Bhagwati Prasad Kashyap

Bio: Bhagwati Prasad Kashyap is an academic researcher from Indian Institute of Technology Bombay. The author has contributed to research in topics: Strain rate & Superplasticity. The author has an hindex of 31, co-authored 148 publications receiving 2796 citations. Previous affiliations of Bhagwati Prasad Kashyap include University of Manitoba & University of California, Davis.

On the uniqueness of stress-strain rate relation for superplastic flow of the Pb-Sn eutectic

Abstract: The uniqueness of stress-strain rate relation in superplastic deformation of the Pb-Sn eutectic alloy for different grain sizes and test temperatures has been explored after subjecting the deformation processed alloy to a standard tensile prestrain. About 30 pct elongation at 421 K was found to eliminate the mechanical and microstructural instabilities that are characteristic of the as-worked material. After this prestraining, the flow stress was uniquely dependent on strain rate for a given grain size and test temperature, irrespective of the cross head speed, the path through which a particular strain rate is achieved, or the strain.

Serrated flow in a modified 9Cr-1Mo steel

Abstract: During high temperature tensile testing of a modified 9Cr-1Mo steel in tempered martensitic condition, serrated plastic flow, implying the occurrence of dynamic strain aging, was observed. The serrated stress-strain curves were unique in the sense that the serrations appeared almost at the beginning of deformation and disappeared before the ultimate strengths were attained. Moreover, the strains to the disappearance of serrations varied systematically with the test temperature and strain-rate. A brief literature survey revealed that in studies on Nickel alloys and ferritic-martensitic steels, the disappearance of serrated flow was found to be a thermally activated process and that the phenomenon manifested in the higher temperature regime by either a progressively larger strains to the onset of serrations or a progressively smaller strain to the disappearance of serrations of the flow curve. However, it appears that the type of serrated flow curves observed in this study, has not yet been reported in any other ferritic-martensitic steels. It was thus felt necessary to carry out a detailed investigation of dynamic strain aging in this steel. In this paper, the possible mechanism controlling the appearance of serrations and their disappearance of the stress-strain curves are discussed.

Stress field estimation around a semi-constrained inclusion and its validation by interpreting hydride platelet orientation around a blister in a Zr–2.5Nb alloy

Abstract: A methodology for estimating the stress field in the matrix surrounding a semi-constrained inclusion is proposed. The stress free misfit volume associated with the inclusion was partitioned into semi-constrained and constrained components. The objective was achieved by carrying out a series of sectioning, cutting and imposition of constrained misfit displacement on an imaginary notch of geometry identical to that of the inclusion–matrix contour. The stress field was computed using elastic finite element analysis for plane stress condition. The misfit displacement model thus developed was applied to compute the stress field around a hydride blister grown under controlled thermal boundary condition in Zr–2.5Nb pressure tube (PT) alloy and was validated by interpreting the hydride platelet orientation in the matrix surrounding the blister. Finally, an assessment of the structural integrity of the Zr–2.5Nb PT material containing hydride blister was made in view of this analysis.

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Mechanical Behavior of Materials

Abstract: A balanced mechanics-materials approach and coverage of the latest developments in biomaterials and electronic materials, the new edition of this popular text is the most thorough and modern book available for upper-level undergraduate courses on the mechanical behavior of materials To ensure that the student gains a thorough understanding the authors present the fundamental mechanisms that operate at micro- and nano-meter level across a wide-range of materials, in a way that is mathematically simple and requires no extensive knowledge of materials This integrated approach provides a conceptual presentation that shows how the microstructure of a material controls its mechanical behavior, and this is reinforced through extensive use of micrographs and illustrations New worked examples and exercises help the student test their understanding Further resources for this title, including lecture slides of select illustrations and solutions for exercises, are available online at wwwcambridgeorg/97800521866758

Recent developments in stainless steels

Abstract: This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Additively manufactured hierarchical stainless steels with high strength and ductility

Abstract: Many traditional approaches for strengthening steels typically come at the expense of useful ductility, a dilemma known as strength-ductility trade-off. New metallurgical processing might offer the possibility of overcoming this. Here we report that austenitic 316L stainless steels additively manufactured via a laser powder-bed-fusion technique exhibit a combination of yield strength and tensile ductility that surpasses that of conventional 316L steels. High strength is attributed to solidification-enabled cellular structures, low-angle grain boundaries, and dislocations formed during manufacturing, while high uniform elongation correlates to a steady and progressive work-hardening mechanism regulated by a hierarchically heterogeneous microstructure, with length scales spanning nearly six orders of magnitude. In addition, solute segregation along cellular walls and low-angle grain boundaries can enhance dislocation pinning and promote twinning. This work demonstrates the potential of additive manufacturing to create alloys with unique microstructures and high performance for structural applications.