In-situ monitoring of decane-in-water emulsion during microwave irradiation

Microwave (MW)-assisted de-emulsification has been attractive in processes of petroleum production and refining. However, the mechanism and optimal operation remain poorly understood. In this study, the behaviour of decane-in-water emulsion under MW irradiation was monitored in-situ through a size measurement system equipped with the reactor and surface tension profiles. The results indicated that the bubble was formed around the oil droplet during MW irradiation. The MW-induced bubbles can enhance de-emulsification in a similar mechanism as the flotation column. The efficiency of MW de-emulsification depends on emulsion content and MW power. Although a higher MW power is more effective, boiling caused by excessive energy must be considered due to the higher local heating. As a result, moderate power is more desirable. For the decane-in-water emulsions in this study, the optimal condition was determined to be around 500 W.     

Stable microwave-assisted magnetization switching for nanoscale exchange-coupled composite grain

Magnetization mechanisms of nanoscale magnetic grains greatly differ from well-known magnetization mechanisms of micrometer- or millimeter-sized magnetic grains or particles. Magnetization switching mechanisms of nanoscale exchange-coupled composite (ECC) grain in a microwave field was studied using micromagnetic simulation. Magnetization switching involving a strongly damped or precessional oscillation was studied using various strengths of external direct current and microwave fields. These studies imply that the switching behavior of microwave-assisted magnetization switching of the ECC grain can be divided into two groups: stable and unstable regions, similar to the case of the Stoner-Wahlfarth grain. A significant reduction in the switching field was observed in the ECC grain when the magnetization switching involved precessional oscillations similar to the case of the Stoner-Wohlfarth grain. This switching behavior is preferred for the practical applications of microwave-assisted magnetization switching.     

Bipolar DC corona discharge from a floating filamentary metalparticle

The motion of a filamentary particle and also the discharge from a particle have been extensively investigated for the development of a prevention and protection method against breakdown in gas-insulated switchgear. The particle showed several different patterns of motion, e.g., "standing," precession motion, oscillating up and down, etc. Each of these types of motion depends on corona discharge from the particle itself. Since this motion cannot be explained only by monopolar discharge from one end of a particle, bipolar discharge from both ends of a particle occurring simultaneously has been investigated by applying the floating particle method. The particle length and the gap between the particle and electrode were chosen as parameters. From experimental results, several interesting features were obtained. The curve of bipolar corona. current lies between negative and positive corona currents of monopolar curves. There is a sudden current increase at the threshold voltage that seems to be a new feature of the corona current from a filamentary particle. So far, the experimental results indicate that this threshold voltage is not a function of particle length, but it could depend slightly on length. Flashover voltage is a function of particle length and the gap. It decreases with length and increases with the gap     

Effect of ion implantation layer on adhesion of DLC film by plasma-based ion implantation and deposition

High adhesive diamond-like carbon (DLC) film on SUS304 was obtained using carbon ion implantation between DLC film and substrate material by plasma-based ion implantation and deposition (PBIID). Implantation of mixed silicon and carbon ions to the substrate resulted in much higher adhesion strength than that of the epoxy resin. Effect of ion implantation on adhesion of DLC film was studied by cross sectional STEM observation and EDS element analysis. Enhancement in adhesive strength by ion implantation of mixed carbon and silicon was ascribed to the formation of the multilayer interface consisting of mixed carbon and silicon ion implanted layer and the amorphous layer of carbon and silicon.     

Influencing factors on nugget formation during multipoint welding by single-side resistance spot welding

ABSTRACT

Recently, weight reduction and improvement of crashworthiness of auto bodies have become important issues. At the same time, stiffness of auto bodies is also needed to ensure a smooth ride. Using hollow parts, such as bended pipes and hydroformed parts, is one of the solutions to the demand for both rigidity and light weight.

To weld hollow parts and sheet panels together, welding methods which allow us to access from one side are required. Single-side resistance spot welding (single-side RSW) process is one of those, and has recently been attracting attention.

However, because of the long current path and small electrode force, it is difficult to concentrate the electric current in the welding spot compared with conventional direct resistance spot welding (direct RSW). Furthermore, in multipoint welding, shunt current will occur easily, and the nugget formation will be inhibited.

To obtain a guideline for making sound nuggets, influencing factors for shunt current were investigated. In addition, a numerical study was carried out to discuss the difference between direct RSW and single-side RSW.

According to the CAE analysis, the shunt current of single-side RSW will be higher rate than direct RSW. The rate of shunt current was influenced by the electrical resistance of its current path. For this reason, with shorter distance between welding points, or with lower electrical resistance of material, it is difficult to get large nuggets. By enhancing the electrical resistance of shunt current path, shunt current could be reduced and a larger nugget would be obtained.     

Lubrication using porous surface layer for cold drawing of steel wire

As a lubricant for steel cold working, metal soap on zinc phosphate coating is widely used. However the lubrication causes hazardous wastes, and hence an alternative system is demanded. The authors proposed to utilize porous layer on workpiece surface as a reservoir of liquid lubricant. In this study, 0.64%C steel wires were oxidized at 923 K under air and chemically reduced by pure hydrogen to form porous surface layer with pores 1–2 μm in diameter. In cold drawing with machine oil, the friction coefficient on the porous surface was 0.06, while that on normal surface was 0.11. The lubrication mechanism with porous surface is discussed.