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.

Fracture modelling of plain concrete using non-local fracture mechanics and a graph-based computational framework

Abstract: In this article, we developed a thermodynamically consistent non-local microcracking model for quasi-brittle materials with application to concrete. The model is implemented using a novel graph-bas...

A New Nonlinear Higher-Order Shear Deformation Theory for Nonlinear Vibrations of Laminated Shells

Abstract: A consistent higher-order shear deformation nonlinear theory is developed for shells of generic shape; taking geometric imperfections into account. The geometrically nonlinear strain-displacement relationships are derived retaining full nonlinear terms in the in-plane displacements; they are presented in curvilinear coordinates in a formulation ready to be implemented. Then, large-amplitude forced vibrations of a simply supported, laminated circular cylindrical shell are studied (i) by using the developed theory, and (ii) keeping only nonlinear terms of the von Karman type. Results show that inaccurate results are obtained by keeping only nonlinear terms of the von Karman type for vibration amplitudes of about two times the shell thickness for the studied case.Copyright © 2010 by ASME

Experimental, theoretical and numerical studies on plain concrete fracture in the low-strain rate regime—A state-of-the-art review

Abstract: Abstract A comprehensive overview of state-of-the-art experimental, theoretical and numerical methods that aid understanding and predicting the quasi-brittle fracture behavior of plain concrete under quasi-static conditions is presented in this work. The main objectives of this paper are as follows: (a) to lay-out a systematic manner for experimental and modeling people to select their choice of a concrete fracture simulating tool, (b) to critically describe the advantages and disadvantages of conducting different experimental set-ups for researchers intending to perform their own experiments for model validation, and (c) to provide modelers with a one-stop-shop for experimental data on plain concrete. In this review paper, the general characteristics of crack propagation in concrete are also presented. Extensive literature on the experimental studies of mode I and mixed-mode quasi-brittle fracture in concrete is discussed. The two main features of numerical modeling of concrete fracture, which are the descriptions of strain-softening and nonlocal regularization, are reviewed, and the application of these features to the various damage models is discussed. The survey of numerical models covered in this paper range from continuum-based to discrete formulations. We also provide a critical discourse on the advantages and disadvantages of the discussed experimental and numerical tools used for studying and modeling concrete fracture, and this is succinctly presented in Tables 2 and 3, respectively. Finally, future considerations of the experimental, theoretical and numerical studies in concrete fracture are presented.

Adaptive isogeometric analysis based on a combined r-h strategy

Abstract: In the present work, an r-h adaptive isogeometric analysis is proposed for plane elasticity problems. For performing the r-adaption, the control net is considered to be a network of springs with the individual spring stiffness values being proportional to the error estimated at the control points. While preserving the boundary control points, relocation of only the interior control points is made by adopting a successive relaxation approach to achieve the equilibrium of spring system. To suit the noninterpolatory nature of the isogeometric approximation, a new point-wise error estimate for the h-refinement is proposed. To evaluate the point-wise error, hierarchical B-spline functions in Sobolev spaces are considered. The proposed adaptive h-refinement strategy is based on using De-Casteljau’s algorithm for obtaining the new control points. The subsequent control meshes are thus obtained by using a recursive subdivision of reference control mesh. Such a strategy ensures that the control points lie ...

Modeling of a biological material nacre: Multi-objective optimization model

Abstract: Nacre is an inner layer of seashells that has a remarkable combination of stiffness, strength, and toughness. Engineers are inspired to mimic it to create engineering composites with properties not...

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.