Avanish Kumar - Academia.edu (original) (raw)

Papers by Avanish Kumar

Research paper thumbnail of Mechanical properties of nanostructured bainitic steels

Materialia, 2021

Abstract Nanostructured bainitic steels possess ultra-high strength and have been the focus of ex... more Abstract Nanostructured bainitic steels possess ultra-high strength and have been the focus of extensive research due to their suitability in many demanding engineering applications, especially in rail-wheel system, gears, bearings and automobile industry. The composite microstructure of nano-scaled bainitic ferrite (BF) and retained austenite (RA) balances the strength-ductility combination to reach 21% elongation for over 2.1 GPa of tensile strength. The strength mainly arises from large numbers of bainitic interfaces and adequate ductility is gained due to the softness as well as transformation-induced plasticity (TRIP) effect of RA. Moreover, recent works devoted to characterize the toughness of nanostructured bainitic steels show that a plane strain fracture toughness of 30 MPam0.5 is routinely obtained for a tensile strength of 1.5 GPa. The toughness values can be increased to as much as 128 MPam0.5 for a tensile strength of 1.6 GPa by appropriately tailoring the microstructure through specially designed thermo-mechanical heat-treatment procedures. However, excellent quasi-static properties alone do not suffice and consequences of microstructural refinement on fatigue properties should also be known for designing a damage tolerant material. Above all, a fundamental understanding of process-microstructure-property correlation in nanostructured bainitic steels is of prime importance. In this review article on the mechanical properties of nanostructured bainitic steels, we have first presented the background on development of these steels through appropriate alloy design and specific heat-treatment procedures. Moreover, the mechanism of phase-transformation and microstructure evolution has been discussed briefly. Subsequently, we have reviewed a range of original works focused on various mechanical properties including tensile properties, torsion, fracture, fatigue and wear behavior of nanostructured bainitic steels. The deformation mechanisms and mechanical properties have been shown to be primarily determined by the volume fraction, morphology and size of BF and RA as well as the alloying content of the steel.

Research paper thumbnail of Microstructural effects on the sub-critical fatigue crack growth in nano-bainite

Materials Science and Engineering: A, 2018

Bainitic transformation at low temperatures in high carbon steels leads to a dual phase nanostruc... more Bainitic transformation at low temperatures in high carbon steels leads to a dual phase nanostructure of bainitic ferrite and retained austenite. Strengths above 1 GPa can be easily achieved in these steels while also preserving significant amount of ductility. However, in order to be used in most structural applications, microstructure tailoring for high damage tolerance under fatigue loading is of utmost importance. In the current study, we have developed three distinct bainitic microstructures by austempering at 250, 300 and 350°C respectively after similar austenitization treatment. Sub-critical fatigue crack growth investigation for all the specimens has been carried out under ambient environmental conditions. It has been found that the specimen with the coarsest morphology of bainitic ferrite and retained austenite and the highest retained austenite content shows the largest crack growth threshold. Threshold has been found to be reached for the specimens when the crack tip opening displacement attains the respective bainitic lath thickness for different isothermal conditions. In Stage II, the specimens with the largest lath thickness and highest austenite content showed marginally slower crack growth rates than the other specimens. This can be attributed to transformation induced plasticity that is expected to be more severe in the specimens with the highest austenite content. The specimens transformed at the highest isothermal temperature also showed the highest plane strain fracture toughness deduced from the stress intensity value at which the crack propagates catastrophically.

Research paper thumbnail of Combining Words and Pictures for Museum Information Retrieval

2012 4th International Conference on Intelligent Human Computer Interaction (IHCI), 2012

ABSTRACT In this paper we propose the use of multilevel classification techniques similar to conc... more ABSTRACT In this paper we propose the use of multilevel classification techniques similar to concept of Bayesian belief networks for Combining Words and Pictures (Images) for Museum Information Retrieval. We have designed our own corpus on Allahabad Museum. This approach is static which allows one to compute the rank of documents of relevant words and pictures with respect to some query and a given corpus. In our case, we view combining words and pictures as a task in which a training dataset of tagged pictures is provided and we need to automatically combine the query relevant words and pictures. To do this, we first describe the picture using feature vector. We do static analysis over computed features to get distinguishing feature descriptors. Maximum similarity i.e. minimum distance allows us to find the query relevant combined pictures and associated relevant words. For textual part of the query we compute the concepts (keywords as well as synonyms of each keyword in the query and their categories). Using the concept of image hierarchy, we calculate the score of each labeled document and select top five documents with its associated pictures.

Research paper thumbnail of Mechanical properties of nanostructured bainitic steels

Materialia, 2021

Abstract Nanostructured bainitic steels possess ultra-high strength and have been the focus of ex... more Abstract Nanostructured bainitic steels possess ultra-high strength and have been the focus of extensive research due to their suitability in many demanding engineering applications, especially in rail-wheel system, gears, bearings and automobile industry. The composite microstructure of nano-scaled bainitic ferrite (BF) and retained austenite (RA) balances the strength-ductility combination to reach 21% elongation for over 2.1 GPa of tensile strength. The strength mainly arises from large numbers of bainitic interfaces and adequate ductility is gained due to the softness as well as transformation-induced plasticity (TRIP) effect of RA. Moreover, recent works devoted to characterize the toughness of nanostructured bainitic steels show that a plane strain fracture toughness of 30 MPam0.5 is routinely obtained for a tensile strength of 1.5 GPa. The toughness values can be increased to as much as 128 MPam0.5 for a tensile strength of 1.6 GPa by appropriately tailoring the microstructure through specially designed thermo-mechanical heat-treatment procedures. However, excellent quasi-static properties alone do not suffice and consequences of microstructural refinement on fatigue properties should also be known for designing a damage tolerant material. Above all, a fundamental understanding of process-microstructure-property correlation in nanostructured bainitic steels is of prime importance. In this review article on the mechanical properties of nanostructured bainitic steels, we have first presented the background on development of these steels through appropriate alloy design and specific heat-treatment procedures. Moreover, the mechanism of phase-transformation and microstructure evolution has been discussed briefly. Subsequently, we have reviewed a range of original works focused on various mechanical properties including tensile properties, torsion, fracture, fatigue and wear behavior of nanostructured bainitic steels. The deformation mechanisms and mechanical properties have been shown to be primarily determined by the volume fraction, morphology and size of BF and RA as well as the alloying content of the steel.

Research paper thumbnail of Microstructural effects on the sub-critical fatigue crack growth in nano-bainite

Materials Science and Engineering: A, 2018

Bainitic transformation at low temperatures in high carbon steels leads to a dual phase nanostruc... more Bainitic transformation at low temperatures in high carbon steels leads to a dual phase nanostructure of bainitic ferrite and retained austenite. Strengths above 1 GPa can be easily achieved in these steels while also preserving significant amount of ductility. However, in order to be used in most structural applications, microstructure tailoring for high damage tolerance under fatigue loading is of utmost importance. In the current study, we have developed three distinct bainitic microstructures by austempering at 250, 300 and 350°C respectively after similar austenitization treatment. Sub-critical fatigue crack growth investigation for all the specimens has been carried out under ambient environmental conditions. It has been found that the specimen with the coarsest morphology of bainitic ferrite and retained austenite and the highest retained austenite content shows the largest crack growth threshold. Threshold has been found to be reached for the specimens when the crack tip opening displacement attains the respective bainitic lath thickness for different isothermal conditions. In Stage II, the specimens with the largest lath thickness and highest austenite content showed marginally slower crack growth rates than the other specimens. This can be attributed to transformation induced plasticity that is expected to be more severe in the specimens with the highest austenite content. The specimens transformed at the highest isothermal temperature also showed the highest plane strain fracture toughness deduced from the stress intensity value at which the crack propagates catastrophically.

Research paper thumbnail of Combining Words and Pictures for Museum Information Retrieval

2012 4th International Conference on Intelligent Human Computer Interaction (IHCI), 2012

ABSTRACT In this paper we propose the use of multilevel classification techniques similar to conc... more ABSTRACT In this paper we propose the use of multilevel classification techniques similar to concept of Bayesian belief networks for Combining Words and Pictures (Images) for Museum Information Retrieval. We have designed our own corpus on Allahabad Museum. This approach is static which allows one to compute the rank of documents of relevant words and pictures with respect to some query and a given corpus. In our case, we view combining words and pictures as a task in which a training dataset of tagged pictures is provided and we need to automatically combine the query relevant words and pictures. To do this, we first describe the picture using feature vector. We do static analysis over computed features to get distinguishing feature descriptors. Maximum similarity i.e. minimum distance allows us to find the query relevant combined pictures and associated relevant words. For textual part of the query we compute the concepts (keywords as well as synonyms of each keyword in the query and their categories). Using the concept of image hierarchy, we calculate the score of each labeled document and select top five documents with its associated pictures.