J. N. Reddy

Bio: J. N. Reddy is an academic researcher from Texas A&M University. The author has contributed to research in topics: Finite element method & Plate theory. The author has an hindex of 106, co-authored 926 publications receiving 66940 citations. Previous affiliations of J. N. Reddy include Instituto Superior Técnico & National University of Singapore.

Alternate forms of thermodynamic laws for thermoelastic solids and the constitutive theories

Abstract: For thermoelastic solids, rate of mechanical work equilibrates with the rate of kinetic energy and rate of strain energy. In this article, this aspect of the physics is utilized to: (i) derive an alternate form of the energy equation based on the first law of thermodynamics and (ii) derive an alternate form of entropy inequality based on the second law of thermodynamics, both free of rate of strain energy. This alternate form of entropy inequality strictly contains physics related to the rates of entropy. This form of entropy inequality is essential to show that the constitutive theories for stress tensor for thermoelastic solids are free of any thermodynamic restrictions and thus can be derived independently of the entropy inequality. In this article, we explore both forms of entropy inequality, one containing rate of strain energy and the alternate form that is free of rate of strain energy in deriving the constitutive theories for the stress tensor. It is shown that the alternate for entropy in...

Bending Analysis of Functionally Graded Axisymmetric Circular Plates using the Dual Mesh Finite Domain Method

Abstract: The dual mesh finite domain method (DMFDM) introduced by Reddy employs one mesh for the approximation of the primary variables (primal mesh) and another mesh for the satisfaction of the governing equations (dual mesh). The present study deals with the extension and application of the DMFDM to functionally graded circular plates under axisymmetric conditions. The formulation makes use of the traditional finite element interpolation of the primary variables with a primal mesh and a dual mesh to satisfy the integral form of the governing differential equations, the basic premise of the finite volume method. The method is used to analyze axisymmetric bending of through-thickness functionally graded circular plates using the classical plate theory (CPT) and first-order shear deformation plate theory (FST). The displacement model of the FST and the mixed model of the CPT using the DMFDM are developed along with the displacement and mixed finite element models. Numerical results are presented to illustrate the methodology and a comparison of the generalized displacements and bending moments computed with those of the corresponding finite element models. The influence of the extensional-bending coupling stiffness (due to the through-thickness grading of the material) on the deflections is also brought out.

An Experimental Study on Ballistics Performance: Functionally Graded Sandwich Plate Impacted by a 9 mm Parabellum Projectile

Abstract: Functionally graded materials have been increasingly used in the design of impact resistant structures. A functionally graded plate with a tailored ceramic to metal through-thickness gradient combines the superior features of ceramics and metals in the same material system. The ceramic-rich side provides good protection against projectiles, while the metal-rich side oers toughness and strength to maintain the integrity of the structure as much as possible. Thus, the ceramic plates are used for single impact applications, whereas the FGM can be used multiple impact applications with high ballistic performance. In this study, the damage and deformation mechanisms of aluminum plates and functionally graded sandwich plates have been investigated and their performances were compared to each other under ballistics impact loadings. The functionally graded sandwich plate is composed of a mixture of ceramic (SiC) and metal (Al) phases, at a ratio of which is determined by a power-law distribution of the volume fraction. In the ballistics tests with 9 mm Parabellum projectiles, having a brass jacket and a lead core were used. Both aluminum and functionally graded sandwich plates were manufactured by means of the powder stacking-hot pressing method, their ballistic tests were performed and it was determined that functionally graded sandwich plates have a better ballistics performance than an aluminum plate by examining almost a full penetration of projectile to the aluminum plate while a signicant penetration to the functionally graded sandwich plate was not observed.

Fluid-Solid Interaction of Incompressible Media Using h, p, k Mathematical and Computational Framework

Abstract: This paper considers multi-media interaction processes in which the interacting media are incompressible elastic solids and incompressible liquids such as Newtonian fluids, generalized Newtonian fluids, dilute polymeric liquids described by Maxwell, and Oldroyd-B models or dense polymeric liquids with Giesekus constitutive model. The mathematical models for both solids and liquids are developed using conservation laws in Eulerian description for isothermal conditions with velocities, pressure, and deviatoric stresses as dependent variables. The constitutive equations for the solids and the liquids provide closure to the governing differential equations resulting from the conservation laws. For Newtonian and generalized Newtonian fluids, the commonly used constitutive equations are well known in terms of first convected derivative of the strain tensor, stress tensor, and the transport properties of the fluids. For dilute and dense polymeric liquids that are viscous as well as elastic, the mathematical mode...

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Robot dynamics and control

Abstract: From the Publisher: This self-contained introduction to practical robot kinematics and dynamics includes a comprehensive treatment of robot control. Provides background material on terminology and linear transformations, followed by coverage of kinematics and inverse kinematics, dynamics, manipulator control, robust control, force control, use of feedback in nonlinear systems, and adaptive control. Each topic is supported by examples of specific applications. Derivations and proofs are included in many cases. Includes many worked examples, examples illustrating all aspects of the theory, and problems.

A Simple Higher-Order Theory for Laminated Composite Plates

Abstract: A higher-order shear deformation theory of laminated composite plates is developed. The theory contains the same dependent unknowns as in the first-order shear deformation theory of Whitney and Pagano (1970), but accounts for parabolic distribution of the transverse shear strains through the thickness of the plate. Exact closed-form solutions of symmetric cross-ply laminates are obtained and the results are compared with three-dimensional elasticity solutions and first-order shear deformation theory solutions. The present theory predicts the deflections and stresses more accurately when compared to the first-order theory.