The possibility of assessing the fracture resistance of brittle materials by testing short cylinders, solid and with a central hole, under diametral compression has been investigated. The computational analysis was performed using the finite element method with the ANSYS program. It was shown that the stress distribution in a disk with a hole is similar to that in a disk without a hole, but it has disturbances caused by the stress concentrator in the form of the hole. The normalized values of the maximum principal stresses for a disk with a hole are more than 5 times higher than those for a disk without a hole. Experimental analysis was carried out by testing short cylinders made of brittle materials—cast iron and graphite—both solid and with a central hole. It was found that the fracture resistance determined by the formula of the ASTM D3967-95a standard is practically the same for solid cast iron specimens, while for graphite specimens it differs by 1.5 times from the true fracture resistance of the materials. When testing specimens of cast iron and graphite with a central hole, the fracture resistance differs from the standard by 1.5 and almost 2.5 times, respectively. The different nature of specimen failure was also noted—slow controlled fracture for cast iron and dynamic fracture for graphite, according to their respective deformation diagrams. As an example, the results of testing real cylindrical specimens with a central hole—uranium dioxide fuel pellets—are presented. It is shown that the results of testing graphite ARV-1 specimens and fuel pellets are in good agreement. Thus, the possibility of testing small short cylinders using the diametral compression scheme for indirect assessment of tensile strength of brittle materials is confirmed. A calculation equation is proposed for the indirect assessment of the tensile strength of brittle materials based on the results of testing small short cylinders with and without a central hole under diametral compression.

This study consideres application of the digital image correlation method for estimating the relative deformations of composite materials obtained with the use of thermal treatment by laser radiation. The use of this technology made it possible to determine the mechanical properties of materials containing macroscopic austenite regions distributed in the martensite matrix according to a given law. The evolution of strain fields that occur when a load is applied to the samples under study is determined. The influence of the shapes and sizes of regions with high plastic properties (austenite) on the integral mechanical characteristics of composite materials has been studied.

Исследованы механические характеристики композитных материалов на основе сплава Fe – 18 % Cr – 10 % Ni, состоящих из пластичных макроскопических областей аустенита, распределенных в высокопрочной мартенситной матрице. Получены кривые напряжение – деформация для образцов, в которых аустенитные области различаются по размерам и форме. На основе анализа построенных диаграмм определены формы аустенитных областей, оптимальные с точки зрения сочетания прочностных и пластических характеристик материала.

Mechanical characteristics of composite materials based on Fe – 18% Cr – 10% Ni alloy and composed of plastic macroscopic austenite regions distributed in a high-strength martensite matrix are studied. Stress-strain curves are obtained for the specimens with austenite regions differing in size and in shape. The plotted curves are used to determine the shapes of the austenite regions optimal in terms of combining the strength and ductility parameters of the material.

Mechanical characteristics of composite materials based on Fe – 18

A number of methods for testing bending of thin discs on an annular support designed to determine the tensile strength of brittle materials, are considered. The methods differ in the type of a loading indenter (with flat, spherical, or toroidal tips), support devices, and calculation equations for determination of the breaking stress. The results of testing samples on an annular support made of two model materials which differ in the degree of brittleness, i.e., cast iron and graphite, are presented. It is shown that the calculated strength of the tested materials depends on the character of the sample destruction and on the type of bending diagram. Cast iron samples were destructed under a significant plastic deformation (characteristic bending diagram passed through the maximum), and the tensile strength of the samples corresponded to the compressive strength of the material being several times higher than the tensile strength of the material. Graphite samples underwent brittle fracture (within the linear section of the bending diagram), and the calculated strength value was comparable to the tensile strength of the material. A conclusion is made that the use of the test method of thin disk samples on an annular support for determination of the tensile strength of the material is substantiated only in the case of absolutely brittle fracture of samples with a bending diagram similar to the fracture diagram of graphite samples. Disk samples made of aluminum oxide obtained by electro-pulse sintering were tested using two methods (with flat and spherical tips). In both cases, the bending diagram of aluminum oxide samples was similar to that of graphite samples, i.e., their destruction occurred at the initial linear section of the diagram and was absolutely brittle. The results of comparative testing of the samples made of aluminum oxide, taking into account the results of testing samples made of model materials (cast iron and graphite), showed that tests on the annular support of disks using a flat-tipped indenter are the most grounded. The samples should be made of brittle materials having a linear bending diagram up to the sample destruction.

A method has been developed for detecting errors in the memory of a microcontroller (MC), which is necessary for research and testing for noise immunity of the MC. The method is based on the operation of the hash function hardware unit for calculating the checksum (CS) of useful data. Based on the method, an approach is proposed for correcting erroneous bits in the memory of various computing devices. The method includes an algorithm for detecting and correcting errors, which allows to restore data in memory by calculating their CS with the organization of data storage in the form of a structure. The proposed method enables helps to recognize the object where an error occurred and to recover the erroneous memory bits. The implementation of the data verification algorithm as a system process of the real-time operating system made it possible to automate the process of searching for errors in the background and determine the cause of the failure. The software implementation of the error detection and correction method, without changing the hardware, can be used in the operation of radioelectronic equipment in difficult conditions containing any computing device.

Currently, low-modulus biocompatible Ti – Nb – Zr alloys are considered promising for medical applications. Superelasticity is a property that is mainly governed by the crystallographic direction in single crystals, i.e. by the predominant orientation of grains in polycrystalline objects. In order to control the crystallographic texture in products (such as foils), one should understand how it forms at various stages of thermomechanical processing. This paper compares the following alloys in terms of their crystallographic texture and how it forms: Ti –18Zr – 15Nb (18-15), Ti – 6Zr – 22Nb (22-6), Ti – 22Nb – (1–1.5)O (1O and 1.5O) (at.%). The composition of an alloy influences the stability of the initial β-phase, which tends to decrease with an increase in the concentration of Zr, which replaces Nb. A decreasing stability triggers martensitic transformations during rolling resulting in the formation of a weak blurry texture {112}<011>, as can be observed during deformation of alloy 18-15. Plastic deformation of a stable β-phase leads to the formation of a sharp twocomponent texture typical of BCC alloys: {110}<001> and {112}<011>, which develops during the rolling of alloys with oxygen and 22-6. Recrystallization of rolled foils (ε = 92%) at 650 оC for 0.5 h leads to sharpening of the texture components in the case of samples with a sharp deformation texture (22-6, 1O, 1 .5O) and to a change in texture in the case of samples with a weak deformation texture (18-15). Cyclic tensile tests conducted in three different directions revealed the presence of anisotropy in foils of all compositions. However, alloy 18-15 has the lowest anisotropy. An increase in the Zr concentration contributes to maximum reversible strain in the process of realizing superelasticity at room temperature. This research was funded by the Ministry of Science and Higher Education of the Russian Federation; Agreement No. 075-15-2021-1352.

The fundamental aspects of the process of high-voltage consolidation of powder materials, as well as its advantages and limits, are discussed in this study. In this respect, the electrothermal processes at the contacts between powder particles (mesoscale), and also at the macroscale of the total volume of the consolidated sample, are investigated. Moreover, the dynamics of interparticle pore closure (collapse) in the consolidated material are calculated. The results of HVC experiments of difficult-to-sinter tungsten-based alloys are presented. The macro- and microstructure examinations of consolidated specimens, as well as stress-strain tests, are also evaluated. Compression tests show that all tested alloys can withstand compressive stress without failure at room temperature. In particular, a criterion for determining the range of technological variables for the fabrication of high-density samples is described. Finally, a promising future research area for this approach is proposed.

The use of selective laser melting (SLM) leads to the formation of a complex material structure with high residual elastic stresses. The work investigates the distribution of macrostresses in SLM samples using five different scanning strategies. The stresses were measured by X-ray method and by recording the change in the shape of the specimens as a result of their separation from the platform using digital correlation image method. The combined use of the two methods provides more reliable results for SLM samples. It is shown that depending on the scanning strategy, the nature and magnitude of macrostresses change which are distributed more isotropically and have a smaller value when using scanning strategies with different directions of the laser beam movement.

Currently, Ti-Zr-Nb-based biocompatible alloys are considered as prospective for medical applications. In this work, the mechanisms of the formation of the crystallographic texture of five alloys Ti-(17-19)Zr-(14-16)Nb (at.%) have been compared. The presence of martensitic transformations during the rolling process determines the features of the formed texture. At the initial stage of deformation (ε = 50%), the texture {112}<011> is formed in all five alloys. With an increase of the degree of deformation to 92%, the texture dissipates somewhat, which is due to an increase in the fraction of the martensitic phase in the foils. Recrystallization of rolled foils (ε = 92%) at 650°C leads to an exacerbation of the texture component close to {100}<011>, the blurring of which varies in different alloys. Cyclic tensile tests along three directions: the rolling direction (RD), the transverse direction, at an angle of 45° to the RD showed the presence of anisotropy in the samples. It was shown, that the effect of superelasticity is orientation-and structure-depending, and the anisotropy of mechanical properties.

Abstract Two methods of bending thin disks on an annular support are compared. The methods differ in the type of loading indenter and the equations that determine the strength of the material by the test results. The end surfaces of the indenter are flat cylindrical (indentor 1) or spherical (indentor 2). The methods were used to test identical disc samples from model materials: cast iron and graphite, as well as aluminum oxide samples obtained by spark-plasma sintering. The results of testing 24 disks of model materials and 10 disks of aluminum oxide on the ring support are presented. Bending diagrams of 12 disks of each model material on the annular support using two types of indentors indicate their different tensile strength. The calculated values of strength and their spread were higher when using indenter 2 than when using indenter 1. Thus, comparative tests have shown that the calculated strength of the tested materials depends on the nature of the failure of the samples and the type of bending diagram. The most reasonable were the test results obtained with the use of a flat-tipped indenter, which coincide with the characteristics of the strength of materials and the minimum spread of values.

Research into the plastic deformation process in the lattice structure produced by selective laser melting (SLM) of powder from 316L austenitic stainless steel was carried out by compression tests along the build direction and perpendicular to it. The resulting stress–strain curve parameters showed anisotropic behaviour of such a structure. Differences in the crystallographic texture of both the bulk and lattice samples were also discovered, so the direct use of the mechanical properties of the bulk materials for calculation of lattice structure deformation behaviour would be incorrect. To overcome this limitation, the crystal plasticity finite element model based on the DAMASK framework was used, and the mechanical properties of the lattice structure material were calculated with respect to the crystallographic texture differences. In turn, the data obtained for the bulk material was used to model the plastic deformation of the lattice structure and these results are in good agreement with the experimental data. Therefore, it is possible to use the bulk material data for forecasting the lattice structure deformation. The resultant model allows for the prediction of the deformation behaviour of the lattice ribs.

The main features of high-voltage electropulse consolidation (H-VEC) of powder materials and the unique possibilities of the method caused by them are considered. The electrothermal processes in the H-VEC at the contacts between the powder particles and in the macroscale of the whole consolidated sample are analyzed. The results of calculations of the dynamics of closure (collapse) of interparticle pores in the consolidated material are presented.

The field of applicability of bending of thin disks test on an annular support and the “Brazilian test” for short cylinders is discussed. These methods are used to determine the tensile strengths of the materials formed by electric pulse powder consolidation. These techniques of testing small samples make it possible to study the influence of technological factors on the strengths of the consolidated materials.

The processes of formation and growth of an incipient crack in EI847 steel have been studied by uniaxial constant-load tension testing on an INSTRON-5982 tensile testing machine using scanning contact potentiometry. The nucleus was detected at the sample surface within the yield strength domain and was stably monitored based on the readings of apparatus under higher loads until the moment of destruction.

The paper considers the possibility of using laser milling technology for precision processing of ceramic samples from pre-sintered and sintered ceramics zirconia and lithium disilicate. To find the best radiation source were compared different lasers. To find highest removal rate with acceptable accuracy was studied influence laser and scanning system parameters on ceramics. Accuracy problem of laser milling was considered. Examples of surfaces of prostheses were made.