On the problem of hydrogen removal during heat treatment of large forgings

The solutions to a differential equation for the problem of heating of a cylinder in a medium with a fixed temperature are used to obtain equations for estimating the change in the hydrogen concentration in forgings from data on the hydrogen concentration at the cylinder axis or on the average bulk hydrogen concentration. Similar equations are also obtained for forgings having square cross sections. The calculation demonstrates that, for the case of a twofold decrease in the hydrogen concentration in a forging, the calculated times of annealing of a cylindrical forging differ by three times.     

Stability of the austenite lattice of a high-nickel iron-based alloy toward the martensitic transformation

First-principles calculations of the variation of the total energy of a ferromagnetic Fe-31.2% Ni alloy upon bainitic transformation are presented. The problem of the loss of stability of the fcc lattice of iron alloys is discussed to show that the fcc lattice is mechanically stable in this alloy.     

The intelligent health index calculation system

The problem of finding logical patterns based on precedents in order to calculate an individual’s health index is considered. Local metrics and informative sets of diverse features are used to distinguish the patterns.     

Formation of hydrogen-vacancy complexes in alpha iron

An extended variant of Smirnov statistic theory [12] is presented that describes the equilibrium concentrations of vacancy-hydrogen atom complexes as a function of temperature. Calculations based on the first-principle values of interaction energy show that, at low temperatures, the majority of vacancies are bound with several hydrogen atoms, and the concentration of vacancies sharply increases.     

Study of the possibilities of thermal performance enhancement of flat plate solar water collectors by using of nanofluids as heat transfer fluid

The current work represents the simulation results of the thermal performances of flat-plate solar collector with heat transfer fluid–nanofluid (SiO₂ + water with 5% concentration) which is obtained experimentally [1]. The dependence of the outlet temperature and gained useful energy of heat transfer fluid (nanofluid) on the flow rates (10, 15 and 20 L/h) at different ranges of incident solar radiation (500–1000 W/m²) was obtained.     

Ab initio Computer Simulation of Carbon–Carbon Interactions for Various Spacings in BCC and BCT Lattices of Ferrite and Martensite

The ab initio computer simulation of lattice parameters and local structure distortions caused by interstitial carbon atoms in the iron-carbon system has been carried out using WIEN2k software. For the calculations, the full-potential method of linearized augmented plane waves (LAPWs) taking into account the generalized gradient approximation of PBE–GGA was used in a supercell of 54 iron atoms with periodic boundary conditions. The carbon dissolution energy has been found to be 0.85 eV for bcc iron, and 0.79 eV for bct iron. The carbon–carbon interaction energies in the ferromagnetic bct iron have been calculated. It has been found that accounting for tetragonal distortions considerably changes the interaction energy of carbon atoms in comparison with that of the bcc iron. Both the maximum degree of tetragonality of iron and the maximum attraction of carbon atoms have been observed for the case of carbon atoms placed in octahedral pores of the same type. If carbon atoms are in different types of octahedral pores, the tetragonal distortion of the lattice is weak. The obtained results are in good agreement with the Zener–Khachaturyan hypothesis and experimental data of Kurdyumov.     

Features of Isothermal Formation of Carbide-Free Bainite in High-Carbon Manganese-Silicon Steel

Change in the stability of overcooled austenite of high-carbon manganese-silicon steel relative to decomposition via the intermediate stage upon isothermal holding and martensitic γ → α transformation upon subsequent cooling has been studied using dilatometry and X-ray diffraction. The kinetics of low-temperature bainite transformation has been studied. The tetragonality of the crystal lattice of bainite α-phase caused by the superequilibrium content of carbon was found.     

Transformation of austenite in Fe-Cu alloys. III: Copper precipitation during cooling and holding of steels alloyed with copper

Strengthening of Fe-Cu alloys during isothermal aging has been considered. The size of particles that provides a maximum strength has been found. A theory of particle growth under the conditions of continuous cooling has been developed. The cooling rate that provides the maximum contribution from age hardening has been calculated.     

Technique for calculating geometric dimensions of a greenhouse-type solar-based one-cascade apparatus for demineralizing water

The results of studying a portable solar-based oblique multistep water demineralizer having increased productivity in obtaining distilled water are presented. The apparatus was designed taking the correlation for its geometric dimensions into account and using a capillary-porous material.