Search

Powder metallurgy is a process for compacting and sintering powders such as metals and ceramics, and has been attracting new attention in recent years. This paper presents research examples in which simulation methods such as molecular dynamics (MD) method, Monte Carlo (MC) method, finite element method (FEM), and discrete element method (DEM) are applied to powder metallurgy. The MD method is used to calculate physical property values such as interfacial energy and diffusion coefficient that change depending on the type of grain boundaries. The MC method is used to calculate the microstructural development due to the sintering and grain growth. The microstructure can be predicted when the sintering process is changed. The FEM is used to calculate deformation and strain. The sintering simulation combined with the MC method can calculate the microstructural changes and deformation simultaneously. In the compaction simulation, density distribution due to the friction with the mold can be analyzed. The DEM is used to calculate the compaction structure. The interaction of the friction and stiffness between particles and particle/mold can be analyzed. As powder metallurgy technology develops, process design that considers the whole process will be important. Supporting technology based on simulation will become increasingly important. [ABSTRACT FROM AUTHOR]

Asphaltenes are the components of heavy fraction of oil. Once they deposit and clog the pore throats of reservoir rock, tubing pipes in production wells, and pipelines for oil transportation, it causes a serious problem for oil production. The objective of this paper is to show the applicability of "digital oil", which is a full molecular model of a crude oil, and Molecular Dynamics（MD）simulation to solve the asphaltene problems. For this purpose, a digital oil of "A-crude oil" produced from an oil field actually confronting asphaltene problems was generated. On the generation of the digital oil, some analytical experiments were conducted and Quantitative Molecular Representation（QMR）method was applied. As a result, the digital oil was successfully generated. Then, asphaltene-asphaltene association energies in 7 different solvents: n-heptane, toluene, benzene, xylene, isopropyl alcohol（IPA）, an azeotrope mixture of toluene and IPA, and a ternary azeotrope mixture of water, toluene, and IPA, were evaluated by calculating the Potential of Mean Force（PMF）using MD simulations and umbrella sampling technique. As expected, aromatics（toluene, benzene, and xylene）presents much lower association energies of asphaltene in absolute value than that in n-heptane. Among the 7 solvents, the ternary mixture provides the lowest association energy in absolute value. Therefore it can be the most effective solvent for the asphaltene of "A-crude oil". Furthermore, it can be supposed from the result of this study that the association energy becomes lower in absolute value when the aromatic asphaltene solvents tend to distribute near around the edge of asphaltene molecule much more. Thus the digital oil and MD simulation would be a useful tool to solve the asphaltene problems in oil production. [ABSTRACT FROM AUTHOR]

Low Salinity Water Flooding (LSWF) is one of the attractive EOR technologies due to a low cost and environment friendly method. Because the operational configuration in LSWF is similar to that in conventional water flooding and no chemical components that are not present in reservoirs are added to injection water. LSWF has been focused on since 1990's and researchers have proposed some potential mechanisms of how low salinity water works for improving oil recovery. However, the mechanisms have not been sufficiently elucidated. Recently JOGMEC started a joint study to understand effects of LSWF on oil recovery through laboratory experiment, simulation work and field applications with Waseda University, Kyoto University and PetroVietnam / Vietnam Petroleum Institute. In the laboratory experiment, the effects of LSWF on oil recovery were observed using Berea sandstone cores containing about 1.5" of kaolinite that is considered to be one of the key factors. The mechanism to improve oil recovery suggested the multi component ion exchange. In the simulation work, we are developing in-house simulator to predict not only oil recovery but also ion and pH changes that are typically observed during LSWF based on the mechanism of multi component ion exchange. In addition, we are exploring an opportunity to apply LSWF to oil fields through a comprehensive study involving laboratory, simulation, field pilot and economic evaluation. [ABSTRACT FROM AUTHOR]

The principle of corresponding state on the fluctuation structure, which is the spatial distribution of various clusters of molecules caused by density fluctuations, in supercritical states around the critical points has been investigated. In this paper, we performed Molecular Dynamics (MD) simulation to extract the fluctuation structure around the critical points of 2-Center-Lennard-Jones (2CLJ) fluids, whose characteristics change by their molecular elongations. First, we indentified some critical points of 2CLJ fluids with comparatively shorter elongations applying Lotfi's function, which correctly describes the liquid-vapor coexistence line of Lennard-Jones (LJ) fluid, and successfully defined each critical point. Next, two methods were applied in the estimation of the fluctuation structure: one is the evaluation of the dispersion of the number of molecules at a certain domain, and the other is the calculation of static structure factor. As a result, in 2CLJ fluids which have shorter molecular elongations comparatively, the principle of corresponding state is satisfied because of the small differences in the fluctuation structures extracted in the present two methods. On the other hand, some results imply that the fluctuation may decrease in 2CLJ fluids which have the longer molecular elongations although more accurate evaluation of the critical points in those fluids is necessary for the further investigation.

In this paper, modeling and simulation of nanofilled crosslinked rubber using beads spring model was reported, and the effects of the crosslinking density, the dispersibility of nanofiller and the strength of filler-polymer interactions on the reinforcement in an elongation simulation were discussed. The models were consisted two fillers, five polymer-chains, and crosslinkers with four types of filler-rubber interaction based on the Lennard-Jones potential. From the uniaxial elongation simulation, it was confirmed that the strength of interaction was affected to the stress. Furthermore, the dependency of the elongation stress and the mobility of polymer beads around filler on temperature was carried out, and it was found that the presence of low-mobility phase around filler by a strong interaction lead to the reinforcement of filled crosslinked rubber.