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

Premises of creation of Internet portal designed to provide access to participants of educational and scientific process for the joint creation, consolidation, concentration and rapid spreading of educational and scientific information resources in its own depository are considered. CMS-based portal content management systems’ potentiality is investigated. Architecture for Internet portal of MES of Ukraine’s information resources is offered.

Створення порталу інформаційно-довідкових ресурсів міністерства освіти і науки україни

Characterization and Properties of Natural Fiber Polymer Composites: A Comprehensive Review

Rapid innovation in nanotechnology in recent years enabled development of advanced metal matrix nanocomposites for structural engineering and functional devices. Carbonous materials, such as graphite, carbon nanotubes (CNT's), and graphene possess unique electrical, mechanical, and thermal properties. Owe to their lubricious nature, these carbonous materials have attracted researchers to synthesize lightweight self-lubricating metal matrix nanocomposites with superior mechanical and tribological properties for several applications in automotive and aerospace industries. This review focuses on the recent development in mechanical and tribological behavior of self-lubricating metallic nanocomposites reinforced by carbonous nanomaterials such as CNT and graphene. The review includes development of self-lubricating nanocomposites, related issues in their processing, their characterization, and investigation of their tribological behavior. The results reveal that adding CNT and graphene to metals decreases both coefficient of friction and wear rate as well as increases the tensile strength. The mechanisms involved for the improved mechanical and tribological behavior is discussed.

Mechanical and tribological properties of self-lubricating metal matrix nanocomposites reinforced by carbon nanotubes (CNTs) and graphene – A review

Friction stir welding (FSW) is a widely used solid state joining process for soft materials such as aluminium alloys because it avoids many of the common problems of fusion welding. Commercial feasibility of the FSW process for harder alloys such as steels and titanium alloys awaits the development of cost effective and durable tools which lead to structurally sound welds consistently. Material selection and design profoundly affect the performance of tools, weld quality and cost. Here we review and critically examine several important aspects of FSW tools such as tool material selection, geometry and load bearing ability, mechanisms of tool degradation and process economics.

Review: friction stir welding tools

Nano-porous ceramics have potential applications as diverse as biomedical implants, catalysis, and armors This work shows that insitu Nano-porous Polymer Derived Ceramics (PDC) can be produced in Metal Matrix Composites (MMCs) using solid state Friction Stir Processing (FSP) Direct insertion of cross-linked polymer into the metal by FSP in solid state is a significant step toward inserting different chemistry of polymer precursors to generate a variety of in-situ porous structures in Polymer Derived (PD)-MMC The PDC route is an efficient and cost effective way to produce SiCNbased PD-MMC and tailored pore architecture suitable for high temperature applications Microstructural observations indicate a uniform distribution of ~100 nm size pores in the ceramic phase after pyrolysis

Evolution of In-Situ Nano-Pores during Friction Stir Processing of Polymer Derived Ceramic Reinforced Metal Matrix Composites

In the present investigation, various kinds of textures, namely, unidirectional, 8-ground, and random were attained on the die surfaces. Pins made of aluminum were then slid against steel plates for various numbers of cycles using a pin-on-plate reciprocating sliding tester. It was observed that the friction and transfer layer formation depended on the die surface textures. Under lubricated conditions, the friction decreased for unidirectional and 8-ground surfaces but increased for random surfaces as a function of cycles. Under dry conditions, the friction increased with increasing number of cycles for all kinds of surfaces. In the tests, the friction was always highest when sliding was perpendicular to the unidirectional textures and was lowest for the random textures under both dry and lubricated conditions. The difference in friction values between these two surfaces decreased with increasing number of cycles. The variation in the friction was attributed to the change in texture of the surfaces during sliding.

Role of surface texture on friction and transfer layer formation when pure aluminum pins slid at various numbers of cycles on steel plates

Evaluation of Boundary Lubrication Properties of Fatty Acids Using a Lateral Force-Controlled Tribometer

Precise control of friction is very important for energy efficiency and sustainability in manufacturing processes. In the present investigation, various surface textures have been employed to vary the frictional conditions. More specifically, textures were varied from unidirectional to criss-cross to unidirectional by grinding the steel surfaces against emery papers for various numbers of cycles. Sliding experiments were conducted using an inclined pin-on-plate apparatus against the prepared steel surfaces under dry and lubricated conditions. In the experiments, it was observed that the coefficient of friction and transfer layer formation on the harder surfaces were controlled by the textures of the harder surfaces under both dry and lubricated conditions. The asperity angle of the harder surface plays a dominant role in controlling the friction and transfer layer at the sliding interface. Thus, by understanding appropriate roughness parameters, the friction and wear performance can be accurately controlled to enhance energy efficiency and the quality of the finished products in manufacturing process.Copyright © 2012 by ASME

Satish V. Kailas

Papers

Evolution of In-Situ Nano-Pores during Friction Stir Processing of Polymer Derived Ceramic Reinforced Metal Matrix Composites

Role of surface texture on friction and transfer layer formation when pure aluminum pins slid at various numbers of cycles on steel plates

Evaluation of Boundary Lubrication Properties of Fatty Acids Using a Lateral Force-Controlled Tribometer

Surface Texturing for Energy Efficiency and Sustainability

In-situ polymer-derived SiOC strengthened aluminum sheets: investigations on its manufacturing and structure-property correlations