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.

Fast parallel algorithms for short-range molecular dynamics

There have been a number of review papers on layered silicate and carbon nanotube reinforced polymer nanocomposites, in which the fillers have high aspect ratios. Particulate–polymer nanocomposites containing fillers with small aspect ratios are also an important class of polymer composites. However, they have been apparently overlooked. Thus, in this paper, detailed discussions on the effects of particle size, particle/matrix interface adhesion and particle loading on the stiffness, strength and toughness of such particulate–polymer composites are reviewed. To develop high performance particulate composites, it is necessary to have some basic understanding of the stiffening, strengthening and toughening mechanisms of these composites. A critical evaluation of published experimental results in comparison with theoretical models is given.

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Effects of particle size, particle/matrix interface adhesion and particle loading on mechanical properties of particulate–polymer composites

Changes in portlandite morphology with solvent composition: Atomistic simulations and experiment

A new approach to the application of Mori-Tanaka's theory in composite materials

The purpose of the present survey is to review the analysis of composite materials from the applied mechanics and engineering science point of view. The subjects under consideration will be analysis of the following properties of various kinds of composite materials: elasticity, thermal expansion, moisture swelling, viscoelasticity, conductivity (which includes, by mathematical analogy, dielectrics, magnetics, and diffusion) static strength, and fatigue failure.

Analysis of Composite Materials—A Survey

\n This work represents the completion of the many developments in recent years on failure theory for homogeneous and isotropic materials. Presented here is the resulting failure formalism in final and technically complete form. Significant further results are also given for the verification of the failure formalism. The scope of this paper goes from the history of misguided failure theory investigations right up to the present final tested forms ready for applications. For every predicted failure level in terms of the stresses, there is an accompanying ductility level. This ranges from brittle failure up to fully ductile failure. The entire theory is calibrated by only two specified parameters (failure properties). Nothing else is needed. The seemingly interminable, actually centuries long search for the missing theory of failure has finally been brought to a resolute and successful conclusion.

The Failure Theory for Isotropic Materials: Proof and Completion

Abstract The mission of the Versatile Test Reactor (VTR) is to enable accelerated testing of advanced reactor fuels and materials as required for advanced reactor technologies. Each advanced reactor type has unique challenges, and these challenges affect the design of the testing vehicles used for accelerated testing. For molten salt reactor testing, some of the key focus areas are (1) understanding the complex thermal-hydraulic systems and materials that will facilitate heat removal from the reactor core, (2) mitigating the corrosion-associated issues that arise from using these materials at high temperatures, and (3) understanding how to measure and control salt composition/chemistry and properties during irradiation. This paper details the progress made toward surmounting these challenges to support future molten salt cartridge experiments in the VTR. Broadly, this work involves two major thrusts: design and analysis of an operating cartridge loop, and development of the instrumentation and control system needed to operate the loop successfully.

Design and Control of a Fueled Molten Salt Cartridge Experiment for the Versatile Test Reactor

The self-consistent scheme is used to model the state of an elastic material with a very high density of nearly connected cracks. Then fracture mechanics is used to pose the problem of the complete and final failure of the material under uniaxial and eqibiaxial tension. These failure states are taken to be those of the extreme case of brittle fracture. A specific form for the resulting extreme brittle failure criterion is given. ©2002 ASME

A Possible Limiting Case Behavior for Brittle Material Fracture

Homogeneous and Isotropic Materials Failure Theory: A Critical Appraisal


 The underlying formalism of isotropic elasticity theory is shown to benefit from a review and re-examination of its structure thereby yielding a realignment of the basic moduli type properties. When this is accomplished the pathway to understanding ductile versus brittle failure behaviors becomes much more accessible. The ductile/brittle transition in uniaxial tension then admits a simple and direct specification in terms of the two elastic moduli 2µ and k. The consequences of these results are discussed in the context of general failure theory.

https://asmedigitalcollection.asme.org/appliedmechanicsreviews/article-pdf/75/3/030801/6993234/amr_075_03_030801.pdf

Richard M. Christensen

Papers

The Failure Theory for Isotropic Materials: Proof and Completion

Design and Control of a Fueled Molten Salt Cartridge Experiment for the Versatile Test Reactor

A Possible Limiting Case Behavior for Brittle Material Fracture

Homogeneous and Isotropic Materials Failure Theory: A Critical Appraisal

Review of the Basic Elastic Mechanical Properties and Their Realignment to Establish Ductile Versus Brittle Failure Behaviors