The procedure of gas-metal arc welding (GMAW) has received much attention in recent years and has numerous beneficial applications in the industry, including car industry and ship building. It is expected that the GMAW parameters, such as arc voltage, welding current and welding speed, strongly affect the mechanical properties of welded joints. As one of the most important mechanical properties that

We study the regularities of strain hardening and structural transformations of a tungsten–nickel–iron heavy alloy under the conditions of cold reduction. It is discovered that the alloy with a tungsten content of 89% is hardened easier than the alloy containing 90% W.

We present the results of simulations of the stress-strain state of a traction chain by the finite-element method with regard for the contact interaction and friction between the chain link and the roller. We propose an analytic relation for the approximate evaluation of the fatigue strength of the chain according to the distribution of stresses. We also establish conditions that should be imposed

We study the wear resistance, fatigue strength, and corrosion-fatigue strength of SShKhN-42 rolls made of cast iron with surface nanostructures obtained as a result of mechanical-pulse treatment under the operational conditions of rolls of the rolling mills. It is shown that the surface nanostructure makes the wear resistance of cast iron three times higher and almost doubles the fatigue strength.

A six-component system of CoNiCuCrx high-entropy alloys with different contents of chromium (where x = 0, 0.5, 1.0, 2.0, and 3.0 mole) is obtained by the method of argon-arc melting in a МІFІ-9 study. By the methods of X-ray diffraction analysis, scanning-electron microscopy, and indentation, we investigate the influence of chromium on the crystalline structure, microstructure, and hardness of these

We present the results of investigations of the influence of hydrogen-free carbonitriding in glow discharge on the physicochemical characteristics of the hardened layer of 40Kh steel depending on the content of propane and the pressure of gas atmosphere. We consider three versions of saturation: carbon + nitrogen, nitrogen + carbon, and simultaneous saturation with nitrogen and carbon. The analysis

We study the microstructure of deposited coatings formed by a composite material based on PG-10N-01 self-fluxing alloy and modified with a mechanically activated composite material obtained as a result of the self-propagating high-temperature sintering process. By the X-ray phase diffraction analysis, in the structure of the coating, we detect the presence of titanium diboride (TiB2), nickel boride

We perform the comparative analysis of the corrosion resistance of St3ps steel in demineralized water and in saturated solutions of the Nurelle-D insecticide and UN-32 complex liquid fertilizer. It is shown that, in demineralized water, the general corrosion of the steel surface is predominant. In a solution of insecticide, parallel with general corrosion, we observe a partial realization of pitting

By using the modular-deformation method of calculations, we established the influence of finely divided filler (talc) and additional heat treatment on the elastoplastic properties of polylactide materials. We detected the changes in the modulus of deformation, elasticity modulus, and thermomechanical characteristics of polylactide composites. The maximum values of the moduli and melting point were

By the method of singular integral equations, we solve a plane elastoplastic problem of fracture mechanics for an isotropic plane with an infinite series of curvilinear holes and plasticity bands at their tips. We study the influence of the shapes of smooth holes and the radii of rounding of the contours at their tips on the opening displacements and lengths of the plasticity bands. The solutions of

We develop an electrochemical method aimed at the evaluation of in-service degradation of the mechanical properties of rolled steels of the frames of marine portal cranes. The regularities of decrease in the impact toughness of steels and their polarization resistance are analyzed. The correlation between these parameters forms a basis for the development of a nondestructive method aimed at prediction

The free energy and density of states are computed by the DFT method for the Zr3NiO and Zr3NiN compounds. Their formation was confirmed and numerous Zr3MNx (M = Co, Ni) compounds were synthesized for the first time. It is shown that all these compounds are insertion derivatives of the Re3B structural type (space group Cmcm). We study the process of gas-phase hydrogenation of the obtained subnitrides

We study a quasicrystalline cast alloy and a film coating obtained by the improved method of threeelectrode ion-plasma sputtering of assembled targets with the following nominal composition: Al60Cu28Fe12 . The structure of the specimens was studied by the methods of quantitative metallography, X-ray diffraction analysis, X-ray energy-dispersive spectrometry, and transmission and scanning electron microscopies

We develop a heat-resistant corrosion-resistant alloy based on nickel and alloyed with rhenium and tantalum. This alloy is intended for the production of blades for a new generation of power-generating and ship gas-turbine engines. It is shown that the introduction of rhenium (3.7–4.3 wt.%) and tantalum (2.5–4.3 wt.%) into the composition of the experimental alloy increases the high-temperature corrosion

We study the dependence of the ratio of the cathodic protection current to the ultimate diffusion current for Kh70 steel within the range of protective polarization potentials (-0.75)–(-1.05) V (relative to the silver-chloride reference electrode) standardized by the DSTU 4219 in media with different degrees of corrosiveness. It is shown that, within the рН range 5.6–9.6, as the potential shifts to

We propose a computational model for the evaluation of the service life of fiber-reinforced concrete structural elements subjected to long-term tension. The model is based on the first law of thermodynamics and a proposed idealized tensile stress-strain diagram of fibrous concrete. This model is used for the evaluation of the service life of a fiber-reinforced concrete plate containing a circular hole

We study the problem of contact of two elastic half planes (plane deformation), one of which has a wavy surface under the conditions of partial filling of the interface gaps with compressible liquid. The formulated contact problem is reduced to a singular integral equation for the derivative of the height of the interface gaps and its analytic solution is obtained. We axnalyze the contact behavior

According to the results of simulation of stressed states, it is shown that coarse graphite inclusions formed in the walls of case-shaped parts of transient in thickness are the sites of initiation of defects due to the changes in the dislocation structure and diffusion of carbon from graphite. The cavities formed in graphite also promote the development of oxidation.

The micromechanisms of biocorrosion damage to specimens of 17G1S-U pipe steel are studied on the basis of a combination of the profilometry approaches with fracture mechanics. We develop new methods for the numerical analysis of stress concentration factors regarded as parameters of localization of the microscopic concentrators of corrosion stresses. The improved approach is applied to the analysis

We perform the comparative analysis of the parameters of acoustic structural noise in specimens of 40G structural steel with the use of ultrasonic flaw detectors with phased arrays. It is shown that the parameter of integral density of B-scan images most completely reproduces the variations of energy of acoustic vibrations reflected from the microstructural inhomogeneities (grain-size inhomogeneity

We propose a computational scheme for the evaluation of the maximal temperature of a pad–disk tribosystem in the course of one-time braking with regard for the time of increase in pressure up to its nominal level, the temperature dependence of the characteristics of materials, and the roughness of the friction surfaces. We perform calculations for a three-disk brake made of Termar-ADF carbon composite

We propose a method for the determination of the residual service life of wide-coverage spraying booms of field sprinklers with regard for the maneuvering mode of their loading and the action of corrosive media. This method is based on the energy approach developed earlier, the computational models of propagation of corrosion cracks under static and cyclic loads, and the scheme of the maneuvering loading

We propose a procedure for the determination of the stress-strain state of exploited metals in gaseous hydrogen at temperature varying as a function of time. In this case, we use the principle of virtual work adapted for the quasistatic equilibrium equations with step-by-step formulation in time. The increments of displacements, hydrogen concentration, temperature, strains, and stresses for a certain

The method of singular integral equations is used to obtain the solution of the antiplane problem of fracture mechanics for an orthotropic plane with two-section kinked crack with regard for the specific features of stresses at the tips of angular cracks. For this purpose, we apply the unified approach developed earlier to the solution of the problems of stress concentration in isotropic bodies with

We study the corrosion and tribocorrosion behaviors of hard alloys of the VN20 + Cr3C2 and VN20 + VC systems in solutions based on 3% NaCl with different рН values. In alkali media, the corrosion currents and friction coefficients are lower than in acid media, which is explained by the inertness of nickel. The VN20 + 1 wt.% Cr3C2 alloy has the highest corrosion and tribocorrosion characteristics.

We study the influence of titanium-containing refractory inoculants (nitrides, carbides, and intermetallic materials) on the structure of metal in the welds of high-strength low-alloy steels. The character of structural-and-phase transformations and the specific features of fine structures are determined by the method of transmission electronic microscopy with regard for the dislocation density distribution

Ternary alloys of the Ti–Nb–Mo system are obtained by the method of arc remelting with subsequent crystallization on a copper water-cooled hearth. In these alloys characterized by contents of alloying elements corresponding to the molybdenum equivalent (Moeqv) within the range 3.2–4.0, we observe the formation of hexagonal (α′) and orthorhombic (α′′ ) martensites. For higher Moeqv (4.6), we detect

It is shown that the addition of 0.01 wt.% of Ti–TiC modifier synthesized by the method of high-voltage electric discharge treatment of Ti powders in kerosene and briquetted with the help of spark plasma sintering makes it possible to reduce the grain size from 1–2 mm to 0.2–0.6 mm in all modified specimens of SM88U heat-resistant alloy. In this case, the tensile strength of modified specimens at a

We perform complex diagnostics of the technical state of steel structure of a grab reloader after operation for more than 40 yr by the methods of destructive and nondestructive testing. Fatigue cracks and mechanical defects caused by wear are detected on the shaped rolled products. By using the magnetic method with determination of the coercive force, we analyze the stress-strain states of various

It is shown that the slope of a tangent to the fatigue curve can be used to analyze the effect of dispersion of pearlite on the fatigue strength of carbon steel. For a constant thickness of the ferrite-pearlite layer, we established an inversely proportional relationship between the indicated parameter and the density of accumulated dislocations. We also estimated the mechanism of influence of the

We study the mechanism of corrosion cracking of Kh70 steel in a neutral soil electrolyte under the conditions of cathodic protection. We distinguished three areas of potentials in which the processes of corrosion cracking of steel are governed by different mechanisms. Thus, the process of local anodic dissolution proves to be predominant under potentials more positive than – 0.75 V, the mechanism of

The process of cold plastic deformation of a hole in a plate made of shape-memory alloy is simulated by the finite-element method by setting the mechanical characteristics and the temperatures of the onset and termination of direct and reverse phase transformations. By using the ANSYS Workbench software, we determine the distribution of residual stresses in the plate in the vicinity of a functional

We analyze the influence of model stratal water with low acidity on the cyclic crack resistance of 20N2M steel of a sucker rod after operation for 5.5 yr. The state of the metal of a sucker rod head is conventionally regarded as the reference state. We revealed insignificant differences between the basic mechanical properties and the characteristics of cyclic crack-growth resistance of steel in air

Magnesium alloys are subjected, after low-pressure casting, to hot-rolling and extrusion. It is shown that their structural states, for different rates of these processes, are determined by the joint development of dynamic recrystallization, formation of twins, and changes in the phase composition. It is demonstrated that the dissolution of metastable phase components and the corresponding decrease

We study the kinetics of propagation of fatigue cracks on the surface of side frame of a rail car with regard for the stochastic nature of the operating load. Its dependence on the initial geometry of the crack is established. Moreover, under given loading conditions, we determine the shape of semielliptic contour of the fatigue crack characterized by the highest growth rate into the depth of the frame

The procedure of gas-metal arc welding (GMAW) has received much attention in recent years and has numerous beneficial applications in the industry. The arc voltage, welding current and welding speed are three independent variables of this process that may affect the mechanical properties of the weld metal. As one of the most important mechanical properties of the weld metal, we can mention its yield

We present a procedure for the evaluation of the strain and fracture energy of the material under the conditions of shear deformation based on the application of the method of digital image correlation. The established characteristics are used to determine the stress-strain state and service life of drill columns and shafts of hydraulic turbine in bending and torsion.

We study a complex anticorrosion pigment based on calcium-containing zeolite with zinc phosphate precipitated on its nanoporous surface. It is discovered that this pigment efficiently retards corrosion in an aluminum alloy placed in a synthetic acid medium and inhibits the subfilm corrosion of the metal near defects of the alkyd paint coating. The proposed pigment may serve as a promising inhibiting

We determine the brittle-fracture resistance of the metal taken from various zones of welded joints of 34KhN3MA steel produced from electrodes with different phase compositions or their combinations. It is shown that, regardless of the zone of welded joint in which a notch is made in the specimen, the highest values of impact toughness are observed for the weld metal obtained from the austenitic electrode

We analyze the existing ordinary and express methods aimed at the determination of the frost resistance of building materials and demonstrate their advantages and disadvantages. We propose a new express method, which enables us to determine the durability of stone with the smallest labor consumption and high efficiency. This method is based on the introduced criterion of frost resistance computed according

We study the problems of compression and shear of an elastic strip containing a semiinfinite crack on the boundary of the strip and a rigid wall. The crack is opened in the middle and closed at the ends, where its faces are under the conditions of friction sliding. By the Wiener–Hopf method, we reduce the system of integral equations of the problem to an infinite system of algebraic equations. The

Within the framework of the refined theory taking into account the transverse shear strains and inertial components, we consider the problem of stationary vibration of an orthotropic plate with holes and absolutely rigid inclusions. The inclusions may have different types of bonds with the plate. We analyze the case of translational motion of the inclusions along the direction of normal to the median

Magnesium hydride (MgH2) is a hydrogen-rich compound generating significant amounts of hydrogen in the process of hydrolysis, i.e., in the course of its chemical interaction with water or with aqueous solutions. This process is of great interest for the on-site hydrogen generation aimed at application of H2 as a fuel for PEM fuel cells. We propose a review of recent reference publications in the field

We study the effect of various electrolytes on the functional characteristics of the coatings deposited by the method of plasma-electrolyte oxidation (PEO) on aluminum and magnesium alloys. The influence of the concentration of alkali on the formation of PEO coatings is demonstrated. The prospects of application of KOH (NaOH)–Na2SiO3 combined electrolytes with various additives (glycerin, borax, fluorides

By using a generalized two-parameter model, we study main regularities of the deformation of an infinite viscoelastic layer on the rigid foundation under the action of concentrated cyclic loads. The process of transition to the steady-state conditions of deformation under periodic nonharmonic loading is simulated. The possibility of taking into account residual strains (displacements) in a layer made

We establish the physicochemical conditions required for the creation of multicomponent Nb–Ti–Al–X (X – Cr, Zr, Mo, Sr) niobium alloys with improved characteristics of high-temperature strength, heat resistance, and technological efficiency. The conclusions are based on the relationship between the physical properties of alloying elements, enthalpy of mixing, compositions of alloys, and the diagrams

We study the properties of ZrO2 –Y2O3 –NiO ceramics obtained by using the technologies of sintering of powders and tape casting in the intact state and after one-time reduction both in pure hydrogen and in Ar–5% H2 and N2 –10% H2 –5% CO2 mixtures. It is demonstrated that, by using the technology of tape casting, it is possible to obtain materials for anodes-substrates of solid-oxide fuel cells with

We study the accumulation of deuterium in coatings made of FeCrAl alloys and stainless steel, as well as (for comparison) in the Zr1%Nb alloy under the conditions of their saturation with a hydrogen isotope (deuterium) from a gaseous medium. By the method of nuclear reactions, we measure the space distribution of the concentration of deuterium in the coatings after their saturation at a temperature

We obtain a numerical-analytic solution of an antiplane problem of the stress-strain state of elastoplastic half space containing a periodic system of thin rigid tunnel inclusions parallel to the boundary of the half space. Prior to loading, these inclusions were in unilateral mechanical contact with the medium. We determine the stress-strain state and study the phenomenon of plastic exfoliation of

We study the friction characteristics of “disk–shoe (segment)” friction couples of 45 steel with applied electric-spark coatings. Their wear resistance under the conditions of boundary lubrication and the morphology of the surface layers or secondary structures formed on the counterbody in the course of friction are analyzed.

We analyze the influence of numerous factors, such as an NS4 model soil medium, the load ratio (R = 0.1 and 0.9), and the potential of cathodic protection (–0.98 V) on the cyclic crack-growth resistance of the base metal and the metal of circular butt weld of 17G1S pipe steel in the intact state and after 30 years of the operation in a gas main. It is shown that the long-term operation of steel maximizes

We study the kinetic parameters of the physicochemical interaction of hydrogen with annealed titanium and titanium whose surface layers are modified by laser treatment and differ, in their phase and chemical compositions, from the volume of the material. The possibilities of attainment of the maximum degree of protection of the material against hydrogen penetration and prevention of the possibility

We analyze the causes of the in-service loss of integrity of the steel rods of pumps due to the fatigue fracture of their main part as a result of propagation of the surface cracks. To increase the service life of the rods, it is proposed to use a special liquid working medium inhibiting the process of propagation of fatigue cracks as a result of the artificial creation of the effect of crack closure

We propose a way to increase the wear and crack resistance of the main working tools for roller mills. Bimetallic rollers (with a diameter of 252 mm and a length of 1620 mm) are produced by sequential pouring of alloys with similar temperatures of phase transformations. The microstructure, phase composition, redistribution of alloying elements, and the properties of bimetallic materials are studied

We propose a computational model for the evaluation of the residual service life of spraying booms of the field sprinklers in the maneuvering loading mode (stationary oscillations of sections of the boom together and separate shocks caused by the irregularities of the field surface). This model is based on the energy approach earlier developed by the authors. A scheme of maneuvering load is proposed

On the basis of the well-known theoretical concepts and some experimentally substantiated hypotheses, we propose a mathematical model aimed at description of the effect of diffusion-mobile hydrogen on the corrosion of pipe materials of crucial metal structures. The influence of hydrogenation of the metal on the corrosion rate of heat-exchange equipment is quantitatively evaluated.

It is shown that the wear kinetics of steels with diffusion coatings under the conditions of rolling friction strongly depends on the physicomechanical properties and phase compositions of the coatings, hardness of the base, and the modes of thermal and thermochemical treatments. The dependence of the degree of wear on the number of loading cycles is always parabolic. The contact fatigue strength in

We propose a procedure of control over the speed of response of thermal conditions in the case of thermal loading of the bodies of revolution made of functionally graded materials. The construction of solutions of the analyzed problems is based on numerical methods. To solve direct problems, we use the method of weighed residuals and the finite-element method. The solution of the posed extreme problem

A plane periodic problem of the theory of elasticity for an isotropic plane with infinite row of closely located curvilinear holes with edge cracks is solved by the method of singular integral equations. The stress intensity factors (SIF) at the tips of edge cracks propagating from symmetric holes of various shapes (elliptic holes, rhombic holes with rounded vertices, and narrow slots) are computed

We obtain the solution of a plane problem of the theory of elasticity on the phenomenon of “healing” of a crack in an anisotropic body. By using the model of Winkler’s base, this problem is reduced to a singular integrodifferential equation for the displacements of points of the crack surface. In the case of a defect in the form of flattened ellipse, we obtain the exact analytic solution of the problem