Relation between Surface Appearance and Coefficient of Friction in Compressive Deformation of Metals

The compression test was performed on aluminium, copper, mild steel, stainless steel and aluminium single crystal by using various lubricants. The following results were obtained from the relationship between the microscope pattern of the compressed surface and the frictional coefficient : (1) The surface pattern of the plate after rolling is similar to that of the specimen after compression. (2) In the case of a large frictional coefficient, a glossy surface appears in the specimen in which a greater part of the surface is in contact with tools. In the case of a small frictional coefficient, a dull face having a rugged surface of a few microns in depth appears. It seems likely that there is a fluid film in the sinks. (3) In the 60% deformation of the various materials by using palm oil as a lubricant, the ratio of the surface covered by the fluid film to the total friction surface is 75～85% for aluminium or copper and about 10% for stainless steel. (4) From the compression test it is conceivable that there are deformation bands in the rugged surface of the dull face, which the lubricants fill. This phenomenon may be one of the great differences between the sliding friction and the compression deformation

Effect of Lubricants on Compressive Deformation

The compression test was carried out with aluminium, copper, mild steel and stainless steel at 100, 200, 300, 400℃ and room temperature by making use of various kinds of lubricant. The results obtained are as follows : (1) It is necessary to take account of the elastic strain of the testing machine for the calculation of the friction coefficient from the load-strain curve of the compression testing. (2) In comparing both friction coefficients of rolling and of compression with each other, there is a tendency that the rolling shows a smaller friction coefficient than in the compression. This is considered to be due to the difference in the amount of friction length. (3) In the compression test with the mineral oils of various viscosities, the friction coefficient decreases with a slight increase of viscosity in the case of the viscosity below 100 Redwood sec at 50℃. However, at the viscosity above 100 Red Wood sec at 50℃, it is little changed by the variety of viscosity. (4) The order of lubricating effects is variant with the variety of lubricants, but the palm oil or beef-tallow oil shows a lower friction coefficient at room temperature and paste oil containing MoS_2, stearic acid sopa or paraffine chrolide shows good lubricating effects at high temperatures

Comparative Amino Acid Sequences of Dengue Viruses

Amino acid (AA) sequences of 4 serotype of dengue viruses deduced from their nucleotide (nt) sequences of genomic RNA were analyzed for each genome segment and each stretch of 10 AA residues. Precursor of membrane protein (pM), and 4 nonstructural proteins (NS1, NS3, NS4B, NS5) were highly conserved, while another nonstructural protein (NS2A) was least conserved among 5 strains of dengue viruses. When homology was compared among heterotypic viruses, type 1 and type 3 dengue viruses showed close relationships, while type 4 dengue virus was relatively remote from other types. When AA sequences were compared for each 10 AA residues, some highly conserved as well as least conserved domains were identified. Significance of these findings for diagnostic virology and epidemiological survey was discussed