Structural transformations and properties of titanium–aluminum composite during heat treatment

The link between the parameters of heat treatment of a layered titanium–aluminum composite material obtained by explosive welding with the formation of intermetallic compounds in it has been analyzed. The results of measurements of the microhardness of the composite and the thickness of the interlayer of the intermetallic phase obtained using different regimes of heat treatment have been discussed. Special attention has been paid to estimating the composition of the intermetallic phase in the composite prepared by explosive welding.     

Single-stage optimization problem with soft restrictions

Most chemical processes are designed with the application of inaccurate mathematical models. Therefore, the objective of optimized chemical processes under uncertainty becomes an actual problem of chemical technology. It is necessary to design a process satisfying all the requirements of the designer regardless of the changing external and internal factors. This paper considers a problem of single-stage optimization with soft restrictions. Moreover, these soft restrictions should be provided with some known probability. It is necessary to note that solution of this problem of single-stage optimization needs the calculation of multidimensional integrals for mathematical expectancy of the criterion functions and probabilistic restrictions. This paper considers an approach to solution of this problem of single-stage optimization based on transforming the probabilistic restrictions into deterministic ones. The efficiency of this approach was illustrated by a computational experiment.     

Interaction of impact-compressed gas in the welding gap with the welded surfaces in explosive welding

It is shown that in explosive welding in conditions preventing the formation of a cumulative jet, the cleaning and activation of the welded surfaces take place ahead of the contact point by the plasma flows. Impact plasma forms in the welding gap during the hypersonic discharge of the high-temperature impact-compressed gas at its boundary with the welded surfaces.     

Parameter determination for contact conductometer sensors

The paper discusses the effects of the components of the electrode impedance for a primary contact sensor in a solution as regards measurement of the resistivity, and a method is proposed for determining the constant and estimating the values of the components. __________ Translated from Izmeritel’naya Tekhnika, No. 3, pp. 61–63, March, 2008.     

Matching the vortex and sample fluxes in remote gas sampling by swirling air jet

A new method is proposed and verified according to which the efficiency of remote gas sampling by means of a swirling air jet is improved through matching the probing and sampling vortex fluxes. It is shown that, under the conditions of matching (with the probing/additional flux ratio of 1.3), a counter flow with a minimum diameter of the vortex core is formed that minimizes the sample losses while retaining high rarefaction at the probed object surface.     

Deformation and thermodynamic processes in explosion cladding of cylindrical components with titanium

The structural special features of the formation of titanium in high-speed compression of a titanium pipe are investigated. The thermodynamic conditions of explosion welding of titanium are studied. It is shown that for high-quality cladding of cylindrical components with titanium it is necessary to prevent localization of deformation as a result of heating of the surface and transfer of titanium to the plastic state when welding is carried out in shielding gases. Long copper+titanium current conductors with the length exceeding 30 diameters were produced.     

Detection of RDX traces at the surface with sonic aerosol flow desorption

The use of a high-speed aerosol flow is proposed for sampling RDX from the surface followed by chromatographic analysis. The aerosol is generated from different solvents by means of a coaxial nebulizer. The effect of the aerosol flow parameters (solvent flowrate, an angle of the nebulizer inclination with respect to the surface) and various solvents (water, acetone, and hexane) on the efficiency of the RDX desorption was investigated. The optimal angle of the nebulizer was found to be 30°, under these conditions, the desorption of RDX from the surfaces of different structure (metal, glass, leather, cotton fabric, and paper) has also been studied. It is shown that under the action of an aerosol created using water and acetone, desorption from a smooth surface occurs most efficiently (1.5 times higher than with hexane). In this case, the sample removes almost completely (about 80%) by the aerosol flow in a few seconds. A relationship between the desorption efficiency and the amount of the solvent sprayed (that is the amount of aerosol particles in desorbing flow) has a characteristic maximum which location depends on the properties of the solvent spray. This effect is associated with a rate of solvent evaporation. Under optimal conditions for desorption of RDX from a smooth surface using an aqueous aerosol, an LOD of ～10?ng can be achieved. For porous and rough surfaces, the efficiency of the analyte desorption decreases (three times for leather and cotton fabric). The results of the experiments conducted allow one to conclude that the RDX solubility in the solvent used does not affect considerably the efficiency of the RDX desorption. It is assumed that small aerosol drops are very active and can capture the particles of the target analyte. This promotes the desorption of RDX molecules from the surface.

© 2018 American Association for Aerosol Research     

Possible Ignition of Particles Ejected into the Gap in Explosive Welding of Titanium

Processes that occur in the welding gap during explosive welding are analyzed. It is shown that metal particles flying out into the gap due to the jetformation effect can ignite in shockcompressed air. For most metals, the energy released thereby is small and has no significant influence on weld formation. In titanium welding on large areas, surface sections located far from the place of detonation initiation, which experience a longterm action of a hot air flow, can dissolve a large amount of oxygen and nitrogen. If particles from these sections enter the gap, it can lead to chemical reactions with formation of TiO₂ and TiN by the mechanism of internal combustion. The energy released in the gap per unit area is commensurable with and even greater than the kinetic energy of the accelerated (flyer) plate. Local bulging and rupture of metal observed in practice can be explained by ignition and combustion of gassaturated titanium particles in the welding gap.