Papers by Author: B.K. Mishra

Abstract: In this work, 2-D/3-D forming problems (extrusion and deep drawing) are numerically simulated by extended finite element method (XFEM). The updated Lagrangian formulation is used to model the large deformation. The von-Mises yield criterion is used to model the elasto-plastic behavior assuming isotropic hardening. Penalty approach is employed to impose the contact constraints and non–penetration condition at the material interfaces. The level set approach is used for locating the material interfaces. The numerical simulations of two forming problems are presented using developed nonlinear XFEM code.

Abstract: In large deformation problems, the contribution of nonlinear terms is quite significant. Hence, components/structures involving large deformation must be analysed using non-linear theories. In this paper, element free Galerkin method (EFGM) has been applied to solve large deformation problems using updated Lagrangian approach. Geometrically nonlinear problems have been simulated assuming linear elastic material behaviour. The results obtained by EFGM have been compared with those obtained by FEM and analytical solutions. An elasto-plastic edge crack problem has been solved using nonlinear material behaviour and large deformation kinematics.

Abstract: The present investigation is about fabrication of single-crystalline ceria (CeO₂) nanoparticle by a hydrothermal route. High surface area CeO₂ was synthesized with transformation of morphology from nanofibers to nanocubes in response to processing conditions. A steady variation of average nanocrystallite size ca. in the range 3.0-16.9 nm and a range of band gap energy from 2.6 to 2.9 eV were measured. The surface area of the nanoparticles varied in the range 16.0136.1 m²/g and the variation in surface area is attributed to the nature of packing of particles. The ceria nanofibers could generate 870.5 µmol of H₂ in 3 h of irradiation.

Abstract: When deformations are carried out with fine grained microstructure and within a narrow range of strain rates and temperature, metals and ceramics have been shown to exhibit superplastic behavior. Under these conditions the material demonstrates unusually high elongation with a relatively stable microstructure. But when the above mentioned parameters lie beyond a limit, near superplastic behavior is observed. The microstructure changes actively during the process of deformation and the response of the material becomes dependant on the history of loading. A model to describe the dependence on loading history by taking into account the change in microstructure is proposed. The model predicts the general trends observed and also provides possible explanation to some of the effects observed in the experimental data.