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High-strength and armored steels are used in different structural elements and in the development of new military equipment operating under extreme conditions, including high-velocity impact interaction and explosive loading. Under such conditions, the fracture is induced by the combination of different mechanisms that depend on the mechanical properties of materials, strain rate, stress state, temperature, etc. Experimental and computational research methods combine to gain additional information on the behavior of high-strength materials essential for modern military equipment in operation. The test results for the penetration of ARMOX 500T steel target 10 mm thick at different loading rates using a ballistic pendulum are presented. The results of a set of piercing tests with the strikers of three types became the basis for evaluating the integral energy characteristics of material deformation and fracture induced by impact interaction; the target penetration pulse against loading rate was constructed and used in the numerical simulation of impact interaction and validation of model material parameters. The finite element method was employed to numerically simulate the processes of dynamic target penetration with the Johnson-Cook material deformation model. The loading and strain rate effects on the results are estimated. The calculation results are compared with experimental data. [ABSTRACT FROM AUTHOR]

We investigate the structure, hardness, strength, plasticity and fracture character of Cu–Cr microlayer composite material for electric contacts with prescribed microlayered structure and chemical composition in the temperature range from 290 to 1070 K. The correlation relationships between the hardness and strength characteristics have been established. [ABSTRACT FROM AUTHOR]

The processes of impact loading have been studied for a long time, but there are still many questions, the solution of which is vital for various industries, especially for the military. This paper presents the results of comprehensive experimental studies to determine the energy characteristics of fracture during crack initiation and propagation in Charpy specimens of high-strength steel Hardox 450 and armored steel Armox 500T, cut from sheets in two different directions, during impact bending tests. The tests were carried out on an instrumented vertical tester equipped with a high-speed data recording system in the temperature range from –196 to 300 °C. According to the test results, the load diagrams in the force-time coordinates were obtained. The total deformation and fracture energy and its components, nucleation energy, ductile growth, brittle crack slip, and ductile fracture energy of the specimen were calculated. Using quantitative fractography methods, the specimens' fracture surfaces were studied, and the specific deformation and fracture energies and their components were determined. It is shown that the direction of cutting of specimens significantly affects the energy characteristics of fracture. On the upper shelf in the specimens cut in the longitudinal direction, the energy value is higher than for the transverse direction for both steels. This difference is approximately 38% for Hardox 450 and almost 118% for Armox 500T. Using a high-speed recording system allows us to determine the average crack propagation velocity and crack velocities in separate areas by comparing the corresponding zones on the load diagram and on the fracture surface of the specimens. The results showed that the average crack propagation velocity for specimens cut in the transverse direction was 10–15% higher than for specimens cut in the longitudinal direction for both steels. [ABSTRACT FROM AUTHOR]

Results of complex experimental investigations on the determination of energy characteristics of fracture propagation in Charpy specimens cut in three different directions during impact bending tests for heat-resistant 15Kh2NMFA steel are presented. Tests were conducted over a wide temperature range on an instrumented vertical coping equipped with a high-rate data logging system. According to the test results, load diagrams were obtained. Total strain and fracture energy and its components were determined: crack nucleation energy, ductile crack growth energy, brittle crack propagation energy, and ductile final rupture energy. The use of quantitative fractography methods made it possible to determine both the specific strain and fracture energies, their components, and the average propagation rates of brittle and ductile cracks in the specimens' material. Critical brittle fracture temperatures were determined by two methods. The cutting direction of specimens significantly influenced the fracture energy characteristics and crack propagation rates in the material, which might affect the accuracy of strength and resource estimation of the NPP first contour components. [ABSTRACT FROM AUTHOR]

This study conducted modernization of the VK-350 instrumented drop weight impact testing machine (DWITM) developed at the Pisarenko Institute of Problems of Strength of the National Academy of Sciences of Ukraine, equipped with a high-speed strain and force recording system that allows recording a load diagram with a sampling rate of up to 20 MHz, and heating and cooling systems for testing specimens in a wide temperature range. Modernization was carried out to expand the functionality of the DWITM, namely, a new dynamometer and specimen fixing units for impact shear, compression and dynamic pushing tests were installed. The new dynamometer was calibrated for two ranges of amplification and test specimens of various types were tested. The DWITM was also equipped with a video recording system, which includes a high-speed PHOTRON FASTCAM NOVA S9 camera that allows recording the deformation and fracture process at a speed of up to 200,000 frames per second. The camera is equipped with a 12x zoom lens and stroboscopic high-frequency lamps for illumination with the GSVITEC MultiLED G8 control system. Based on the results of the impact bending and shear tests, video signals of the deformation and fracture of the specimens were obtained, which made it possible to determine the time of onset of plastic deformation and formation of adiabatic shear zones in the impact shear specimens, as well as the moment of crack appearance on the side surface of the Charpy specimen and to estimate the rate of its propagation. [ABSTRACT FROM AUTHOR]

Using the created experimental equipment for testing metals by the method of instrumented indentation, a procedure for determining Brinell hardness during the nondestructive testing of structural elements has been developed. In contrast to the conventional method, the hardness is determined by the proposed procedure using the proportionality parameter of plastic indentation, a, which is equal to the slope of the instrumented indentation diagram in the coordinates maximum force of cycle Fmax – residual indentation depth hp after removing the test load of this cycle. Based on the results of a series of tests by the method of instrumented indentation of hardness standards, a linear correlation dependence was obtained between the Brinell hardness value and the proportionality parameter of plastic indentation in a wide range of measured hardness values of 110–650 HBW. The peculiarities of using this procedure and its limitations are analyzed on a number of structural carbon, heat-resistant, and high-strength steels. It is shown that the Brinell hardness measurement results, obtained by the improved procedure, agree within the permissible error with the results of the conventional DSTU ISO 6506-1:2019 method. The difference between their values does not exceed 3.9%. The presented improved procedure can be used in the laboratories of research and educational institutes, central factory laboratories and specialized divisions of various subordination, and other organizations involved in monitoring the condition of the operating critical equipment and setting its further service life both in the laboratory and in the field. [ABSTRACT FROM AUTHOR]

The instrumented indentation method, based on the digital recording of the parameters of the entire process of continuous local deformation of the material by an indenter, provides more complete and accurate information about the material's behavior under load. Obtaining such information without compromising the integrity of a critical structure during operation increases its value. Therefore, more and more attention has recently been paid to portable installations and devices that use the instrumented indentation method. To date, no such equipment is manufactured in Ukraine. Therefore, there is a need to develop portable equipment for conducting such tests in the field under various modes of static and cyclic loading in the macro range of forces. The paper describes an updated portable installation PIIT-02M for determining the strength characteristics of structural elements in service by instrumented indentation, which was developed following the requirements of ISO 14577 and is intended for testing at the macro level. The system of fastening the portable installation on the test object was updated from mechanical (hooks and chains) to electromagnetic. This made it possible to conduct tests on pipes and flat surfaces, including sheet materials and structures made of them, significantly increasing the test efficiency and expanding the range of applications. Comparative tests on a 12 mm thick structural carbon 20 steel plate using the previous mechanical fastening system and the new electromagnetic one showed that the indentation diagrams obtained overlap well. Based on the results of tests of high-strength steels, the portable installation PIIT-02M allows one under both laboratory and operating conditions to record the process of indentation of the indenter into specimens of structural materials with high accuracy and, accordingly, to determine their mechanical characteristics by instrumented indentation. [ABSTRACT FROM AUTHOR]

Reliable operation of products made of high-strength alloy steels is ensured by the availability of effective methods and equipment for studying their mechanical properties during manufacturing and operation. One of the most important properties of such products is resistance to impact damage. The implementation of such tests is limited by the high financial costs of manufacturing specimens and impactors (ammunition), the complexity of conducting them, recording the results, and the lack of initial data. Recently, alternative methods have been developed, such as static and dynamic pressing of plate specimens. In this case, the shape of the impactors (punches) is similar to the shape of the impactors used in punching due to similar material behavior. The pressing tests make it possible to confirm the parameters of the models of material deformation and fracture, which are necessary for numerical calculations of complex structures under various types of loads. The equipment and methodology for studying the behavior of high-strength materials under static pressing are presented. It is established that recording the punch movement using a strain gauge can significantly reduce the elastic deformation component of the power chain of the test machine and fixture loading. A series of tests were performed on specimens cut from Armox 500T steel sheets with thicknesses of 3, 5, and 10 mm for static pressing by different punches (conical, flat, and hemispherical). It was shown that the plastic properties of the material decrease with increasing thickness of rolled steel, regardless of the type of punch. The obtained results confirmed the operability of the presented equipment and methodology and can be used in numerical modeling of deformation and fracture processes of high-strength steels. [ABSTRACT FROM AUTHOR]

Recently, much attention has been paid to the study of the deformation and failure features of high-strength steels under extreme loads, under which they are mainly operated. One of the topical issues is the correct determination of the parameters of deformation models of materials. The use of tests for barrier penetration at high speeds of 100–1000 m/s is quite complicated and expensive, and also does not allow to obtain enough information. Therefore, alternative experimental methods have been developed recently, which include static and dynamic punching tests of thin sheet specimens at speeds of up to 10 m/s. Such tests are simpler and allow to obtain more information about the behavior of high-strength materials in conditions that simulate operational ones. This paper presents the results of static and dynamic punching tests on thin sheet specimens of 50×50 mm size and 1 mm thickness made of Armox 500T armor steel. The static punching tests were carried out on an Instron 8802 servohydraulic machine, for which special equipment was manufactured. The dynamic punching of thin-sheet specimens was carried out on an instrumented vertical impact tester equipped with a high-speed strain and force recording system. To conduct such tests, the experimental equipment was updated, and a design of special supports for the rigid fixing of thin-sheet specimens was developed. The loading speed was varied from 0.5 to 10 mm/min for static punching and from 3 to 5 m/s for dynamic punching. The tests were conducted using three types of punches: conical, flat and hemispherical. According to the test results, new data on the influence of strain rate on the features of deformation and failure of Armox 500T armor steel were obtained. The influence of the type of punches on the nature and mechanisms of failure of thin-sheet specimens under static and dynamic punching was investigated. It was found that an increase in loading speed leads to an increase in specimen failure force. Thus, the resistance to deformation increases by approximately 20% with an increase in the loading speed from 0.5 mm/min to 5 m/s. [ABSTRACT FROM AUTHOR]

The shortage of metal, which can be used to assess the degree of its degradation, makes it necessary to look for ways to increase the information content of tests to justify the extension of the service life of critical equipment and structural elements of various industries. Today, impact bending tests of various types of specimens are one of the most common types of experimental determination of the energy and mechanical characteristics of structural materials. Different types of impact testers are used to perform them. Conventional pendulum impact testers do not allow us to obtain detailed information about the nature of specimen failure and features of crack propagation in the material, so recently, much attention has been given to the instrumentation of experimental equipment using modern recording systems. In this work, the instrumentation of an MK-30 pendulum impact tester was carried out using a multichannel high-speed strain and force recording system, which allows obtaining results with a sampling rate of up to 20 MHz. A procedure for the calibration of the strain gauges located on the pendulum blade and calibration of the recording system and amplifier blockt for three different signal levels is described. Test trials of specimens of different sizes made of different types of steels were carried out, and loading diagrams in the force–time coordinates were obtained. It is shown that the obtained loading diagrams can be used to calculate the values of the total energy of both deformation and fracture and its components: crack nucleation energy, ductile crack growth energy, brittle crack breakthrough energy and final ductile fracture energy. Using fractographic analysis, the characteristic portions of loading diagrams were compared with the corresponding zones of the fracture surfaces of specimens. The high sensitivity of the recording system allowed us to calculate with high accuracy the values of the crack at brittle fracture and its average velocity in test specimens. [ABSTRACT FROM AUTHOR]

The methodology for determining more reliable values of hardness of high-strength steels has been improved, which contains, in addition to the requirements of DSTU ISO 6506 standards, requirements for the preparation of the outer (front) and back sides of the sheet in the plane of rolling by removing the decarburized metal layer, requirements for surface cleanliness and the choice of indenter load. The influence on the measured hardness values of the surface decarburized metal layer that occurs on the front surfaces of the sheet as a result of "burnout" of oxygen on the surfaces of the sheets during the manufacturing process is determined. This decarburized metal layer distorts the hardness values obtained during indentation. By layer-by-layer metal removal, the size of the decarburized layer was determined. The obtained results made it possible to determine the nature of the hardness distribution over the thickness of the sample, to establish the thickness of the decarburized layer and to determine the level of surface cleanliness of the base metal sufficient to obtain reliable hardness values. The results of experimental studies on determining the Brinell hardness values of high-strength steels are presented. The experimental data show that the existing regulatory documents do not fully provide reliable information about the properties of materials. The requirements for instruments for testing high-strength steels for hardness by the Brinell method are considered. The analysis on the choice of load on the indenter is made. The load is selected such that the ratio of the diameter of the imprint to the diameter of the ball is in the range from 0.3 to 0.4. [ABSTRACT FROM AUTHOR]

Based on the experimental studies and the corresponding analysis of regulatory documents governing the hardness measurements by the Brinell method, the methodology for determining the hardness of high-strength sheet steels was developed. It allows one to obtain more accurate values of some characteristic cases that led in practice to issues of the inconsistency of metal quality with the stated characteristics. In addition to compliance with the requirements of DSTU ISO 6506, the methodology contains additional requirements to take into account several factors specific to this class of materials, the choice of ball indentation, the load level, the friction force during ball indentation, heterogeneity of structures, surface preparation purity, etc. In developing the methodology, a cycle of studies was carried out to determine reliable Brinell hardness measurements according to DSTU ISO EN 6506 on the example of Armox 500T and Hardox 450 sheet steel, which made it possible to determine the hardness distribution pattern over the sample thickness, to establish the thickness of the decarburized layer, to determine the purity of the base metal surface sufficient to obtain reliable hardness measurements, that is without decarburized layer and to decide the indenter choice and the load level on it. It is recommended that the direction of the line along which the measured hardness is measured be placed along the sheet rolling axis with subsequent determination of the average hardness value. Increasing the number of prints significantly reduces measurement errors due to the ambiguity of the contour of the print caused by the metal sliding. [ABSTRACT FROM AUTHOR]

The tribological properties of matrix and skeletal titanium carbonitride composites were studied in dry friction conditions in air. Experiments on wetting of the TiCN–Cr3C2 composite by nickel–chromium alloys and copper using the sessile drop method were performed to choose matrix composition and ascertain whether the samples could be produced by impregnation of the porous skeleton. The sessile drop experiments showed that nickel and its alloys formed a low contact angle on the TiCN–Cr3C2 composite (θ ≈ 8°). In particular, Ni3Al intermetallic had θ < 5°, allowing it to be used as a metal matrix. The same situation was observed for copper. A technique was developed for producing TiN–Cr3C2 composites by impregnation of the porous skeleton with Ni3Al and copper melts, and the tribological behavior of the cermets was tested in dry friction conditions. When the starting composite was impregnated with Ni3Al intermetallic, the friction coefficient decreased (μ = = 0.25). Structural studies were conducted with a MIM-10 metallographic microscope and X-ray diffraction with a DRON-2 diffractometer. The hardness and contact area thickness were measured employing a Falcon 9 hardness tester (manufactured in the Netherlands). Thin cross sections were made to examine the structure and phase composition of the contact area. The structure was analyzed using X-ray diffraction and scanning electron microscopy. The effect exerted by hardness of the counterface (steel 45, 40Kh, ShKh15) on the tribological properties of the TiCN–Cr3C2 composite was established. When steel hardness was 60 HRC, the friction coefficient increased with friction distance. These results were, however, obtained at low speeds and loads. Friction losses decreased with loading increasing from 2 to 6 MPa at 12 m/sec: friction coefficient reduced to 0.23. The TiCN–20% Cr3C2 cermets impregnated with Ni3Al may be recommended as antifriction materials for use in high-speed and high-load friction units. [ABSTRACT FROM AUTHOR]

The article is devoted to scientific biography of the prominent neuroanatomist, Doctor of Medical Sciences, Professor L. A. Shangina, representative of the scientific school of Tonkov-Bushmakin. Her input into becoming of the chairs of normal anatomy of medical institutes in Irkutsk, Moscow, Kursk, Dushanbe (Tajikistan) and Smolensk and in organization of scientific community of neuromorphologists in the USSR in the middle and second half of the twentieth century is demonstrated. The special attention is paid to the results of scientific studies of L. A. Shangina and her post-graduate students of topography of nerves innervating human heart, of topography of accessory nerve (XI pair of cranial nerves), of structure of receptors of autonomic nervous system in walls of alimentary tract and urinary system.

The glaucoma is a leading cause of irreversible blindness in all countries. In the nearest years an increasing of patients with the given pathology is prognosticated. Nowadays, development of disease is related to alteration of interleukin profile in lacrimal fluid. however, diagnostic significance of interleukins is studied insufficiently. The purpose of study. To determine diagnostic significance of interleukins on a local level for amelioration of diagnostic and prognostication of development of glaucoma. The content of interleukins in lacrimal fluid was analyzed in 80 patients with glaucoma stage II and 45 healthy individuals using technique of sandwich-linked enzyme-linked immunosorbent assay with calculation of informativeness of indices of immunity. The results. The analysis established high diagnostic significance of IL-2, IL-17, IL-8 for verification of glaucoma. They are proposed to be applied in laboratory diagnostic and prognostication of disease. The developed regression model ensures with high accuracy prognostication of development of glaucoma in case of increased level of IL-2, IL-17, IL-8., Competing Interests: The authors declare no conflict of interest.