Influence of the plastic properties of a material on the forming limit diagram for sheet metal in tension

A development of the theory of the formation of a groove, which appears before fracture in sheet metal subject to tension is presented, and is based on the assumption of initial non-homogeneity of the material in order to facilitate the determination of the limit strain of sheet metal subject to biaxial tension. Additional considerations in the present paper include strain-rate sensitivity, plane anisotropy and the difference in the values of the fracture strain which depends on the direction of the fracture with reference to that of rolling. The influence of the above properties of the material on the limit strain curve is analysed over the entire range of biaxial tension.Theoretical curves of limit strain are compared with experimental results for sheet metal in biaxial tension under conditions which eliminate the influence of friction and which ensure uniform strain distribution over the entire surface of the test piece, except in places of strain concentration. The discrepancies between the experimental and theoretical limit strain curves are analysed.     

Studies on interaction of Nd3+ — Glass laser light with armco-Fe high pressure nitrogen medium

Some effects of the interaction of Nd³⁺-glass laser, working in ordinary generation regime, with Armco-Fe surrounded by nitrogen in the pressure range (1–109) atm. have been investigated. Thephenomenon of capillary waves and the increase of the N₂ content have been observed in the irradiated area. The mechanism of the laser light interaction with the metal is discussed in terms of plasma theory and X-ray analysis.     

Formation of porous structures in activated brown-coal chars using O2, CO2 and H2O as activating agents

Two brown coals, xylitic and earthy, carbonized at 1173 K were activated with water vapour, carbon dioxide and oxygen, each producing a different distribution of porosity. In the xylitic coke, activated in the range of burn-offs from 1 to 70%, the action of water vapour results in the development of pores of all dimensions. At the highest burn-off the product has an effective surface area of 920 m² g^?1 and a total sorptive pore volume of 0.83 cm³ g^?1, 33% of which is in micropores. Carbon dioxide creates, from the xylitic coke at the burn-off of 70%, a highly microporous adsorbent with about the same surface area (890 m² g^?1) as the corresponding water-vapour activated product. The pore volume of the carbon dioxide sample is lower (0.49 cm³ g^?1) but these contain 63% of micropores, which amounts to a contribution of 92% of these pores to the effective total surface area. The activation of the xylitic coke with oxygen leads to a high development of porosity at low burn-offs, but becomes ineffective on continuation of the process to medium and high burn-offs. This is thought to be due to a blocking of the entrances of the micropores by surface oxygen complexes formed on the surface of the coke. Oxygen gives, at a high burn-off, a product with the lowest total adsorptive volume (0.45 cm³ g^?1) and surface area (650 m² g^?1). All the activated products obtained from the xylitic coke can be regarded, when effective surface areas are considered, as microporous adsorbents. With the earthy coke a total adsorptive pore volume (consisting mainly of wide mesopores) is developed which is higher than with the corresponding xylitic coke, but this result is difficult to reproduce, because the earthy coke samples are easily influenced by temperature in the process of activation, especially that by oxygen.     

The Stokes coagulation model

The coagulation problem related to the kinetic theory of motion of particles according to the Boltzmann equation. The coagulation equation brought from the infinite space to the limited one. A real boundary condition for the Stokes coagulation limiting the purified zones without the nonmetallic inclusions. The equivalent relative boundary conditions. The Stokes coagulation as function of time.     

The effect of stainless steel structure on the performance of rubber-graphite under conditions of water lubrication

A new sliding bearing material based on rubber filled with different graphites was assessed against stainless steels of various structures under conditions of water lubrication in an Amsler machine. The tribological characteristics of the rubber-graphite depend upon the fillers used. The wear of stainless steel journals depends upon the material structure and the chromium carbide present.     

Microcalorimetric measurements in Fe-C and Fe-C-Si-Mn alloys

Microcalorimetric measurements of heat related to fusion and crystallization of the eutectic in Fe-C and Fe-C-Si-Mn alloys have been carried out. In the case of Fe-C alloys, the heat related to fusion and crystallization of the eutectic changed from 0 to 215 kJ/kg and from 0 to 207 kJ/kg, respectively. For Fe-C-Si-Mn alloys, the heat related to fusion and crystallization of the eutectic changed from 178 to 220 kJ/kg and from 169 kJ/kg to 216 kJ/kg, respectively. This was attributed to the change of the content of eutectic in the alloys.     

Development of porosity in brown-coal chars on activation with carbon dioxide

Two petrographic types of Tertiary brown coals, xylitic and earthy, were carbonized, and activated with carbon dioxide between 1123 and 1273 K. The development of porosity in the activated chars was studied by adsorption of benzene and carbon dioxide at 298 K and by mercury porosimetry. The type of brown coal exerts a dominant influence on the properties of the activated chars. The xylitic brown-coal, when compared with the earthy brown-coal, yields products with a higher pore volume and better sorptive properties. Activated chars from the xylitic brown-coal reach a surface area of 800 m² g^?1, contained principally in micropores and very narrow mesopores (radius below 3.0 nm). Dimensions of pores in the activated chars from the earthy brown-coal are less uniform, the mesopores are broader (an important part of them has a radius between 5.0 and 100.0 nm), and micropores are present to a smaller extent; the surface area of these products is between 200 and 350 m² g^?1. Activated chars from both types of brown coals have a well developed system of macropores.     

Ultraviolet surface plasmon-coupled emission using thin aluminum films

Surface plasmon-coupled emission (SPCE) is the directional radiation of light into a substrate due to excited fluorophores above a thin metal film. To date, SPCE has only been observed with visible wavelengths using silver or gold films. We now show that SPCE can be observed in the ultraviolet region of the spectrum using thin (20 nm) aluminum films. We observed directional emission in a quartz substrate from the DNA base analogue 2-aminopurine (2-AP). The SPCE radiation occurs within a narrow angle at 59 degrees from the normal to the hemicylindrical prism. The excitation conditions precluded the creation of surface plasmons by the incident light. The directional emission at 59 degrees is almost completely p-polarized, consistent with its origin from surface plasmons due to coupling of excited 2-AP with the aluminum. The emission spectra and lifetimes of the SPCE are those characteristic of 2-AP. Different emission wavelengths radiate at slightly different angles on the prism providing intrinsic spectral resolution from the aluminum film. These results indicate that SPCE can be used with numerous UV-absorbing fluorophores, suggesting biochemical applications with simultaneous surface plasmon resonance and SPCE binding assays.