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

End forming behaviour of friction stir processed aluminum tubes at different tool traverse speed

Towards Sustainable and Eco-Friendly Cutting Oils

Surface texture influences friction and transfer layer formation during sliding. In the present investigation, three well-defined surface textures - namely unidirectional, 8-ground, and random - were employed on steel plates. Experiments were conducted by sliding pins made of FCC metals (Al, Cu and Pb) against the steel plates using an inclined pin-on-plate sliding tester. Tests were conducted at a sliding velocity of 2 mm/s in ambient conditions under both dry and lubricated conditions. The morphologies of the worn surfaces of the pins and the formation of transfer layer on the counter surfaces were observed using a scanning electron microscope. Surface roughness parameters of the plate were measured using an optical profilometer. It was observed that the transfer layer formation and the value of the friction (including adhesion and plowing components) depend primarily on texture of plate surfaces. The effect of surface texture on the friction was attributed to the variation of the plowing component of friction for different surfaces. It was also observed that among the surface roughness parameters, the mean slope of the profile, Δa, correlated best with the friction. Furthermore, dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing taking place at the asperity level.

Friction and transfer layer formation in FCC metals: Role of surface texture and roughness parameters

The present study evaluates the effect of aging and aging temperature on the frictional properties of Unrefined Coconut oil (URCO), Refined Coconut oil (RCO) and Virgin Coconut oil (VCO) samples using four ball tester. It was observed that the variations in the physicochemical properties of fresh URCO, RCO and VCO samples were attributed to the difference in their composition. This study showed that URCO, RCO and VCO samples followed same trend in their physicochemical and tribological properties when subjected to aging. The drop in flash point of aged oil samples with aging was attributed to the increased content of free fatty acids generated due to the degradation of triglyceride molecules. It was observed that the degradation of peroxide molecules has resulted in the stabilization in the peroxide content of URCO, RCO and VCO samples when aged at 100 C.

Study on Effect of Aging and Aging Temperature on Frictional Properties of Coconut Oil Samples

In welding, the process parameters influence the mechanical properties of the joint. However, such investigations on laser welding of Inconel X750 are lacking despite its industrial significance. We performed such an investigation in which three parameter combinations, out of seven, exhibited full laser penetration (S1 (75 mm/min, 800 W), S2 (75 mm/min, 1200 W), and S3 (150 mm/min and 1200 W)). Microstructural analysis exhibited changes in the grain and dendrite morphology with columnar to equiaxed transition from the fusion boundary to the interior. S3 exhibited superior mechanical properties than others due to the smaller grain size and fusion zone. 

Satish V. Kailas

Papers

End forming behaviour of friction stir processed aluminum tubes at different tool traverse speed

Towards Sustainable and Eco-Friendly Cutting Oils

Friction and transfer layer formation in FCC metals: Role of surface texture and roughness parameters

Study on Effect of Aging and Aging Temperature on Frictional Properties of Coconut Oil Samples

Influence of laser beam welding parameters on the microstructure and mechanical behavior of Inconel X750 superalloy