is presented. The accuracy of the proposed modification is validated up to an eccentricity ratio of 0.99. The effective temperature rise, which depends on the fraction of heat generation carried away by lubricant, is chosen to be a function of the eccentricity ratio. An expression for maximum temperature, based on existing experimental findings, is given. A journal bearing design table is provided to help the designer without the involvement of numerical and mathematical complexities.

Research paper thumbnail of Parametric study on balance ratio of mechanical face seal in steam environment

Tribology International, 2010

... An experimental parametric study on four balance ratio conditions with constant speed and var... more ... An experimental parametric study on four balance ratio conditions with constant speed and variable steam pressures has been performed, which has ... loading arising from the intimate contact in between the mating surfaces of seal and shaft, and seal and housing during running ...

Research paper thumbnail of Design, development, and performance evaluation of high-speed magnetorheological brakes

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 2008

Magnetorheological (MR) fluids change their flow resistance on the application of magnetic field.... more Magnetorheological (MR) fluids change their flow resistance on the application of magnetic field. This variation in resistance to shear, offered by MR fluid, is rapid and almost completely reversible (no hysteresis). This unique feature has motivated authors to design a variable resistance brake using MR fluid. The present paper describes the design procedure of MR brake and discusses the effect of MR gap on its braking torque. Two brakes, Brake 1 with MR gap 1 mm and Brake 2 with MR gap 2 mm have been designed and fabricated. To generate magnetic field one central electro-magnet and two side electromagnets have been suggested. To validate the theoretical design and its findings, prototyping, and experimental study of MR brake have been performed. Vibrating sample magnetometer test has been carried out to obtain magnetic properties of the MR fluid and its magnetic phase. An experimental test setup has been developed to measure the braking torque under various operating speeds (200 t...

Research paper thumbnail of Multiobjective optimization of a journal bearing using the Pareto optimality concept

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2004

This paper deals with multiobjective optimization (minimization of temperature rise, minimization... more This paper deals with multiobjective optimization (minimization of temperature rise, minimization of oil feed flow, minimization of power loss) and discrete design variables (lubricant viscosity, radial clearance, length-diameter ratio) related to the design of a journal bearing. The aim of this paper is to show the sensitivity of radial clearance, oil viscosity and length-diameter ratio on bearing power loss and oil flow. The paper attempts to remove the difficulty of selecting the weighting factor in multiobjective journal bearing optimization problems. The optimization model is based on a hybrid solution scheme for journal bearings. The objective of bearing optimization is to minimize a linear combination (weighted sum) of power loss and oil flow. Constraints are imposed on the maximum fluid film pressure, minimum film thickness, maximum temperature rise and critical speed. A generic algorithm is used as the optimization tool with a penalty to those solutions that violate constra...

Research paper thumbnail of Performance evaluation of a magnetorheological fluid variable valve

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2007

Magnetorheological (MR) fluids which can exhibit substantial reversible rheological changes under... more Magnetorheological (MR) fluids which can exhibit substantial reversible rheological changes under the excitation of external magnetic fields, have enabled the construction of many novel and robust electromechanical devices in recent years. Generally, Bingham plastic model is utilized for the estimation of the characteristics of MR fluids. However, when the geometry and design of the MR device as well as the rheological conditions of the fluid itself become complicated due to the engineering application requirements, the accuracy of Bingham plastic model, which simplifies the relation between the fluid shear stress, and shear rate into a linear function, is degraded. In this paper, a multi-degree-of-freedom (MDOF) magnetorheological fluid damper with a novel ball-and-socket structure was developed, which was aimed to enhance the human shoulder rehabilitation treatment. The performance of the proposed smart device with its complex design was estimated numerically using a finite element method (FEM) with a Herschel-Bulkley model and theoretically with a model that is based on a Bingham plastic fluid characteristics. The performance of the developed damper was validated experimentally using a dedicated testing facility for various input conditions. It was found that the FEM simulations with the Herschel-Bulkley model showed a better agreement with the experimental results in comparison with the theoretical predictions which were somewhat degraded with the employed Bingham plastic model.

Research paper thumbnail of A Hybrid Solution Scheme for Performance Evaluation of Crankshaft Bearings

Journal of Tribology, 2000

In the past few decades the research efforts towards efficient solutions of crankshaft bearing us... more In the past few decades the research efforts towards efficient solutions of crankshaft bearing using both rapid (e.g., analytical, semi-analytical, curve fits) and rigorous numerical approaches have made sufficient progress. Analytical solutions compromise on accuracy. In contrast numerical methods require very high computational time and facilities with large memory requirements. These features make it very difficult to obtain a solution that is optimal with respect to memory requirements, computational speed and accuracy. Therefore, here a hybrid procedure for thermal analysis of crankshaft bearings is attempted, which uses a combination of both the analytical and numerical solution techniques. Operational parameters such as journal velocity and effective viscosity are calculated with reasonable accuracy using analytical method. Other parameters such as maximum pressure, oil-flow, and power loss are evaluated by numerical technique. Experiments to validate the proposed hybrid proc...

Research paper thumbnail of Magnetic Bearing Configurations: Theoretical and Experimental Studies

IEEE Transactions on Magnetics, 2008

A radial magnetic bearing, consisting of two permanent magnets, is an attractive choice because o... more A radial magnetic bearing, consisting of two permanent magnets, is an attractive choice because of its zero wear, negligible friction, and low cost, but it suffers from low load capacity, low radial stiffness, lack of damping, and high axial instability. To enhance the radial load and radial stiffness, and reduce the axial thrust, we have made a theoretical and experimental study of various radial configurations, including hydrodynamic lubrication to improve dynamic performance of the magnetic bearing. We developed an experimental setup to investigate the performance of bearing configurations under different operating conditions. The motion of a rotating shaft is mapped by two displacement sensors with a data acquisition system and personal computer. The first critical speed of each configuration is determined experimentally and verified through frequency analysis. We present a polar plot of displacement data.