Estimation of residual strength of components of composite constructions after low-speed impact

A methodology of computing the damageability of composite materials at low-speed impact is suggested. The methodology is based on applying a fracture criterion of the monolayer and following computation of material damageability taking the interaction of different damage evolution mechanisms into account. This approach allows us to obtain the distribution of damageability parameters in the surface of the monolayer and the width of material at an arbitrary moment of time until complete destruction of the construction component, computing the degradation of elastic properties, and the position and sizes of delamination regions after the impact. Applying this methodology for estimating residual strength permits the avoidance of excessive conservatism of the projected strength of construction components from composite materials which have incurred impact damage.     

Developing technology for removing contaminants from the surface of cotton-polyester textile materials

The expediency of using Everlase in desorption of protein contaminants from cotton-polyester fabrics was established. The optimum treatment conditions were established (pH of the medium, temperature, incubation time) in which Everlase manifests the maximum catalytic activity. The physicochemical mechanism of action of Everlase in removing protein stains from the surface of fabrics was revealed. The effect of adding SF and inorganic salts to the solution containing Everlase enzyme was studied, and it was found that adding them increases the quality of removal of protein stains from the surface of the fabrics. Addition of 0.7% ASF, 0.5% Na₅P₃O₁₀ and CaCl₂ is most effective. An effective product for removing spots of protein origin while increasing the quality of dry cleaning of clothing and improving the environmental safety of the process and economy of resources was developed based on the experimental data.     

Thermodynamic model for estimating the composition of passive films and Flade potential on Fe-Cr alloys in aqueous solutions

A thermodynamic model of a passive film is developed, in which the formation of the film on the surface of an Fe-Cr alloy in an aqueous solution is considered to be a result of the stable solid-phase chemical and adsorption equilibrium at the alloy-inner passive film layer interface. In the calculations, the Cr₂O₃ content in the passive film is determined by both the Gibbs energy change (ΔG < 0) in the chemical oxidation of the alloy components by the water oxygen and the change in the surface Gibbs energy (ΔG _S > 0) of the alloy. The ΔG _S change results in the negative adsorption of chromium atoms, which shifts the 3Fe + Cr₂O₃ ↔ 3FeO + 2Cr equilibrium toward the FeO formation in the passive film. Calculations showed that the enrichment of the passive film in chromium oxide should sharply increase in a chromium content range of 10–20% in the alloy, which agrees with the known data of X-ray photoelectron spectroscopy of the passive films. A formula is derived for estimating the Flade potential of Fe-Cr alloys, which relates the Flade potentials of individual Fe and Cr components to the FeO and Cr₂O₃ contents in the passive film.     

Mathematical description of the technological process of injection pultrusion

During injection pultrusion of composite items, reinforcing filler is impregnated by resin binder inside a draw plate. In order to have successful impregnation, it is necessary to solve several technological tasks: locate points of resin injection, and optimize injection speed and pressure of the binder in the draw plate. A mathematical model for impregnation is described. Numerical solution was found using a combination of methods of final elements and control volumes. A two-iteration task involving impregnation of a plate is studied as an example.     

Experimental investigation of the working process in a vortex tube

The authors present the results of an experimental investigation of the temperature separation process in the chamber of an energy separation vortex tube.     

Experimental Investigation and Mathematical Modeling of a Coaxial Tubular Apparatus for Steam Methane Conversion

A tubular steam methane conversion apparatus containing a coaxial insert coated with a nickel–chromium catalyst by thermal gas deposition was experimentally studied and mathematically modeled. By solving the inverse problem, the parameters of the kinetic function of the steam–methane reaction were found. The efficiency of the coaxial tubular apparatus was shown to considerably exceed the efficiencies of its modern industrial analogs, namely, the PPR-600 and PPR-1360 furnaces and the Kellog tubular reactor.