Key Engineering Materials Vol. 743

Abstract: The paper presents a method for of contact load (stress) research over a flank land of a cutter by a “split cutter” (sectional cutter) method which is more preferable in cutting steels and durable materials in industrial cutting mode. The research of contact stresses distribution over surfaces of a cutter must be carried out on the special rigid four-component dynamometer for the “split cutter” with inspection of total components of cutting force Pz and Py. However, the investigation of contact loads distribution over the flank land faces the problem due to elastic deformation of measuring elements and penetration of work material into a slit between the two parts of the “split cutter”. The research of contact stresses distribution over a face of a cutter should be carried out on a lathe with horizontal radial feed, while the research of contact stresses distribution over a flank land should be done on a horizontal-milling machine with vertical radial feed of a table. The distributions of contact stresses over the flank land of the cutter in free orthogonal turning of a disk made from ductile brass (63Cu-37Zn), brittle brass (57Cu-39Zn-1Al-3Mn) are described. In machining ductile brass with formation of a continuous chip, extreme pattern of normal σ_h and tangential τ_h contact stresses epures (curves of distribution) over a flank land is observed, i.e. the highest contact stress is at some distance from the cutting edge. In machining brittle brass with formation of a discontinuous chip, the highest contact stress is observed, on the contrary, near the cutting edge. The character of normal contact stresses over a flank-land depends on the type of the chip formation due to a sag of the transient surface under the act of a radial component of the cutting force on the rake surface.

Abstract: The structure and mechanical properties of welded joints of VT23 titanium alloy received by method of laser welding after modifying the surface layers by ultrasonic mechanical forging (Treatment 1 and Treatment 2) were investigated. The experimental tests have revealed that the Treatment 2 provides a multiple increase in the relaxation property in fatigue life test. The formation of nonuniform distribution of vanadium, chromium and molybdenum in the welded joint increases the strength and, at the same time, the brittleness of β-phase. Mechanical treatment of the surface layers in the second mode provides a multiple increase in ductility up to 13%, in the as-received condition up to 9.9%. In consequence of plastic deformation, the β-phase intensity reduces twice with Treatment 2 which is related to its clustering. As follows from a presented data, the fatigue life of the VT23 titanium alloy has increased more than threefold.

Abstract: The paper presents the experimental results that allow determining optimum quenching conditions for solid rocket motors (SRM) at the stage of firing bench tests (FBT) in gas dynamic tunnels (GDT) with altitude simulation. The work describes main design approaches for quenching unit enabling reduced thermal insulation (TI) destruction by 15-20% after finish of SRM operation due to aftereffect decrease, as well as reduced values of scattering of TI undamaged layer thickness up to 10% owing to uniform cooling.If necessary, drying accompanied with emissions of TI gaseous products and remnants of k-phase fuel components is run in GDT, which allows improving environmental safety of working facilities and shortening the time for evaluation of SRM design parameters.

Abstract: This study discusses the role of thermal processes, including repair welding, and maintenance heat-up of cryogenic equipment, in the alteration of the properties of base metal and formation of thermal impact zones during repair and installation of joints from chromium-nickel steels with different nickel content. The tests have confirmed the primary role of nickel in the change of the properties of base metal and welded joints of low-temperature structures during operation and maintenance heat-up. It was shown that maintenance, repair and welding heat-up can lead to structure alteration and material embrittlement, which occurs in all steels, regardless of nickel content. The research has identified the areas that are potentially dangerous from the perspective of the brittle defect evolution in cryogenic equipment operating under complex thermal cycles during operation or maintenance heat-ups.

Abstract: This paper presents the results of performance evaluation of anode-supported solid oxide fuel cells (SOFC) with magnetron sputtered YSZ/CGO bilayer electrolyte, and composite LSCF-CGO cathode. Deposition of the YSZ/CGO electrolyte with the thickness of up to 14 microns was performed on the commercial anode substrates with dimensions of 5×5 cm². The LSCF-CGO cathode of the fuel cells was formed by the screen-printing method. The microstructure of the YSZ/CGO bilayer electrolyte and LSCF-CGO cathode was studied by scanning electron microscopy. Comparison of the fuel cells performance with different thicknesses of the YSZ and CGO layers was carried out by measuring current-voltage and power characteristics, and also by testing the long-term stability of cell power at the temperature of 750 °C and voltage of 0.7 V.

Abstract: It was established that the silver nanoparticles (AgNPs) in an equimolar ratio have the highest electrochemical activity on a graphite electrode (GE) surface in an alkaline medium. The electrocatalytic oxidation mechanism of hydrogen peroxide on the GE surface was proposed. We detected an additional maximum at E = 0.3 V on the cathodic branch of the cyclic curve in the potential range from +2.0 to -1.0 V. The appearance of this maximum indicates the reduction of hydrogen peroxide generated during AgNPs electrooxidation in the potential range from -1.0 to +2.0 V.

Abstract: The porous structure of copper-cadmium oxide system produced by electrochemical synthesis using alternating current in ammonium chloride solutions with concentrations of 3 and 25 wt% was studied. It was shown that the composition of electrolysis products is represented by oxides of copper (I) and (II), hydroxides of cadmium; it depends on the current density and the solution concentration. The products of joint electrochemical oxidation of copper and cadmium obtained in ammonium chloride solution with concentrations of 3 and 25 wt% and current densities of 1 and 3 A/cm² are characterized by mesoporous structure.

Abstract: The purpose of this study is to improve the kinetics of styrene monomer accumulation in polyvinylidene fluoride films with radiation-chemical grafting of styrene monomer. The work has proved that the degree of grafting depends on the absorbed dose of helium ions, temperature and composition of the grafting solution.

Abstract: The liquid-phase oxidative destruction of 30% solution of tributyl рhosphate in kerosene has been carried out under the action of oxidants generated by the electrical current which has been passed through 40% aqueous solutions of the sulfuric acid under atmospheric pressure and at temperature of 50 °C. Tributyl phosphate and its solvent have been partly destroyed due to the electrochemical processes on the lead electrodes, however, a large part of components has been subjected to deep oxidation in the volume of electrolyte. As a result of oxidation, the following final products have been formed: phosphoric acid, mono- and dicarboxylic acids, carbon dioxide and water.

Abstract: The paper has demonstrated that modification of alumino-phenylsiloxane alkaline solution at different molar ratio of sodium hydroxide to alumino-phenylsiloxane in a heterogeneous system of toluene-water produces synthetic sorbents. The compounds were characterized by the methods of elemental analysis, FTIR and XRD spectroscopy. The study of specific surface area and pore size distribution showed that the sorbents have more extended surface as compared to the original alumino-phenylsiloxane. The determination of sorption activity of the products by methylene blue has showed that their sorption activity exceeds that of natural zeolite.