Surajit Kumar Paul | Indian institute of technology (original) (raw)

Papers by Surajit Kumar Paul

Journal of Alloys and Metallurgical Systems, 2023

The influence of the central hole-edge condition on the hole expansion ratio (HER) of four automo... more The influence of the central hole-edge condition on the hole expansion ratio (HER) of four automotive-grade steel sheets is experimentally investigated in this work. The punched hole shows inferior HER for all selected automotive-grade steel sheets than the wire-electrical discharge machined (WEDM) hole. The finite element simulation approach is used to determine the influence of the coefficient of friction and spring-back on HER. With an increased coefficient of friction, the punch force increases. Material near the inner edge of the central hole comes out in the direction of the sliding punch in the presence of friction. Spring-back has a small effect on HER, and its importance increases for lesser HER materials.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2022

Hole expansion ratio (HER) is widely used to quantify the stretch-flangeability of sheet metal. H... more Hole expansion ratio (HER) is widely used to quantify the stretch-flangeability of sheet metal. HER is determined from the maximum limit of successful expansion of a central hole by a conical punch. The central hole edge is prepared by the punching process. Around 45° cracks are noticed at the central hole edge after successfully completing the hole expansion test. HER of punched hole correlates with uniaxial tensile properties like yield strength, ultimate tensile strength, total elongation, post-uniform elongation, and coefficient of normal anisotropy. Comparisons of strength (yield strength, ultimate tensile strength), anisotropy (coefficient of normal anisotropy) and deformation (total elongation, post-uniform elongation) parameters among steel grades are essential to relate HER among steel grades. Interstitial free steel is the highest, and SPFH steel is the lowest HER among the four steel grades. HER correlates nicely with the notch mouth opening displacement at peak load.

Journal of Alloys and Metallurgical Systems, 2023

This study explores the impact of pre-strain on the uniaxial tensile stress-strain behavior of ex... more This study explores the impact of pre-strain on the uniaxial tensile stress-strain behavior of extra deep drawing (EDD) steel at varying strain rates. The EDD steel blanks were subjected to a uniaxial pre-strain of 15 % in either the transverse or rolling direction. Subsequently, uniaxial tensile tests were conducted at different strain rates, both orthogonal and parallel to the initial pre-straining direction. The study also investigates the alterations in yield stress (YS), ultimate tensile strength (UTS), uniform elongation (UEL), total elongation (TEL), and strain energy absorption (SED, represented by the area under the tensile stress-strain curve) at diverse strain rates after pre-straining. The experimental findings indicate that pre-straining is advantageous for enhancing YS, UTS, and SED. However, this improvement comes at the expense of UEL or TEL. A square crush tube, which shares similarities with automotive components, was examined to assess the crash performance of several automotive structural parts during crash events. A validated constitutive model was used to predict the square tube's energy absorption and crush performance under high-velocity conditions for different pre-straining scenarios.

Theoretical and Applied Fracture Mechanics, 2023

Inherent manufacturing defects are observed in additively manufactured and casted metallic alloys... more Inherent manufacturing defects are observed in additively manufactured and casted metallic alloys. During loading, the stress concentration due to defect results in poor tensile ductility and fatigue performance. A physics-based defect tolerant design approach is used in the present work to calculate the uniaxial tensile performance of cast ADC12 Aluminum alloys. The proposed model elucidates the correlation between tensile ductility and the dimensions of material defects. It derives a material constant referred to as the critical defect size, which is determined through a combination of uniaxial tensile testing on specimens with defects and employing finite element simulations. The proposed approach calculates well the tensile properties such as complete tensile stress-strain curve, ultimate tensile strength, and uniaxial tensile elongation.

Forces in Mechanics, 2023

The primary obstacles to utilizing additively manufactured metallic alloys in industry are their ... more The primary obstacles to utilizing additively manufactured metallic alloys in industry are their inadequate ductility and manufacturing imperfections. Defects in the alloys can result in stress concentration, which can further deteriorate their tensile ductility and fatigue performance. In this study, defect tolerant design methods based on physics are explored to forecast the fatigue performance of 17-4 PH stainless steel that has been additively manufactured. A cyclic plastic zone size-based finite element approach is proposed in this work to predict the fatigue performance of additively manufactured alloys. Initially, defects will be identified from the microstructure of the material, and a finite element model will be created from the microstructure; then, a kinematic hardening model will be used to determine the size of cyclic plastic zone around all defects. The largest size of cyclic plastic zone will cause failure and be identified as a killer defect, and the fatigue life will be calculated on the basis of that killer defect. The proposed method predicts the fatigue life of additively manufactured alloys well.

Materialia, 2021

This study aims to improve the mechanical properties of pre-strained steel specimens by applying ... more This study aims to improve the mechanical properties of pre-strained steel specimens by applying pulsed electric current. Initial damage in steel specimens is introduced utilizing uniaxial tensile pre-straining. The damaged specimens are treated with pulsed electric current using different electro-pulsing parameters. Electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and scanning electron microscopy (SEM) are used to observe and quantify the change in microstructure before and after the application of pulsed electric current. The experimental results indicate that the electro-pulsing parameters play a crucial role in damage recovery. A small change in the pulse duration shows a high impact on the tensile properties of pre-strained specimens. Damage healing and mechanical properties improvement are observed due to Joule heating, thermal compressive stress, annihilation of dislocations, and collapse of microvoids.

Materialia, 2020

This study aims to the fatigue crack healing in a steel specimen by the application of pulsed ele... more This study aims to the fatigue crack healing in a steel specimen by the application of pulsed electric current. The initial crack in the specimen is introduced by means of notch fatigue test. Electron backscatter diffraction and scanning electron microscopy are used to observe and quantify the change in microstructure before and after the electro-pulsing treatment. The study indicates that with suitable electro-pulsing parameters, a complete crack healing could be achieved. The region reasonably far away from the crack shows no impact of electro-pulsing on microstructure. The possible reasons behind fatigue crack healing could be Joule heating, thermal compressive stress, and micro-welding.

Advances in Industrial and Manufacturing Engineering, 2021

Abstract Sheet metal forming industry widely adopted the forming limit curve (FLC) as a limiting ... more Abstract Sheet metal forming industry widely adopted the forming limit curve (FLC) as a limiting criterion in sheet metal forming. Regardless of its commercial importance, controlling factors of FLC are not systematically investigated up to date. The present paper comprehensively discussed the effect of different influencing factors on FLC, including limiting strain determination method, punch geometry, microstructure, pre-straining path, strain rate, and temperature. Different tensile properties and their correlations with FLC are also investigated. The introduction of microstructural features such as reducing void nucleation sites i.e., non-coherent particles, evenly distribution of fine hard phases, the introduction of twin and transformation induced plasticity (TRIP & TWIP), are favourable for higher FLC.

Transactions of the Indian Institute of Metals, 2021

Hole expansion ratio (HER) is extensively used in the sheet metal forming industry to assess the ... more Hole expansion ratio (HER) is extensively used in the sheet metal forming industry to assess the sheet metal’s stretch-frangibility limit. Cold-rolled dual-phase steel (DP 590) showed planar anisotropy during the uniaxial tensile test. Hill-48 yield criterion was selected to represent the planar anisotropy of DP 590 steel sheet. Material constants i.e. anisotropic yield stress ratios of Hill-48 yield criterion were calculated from the r -values (Lankford coefficient) determined from the uniaxial tensile test. The finite element simulation result showed that the thickness reduction was maximum at 45° to rolling direction during hole expansion, and a crack was visible in the same location during hole expansion experimentation. HER of DP 590 steel and crack location were successfully predicted from the finite element model for Wire-Electrical Discharge Machine cut central hole edge in the present work.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2021

In the present study, the bake hardening (BH 240) steel sheet’s formability behavior is studied e... more In the present study, the bake hardening (BH 240) steel sheet’s formability behavior is studied experimentally based on the Nakajima test method. A forming limit diagram is successfully constructed using universal sheet metal forming machine by offline measuring the strains of deformed specimens. In-process strain measurement based on a digital image correlation technique is also performed for a few selected samples to compare the results with manual strain measurement techniques. All the deformed specimens are also characterized to correlate the sample geometries with hardness values and microstructure. It is observed that the hardness value gradually decreases with an increase in sample width for all the deformed specimens up to the width of 150 mm, except for full-width sample of 200 mm. Microstructural analysis reveals that the morphology of ferrite grains changes with the sample geometry in all the deformed specimens. Microstructural characterization at the top surface of the s...

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2020

Alteration of forming and failure limits due to planar anisotropy of the sheet metal significantl... more Alteration of forming and failure limits due to planar anisotropy of the sheet metal significantly affects the safe forming operation region and finally successfully manufacturing of a sheet metal formed component. This article presents the effect of planar anisotropy on uniaxial tensile properties, forming and failure limits of cold-rolled ferritic and dual-phase steels. In-situ three dimensional digital image correlation technique is used to measure the evolution of local strain components during uniaxial tensile test. For both the steels, necking limit is highest for the specimen at an orientation of 90° to rolling direction, while failure limit is highest for those specimen whose orientation is 45° to rolling direction for ferritic steel, and both 0° and 90° to rolling direction for dual-phase steel. Uniaxial tensile deformation path for ferritic steel holds lower slope than dual-phase steel as depicted in major versus minor strain plot.

Sādhanā, 2020

Deformation band localization modes, uniform tensile strength, and uniform elongation of Ferrite-... more Deformation band localization modes, uniform tensile strength, and uniform elongation of Ferrite-Martensite Dual-Phase (DP) steels are analyzed by finite element (FE) study. Treating the microstructure inhomogeneity as the sole cause of imperfection, failure initiation is predicted as the natural fallout of plastic instability caused by load drop because of localized plastic strain in the Representative Volume Element (RVE) during straining. Strain partitioning between two phases (ferrite matrix and martensite island) are investigated on RVEs, and it reveals that the increase of martensite yield stress decreases the plastic deformation and increases the stress state in martensite. Whereas, a decrease in martensite island volume fraction (V m) results in the reduction of plastic deformation and stress state in the island. Studies are then carried out to investigate the effects of the ferrite-martensite flow properties and martensite volume fraction on the macroscopic tensile deformation behavior and band localization of DP steels. Micromechanical based FE simulation results emphasize that an increase in initial yield strength and volume fraction of martensite increases the ultimate tensile stress (UTS) with the decrease in uniform elongation. Similarly, as the hardening rate of ferrite increases, it increases the ultimate tensile stress (UTS) and uniform elongation. Additionally, deformation band localization modes alter from inclined to perpendicular to the loading axis with an increase in martensite volume fraction and initial yield strength of martensite. The knowledge of this work can be used to design DP steels with desired mechanical properties.

Materials Today Communications, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Fatigue & Fracture of Engineering Materials & Structures, 2020

The present aim of this paper is to predict the cornering fatigue life of a wheel disc through a ... more The present aim of this paper is to predict the cornering fatigue life of a wheel disc through a preformed bend DP600 steel specimen. To accomplish this objective, a newly designed preformed specimen with a bend radius equivalent to the weakest section of the wheel disc is fabricated by stamping operation followed by load-controlled high-cycle fatigue tests. Finite element (FE) simulation of stamping operation shows that an equivalent strain of 13% is induced to the bend specimen. Preformed bend specimen exhibits less fatigue resistance than the prestrained straight specimen for the same equivalent prestrain. A combined state of loading induces multiaxial stress state, giving rise to asymmetry of stresses along the thickness at the bend root of the DP600 steel specimen. Distribution of equivalent plastic strain and stress triaxiality from FE simulation indicates that fatigue crack occurs at the centre of the inner fibre of the bend root.

Materialia, 2020

Cyclic plastic deformation is an essential condition for fatigue crack initiation. The experiment... more Cyclic plastic deformation is an essential condition for fatigue crack initiation. The experimental result shows that the cyclic plastic deformation takes place at the micro-level for applied stress amplitude equal to the cyclic yield stress of the metal. Physics of fatigue crack initiation justifies the fatigue crack initiation in cyclic yield stress, which is far below the tensile yield stress of the metal. Cyclic yield stress is determined from a stable stress-strain hysteresis loop of low cycle fatigue test. The author demonstrates from the experimental result of different metals collected from the literature that endurance limit and cyclic yield stress are alike.

CIRP Journal of Manufacturing Science and Technology, 2020

Friction stir welding (FSW) is generally associated with a gradient in plastic deformation and te... more Friction stir welding (FSW) is generally associated with a gradient in plastic deformation and temperature, which results in the evolution of heterogeneous microstructure thereby, the variation of mechanical properties along the weld. It becomes critical to study this variation in mechanical properties to understand the mechanism involved in the failure of the FSW joints. In the present study, the local strain response is investigated using digital image correlation (DIC) for FSW joints of similar AA6061-AA6061 and dissimilar AA6061-AA7075 alloys (placing AA6061-T6 and AA7075-T6 in advancing and retreating side respectively). Local strain evaluated through DIC revealed the localization of strain at the heat-affected zone (HAZ) in similar FSW joint and joint failed from the HAZ. Opposing to this, in dissimilar FSW joint the localization of strain occurs at two sections, in HAZ and at the stir zone (SZ) edge in the advancing side (AS) of the joint. However, the failure occurred at SZ edge containing defects such as microvoids. On the other hand, dissimilar FSW joint without defects failed from HAZ in AS of the joint. The microhardness measurement revealed low hardness in HAZ of the weld. Notch tensile tests are carried out to allow the failure to occur in different zones found in the similar and dissimilar FSW joint. The HAZ in a similar FSW has shown the least resistance to failure induced by the notch. Fractography of the similar FSW joint revealed a ductile failure. However, the fractography of dissimilar FSW suggested a failure affected by defects and weak bonding at SZ edge in AS.

Theoretical and Applied Fracture Mechanics, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Materials Research Express, 2019

Results in Materials, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Manufacturing Letters, 2019

Hole expansion ratio (HER) is widely used to represent stretch-flangeability of sheet metal. The ... more Hole expansion ratio (HER) is widely used to represent stretch-flangeability of sheet metal. The state of stress at the edge of central hole is uniaxial tensile in nature during hole expansion test (HET). The strain/deformation is uniform throughout the width of the sample prior to the commencement of necking in a tensile test specimen. However, finite element investigation confirms the presence of prominent strain/ deformation gradient in HET sample. Only one free edge i.e. central hole edge presents in HET sample. These two effects are responsible for the higher HER than the uniaxial tensile total elongation of the material.

Journal of Alloys and Metallurgical Systems, 2023

The influence of the central hole-edge condition on the hole expansion ratio (HER) of four automo... more The influence of the central hole-edge condition on the hole expansion ratio (HER) of four automotive-grade steel sheets is experimentally investigated in this work. The punched hole shows inferior HER for all selected automotive-grade steel sheets than the wire-electrical discharge machined (WEDM) hole. The finite element simulation approach is used to determine the influence of the coefficient of friction and spring-back on HER. With an increased coefficient of friction, the punch force increases. Material near the inner edge of the central hole comes out in the direction of the sliding punch in the presence of friction. Spring-back has a small effect on HER, and its importance increases for lesser HER materials.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2022

Hole expansion ratio (HER) is widely used to quantify the stretch-flangeability of sheet metal. H... more Hole expansion ratio (HER) is widely used to quantify the stretch-flangeability of sheet metal. HER is determined from the maximum limit of successful expansion of a central hole by a conical punch. The central hole edge is prepared by the punching process. Around 45° cracks are noticed at the central hole edge after successfully completing the hole expansion test. HER of punched hole correlates with uniaxial tensile properties like yield strength, ultimate tensile strength, total elongation, post-uniform elongation, and coefficient of normal anisotropy. Comparisons of strength (yield strength, ultimate tensile strength), anisotropy (coefficient of normal anisotropy) and deformation (total elongation, post-uniform elongation) parameters among steel grades are essential to relate HER among steel grades. Interstitial free steel is the highest, and SPFH steel is the lowest HER among the four steel grades. HER correlates nicely with the notch mouth opening displacement at peak load.

Journal of Alloys and Metallurgical Systems, 2023

This study explores the impact of pre-strain on the uniaxial tensile stress-strain behavior of ex... more This study explores the impact of pre-strain on the uniaxial tensile stress-strain behavior of extra deep drawing (EDD) steel at varying strain rates. The EDD steel blanks were subjected to a uniaxial pre-strain of 15 % in either the transverse or rolling direction. Subsequently, uniaxial tensile tests were conducted at different strain rates, both orthogonal and parallel to the initial pre-straining direction. The study also investigates the alterations in yield stress (YS), ultimate tensile strength (UTS), uniform elongation (UEL), total elongation (TEL), and strain energy absorption (SED, represented by the area under the tensile stress-strain curve) at diverse strain rates after pre-straining. The experimental findings indicate that pre-straining is advantageous for enhancing YS, UTS, and SED. However, this improvement comes at the expense of UEL or TEL. A square crush tube, which shares similarities with automotive components, was examined to assess the crash performance of several automotive structural parts during crash events. A validated constitutive model was used to predict the square tube's energy absorption and crush performance under high-velocity conditions for different pre-straining scenarios.

Theoretical and Applied Fracture Mechanics, 2023

Inherent manufacturing defects are observed in additively manufactured and casted metallic alloys... more Inherent manufacturing defects are observed in additively manufactured and casted metallic alloys. During loading, the stress concentration due to defect results in poor tensile ductility and fatigue performance. A physics-based defect tolerant design approach is used in the present work to calculate the uniaxial tensile performance of cast ADC12 Aluminum alloys. The proposed model elucidates the correlation between tensile ductility and the dimensions of material defects. It derives a material constant referred to as the critical defect size, which is determined through a combination of uniaxial tensile testing on specimens with defects and employing finite element simulations. The proposed approach calculates well the tensile properties such as complete tensile stress-strain curve, ultimate tensile strength, and uniaxial tensile elongation.

Forces in Mechanics, 2023

The primary obstacles to utilizing additively manufactured metallic alloys in industry are their ... more The primary obstacles to utilizing additively manufactured metallic alloys in industry are their inadequate ductility and manufacturing imperfections. Defects in the alloys can result in stress concentration, which can further deteriorate their tensile ductility and fatigue performance. In this study, defect tolerant design methods based on physics are explored to forecast the fatigue performance of 17-4 PH stainless steel that has been additively manufactured. A cyclic plastic zone size-based finite element approach is proposed in this work to predict the fatigue performance of additively manufactured alloys. Initially, defects will be identified from the microstructure of the material, and a finite element model will be created from the microstructure; then, a kinematic hardening model will be used to determine the size of cyclic plastic zone around all defects. The largest size of cyclic plastic zone will cause failure and be identified as a killer defect, and the fatigue life will be calculated on the basis of that killer defect. The proposed method predicts the fatigue life of additively manufactured alloys well.

Materialia, 2021

This study aims to improve the mechanical properties of pre-strained steel specimens by applying ... more This study aims to improve the mechanical properties of pre-strained steel specimens by applying pulsed electric current. Initial damage in steel specimens is introduced utilizing uniaxial tensile pre-straining. The damaged specimens are treated with pulsed electric current using different electro-pulsing parameters. Electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and scanning electron microscopy (SEM) are used to observe and quantify the change in microstructure before and after the application of pulsed electric current. The experimental results indicate that the electro-pulsing parameters play a crucial role in damage recovery. A small change in the pulse duration shows a high impact on the tensile properties of pre-strained specimens. Damage healing and mechanical properties improvement are observed due to Joule heating, thermal compressive stress, annihilation of dislocations, and collapse of microvoids.

Materialia, 2020

This study aims to the fatigue crack healing in a steel specimen by the application of pulsed ele... more This study aims to the fatigue crack healing in a steel specimen by the application of pulsed electric current. The initial crack in the specimen is introduced by means of notch fatigue test. Electron backscatter diffraction and scanning electron microscopy are used to observe and quantify the change in microstructure before and after the electro-pulsing treatment. The study indicates that with suitable electro-pulsing parameters, a complete crack healing could be achieved. The region reasonably far away from the crack shows no impact of electro-pulsing on microstructure. The possible reasons behind fatigue crack healing could be Joule heating, thermal compressive stress, and micro-welding.

Advances in Industrial and Manufacturing Engineering, 2021

Abstract Sheet metal forming industry widely adopted the forming limit curve (FLC) as a limiting ... more Abstract Sheet metal forming industry widely adopted the forming limit curve (FLC) as a limiting criterion in sheet metal forming. Regardless of its commercial importance, controlling factors of FLC are not systematically investigated up to date. The present paper comprehensively discussed the effect of different influencing factors on FLC, including limiting strain determination method, punch geometry, microstructure, pre-straining path, strain rate, and temperature. Different tensile properties and their correlations with FLC are also investigated. The introduction of microstructural features such as reducing void nucleation sites i.e., non-coherent particles, evenly distribution of fine hard phases, the introduction of twin and transformation induced plasticity (TRIP & TWIP), are favourable for higher FLC.

Transactions of the Indian Institute of Metals, 2021

Hole expansion ratio (HER) is extensively used in the sheet metal forming industry to assess the ... more Hole expansion ratio (HER) is extensively used in the sheet metal forming industry to assess the sheet metal’s stretch-frangibility limit. Cold-rolled dual-phase steel (DP 590) showed planar anisotropy during the uniaxial tensile test. Hill-48 yield criterion was selected to represent the planar anisotropy of DP 590 steel sheet. Material constants i.e. anisotropic yield stress ratios of Hill-48 yield criterion were calculated from the r -values (Lankford coefficient) determined from the uniaxial tensile test. The finite element simulation result showed that the thickness reduction was maximum at 45° to rolling direction during hole expansion, and a crack was visible in the same location during hole expansion experimentation. HER of DP 590 steel and crack location were successfully predicted from the finite element model for Wire-Electrical Discharge Machine cut central hole edge in the present work.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2021

In the present study, the bake hardening (BH 240) steel sheet’s formability behavior is studied e... more In the present study, the bake hardening (BH 240) steel sheet’s formability behavior is studied experimentally based on the Nakajima test method. A forming limit diagram is successfully constructed using universal sheet metal forming machine by offline measuring the strains of deformed specimens. In-process strain measurement based on a digital image correlation technique is also performed for a few selected samples to compare the results with manual strain measurement techniques. All the deformed specimens are also characterized to correlate the sample geometries with hardness values and microstructure. It is observed that the hardness value gradually decreases with an increase in sample width for all the deformed specimens up to the width of 150 mm, except for full-width sample of 200 mm. Microstructural analysis reveals that the morphology of ferrite grains changes with the sample geometry in all the deformed specimens. Microstructural characterization at the top surface of the s...

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2020

Alteration of forming and failure limits due to planar anisotropy of the sheet metal significantl... more Alteration of forming and failure limits due to planar anisotropy of the sheet metal significantly affects the safe forming operation region and finally successfully manufacturing of a sheet metal formed component. This article presents the effect of planar anisotropy on uniaxial tensile properties, forming and failure limits of cold-rolled ferritic and dual-phase steels. In-situ three dimensional digital image correlation technique is used to measure the evolution of local strain components during uniaxial tensile test. For both the steels, necking limit is highest for the specimen at an orientation of 90° to rolling direction, while failure limit is highest for those specimen whose orientation is 45° to rolling direction for ferritic steel, and both 0° and 90° to rolling direction for dual-phase steel. Uniaxial tensile deformation path for ferritic steel holds lower slope than dual-phase steel as depicted in major versus minor strain plot.

Sādhanā, 2020

Deformation band localization modes, uniform tensile strength, and uniform elongation of Ferrite-... more Deformation band localization modes, uniform tensile strength, and uniform elongation of Ferrite-Martensite Dual-Phase (DP) steels are analyzed by finite element (FE) study. Treating the microstructure inhomogeneity as the sole cause of imperfection, failure initiation is predicted as the natural fallout of plastic instability caused by load drop because of localized plastic strain in the Representative Volume Element (RVE) during straining. Strain partitioning between two phases (ferrite matrix and martensite island) are investigated on RVEs, and it reveals that the increase of martensite yield stress decreases the plastic deformation and increases the stress state in martensite. Whereas, a decrease in martensite island volume fraction (V m) results in the reduction of plastic deformation and stress state in the island. Studies are then carried out to investigate the effects of the ferrite-martensite flow properties and martensite volume fraction on the macroscopic tensile deformation behavior and band localization of DP steels. Micromechanical based FE simulation results emphasize that an increase in initial yield strength and volume fraction of martensite increases the ultimate tensile stress (UTS) with the decrease in uniform elongation. Similarly, as the hardening rate of ferrite increases, it increases the ultimate tensile stress (UTS) and uniform elongation. Additionally, deformation band localization modes alter from inclined to perpendicular to the loading axis with an increase in martensite volume fraction and initial yield strength of martensite. The knowledge of this work can be used to design DP steels with desired mechanical properties.

Materials Today Communications, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Fatigue & Fracture of Engineering Materials & Structures, 2020

The present aim of this paper is to predict the cornering fatigue life of a wheel disc through a ... more The present aim of this paper is to predict the cornering fatigue life of a wheel disc through a preformed bend DP600 steel specimen. To accomplish this objective, a newly designed preformed specimen with a bend radius equivalent to the weakest section of the wheel disc is fabricated by stamping operation followed by load-controlled high-cycle fatigue tests. Finite element (FE) simulation of stamping operation shows that an equivalent strain of 13% is induced to the bend specimen. Preformed bend specimen exhibits less fatigue resistance than the prestrained straight specimen for the same equivalent prestrain. A combined state of loading induces multiaxial stress state, giving rise to asymmetry of stresses along the thickness at the bend root of the DP600 steel specimen. Distribution of equivalent plastic strain and stress triaxiality from FE simulation indicates that fatigue crack occurs at the centre of the inner fibre of the bend root.

Materialia, 2020

Cyclic plastic deformation is an essential condition for fatigue crack initiation. The experiment... more Cyclic plastic deformation is an essential condition for fatigue crack initiation. The experimental result shows that the cyclic plastic deformation takes place at the micro-level for applied stress amplitude equal to the cyclic yield stress of the metal. Physics of fatigue crack initiation justifies the fatigue crack initiation in cyclic yield stress, which is far below the tensile yield stress of the metal. Cyclic yield stress is determined from a stable stress-strain hysteresis loop of low cycle fatigue test. The author demonstrates from the experimental result of different metals collected from the literature that endurance limit and cyclic yield stress are alike.

CIRP Journal of Manufacturing Science and Technology, 2020

Friction stir welding (FSW) is generally associated with a gradient in plastic deformation and te... more Friction stir welding (FSW) is generally associated with a gradient in plastic deformation and temperature, which results in the evolution of heterogeneous microstructure thereby, the variation of mechanical properties along the weld. It becomes critical to study this variation in mechanical properties to understand the mechanism involved in the failure of the FSW joints. In the present study, the local strain response is investigated using digital image correlation (DIC) for FSW joints of similar AA6061-AA6061 and dissimilar AA6061-AA7075 alloys (placing AA6061-T6 and AA7075-T6 in advancing and retreating side respectively). Local strain evaluated through DIC revealed the localization of strain at the heat-affected zone (HAZ) in similar FSW joint and joint failed from the HAZ. Opposing to this, in dissimilar FSW joint the localization of strain occurs at two sections, in HAZ and at the stir zone (SZ) edge in the advancing side (AS) of the joint. However, the failure occurred at SZ edge containing defects such as microvoids. On the other hand, dissimilar FSW joint without defects failed from HAZ in AS of the joint. The microhardness measurement revealed low hardness in HAZ of the weld. Notch tensile tests are carried out to allow the failure to occur in different zones found in the similar and dissimilar FSW joint. The HAZ in a similar FSW has shown the least resistance to failure induced by the notch. Fractography of the similar FSW joint revealed a ductile failure. However, the fractography of dissimilar FSW suggested a failure affected by defects and weak bonding at SZ edge in AS.

Theoretical and Applied Fracture Mechanics, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Materials Research Express, 2019

Results in Materials, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Manufacturing Letters, 2019

Hole expansion ratio (HER) is widely used to represent stretch-flangeability of sheet metal. The ... more Hole expansion ratio (HER) is widely used to represent stretch-flangeability of sheet metal. The state of stress at the edge of central hole is uniaxial tensile in nature during hole expansion test (HET). The strain/deformation is uniform throughout the width of the sample prior to the commencement of necking in a tensile test specimen. However, finite element investigation confirms the presence of prominent strain/ deformation gradient in HET sample. Only one free edge i.e. central hole edge presents in HET sample. These two effects are responsible for the higher HER than the uniaxial tensile total elongation of the material.