sunil bhat - Academia.edu (original) (raw)

Papers by sunil bhat

Journal of PeriAnesthesia Nursing, 2002

Recent patents on engineering, 2024

In the domain of industrial building and production technology, the welding of dissimilar materia... more In the domain of industrial building and production technology, the welding of dissimilar materials finds a wide range of applications. Unique properties of different materials are utilized to produce addition and cost effectiveness of the product for intended applications. For determining
the feasibility of welding of dissimilar metals together to create a strong joint, a number of factors need to be taken into account. This paper discusses critical factors and conditions for welding of dissimilar metals and touches upon the practical challenges arising from different physical
and chemical properties of the metals. It presents the latest and pertinent literature dealing with the details about the current fusion and non-fusion processes employed for welding common dissimilar metal combinations. The results suggest that research and development in the field of dissimilar metal welding is still needed, especially in light of the growing need for customized materials in contemporary engineering and industrial applications

IOSR, Journal of mechanical and civil engineering, 2024

The field and scope of composites is constantly widening with the introduction of new materials a... more The field and scope of composites is constantly widening with the introduction of new materials and manufacturing technologies. Unknown properties of different engineering, non-engineering and bio-materials are regularly explored for the development of modern composites that show immense potential in future for applications in domestic, automotive, defence and aerospace industries. Some fundamental aspects, processing techniques, properties and applications of such composites are reviewed in the paper.

The primary purpose of the book is to present the models, both theoretical and numerical, for inv... more The primary purpose of the book is to present the models, both theoretical and numerical, for investigation of the mechanisms of crack tip stress amplification, shielding and fiber bridging in Type I and Type II fiber metal laminates under the influence of residual stresses that are generated due to curing during fabrication of the laminates. The models are well validated by experiments.

Advances in explosive welding of dissimilar metals: A mini literature survey, 2024

Explosive welding, which has emerged as a promising field of research in the recent past, is a so... more Explosive welding, which has emerged as a promising field of research in the recent past, is a solid-state welding process that uses controlled explosive detonation to join two pieces of metal. A flyer plate collides with the base plate at high velocity, leading to significant local plastic deformation at the interface of the metals, resulting in a metallurgical bond between the metals. A high-velocity jet is formed in the process that eliminates the contaminants on the metal surfaces. Explosive welding can join materials that are similar or different. Some of the recent and important research work pertaining to explosive welding of dissimilar metals is briefly reviewed in this paper. Various aspects of the explosive welding process have been touched upon. A study of several parameters involved in the welding process is undertaken.

European Journal of Mechanics A-solids, 2014

ABSTRACT Glare, a fibre metal laminate (FML), consists of several thin 2014-T6 aerospace aluminiu... more ABSTRACT Glare, a fibre metal laminate (FML), consists of several thin 2014-T6 aerospace aluminium alloy layers alternately bonded with E-glass fibre based composite prepregs in the present work. As cracked Glare is subjected to load, load or fibre bridging over cracks in soft aluminium layers causes diversion of load away from the cracks towards stronger intact fibres in the prepregs resulting in stress reduction or shielding effect at the crack tips. Fibre bridging diminishes if delaminations, caused by the development of interfacial cracks at the interfaces of aluminium and fibre layers, exist in the laminate. The paper investigates the cracked but non-delaminated Glare containing normal Mode I cracks in all its aluminium layers. Different crack lengths are considered in the laminates to examine the influence of crack size over bridging. A theoretical model is presented to determine fibre bridging stress for estimation of fibre bridging stress intensity parameter that quantifies the effect of bridging in the laminate. Crack tip stress intensity parameter is also found. The model is successfully validated by undertaking finite element analysis of series of un-identically cracked Glare laminates without delaminations under critical or fracture loads that are obtained experimentally by subjecting the laminates to load-extension test. Plain aerospace aluminium alloy specimens are also tested for fracture. Fracture toughness values of the laminates are seen to be significantly higher than that of plain aluminium specimens. The phenomenon of fibre bridging in the laminates is well substantiated and quantified by all the adopted procedures.

11TH INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2013: ICNAAM 2013, 2013

ABSTRACT A finite element examination of the effect of delaminations on fracture characteristics ... more ABSTRACT A finite element examination of the effect of delaminations on fracture characteristics of fibre metal laminate (Glare), by comparing energy release rates of normal cracks in laminates with and without delaminations, is presented in the paper. Glare comprising thin cracked 2024-T3 aerospace aluminum alloy layers alternately bonded with E-glass fibre based composite prepregs is considered for the analysis. Delaminations are modeled with interface cohesive elements. Energy release rates of normal cracks in laminates with delaminations are found to be higher than those in the laminates without delaminations.

Advanced Materials Research, Aug 1, 2013

The paper presents the stress field, obtained with the help of finite element method, around Mode... more The paper presents the stress field, obtained with the help of finite element method, around Mode I crack tip in ductile steel under EPFM regime. Process, plastic and non-K compliant elastic zones develop. Void nucleation ahead of the crack tip is observed in the process zone. The stress solution in the plastic zone is validated with theoretical HRR solution. In the elastic zone, as expected, substantial error is observed between K dominated LEFM solution and numerical EPFM values.Nomenclature

Acta Mechanica, Jul 25, 2010

The stress field around the crack tip near an elastically matched but strength-mismatched interfa... more The stress field around the crack tip near an elastically matched but strength-mismatched interface body in a bimetallic system is influenced when the crack tip yield or cohesive zone spreads to the interface body. The concept of crack tip stress intensity parameter, K tip , is therefore employed in fracture analysis of the bimetallic body. A computational model to determine K tip is reviewed in this paper. The model, based upon i) Westergaard's complex potentials coupled with Kolosov-Muskhelishvili's relations between a crack tip stress field and complex potentials and ii) Dugdale's representation of the cohesive zone clearly indicates shielding or amplifying effects of strength mismatch across the interface, depending upon the direction of the strength gradient, over the crack tip. The model is successfully validated by conducting series of high cycle fatigue tests over Mode I cracks advancing towards various strength-mismatched interfaces in bimetallic compact tension specimens prepared by electron beam welding of elastically identical weak ASTM 4340 alloy and strong MDN 250 maraging steels. List of symbols a Distance of crack tip from interface a * Radial coordinate of point near crack tip A Parent body/parent steel containing crack B Interface body/back up steel b Length of cohesive zone across interface c Crack length c c Crack length ahead of load axis c min Crack length required for linear elastic regime C Paris constant e, e av Percent difference between theoretical and experimental result, average of percent differences E Modulus of elasticity f (θ) A function of angle w.r.t. crack axis F Applied load i Imaginary quantity, √ −1

Applied Mechanics and Materials, 2013

The paper reviews the numerical methodology to investigate fracture parameter namely energy relea... more The paper reviews the numerical methodology to investigate fracture parameter namely energy release rate, G, of a mixed mode crack. An inclined, through, centre crack is assumed in a ductile steel plate subjected to bi-axial tension. Applied stress and crack size are suitably selected to simulate small scale yielding (SSY) condition at the crack tips. The cracked plate is modelled by finite element method. Both plane stress and plane strain situations are examined. G value is found from J integral. Equations of transformation are employed to obtain normal and shear stress in the plane of the crack. G is then again determined for Mode I and Mode II cracks by modelling each case separately. The analysis is finally validated by fulfilment of the conservation of energy release rate criterion, G (Mixed mode) = G (Mode I) + G (Mode II).

International Journal of Structural Integrity, Aug 8, 2016

Purpose – Since failure of laminated composites by delaminations is common, the purpose of this p... more Purpose – Since failure of laminated composites by delaminations is common, the purpose of this paper is to present a numerical procedure to check the stability of delaminations in fiber metal laminate (Glare), with different possible damage configurations, under uni-axial tension. Deformation behavior of the laminate is also examined. Influence of the type and the extent of damage, represented by varying sizes and number of delaminations, on delamination driving force and laminate deformation is found. Design/methodology/approach – Delaminated Glare is modeled by finite element method. Interface cohesive elements are used to model the delaminations. Finite element results provide the deflection/deformation characteristics of the laminate. Driving forces of delaminations are estimated by J integrals that are numerically obtained over cyclic paths near delamination tips. Laminates with different types of delaminations are also fabricated and externally delaminated for measurement of their interlaminar fracture toughness. The delamination is considered to be stable if its driving force is less than corresponding interlaminar fracture toughness of the laminate. Findings – Delaminations are found to be stable in laminates with lower number of delaminations and unstable in laminates with higher number of delaminations. Increase in size of delaminations increases the deformations but reduces the delamination driving force whereas increase in number of delaminations increases both deformations and driving forces. The trends change in case of laminates with symmetrical damage. Shape of delamination is also found to influence the deformations and driving forces. The finite element model is validated. Research limitations/implications – There is scope for validating the numerical results reported in the paper by theoretical models. Practical implications – Checking the stability of delaminations and their effect on deformation behavior of the laminate helps is assessment of safety and remaining life of the laminate. If failure is predicted, preemptive action is taken by using repair patch ups at identified critical locations in order to avoid failures in service conditions. Originality/value – The paper offers the following benefits: use of cohesive zone method that is readily possible in finite element procedures and is relatively simple, fast and reasonably accurate is demonstrated; suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested; and influence of the type and the extent of damage in the laminate on its deformation behavior and delamination driving forces is found. This type of work has not been reported so far.

International Journal of Mechanical and Materials Engineering, Oct 15, 2014

Notched Glare 4A-3/2 laminates, comprising thin 2014-T6 aerospace aluminum alloy sheets alternate... more Notched Glare 4A-3/2 laminates, comprising thin 2014-T6 aerospace aluminum alloy sheets alternately bonded with unidirectional E-glass fiber-based composite prepregs, are tested under tensile-tensile fatigue load with different stress ratio's ranging from 0.1 to 0.5 in ambient, aqueous, and corrosive environments in high-cycle conditions. Fatigue characteristics of the laminates are found to be influenced by the operating environment and the magnitude of stress ratio. Notched plain 2014-T6 aerospace aluminum alloy specimens are also subjected to identical cyclic stress levels as in aluminum alloy layers of the laminates for comparative analysis of their fatigue behavior with those of the laminates. Retarded crack growth rates in the laminates leading to their enhanced fatigue lives and higher cyclic fracture toughness values vis-à-vis plain specimens substantiate fiber bridging effect in the laminates.

International Journal of Structural Integrity, Apr 9, 2018

Behavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or pl... more Behavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or plain specimen made of metal used in the laminate due to the load transfer effect in the laminate caused by property mismatch between dissimilar material layers. The purpose of this paper is to present a finite element investigation on the characteristics of crack tip in monotonically loaded and residually stressed FML.,Crack tip characteristics are assessed by: the sizes of various zones that form at the tip; and crack tip energy release rates. The same are found by modeling two types of Glare laminates under monotonic tension with different crack orientations in SSY regime – Type I and Type II. Residual stresses are externally introduced in the models. Delaminations are modeled by cohesive elements. Crack tip zone sizes are measured from finite element solutions. Values of J integrals are computed over cyclic paths near the crack tips. Identically cracked and loaded plain aluminum alloy specimens are also modeled for comparison.,The sizes of crack tip zones in Glare laminates are found to be different than those in plain specimens. Process zone is observed to form at crack tip in Type I laminate whereas it does not develop in Type II laminate, the reverse being true in plain specimens. Values of J integrals near crack tips are also found to deviate from those in plain specimens, higher in Type I laminate due to crack tip stress amplification and lower in Type II laminate due to stress reduction. Crack orientation decides the amplification or shielding effect in the laminate.,There is scope for validating the numerical results reported in the paper by theoretical models.,The method to quantify crack tip shielding and amplification is presented that shall be useful in checking the structural integrity/safety of the laminate during actual service conditions.,Shielding and amplification effects are explicitly described and illustrated in the paper. Suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested. Use of cohesive zone method that is readily applicable in finite element procedures and is relatively simple, fast and reasonably accurate is also demonstrated.

Defect and Diffusion Forum, 2023

A mode I, centre crack, in ductile steel plate of finite dimensions is modeled in ANSYS software.... more A mode I, centre crack, in ductile steel plate of finite dimensions is modeled in ANSYS software. Non-linear stress-strain data of steel are used. Plane strain case is adopted. A suitable value of far field tensile stress (pressure) is chosen such that EPFM condition prevails at the crack tip. Process and plastic zones are obtained at the crack tip. Desired values are noted. Areas of high stress and high strain are identified. Validation of void nucleation taking place ahead of crack tip and not exactly at the crack tip and coalescence of voids happening at the crack tip are confirmed from the results. Plots between the distance of desired location from the crack tip and load line stresses and strains are drawn. The plots are in accordance with the expectations.

International Review of Mechanical Engineering, 2023

Vibrations are known to cause problems in many automotive systems and industrial equipment. There... more Vibrations are known to cause problems in many automotive systems and industrial equipment. Therefore, vibration control devices such as traditional hydraulic dampers are used to minimize the vibrations. Off late, MR dampers, in which MR fluid is used to enhance the vibration reduction performance, are introduced. An electromagnetic piston is positioned within the MR damper cylinder that creates the magnetic field necessary to operate the MR fluid. However, due to the internal electromagnetic piston arrangement in the conventional MR damper, some serious issues like remenance phenomenon, clumping and heat effect are observed. Consequently, a modified MR damper with an external permanent magnet assembly is proposed. Viability of modified MR damper concept is checked vis-à-vis conventional MR damper. After a successful check, a handy prototype of the modified MR damper is fabricated. The performance of the modified MR damper prototype is tested by changing the MR fluid configuration, the excitation frequency of exciter, the excitation current, and the magnetic flux density. A test rig is designed and fabricated for this purpose. The MR effect on velocity and damping force in the prototype is recorded and the observations are utilised in performance optimization. The Overall Evaluation criterion is employed in the optimization process with MR fluids of 76%, 80% and 82% weight percentage of ferromagnetic particles (AMT-Dampro, AMT-Magnaflo and AMT-Smartech MR fluids respectively). The regression analysis for most suitable MR fluid configuration is also undertaken. The modified MR damper prototype is found to work effectively as confirmed by optimization and regression analysis results. The idea of the modified MR damper can be suitably applied to number of existing practical systems to handle intense vibrations.

Lecture notes in mechanical engineering, Springer

A novel theoretical model for calculating the intensity of energy release rate at mode I crack ti... more A novel theoretical model for calculating the intensity of energy release rate at mode I crack tip in the bi-material has been developed. The study discusses the state at crack tip in the bi-material of identical steels connected by a thick but weaker weld inter layer of steel. In such a body, there are two interfaces: one between the stronger parent steel and the weaker weld, and another between the weaker weld and the stronger back up steel. As the fracture develops across the weld interlayer, i.e. strong-weak-strong transition, in the K dominating or SSY regime, the effect of energy transfer owing to the existence of elastically similar but strength mismatched surfaces is measured. The model accounts for non-linearity in plastic characteristics of steel. When the crack tip in parent steel faces the approaching interface of weaker weld during strong-weak transition, the rate of energy release at the crack tip is seen to be greater than the far field value. But when the tip in the weaker weld faces the interface of stronger back up steel during weak-strong transition, the tip energy release rate is reduced. When the crack tip is at the interfaces, the impact of shielding as well as amplification increases.

Materials Today: Proceedings, Elsevier

Abstract Magnesium (Mg) alloys possess high usage prospects in various fields such as aerospace, ... more Abstract Magnesium (Mg) alloys possess high usage prospects in various fields such as aerospace, electronics, automotive and biomedical sectors owing to properties such as excellent castability, high specific strength, low density etc. However, such materials are prone to corrosion and wear due to the heat produced in the areas of application. This paper addresses the usage of sol–gel-based technique to develop coatings made of Alumina (Al2O3) and Ceria (CeO2) over alloy Mg AZ91. These additive materials exhibit exceptional resistance to wear and corrosion. Further, the study investigates the role of CeO2 doping in Al2O3 coating. The surface properties are assessed using scanning electron microscope. Density, porosity, corrosion and thermal properties of the coating are measured and the feasibility of using sol–gel route for developing corrosion resistant coatings is examined.

International Journal of Mechanical Engineering and Robotics Research, 2022

Many vehicle systems and industrial equipment face the issue of vibrations. As such, vibration co... more Many vehicle systems and industrial equipment face the issue of vibrations. As such, vibration control devices like classical hydraulic dampers are utilized to minimize vibrations. In this context, magenetorheological fluid is introduced as a damper fluid to improve the damper's vibration reduction capability. This damper is known as the MR damper in which the magnetic field required to activate MR fluid is produced by using an electromagnet over the piston inside the damper cylinder. However, some severe problems are observed due to internal electromagnetic piston configuration in the conventional MR damper. Therefore, modification is suggested in the damper in the form of an external permanent magnet assembly's fitment.The proposed model consists of a damper cylinder filled with MR fluid and an external assembly of permanent magnets positioned near the cylinder. The conventional and modified MR dampers have been tested on a test rig by changing the MR fluid configuration, excitation frequency of exciter, and excitation current. The MR effect on velocity and damping force in conventional and modified dampers has been recorded and compared. The results convincingly indicate that the modified MR damper delivers good performance by generating sufficient damping capacity that can be utilized for necessary applications. Importantly, it resolves the problems associated with conventional MR dampers like electric current unavailability at field, clumping, hard cake formation, remanence phenomenon, and excessive heat formation. Index Terms-Magnetorheological Damper (MR damper); Magnetorheological Fluid (MR fluid/MRF), force-velocity characteristics, external permanent magnet, excitation current and frequency I. INTRODUCTION Vibration control technology has remained a challenging area of study for many engineers and researchers. Civil structures, vehicle systems, industrial equipment, etc., have been facing the problem of Manuscript

Alloy Steel - Properties and Use, InTech Open, 2011

Journal of PeriAnesthesia Nursing, 2002

Recent patents on engineering, 2024

In the domain of industrial building and production technology, the welding of dissimilar materia... more In the domain of industrial building and production technology, the welding of dissimilar materials finds a wide range of applications. Unique properties of different materials are utilized to produce addition and cost effectiveness of the product for intended applications. For determining
the feasibility of welding of dissimilar metals together to create a strong joint, a number of factors need to be taken into account. This paper discusses critical factors and conditions for welding of dissimilar metals and touches upon the practical challenges arising from different physical
and chemical properties of the metals. It presents the latest and pertinent literature dealing with the details about the current fusion and non-fusion processes employed for welding common dissimilar metal combinations. The results suggest that research and development in the field of dissimilar metal welding is still needed, especially in light of the growing need for customized materials in contemporary engineering and industrial applications

IOSR, Journal of mechanical and civil engineering, 2024

The field and scope of composites is constantly widening with the introduction of new materials a... more The field and scope of composites is constantly widening with the introduction of new materials and manufacturing technologies. Unknown properties of different engineering, non-engineering and bio-materials are regularly explored for the development of modern composites that show immense potential in future for applications in domestic, automotive, defence and aerospace industries. Some fundamental aspects, processing techniques, properties and applications of such composites are reviewed in the paper.

The primary purpose of the book is to present the models, both theoretical and numerical, for inv... more The primary purpose of the book is to present the models, both theoretical and numerical, for investigation of the mechanisms of crack tip stress amplification, shielding and fiber bridging in Type I and Type II fiber metal laminates under the influence of residual stresses that are generated due to curing during fabrication of the laminates. The models are well validated by experiments.

Advances in explosive welding of dissimilar metals: A mini literature survey, 2024

Explosive welding, which has emerged as a promising field of research in the recent past, is a so... more Explosive welding, which has emerged as a promising field of research in the recent past, is a solid-state welding process that uses controlled explosive detonation to join two pieces of metal. A flyer plate collides with the base plate at high velocity, leading to significant local plastic deformation at the interface of the metals, resulting in a metallurgical bond between the metals. A high-velocity jet is formed in the process that eliminates the contaminants on the metal surfaces. Explosive welding can join materials that are similar or different. Some of the recent and important research work pertaining to explosive welding of dissimilar metals is briefly reviewed in this paper. Various aspects of the explosive welding process have been touched upon. A study of several parameters involved in the welding process is undertaken.

European Journal of Mechanics A-solids, 2014

ABSTRACT Glare, a fibre metal laminate (FML), consists of several thin 2014-T6 aerospace aluminiu... more ABSTRACT Glare, a fibre metal laminate (FML), consists of several thin 2014-T6 aerospace aluminium alloy layers alternately bonded with E-glass fibre based composite prepregs in the present work. As cracked Glare is subjected to load, load or fibre bridging over cracks in soft aluminium layers causes diversion of load away from the cracks towards stronger intact fibres in the prepregs resulting in stress reduction or shielding effect at the crack tips. Fibre bridging diminishes if delaminations, caused by the development of interfacial cracks at the interfaces of aluminium and fibre layers, exist in the laminate. The paper investigates the cracked but non-delaminated Glare containing normal Mode I cracks in all its aluminium layers. Different crack lengths are considered in the laminates to examine the influence of crack size over bridging. A theoretical model is presented to determine fibre bridging stress for estimation of fibre bridging stress intensity parameter that quantifies the effect of bridging in the laminate. Crack tip stress intensity parameter is also found. The model is successfully validated by undertaking finite element analysis of series of un-identically cracked Glare laminates without delaminations under critical or fracture loads that are obtained experimentally by subjecting the laminates to load-extension test. Plain aerospace aluminium alloy specimens are also tested for fracture. Fracture toughness values of the laminates are seen to be significantly higher than that of plain aluminium specimens. The phenomenon of fibre bridging in the laminates is well substantiated and quantified by all the adopted procedures.

11TH INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2013: ICNAAM 2013, 2013

ABSTRACT A finite element examination of the effect of delaminations on fracture characteristics ... more ABSTRACT A finite element examination of the effect of delaminations on fracture characteristics of fibre metal laminate (Glare), by comparing energy release rates of normal cracks in laminates with and without delaminations, is presented in the paper. Glare comprising thin cracked 2024-T3 aerospace aluminum alloy layers alternately bonded with E-glass fibre based composite prepregs is considered for the analysis. Delaminations are modeled with interface cohesive elements. Energy release rates of normal cracks in laminates with delaminations are found to be higher than those in the laminates without delaminations.

Advanced Materials Research, Aug 1, 2013

The paper presents the stress field, obtained with the help of finite element method, around Mode... more The paper presents the stress field, obtained with the help of finite element method, around Mode I crack tip in ductile steel under EPFM regime. Process, plastic and non-K compliant elastic zones develop. Void nucleation ahead of the crack tip is observed in the process zone. The stress solution in the plastic zone is validated with theoretical HRR solution. In the elastic zone, as expected, substantial error is observed between K dominated LEFM solution and numerical EPFM values.Nomenclature

Acta Mechanica, Jul 25, 2010

The stress field around the crack tip near an elastically matched but strength-mismatched interfa... more The stress field around the crack tip near an elastically matched but strength-mismatched interface body in a bimetallic system is influenced when the crack tip yield or cohesive zone spreads to the interface body. The concept of crack tip stress intensity parameter, K tip , is therefore employed in fracture analysis of the bimetallic body. A computational model to determine K tip is reviewed in this paper. The model, based upon i) Westergaard's complex potentials coupled with Kolosov-Muskhelishvili's relations between a crack tip stress field and complex potentials and ii) Dugdale's representation of the cohesive zone clearly indicates shielding or amplifying effects of strength mismatch across the interface, depending upon the direction of the strength gradient, over the crack tip. The model is successfully validated by conducting series of high cycle fatigue tests over Mode I cracks advancing towards various strength-mismatched interfaces in bimetallic compact tension specimens prepared by electron beam welding of elastically identical weak ASTM 4340 alloy and strong MDN 250 maraging steels. List of symbols a Distance of crack tip from interface a * Radial coordinate of point near crack tip A Parent body/parent steel containing crack B Interface body/back up steel b Length of cohesive zone across interface c Crack length c c Crack length ahead of load axis c min Crack length required for linear elastic regime C Paris constant e, e av Percent difference between theoretical and experimental result, average of percent differences E Modulus of elasticity f (θ) A function of angle w.r.t. crack axis F Applied load i Imaginary quantity, √ −1

Applied Mechanics and Materials, 2013

The paper reviews the numerical methodology to investigate fracture parameter namely energy relea... more The paper reviews the numerical methodology to investigate fracture parameter namely energy release rate, G, of a mixed mode crack. An inclined, through, centre crack is assumed in a ductile steel plate subjected to bi-axial tension. Applied stress and crack size are suitably selected to simulate small scale yielding (SSY) condition at the crack tips. The cracked plate is modelled by finite element method. Both plane stress and plane strain situations are examined. G value is found from J integral. Equations of transformation are employed to obtain normal and shear stress in the plane of the crack. G is then again determined for Mode I and Mode II cracks by modelling each case separately. The analysis is finally validated by fulfilment of the conservation of energy release rate criterion, G (Mixed mode) = G (Mode I) + G (Mode II).

International Journal of Structural Integrity, Aug 8, 2016

Purpose – Since failure of laminated composites by delaminations is common, the purpose of this p... more Purpose – Since failure of laminated composites by delaminations is common, the purpose of this paper is to present a numerical procedure to check the stability of delaminations in fiber metal laminate (Glare), with different possible damage configurations, under uni-axial tension. Deformation behavior of the laminate is also examined. Influence of the type and the extent of damage, represented by varying sizes and number of delaminations, on delamination driving force and laminate deformation is found. Design/methodology/approach – Delaminated Glare is modeled by finite element method. Interface cohesive elements are used to model the delaminations. Finite element results provide the deflection/deformation characteristics of the laminate. Driving forces of delaminations are estimated by J integrals that are numerically obtained over cyclic paths near delamination tips. Laminates with different types of delaminations are also fabricated and externally delaminated for measurement of their interlaminar fracture toughness. The delamination is considered to be stable if its driving force is less than corresponding interlaminar fracture toughness of the laminate. Findings – Delaminations are found to be stable in laminates with lower number of delaminations and unstable in laminates with higher number of delaminations. Increase in size of delaminations increases the deformations but reduces the delamination driving force whereas increase in number of delaminations increases both deformations and driving forces. The trends change in case of laminates with symmetrical damage. Shape of delamination is also found to influence the deformations and driving forces. The finite element model is validated. Research limitations/implications – There is scope for validating the numerical results reported in the paper by theoretical models. Practical implications – Checking the stability of delaminations and their effect on deformation behavior of the laminate helps is assessment of safety and remaining life of the laminate. If failure is predicted, preemptive action is taken by using repair patch ups at identified critical locations in order to avoid failures in service conditions. Originality/value – The paper offers the following benefits: use of cohesive zone method that is readily possible in finite element procedures and is relatively simple, fast and reasonably accurate is demonstrated; suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested; and influence of the type and the extent of damage in the laminate on its deformation behavior and delamination driving forces is found. This type of work has not been reported so far.

International Journal of Mechanical and Materials Engineering, Oct 15, 2014

Notched Glare 4A-3/2 laminates, comprising thin 2014-T6 aerospace aluminum alloy sheets alternate... more Notched Glare 4A-3/2 laminates, comprising thin 2014-T6 aerospace aluminum alloy sheets alternately bonded with unidirectional E-glass fiber-based composite prepregs, are tested under tensile-tensile fatigue load with different stress ratio's ranging from 0.1 to 0.5 in ambient, aqueous, and corrosive environments in high-cycle conditions. Fatigue characteristics of the laminates are found to be influenced by the operating environment and the magnitude of stress ratio. Notched plain 2014-T6 aerospace aluminum alloy specimens are also subjected to identical cyclic stress levels as in aluminum alloy layers of the laminates for comparative analysis of their fatigue behavior with those of the laminates. Retarded crack growth rates in the laminates leading to their enhanced fatigue lives and higher cyclic fracture toughness values vis-à-vis plain specimens substantiate fiber bridging effect in the laminates.

International Journal of Structural Integrity, Apr 9, 2018

Behavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or pl... more Behavior of mode I crack tip in fiber metal laminate (FML) differs from that in homogeneous or plain specimen made of metal used in the laminate due to the load transfer effect in the laminate caused by property mismatch between dissimilar material layers. The purpose of this paper is to present a finite element investigation on the characteristics of crack tip in monotonically loaded and residually stressed FML.,Crack tip characteristics are assessed by: the sizes of various zones that form at the tip; and crack tip energy release rates. The same are found by modeling two types of Glare laminates under monotonic tension with different crack orientations in SSY regime – Type I and Type II. Residual stresses are externally introduced in the models. Delaminations are modeled by cohesive elements. Crack tip zone sizes are measured from finite element solutions. Values of J integrals are computed over cyclic paths near the crack tips. Identically cracked and loaded plain aluminum alloy specimens are also modeled for comparison.,The sizes of crack tip zones in Glare laminates are found to be different than those in plain specimens. Process zone is observed to form at crack tip in Type I laminate whereas it does not develop in Type II laminate, the reverse being true in plain specimens. Values of J integrals near crack tips are also found to deviate from those in plain specimens, higher in Type I laminate due to crack tip stress amplification and lower in Type II laminate due to stress reduction. Crack orientation decides the amplification or shielding effect in the laminate.,There is scope for validating the numerical results reported in the paper by theoretical models.,The method to quantify crack tip shielding and amplification is presented that shall be useful in checking the structural integrity/safety of the laminate during actual service conditions.,Shielding and amplification effects are explicitly described and illustrated in the paper. Suitability of using J integrals over paths crossing non-homogeneous and property mismatched material layers is tested. Use of cohesive zone method that is readily applicable in finite element procedures and is relatively simple, fast and reasonably accurate is also demonstrated.

Defect and Diffusion Forum, 2023

A mode I, centre crack, in ductile steel plate of finite dimensions is modeled in ANSYS software.... more A mode I, centre crack, in ductile steel plate of finite dimensions is modeled in ANSYS software. Non-linear stress-strain data of steel are used. Plane strain case is adopted. A suitable value of far field tensile stress (pressure) is chosen such that EPFM condition prevails at the crack tip. Process and plastic zones are obtained at the crack tip. Desired values are noted. Areas of high stress and high strain are identified. Validation of void nucleation taking place ahead of crack tip and not exactly at the crack tip and coalescence of voids happening at the crack tip are confirmed from the results. Plots between the distance of desired location from the crack tip and load line stresses and strains are drawn. The plots are in accordance with the expectations.

International Review of Mechanical Engineering, 2023

Vibrations are known to cause problems in many automotive systems and industrial equipment. There... more Vibrations are known to cause problems in many automotive systems and industrial equipment. Therefore, vibration control devices such as traditional hydraulic dampers are used to minimize the vibrations. Off late, MR dampers, in which MR fluid is used to enhance the vibration reduction performance, are introduced. An electromagnetic piston is positioned within the MR damper cylinder that creates the magnetic field necessary to operate the MR fluid. However, due to the internal electromagnetic piston arrangement in the conventional MR damper, some serious issues like remenance phenomenon, clumping and heat effect are observed. Consequently, a modified MR damper with an external permanent magnet assembly is proposed. Viability of modified MR damper concept is checked vis-à-vis conventional MR damper. After a successful check, a handy prototype of the modified MR damper is fabricated. The performance of the modified MR damper prototype is tested by changing the MR fluid configuration, the excitation frequency of exciter, the excitation current, and the magnetic flux density. A test rig is designed and fabricated for this purpose. The MR effect on velocity and damping force in the prototype is recorded and the observations are utilised in performance optimization. The Overall Evaluation criterion is employed in the optimization process with MR fluids of 76%, 80% and 82% weight percentage of ferromagnetic particles (AMT-Dampro, AMT-Magnaflo and AMT-Smartech MR fluids respectively). The regression analysis for most suitable MR fluid configuration is also undertaken. The modified MR damper prototype is found to work effectively as confirmed by optimization and regression analysis results. The idea of the modified MR damper can be suitably applied to number of existing practical systems to handle intense vibrations.

Lecture notes in mechanical engineering, Springer

A novel theoretical model for calculating the intensity of energy release rate at mode I crack ti... more A novel theoretical model for calculating the intensity of energy release rate at mode I crack tip in the bi-material has been developed. The study discusses the state at crack tip in the bi-material of identical steels connected by a thick but weaker weld inter layer of steel. In such a body, there are two interfaces: one between the stronger parent steel and the weaker weld, and another between the weaker weld and the stronger back up steel. As the fracture develops across the weld interlayer, i.e. strong-weak-strong transition, in the K dominating or SSY regime, the effect of energy transfer owing to the existence of elastically similar but strength mismatched surfaces is measured. The model accounts for non-linearity in plastic characteristics of steel. When the crack tip in parent steel faces the approaching interface of weaker weld during strong-weak transition, the rate of energy release at the crack tip is seen to be greater than the far field value. But when the tip in the weaker weld faces the interface of stronger back up steel during weak-strong transition, the tip energy release rate is reduced. When the crack tip is at the interfaces, the impact of shielding as well as amplification increases.

Materials Today: Proceedings, Elsevier

Abstract Magnesium (Mg) alloys possess high usage prospects in various fields such as aerospace, ... more Abstract Magnesium (Mg) alloys possess high usage prospects in various fields such as aerospace, electronics, automotive and biomedical sectors owing to properties such as excellent castability, high specific strength, low density etc. However, such materials are prone to corrosion and wear due to the heat produced in the areas of application. This paper addresses the usage of sol–gel-based technique to develop coatings made of Alumina (Al2O3) and Ceria (CeO2) over alloy Mg AZ91. These additive materials exhibit exceptional resistance to wear and corrosion. Further, the study investigates the role of CeO2 doping in Al2O3 coating. The surface properties are assessed using scanning electron microscope. Density, porosity, corrosion and thermal properties of the coating are measured and the feasibility of using sol–gel route for developing corrosion resistant coatings is examined.

International Journal of Mechanical Engineering and Robotics Research, 2022

Many vehicle systems and industrial equipment face the issue of vibrations. As such, vibration co... more Many vehicle systems and industrial equipment face the issue of vibrations. As such, vibration control devices like classical hydraulic dampers are utilized to minimize vibrations. In this context, magenetorheological fluid is introduced as a damper fluid to improve the damper's vibration reduction capability. This damper is known as the MR damper in which the magnetic field required to activate MR fluid is produced by using an electromagnet over the piston inside the damper cylinder. However, some severe problems are observed due to internal electromagnetic piston configuration in the conventional MR damper. Therefore, modification is suggested in the damper in the form of an external permanent magnet assembly's fitment.The proposed model consists of a damper cylinder filled with MR fluid and an external assembly of permanent magnets positioned near the cylinder. The conventional and modified MR dampers have been tested on a test rig by changing the MR fluid configuration, excitation frequency of exciter, and excitation current. The MR effect on velocity and damping force in conventional and modified dampers has been recorded and compared. The results convincingly indicate that the modified MR damper delivers good performance by generating sufficient damping capacity that can be utilized for necessary applications. Importantly, it resolves the problems associated with conventional MR dampers like electric current unavailability at field, clumping, hard cake formation, remanence phenomenon, and excessive heat formation. Index Terms-Magnetorheological Damper (MR damper); Magnetorheological Fluid (MR fluid/MRF), force-velocity characteristics, external permanent magnet, excitation current and frequency I. INTRODUCTION Vibration control technology has remained a challenging area of study for many engineers and researchers. Civil structures, vehicle systems, industrial equipment, etc., have been facing the problem of Manuscript

Alloy Steel - Properties and Use, InTech Open, 2011

Book Rivers, 2023

The book presents explicit theoretical analysis of a Mode I crack in the bimetallic body with pla... more The book presents explicit theoretical analysis of a Mode I crack in the bimetallic body with plasticity mismatch between elastically identical constituents. Emphasis is laid on the examination of crack near the bimetallic interface. The spread of crack tip plasticity across the interface and its effect on the crack tip is investigated by Dugdale’s cohesive zone model for elastic-perfectly plastic material. Analysis of cohesive zone is undertaken with the help of fundamental principles of complex potentials. Commonly encountered load regimes, viz., linear elastic, elastic plastic and high cycle fatigue regimes are modeled to obtain the crack tip stress intensity parameter. Finite element analysis of cohesive zone across the interface is also undertaken. Theoretical and numerical concepts are substantiated by experiments in high cycle fatigue regime with bimetallic specimens prepared by welding weak alloy and strong maraging steels.

Book Publisher International, 2023

The primary purpose of the book is to present the models, both theoretical and numerical, for inv... more The primary purpose of the book is to present the models, both theoretical and numerical, for investigation of the mechanisms of crack tip stress amplification, shielding and fiber bridging in Type I and Type II fiber metal laminates under the influence of residual stresses that are generated due to curing during fabrication of the laminates. The models are well validated by experiments.