Tensile Fracture Location Characterizations of Friction Stir Welded Joints of Different Aluminum Alloys

The tensile fracture location characterizations of the friction stir welded joints of the AA1050-H24 and AA6061-T6 Al alloys were evaluated in this study. The experimental results show that the fracture locations of the joints are different for the different Al alloys, and they are affected by the FSW parameters. When the joints are free of welding defects, the AA1050-H24 joints are fractured in the HAZ and TMAZ on the AS and the fracture parts undergo a large amount of plastic deformation, while the AA6061-T6 joints are fractured in the HAZ on the RS and the fracture surfaces are inclined a certain degree to the bottom surfaces of the joints. When some welding defects exist in the joints, the AA1050-H24 joints are fractured on the RS or AS, the AA6061-T6 joints are fractured on the RS, and all the fracture locations are near to the weld center. The fracture locations of the joints are dependent on the internal structures of the joints and can be explained by the microhardness profiles and defect morpho     

Field test of a novel combined system of a high-efficiency heating/cooling heat pump and a clathrate cool storage unit

The Research Laboratory of Kyushu Electric Power Co., Inc. (KEPCO) installed a novel system in March 1992 which is a combination of a super heat pump with about twice the performance of a conventional one and a compact chemical storage-type clathrate cool storage unit. A field test was implemented by integrating these units into an actual air-conditioning system. As a result of the test, system performance was determined and the effectiveness of the system was confirmed. © 1998 Scripta Technica. Heat Trans Jpn Res, 26(6): 410–418, 1997     

Synthesis and properties of novel sulfonated polyimides bearing sulfophenyl pendant groups for polymer electrolyte fuel cell application

A novel sulfonated diamine bearing sulfophenyl pendant groups of 2,2′-(4-sulfophenyl) benzidine (BSPhB) was synthesized. Sulfonated polyimides (SPIs) derived from 1,4,5,8-naphthalene tetracarboxylic dianhydride, BSPhB and other non-sulfonated diamines were successfully synthesized. The SPIs with ion exchange capacity (IEC) of 1.5-2.8 meq g⁻¹ showed high reduced viscosity of 3-10 dL g⁻¹ and high desulfonation temperature of 320 °C. The SPI membranes were tough and flexible, having high stress at break of more than 80 MPa and elongation of 80-100%. They showed highly anisotropic membrane swelling in water with larger swelling in thickness direction than in plane direction. They showed fairly high proton conductivity (σ). For example, the membrane with IEC of 1.77 meq g⁻¹ exhibited σ values of 120 and 260 mS cm⁻¹ at 60 and 120 °C, respectively, in water. They also showed fairly high water stability.     

Mechanical properties of friction stir butt welds of high nitrogen-containing austenitic stainless steel

In this study, the friction stir butt welding of 2-mm-thick high nitrogen-containing stainless steel (HNS; Ni-free austenitic stainless steel containing 1 mass% nitrogen) plates was performed using a load-controlled friction stir welding (FSW) machine with a Si₃N₄-based tool at various welding speeds, i.e., 50 mm/min, 100 mm/min, 200 mm/min and 300 mm/min, and a constant tool rotating speed of 400 rpm. To determine the optimum welding conditions to create reliable HNS FSW joints, the effect of the heat input on the mechanical properties of the HNS FSW joints was studied. The mechanical properties were evaluated by the Vickers hardness test and the tensile strength test. Full-penetrated and defect-free butt welded joints were successfully produced, under all the applied welding conditions. The stir zones consisted of very fine grained structures and showed an increase in the Vickers hardness. These joints also showed a higher tensile strength and yield strength than the base metal. In particular, the FSW welds obtained at a welding speed of 100 mm/min, which showed the best mechanical properties, had a relatively higher Vickers hardness, which indicates a good relationship between the welding parameter (heat input) and the hardness profile due to the microstructure refinements. It was estimated that these welding conditions were optimal, and under these conditions both grain growth and α-phase formation were prevented.     

Effect of initial grain size on the joint properties of friction stir welded aluminum

In this study, 2 mm-thick commercial 1050-Al plates with an ultrafine grained (UFG) structure were obtained by the accumulative roll bonding (ARB) technique after a 5 cycle process and were subsequently joined by friction stir welding (FSW) at various revolution pitches (welding speed/rotation speed) of 1 mm/r, 1.67 mm/r and 2.5 mm/r. To understand the effect of the initial grain size on the welding properties, ARB processed samples followed by annealing under H24 conditions as well as the as-received samples in the fully annealed state were also applied to the FSW process. The microstructure evolution and Vickers hardness in the stir zone of all the samples were investigated. It was revealed that the annealed samples with an intermediate grain size finally obtained the most refined grain size and highest value of Vickers hardness in the stir zone. However, for the UFG samples, significant grain growth and corresponding decrease in hardness can be found in the stir zone.     

Reaction–diffusion algorithm for stereo disparity detection

The present paper proposes a novel stereo algorithm utilizing multi-sets of reaction–diffusion equations. The problem of detecting a stereo disparity map becomes the segmentation problem, in which the uniqueness assumption and the continuity assumption on disparity distribution are taken into account. A set of reaction–diffusion equations realizes the continuity assumption, while a mutual-inhibition mechanism among the multi-sets realizes the uniqueness one. In addition, each set of equations has a self-inhibition mechanism, which is necessary for the reaction-diffusion equations applied to stereo disparity detection. Performance of the proposed algorithm is evaluated for well-known test stereo images.     

Polyelectrolyte membranes based on hydrocarbon polymer containing fullerene

In the present study, composite polyelectrolyte membranes were prepared from sulfonated polystyrene and fullerene. The additive effect of the fullerene on the membrane properties – electric resistance, mechanical strength, oxidation resistance, and methanol permeability – were measured. The addition of fullerene improved the oxidation resistance, and reduced the methanol crossover. The mechanical strength of the fullerene-composite membrane, on the other hand, was not improved. The direct methanol fuel cell (DMFC) based on a 1.4 wt% fullerene-composite membrane showed the highest power density of 47 mW cm⁻² at the current density of 200 mA cm⁻² (this value is 60% of the Nafion-based DMFC). The transmission electron microscopy (TEM) observations suggest that the improved dispersity of the fullerene and the reduced number of micropores in the membranes would improve its performance in the fuel cell.     

Lifestyle change and energy use in Japan: Household equipment and energy consumption

Energy use in the Japanese residential sector has more than doubled (on a per-household basis) during the post-war period. Important factors contributing to the increase include changes in the types of housing built, heating, cooling, water-heating equipment, and other appliances. In this paper, the developments of household equipment and living conditions in Japan are described, from their 1950s state to the present. Trends in energy consumption by fuel types and end uses are reviewed over the same period. The past trends are combined with expectations for future developments in household equipment and quality, as well as with international comparisons of household-energy use, to predict further increases in household-energy consumption. The results indicate the importance of a renewed emphasis on energy efficiency in the residential sector.