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A steadily rising interest which specialists in various fields show towards the problem of hydrogen affecting metallic materials and causing their failure is connected to all-increasing requirements set on the durability of machines and equipment in operation. Metallic structures are most often surrounded by such environment which contains hydrogenous components or hydrogen itself (in chemical industry, power engineering, etc). And it leads to various types of degradation in metals (hydrogen embrittlement, hydrogen corrosion, and so on), which, in its turn, could cause catastrophic results. Ultimate strength is considered to be a representative parameter of the process of hydrogen degradation in steels. The authors cite the results of testing conducted on hydrogen-saturated specimens made of A516-55 steel which register a significant decrease in the ultimate strength. It is proposed to use a diagram which describes a fall in metal strength and transition of structural materials into their brittle states following an increase in hydrogen concentration. Discussion is made on criteria for hydrogen-saturated materials of metallic structures failing when a momentary overload occurs under default working conditions.

Estimation of strength and durability of any structure can be carried out after finding components of stress-strain state of all its parts. The present work shows that in order to calculate stresses in a certain element of a structure that works under thermo-mechanical loading and contacts hydrogenous media, one should trace distribution of heat and hydrogen concentration in this element. Based on the results obtained when having solved thermo-diffusion problem of heat and hydrogen distribution in a casing of a diffusion apparatus, its stress state was found. Casing of the diffusion apparatus is represented in a shape of a shell of revolution. It was determined that in a thin shell, homogenous fields of temperature and hydrogen concentration are being set for a period that is significantly less than the design operating life of the apparatus. To solve the problem of stress distribution in a shell, S.K. Godunov’s method of discrete orthogonalization was used. In the structure that does not have any manifested stress raisers, a critical point with maximum value of shear stress intensity was found. Consistent patterns of change of the intensity in the critical point were found under the emergency pressure boost in the apparatus at various hydrogen densities. The paper shows that emergency pressure boost in a shell may cause the appearance of zones of plastic yield; when this boost is accompanied by increase in hydrogen concentration, the fracture pattern changes from viscous to brittle.

The method of determining safe operating conditions for a supporting beam-rod structure under an abnormal load has been proposed. The locomotive cab frame loading in the case of obstacle collision has been considered. The proposed deterministic engineering evaluation of complex structural stress makes it possible to determine the limiting surface in the three-dimensional space of the representative parameters of the obstacles and locomotive speed. This surface limits the safe operating area of the vehicle in predetermined variation ranges of obstacle parameters. Based on the example of the locomotive cab calculation, it has been shown how its requirements of strength retention should be justified in order to preserve the safety of the drivers and expensive cab equipment.

Increasing the reliability of equipment used for production, transportation, storage and utilization of hydrogen is directly related to solving the problem of hydrogen embrittlement of metals. Without a fundamental physical theory, it is necessary to predict the bearing capacity of metal structures on the basis of obtained experimental data on the effect which hydrogen have on metal properties. This paper presents a solution (based on the method of discrete orthogonalization proposed by S.K. Godunov) of a physically-nonlinear problem of stress distribution in a titanium shell. Since hydrogen, most notably, reduces plastic properties of metals utilized in structural elements, a critical point was determined where the intensity of shear deformation is maximal. It was found how the intensity changes at a critical point of a shell if the pressure within the device rises to an emergency level. Such a rise of the pressure in the shell could lead to appearance of plastic deformation regions, and hydrogen exposure is manifested in reduced breaking stress and changed fracture pattern. © 2019 Published under licence by IOP Publishing Ltd.

The estimation of fracture strength of a spatial beam–rod structure is demonstrated in the sample of a locomotive cab. The calculated case of collision of the locomotive with an obstacle is considered. The estimation consists of three interrelated tasks. At the first stage, the finite-element model of a cab frame, taking into account a buffer device, is built and the structure rigidity determined. At the second stage a two-mass design diagram (locomotive–obstacle) is considered and the interaction force is determined. At the third stage, the finite-element model describing the stressed–deformed state of the cab design at the collision with the obstacle is built. The resulting load, determining the bearing capacity of the cab, is compared with different variants of calculated forces defined for interaction of the locomotive with various obstacles.

The contact pressure and contact region are determined for a shell lying on a base with notches. A method of contact elements was used as the method of investigations. The contact interaction between a thin isotropic cylindrical shell lying on the elastic and rigid bases is considered as an example.

The article considers the multiparameter problem of the mechanical system behavior and its survivability when destructing individual elements. The technique for constructing the area of safe operation of the cabin of the GT1-h gas turbine locomotive was illustrated on the example of collision of a locomotive with an obstacle at a crossing. The main parameters determining the energy of interaction between the cabin and the obstacle was singled out, and their influence on the survivability of the structure was analyzed. The finite element method was used to calculate the load-bearing capacity of a power frame with a buffer device in the initial state and after the destruction of individual structural elements by the dynamic strength criterion. The force of elastic interaction between the locomotive and the obstacle was estimated through the spring, the rigidity of which was estimated on the basis of the finite element calculation results. As a result of the calculations, proposals were developed to strengthen the cabin frame to ensure the safety of the crew and the instrument part in case of unauthorized collision with an obstacle of considerable mass and violation of the speed regime.

Based on the view on the abnormality of the surface layer mechanical properties the process of cyclic degradation of the material in the structural element is modeled. The kinetics of the process is determined using nonstandard experiment with construction of total equilibrium curves for the preliminary cyclically loaded specimens. The paper presents the results of numerical solution of the problem, which are in agreement with the experimental ones, on the propagation of fatigue crack in the plate with an opening.

An approach is proposed to solve the problem of estimating the stress state of a shell structure loaded with a thermomechanical load and in contact with a hydrogen-containing medium. The stress state of the steel housing of the diffusion apparatus for the production of highly pure hydrogen was determined. The object of study is presented in the form of a composite shell of rotation, loaded by internal pressure and operating at elevated temperatures. The purpose of the work is to determine the stress state of the shell at normal and elevated pressure, taking into account changes in the mechanical properties of the combined effect of temperature and hydrogen. In the general case, the task of calculating such a structure under given operating conditions is related. In the phenomenological approach, the relationship between thermal diffusion and mechanical problems is manifested in a change in the parameters of the sample deformation diagram with increasing temperature and hydrogen concentration. The integration of differential equations of a boundary value problem for a shell under pressure is performed by the discrete orthogonalization method S.К. Godunov.

When operating a railway rolling stock, one may face a situation that locomotives encounter various obstacles or trains collide with each other, etc. Therefore, it is necessary to create locomotive cab structures that would provide protection for the crew of drivers and cab equipment in such accidents. To absorb the impact energy, installation of various damping structures is provided in the design of a locomotive cab. It is necessary to determine the absorbing capacity of such damping structures at the product design stage, before carrying out full-scale tests. This paper presents the results of calculating the energy-absorbing capacity of damping honeycomb elements for the cab of a GT1h gas turbine locomotive. This does not exclude the operation of some elements of the cab and honeycombs in the region of plastic deformation.

The contact pressure and the stress state of a shell construction lying on supports were determined. By the results of experimental investigations of samples of the material of the construction under consideration, the identification of the model of the cyclic degradation of the material was car ried out. With allowance for fatigue changes of the material properties, an evaluation of the durability of a randomly loaded shell on a discrete base is given.

Stress-strain diagrams and coercive force-strain diagrams for carbon steel samples under uniaxial tension were obtained experimentally during loading and after unloading. These diagrams were used to develop a procedure for determining the stress acting in structural members from the value of the coercive force in the loaded state. A method is proposed to estimate the previous maximum stress from the values of the coercive force measured in the unloaded state.

Stress-strain and coercive force-strain diagrams are experimentally obtained for grade 45 and St3 steels. These diagrams are used to construct matrix dependences between the elastoplastic and magnetic properties of the steels in order to determine the level of stresses in construction members made of these steels.

In this paper, we propose an approach for the determination of the resistance area boundaries for a locomotive cab under possible ad hoc (non-regulated) loads. This limiting surface (boundaries of the area) for the incoming parameters determines the area of safe operation for a locomotive cab. If the parameters of the locomotive and the obstacles are below this limiting surface, the protection of personnel and cab equipment will be provided.

The finite element method is used to determine the stress and strain state of a shell structure supported with lodgment-type elements under the effect of characteristic loads of different types. The lifetime of a structure experiencing irregular loads, which operates in the multicycle fatigue area, is assessed applying the linear hypothesis of accumulation of fatigue damage. An alternative approach to determination of the lifetime of a structure is proposed. This approach involves nonstandard experiments with specimens of materials and nonlinear summation of damage.

Evolution of magnetic properties during tension of multilayer products have been studied on two-layer specimens composed of low-carbon and medium-carbon steel plates with different values of magnetic hardness. The magnetic properties were measured in a loaded state. A model of the stress-strain state of a two-layer specimen has been designed. A technique for restoring stress-strain curves of multicomponent steel products from magnetic characteristics of its components determined directly during tension has been suggested. The values of the field of the maximum magnetic permeability of the components have been recommended as a parameter for nondestructive testing of stresses and strains, namely, at small deformations, the field of the maximum magnetic permeability of the magnetically soft component and at higher deformations, the field of the maximum magnetic permeability of the magnetically hard component. The results obtained are of considerable interest for technical diagnostics of loaded two-layer elements of constructions, including surface-hardened, welded, and bimetallic ones.

We propose an approach to determination of a stressed state of shells of revolution contacting with rigid bodies under the action of loads periodically varying with time and consider two variants of contact interaction: bilateral and unilateral connections of a shell with a rigid body. A stressed state of the shell on a rigid support is investigated.

An approach is proposed to solve problems on the contact interaction of layers in structurally inhomogeneous shells of revolution with allowance for both the normal and tangential stresses in the contact zones. A system of algebraic equations is constructed by using a method for solution of static problems for arbitrary shells of revolution. From this system, the contact zones and contact stresses are determined by the iteration method. The restricted behavior of the adhesion layer in cleavage and shear is taken into account. As an example, the stress state of a two-layer cylindrical shell under a concentrated load is determined

We propose a new approach to the determination of temperature fields and stresses formed in elastic structures of various shapes with complex boundary conditions. As an example, we present the numerical analysis of a structure of this sort, namely, of a crucible subjected to the action of thermal and gravitational loads. We solve this problem in the 3D statement by using the finite-element method and the method of substructures. The boundary conditions for temperature fields are formulated according to the results of thermometry. The conditions of contact interaction between the components of the crucible are simulated by a spring-type finite element. We present the solution of this problem for the lateral wall of the crucible.

An approach is proposed for investigation of the stressed state of three-layer orthotropic cylindrical shells with allowance for possible layer separation. The regions of layer contact and separation and the contact-pressure distribution are found.

The authors examine a problem for a thin cylindrical shell loaded with an arbitrary system of forces and placed on a rigid ciruclar base. A numerical approach to solving problems of this type is proposed. As a result of solving the problem the authors determine the contact zone, the law of distribution of contact pressure, and the stress-strain state of the shell.