Resume

• 2011

  Master of Science (MS)

  Problems-in-lieu-of-thesis entitled \"From Newton's Universal Gravitation to Einstein's Geometric Theory of Gravity\".\nMajor Professor: Dr. Donald Kobe

  Physics

  The Honor Society of Phi Kappa Phi

  Alpha Chi National College Honor Society

  University of North Texas

• 2009

  Doctor of Philosophy (PhD)

  Dissertation entitled \"Mechanics and mechanisms of creep and ductile fracture\".\nDoctoral adviser: Dr. Alan Needleman

  Materials Science and Engineering

  The Honor Society of Phi Kappa Phi

  Alpha Chi National College Honor Society

  Exceptional Engineers-Volunteer Tutor

  ASME

  ASM Material Advantage

  University of North Texas

  Master of Science (MS)

  Thesis entitled “Void Growth and Collapse in a Creeping Single Crystal”.\nThesis Adviser: Dr. Alan Needleman

  Materials Science and Engineering

  The Honor Society of Phi Kappa Phi

  ASM Material Advantage

  University of North Texas

• 2007

  Post Graduate Diploma

  Thesis entitled \"Plastic collapse and J-integral estimation of part-through circumferential cracks at intrados in pipe bends under in-plane bending moment\".\nMentor: Dr. K.M. Prabhakaran\nTraining School Batch # 51.\nRelevant Courses: Computational and Experimental Mechanics; Fracture and Damage Mechanics; Finite Element Method; Computational Fluid Dynamics; Materials and Corrosion; Nuclear Physics and Engineering; ASME (Design Codes) Section III

  VIII

  XI.

  Engineering Sciences

  Library Resource Management

  Bhabha Atomic Research Centre Training School

• 2003

  Bachelor of Technology (BTech)

  Mechanical Engineering

  Institution of Engineers (India)

  Mechanical Engineering Forum

  Kamla Nehru Institute of Technology

• Exceptional Engineers Volunteer Tutor

  University of North Texas

  Denton

  TX

  Volunteer Tutor

  Constitutive Modeling

  Fracture Mechanics

  Mathematica

  Failure Analysis

  Materials Modeling

  Scanning Electron Microscopy

  Physics

  Solid Mechanics

  Materials

  Abaqus

  Mathematical Modeling

  Materials Science

  Nanoindentation

  Characterization

  Engaging Public Speaker

  Applied Mechanics

  Finite Element Analysis

  ANSYS

  Mechanical Testing

  Mechanics

  Effect of inclusion density on ductile fracture toughness and roughness

  Alan Needleman

  V. Tvergaard

  E. Bouchaud

  L. Ponson

  Three dimensional calculations of ductile fracture under mode I plane strain

  small scale yielding conditions are carried out using an elastic-viscoplastic constitutive relation for a progressively cavitating solid with two populations of void nucleating second phase particles. Larger inclusions that result in void nucleation at an early stage are modeled discretely while smaller particles that require large strains to nucleate voids are homogeneously distributed. Full field solutions are obtained for eight volume fractions

  ranging from 1% to 19%

  of randomly distributed larger inclusions. For each volume fraction calculations are carried out for seven random distributions of inclusion centers. Crack growth resistance curves and fracture surface roughness statistics are calculated using standard procedures. The crack growth resistance is characterized in terms of both JIC and the tearing modulus TR. For all volume fractions considered

  the computed fracture surfaces are self-affine over a size range of nearly two orders of magnitude with a microstructure independent roughness exponent of 0.53 with a standard error of 0.0023. The cut-off length of the scale invariant regime is found to depend on the inclusion volume fraction. Consideration of the full statistics of the fracture surface roughness revealed other parameters that vary with inclusion volume fraction. For smaller values of the discretely modeled inclusion volume fraction (≤7%)

  there is a linear correlation between several measures of fracture surface roughness and both JIC and TR. In this regime crack growth is dominated by a void-by-void process. For greater values of the discretely modeled inclusion volume fraction

  crack growth mainly involves multiple void interactions and no such correlation is found.

  Effect of inclusion density on ductile fracture toughness and roughness

  Effect of specimen thickness on the creep response of a Ni-based single-crystal superalloy

  R Banerjee

  A Staroselsky

  V Seetharaman

  A Needleman

  Creep tests on Ni-based single-crystal superalloy sheet specimens typically show greater creep strain rates and/or reduced strain or time to creep rupture for thinner specimens than predicted by current theories

  which predict a size-independent creep strain rate and creep rupture strain. This size-dependent creep response is termed the thickness debit effect. To investigate the mechanism of the thickness debit effect

  isothermal

  constant nominal stress creep tests were performed on uncoated PWA1484 Ni-based single-crystal superalloy sheet specimens of thicknesses 3.18 and 0.51 mm under two test conditions: 760 °C/758 MPa and 982 °C/248 MPa. The specimens contained initial microvoids formed during the solidification and homogenization processes. The dependence of the creep response on specimen thickness differed under the two test conditions: at 760 °C/758 MPa there was a reduction in the creep strain and the time to rupture with decreasing section thickness

  whereas at 982 °C/248 MPa a decreased thickness resulted in an increased creep rate even at low strain levels and a decreased time to rupture but with no systematic dependence of the creep strain to rupture on specimen thickness. For the specimens tested at 760 °C/758 MPa microscopic analyses revealed that the thick specimens exhibited a mixed failure mode of void growth and cleavage-like fracture while the predominant failure mode for the thin specimens was cleavage-like fracture. The creep specimens tested at 982 °C/248 MPa in air showed the development of surface oxides and a near-surface precipitate-free zone. Finite-element analysis revealed that the presence of the alumina layer at the free surface imposes a constraint that locally increases the stress triaxiality and changes the value of the Lode parameter (a measure of the third stress invariant).

  Effect of specimen thickness on the creep response of a Ni-based single-crystal superalloy

  Srivastava

  Brown University

  University of North Texas

  Texas A&M University

  Bhabha Atomic Research Centre

  Denton

  Texas

  Department of Material Science and Engineering\nAdviser: Dr. Alan Needleman

  Graduate Research Assistant

  University of North Texas

  Mumbai

  India

  Reactor Engineering Division / Reactor Design and Development Group.

  Scientific Officer

  Bhabha Atomic Research Centre

  School of Engineering\nAdviser: Dr. Allan F. Bower

  Postdoctoral Research Associate

  Providence

  Rhode Island Area

  Brown University

  Department of Materials Science and Engineering

  Dwight Look College of Engineering.

  Assistant Professor

  Bryan/College Station

  Texas Area

  Texas A&M University

  English

  Hindi

  The Haythornthwaite Foundation Travel Award

  The award is sponsored by the Haythornthwaite Foundation.

  Applied Mechanics Division

  ASME

  First Place in the Best Student Paper Award

  The award is sponsored by the Haythornthwaite Foundation and the ASME Applied Mechanics Division.

  Applied Mechanics Division

  ASME