I. G. Emel’yanov

Variation of magnetic properties of two-layer carbon-steel products under tension

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.

Estimation of the fracture strength of a spatial beam–rod structure

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.

Evaluation of the life of a shell construction lying on supports

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.

Determining the stress state and the lifetime of a shell structure

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.

Investigation into the contact interaction between shell and base with notches

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.

Consideration of Cyclic Degradation of the Material and Abnormality of the Surface Layer Mechanical Properties in Calculating the Life of a Plate with an Opening

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.

Model of the state of stress in a bilayer steel workpiece during uniaxial tension

A model for the state of stress in a planar bilayer workpiece under uniaxial tension conditions is proposed, and a method for the calculation of its stress-strain diagram from the experimentally obtained tensile curves of its components is developed. This method can be used to solve the inverse problem: using the stress-strain diagrams of one of the components and the entire workpiece, one can calculate the tensile curve of the second component. Since stress-strain diagrams can be obtained by nondestructive magnetic methods directly during loading, the results obtained are important for the diagnostics of loaded bilayer steel construction members.

Determination of safe operating conditions for supporting structures under abnormal loads

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.

Determination of Matrix Dependences between the Magnetic and Elastoplastic Characteristics of Steels during Tension

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.