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Installation and test procedure for frequency stability under cyclic loading of metals and alloys

Manufacture of parts operating under difficult conditions of cyclic loading, as well as products with stable dimensions necessitates the use of materials with minimal manifestations of inelastic properties. Study of these materials suggests conducting specialized narrowly focused tests using newly developed machines and installations with appropriate experimental techniques. We present the design, operation and control features of the original electromagnetic installation for testing fatigue and frequency stability and operating in a self- oscillating mode, which provides the equality of the frequency of cyclic loading and natural frequency of the sample. The system of the installation control contains two closed circuits: for excitation of self-oscillations and for stabilization of the oscillation amplitude. The sample is loaded by electromagnetic force, and unloading occurs due to the elastic forces of the material. The methodology and algorithms for calculating the stresses of samples of various geometric shapes for estimating changes in amplitude-frequency characteristics are presented. The calculated relationship between the force applied to the sample and its movement at the point of application of force is derived with subsequent determination of the stress by a known force. The results of calibration tests for the static mode of sample loading are presented and the forces acting on the sample (external, inertia, and elastic forces) are evaluated taking into account the maximum stress and maximum strain amplitude. Static and cyclic loading modes are compared. The frequency characteristics obtained during testing steel samples according to the proposed method are obtained. The experimental results of tests with interruptions in the process of cyclic loading and continuous testing are analyzed. It is shown that interruptions in cyclic tests lead to a jump-like increase in the frequency, whereas continuous tests revealed no jumps. At the same time, a comparative analysis with the results of continuous tests showed that the overall frequency deviation is approximately the same for the entire operating cycle in both cases. It is shown that an increase in the frequency after rest is random and does not depend on the number of operating cycles.

Economic development and economic policy in the transition to post-normality

Aim. To study the transformations of economic development trends and changes in the priorities of economic policy in the period of modern political and economic turbulence associated with the transition to a new quasi-stable state of the economy — post-normality.Tasks. To consider the features of the modern Russian economic model; to describe the mechanism of the impact of macro shocks of 2020 and 2022 on the Russian and world economy; to characterize the target — postnormal — state of the national and world economy; to offer recommendations for improving economic policy in the new conditions.Methods. The author of the article used both general scientific methods of research, including systemic, retrospective, institutional and macroeconomic (positive and normative) analysis, and specialized methods of studying economic evolution, economic dynamics and statics, situational and scenario modeling, economic statistics and others.Results. In recent years, the conditions of foreign economic interaction of many national economies, especially the Russian economy, have changed. During the post-Soviet period, Russia has consistently and systematically pursued a policy of economic liberalization, in particular, foreign economic liberalization. The first significant blow to the openness of national economies was the COVID-19 pandemic. The second was the sanctions imposed against Russia by the countries of the “collective West”, which gradually affected an increasing number of countries. The essence of these shocks from the point of view of macroeconomic analysis is a jump-like increase in the closedness of the national economy. Under these conditions, it is established that national economies of post-industrial type turn out to be unstable and unviable under the new realities. This should be taken into account in economic policy. Attention should also be paid to the fact that the processes of growing crisis of the currently prevailing model of open economy will inevitably affect not only economic, but also political, cultural and other processes. An attempt to overcome the sanctions on Russia by geographical reorientation of foreign economic interactions can be effective only in the short term, as a tactical measure. Strategically, it will not work, because the flaws of the open economy model, consisting in high (and in some cases — critical) dependence of the national economy on foreign economic interactions, cannot disappear. Therefore, this openness should be reduced in areas critical for national development. Special attention in economic policy should be paid to the issues of social justice, without the solution of which it is impossible to achieve public consensus and ensure the effectiveness of the institutional changes necessary in connection with the transition to post-normality. Conclusions. The modern Russian economy is at another transitional stage of development. In general, constant transformations are a systemic property of the economy, a condition for its existence. At the same time, in modern realities there is a transformation of strategic nature associated with the change of the key feature of the existing economic model — its degree of openness. Although the Russian economy as a whole has been able to adapt to the new conditions of functioning, but this is a tactical adaptation, in the strategic aspect it is not enough for a successful transition to the post-normal stage of development. In this regard, a more balanced and active participation of the state in the management of economic development processes and their regulation is required, subject to the formation of effective economic and other incentives to support such processes for both business and the population. In view of this, it is advisable to take into account the recommendations proposed by the author of the article in the economic policy.

Study on multiple fatigue cracks growth in the web of a hollow compressor impeller

The fatigue crack growth characteristics of a hollow impeller whose thin-walled web has the propensity to nucleate multiple site damage (MSD) were investigated. To study its MSD crack growth, a simulation framework was proposed to accomplish noncoplanar crack coalescence and user-defined growth. It employed a modified linkup criterion and could account for the geometric constraints of cracked bodies, crack closure, and the kinking and twisting angle introduced by KII and KIII. Interaction features of the multisite crack growth were studied by simulating carefully designed cracking scenarios, and the crack cascade’s typical evolution over time and space was deduced. Results showed that larger adjacent cracks would introduce a stronger interaction effect. For crack colonies, the stress intensity factor would increase and remain higher between different merging positions. The crack growth was predominantly in tensile mode (greater than 95%) before coalescence, whereas the in-plane and out-of-plane shear modes increased noticeably to about 30% during and after coalescence. MSD will adversely affect the impeller fatigue evaluation due to faster crack growth, more complex crack profiles, and difficulty in determining the critical crack size due to the jump-like increase of crack colonies that makes applying damage tolerance difficult.

Titanium alloy fatigue strength and eigenfrequency stability

We conducted a study on fatigue in flat samples of the VT3-1 titanium alloy using “soft” cyclic beam bending tests. For this purpose, we developed an innovative electromagnetic test bench. The test bench's electromechanical system induces mechanical vibrations at a frequency that matches the eigenfrequency of the sample, ensuring that the cyclic load frequency remains constant. The electromagnetic force bends the sample while the elastic force unbends it, producing a quasi-sinusoidal cyclic load. Through our investigation, we determined the impact of this cyclic loading on both cyclic strength and durability. Our findings indicate that the VT3-1 titanium alloy possesses high resistance to fatigue and an endurance limit. Furthermore, we observed a low variability of the experimental fatigue resistance in relation to the approximating fatigue curve, suggesting the alloy has high structural stability. This finding indicates that the VT3-1 titanium alloy possesses high structural stability. To assess eigenfrequency stability, we subjected the alloy samples to cyclic tests, interrupting them at a reference number of 50 million cycles to evaluate changes in eigenfrequencies and stability under loads close to the fatigue limit. The results showed that the titanium alloy has a high level of eigenfrequency stability. Interruptions in cyclic tests resulted in jump-like increases in eigenfrequencies, which was not observed in continuous tests. Nevertheless, the total eigenfrequency deviations from the initial value at the end of the tests were similar in both cases

ПРИБОР ДЛЯ ИССЛЕДОВАНИЙ ДЕФОРМАЦИИ И РАЗРУШЕНИЯ ЗЕРНОВОК ПРИ СТАТИЧЕСКОМ СЖАТИИ

The strength properties of grains must be taken into account in the development and modernization of machinery and equipment for the implementation of many technological processes in agricultural production. Known devices and methods for determining the forces of destruction of grains under external influences are considered. A device has been developed for studying the process of deformation and destruction of grains under static compression, which makes it possible to establish the strength properties of various grain materials. The results of studies on the deformation and destruction of wheat grain under static compression are presented. It has been established that, regardless of the spatial orientation of the grain, the dependence of the deformation on the loading force has straight sections, indicating its uniform compaction. An abrupt increase in deformation occurs when the grain of wheat is oriented with the groove up and the load P = 10.37 kgf, after which there is no significant increase in deformation with an increase in P to 11.67 kgf. With further loading within P = 12.04 - 15.18 kgf, the grain deformation increases again with its compaction. At a load P = 15.55 kgf, an abrupt increase in deformation is again observed, after which the grain was destroyed. In the case of grain orientation with a groove down, a characteristic jump-like increase in its deformation occurred at a force of 17.31 kgf, which is 6.94 kgf more than in the opposite placement. After that, the dynamics of deformation increased significantly, and the destruction of the grain occurred at a force of 19.25 kgf, which is only 3.51 kgf higher than the similar value for the grain oriented with the groove up.

Predicting Time-to-Failure of Red Sandstone by Temporal Precursor of Acoustic Emission Signals

The evolution pattern of rock damage is a progressive failure process of rock materials. It is the basis for predicting failure time of rock materials. By theoretical and experimental analysis, the acoustic emission (AE) precursor characteristics of rock fracture and the gradual evolution pattern of rock damage were analyzed detailedly. Then, the time-to-failure of red sandstone was predicted and compared by several different methods. The results demonstrated that the failure process of red sandstone can be divided into the stable deformation stage and the critical acceleration failure stage. In the critical acceleration failure stage, the AE precursor of rock failure was easy to be observed, and the AE event rate occurred as jump-like increase phenomenon. Moreover, the gradual evolution pattern of rock damage obeyed an exponential function, and the damage acceleration phenomenon existed in the critical failure stage. Furthermore, the higher values of the average of rock damage was, the more obvious linear evolution pattern will be, which was beneficial to improve the prediction accuracy of time-to-failure of rocks. Clearly, the linear prediction results of rock failure time, after taking average values of five rock damage variables, had more higher accuracy when damage variable exceeded D = 0.5 . The predicting result of specimen R1 was 0.2 s ahead of its actual failure time, and the predicting result of specimen R6 was 8.1 s ahead of its actual failure time. Therefore, this method is meaningful and it can be used for the early warning of rockburst.

Recovery of LED Emission Power under the Exposure to γ-n-Pulse

The article presents results of the study of the effect of LED power modes based on AlGaAs heterostructures (short-circuit, open circuit, and active mode with the passage of operating current during irradiation) on the resistance to γ-n-pulse exposure. Reduction of LED emission power under the influence of γ-n-pulse occurs in two stages irrespective of irradiation power mode, with each stage characterized by its own regularity and its own factor. Built-in electric field of p-n-junction does not contribute significantly to the degradation of LED power when exposed to γ-n-pulse. At irradiation of LED in active power mode after exposure to γ-n-pulse (Fn ≤ 1.5·1012n/cm2, Dγ ≤ 20 Gy (Si)) a recovery of LED power by the value of ΔP is observed. Recovery of ΔP power leads to reduction of the damage factor at the first stage, to increase of the LED resistance, and to shift of the boundary between the stages to the area of higher neutron fluences. It is supposed, that the observed jump-like increase of ΔP radiation power under the influence of γ-n-pulse is caused by radiation-stimulated annealing of local mechanical stresses that is generated under the condition of passing of operating current through LED.

Comparative study of multiple heat indices in revisiting summer heat across China based on meteorological observations

Multiple indices have been created to measure hot conditions that may cause discomfort, stress even death to humans. However, distinctions among these indices and their performance in measuring heat remain undisclosed. We conduct a comparative study of multiple heat indices and revisit the spatiotemporal changes in summer heat across China. The maximum temperature-based index, more sensitive to average and maximum temperatures, suggests a larger increasing trend (0.42°C/10a) in heat intensity than those average temperature-based ones which are more sensitive to minimum temperature. The absolute threshold-based heat-day indices are not so applicable as the relative ones in measuring the increasing heat days over the Tibetan Plateau. During 1960–2018, significant ( p < 0.05) increasing trends in heat intensity (0.11–0.42°C/10a) and heat day (0.63–2.67 days/10a) are revealed with a jump-like increase after the mid-1990s at the country level. Stronger heat intensity occurs over the southeast and north China with larger increasing trends over the Tibetan Plateau and northwest China. Northern China with larger increasing heat intensity and days should take effective measures of adaptation to reduce suffering from the summer heat. Given differences among multiple indices and the performance over different regions, a rational selection of heat index considering the research subject of interest and regional climatology is highly recommended.

Transport transitions at high electron cyclotron resonance heating powers at the L-2M stellarator

The experimental results are presented from the experiments on the high-power electron cyclotron resonance heating (ECRH) of the current-free plasma with the power 200–500 kW (the specific power was 0.8–2 MW/m3). The spontaneous transport transitions were observed that resulted in an increase in the plasma density and energy. At the ECRH powers exceeding 150 kW, the processes are observed accompanied by the abrupt changes in the plasma edge parameters, while the core plasma parameters change only slightly. At the ECRH powers exceeding 400 kW, a jump-like increase in the plasma density and energy is observed. At a power of approximately 500 kW, the regime was obtained, in which at time of transition, the plasma energy and lifetime increase by 20%, despite a decrease in the electron temperature. At the same time, at heating powers up to 700 kW, the energy lifetime corresponds on average to the L-2M single-machine stellarator scaling.

Pf-hybridization and magnetic phase transitions in ferromagnetic superconductors

Abstract In the framework of the Anderson pf-model, magnetic phase transitions in 5f-ferromagnetic superconductors with hybridization of localized (f-) and delocalized (p-) electrons are discussed. We consider a free-energy functional containing a contribution due to the mode-mode coupling spin fluctuations. The calculated p-T-diagram of magnetic states describes transitions of the first and second order and the region of the ferromagnetic short-range order too. It is shown that when the temperature and pressure change, a shift of the chemical potential to the pseudogap region is possible, with a jump-like increase in the occupation of the spin-symmetrized electronic states and an increase in the screening of the local magnetic moments.

On the Appearance of Mixed Dynamics as a Result of Collision of Strange Attractors and Repellers in Reversible Systems

In this work, we propose a scenario of appearance of mixed dynamics in reversible two-dimensional diffeomorphisms. A jump-like increase in the sizes of the strange attractor and strange repeller, which is due to the heteroclinic intersections of the invariant manifolds of the saddle points belonging to the attractor and the repeller, is the key point of the scenario. Such heteroclinic intersections appear immediately after the collisions of the strange attractor and the strange repeller with the boundaries of their attraction and repulsion basins, respectively, after which the attractor and the repeller intersect. Then the dissipative chaotic dynamics related to the existence of the mutually separable strange attractor and strange repeller immediately becomes mixed when the attractor and the repeller are essentially inseparable. The possibility of realizing the proposed scenario is demonstrated using a well-known problem of the rigid-body dynamics, namely, the nonholonomic model of the Suslov top.

Correlation between the sudden jump-like increases of the atrio-Hisian interval induced during burst atrial pacing and during programmed atrial stimulation in patients with atrioventricular nodal reentrant tachycardia

PurposeTo study the correlation between the sudden prolongations of the atrio-Hisian (AH) interval with ≥50 ms during burst and programmed atrial stimulation, and to define whether the AH jump during burst atrial pacing is a reliable diagnostic criterion for dual AV nodal physiology. MethodsRetrospective data on 304 patients with preliminary ECG diagnosis of AV nodal reentrant tachycardia (AVNRT), confirmed during electrophysiological study, was analyzed for the presence of AH jump during burst and programmed atrial stimulation, and for correlation between the pacing modes for inducing the jump. Wilcoxon signed-ranks test and Spearman's bivariate correlation coefficient were applied, significant was P-value <0.05. ResultsThe population was aged 48.5 ± 15.7 (12-85) years; males were 38.5%. AH jump occurred during burst atrial pacing in 81% of the patients, and during programmed stimulation – in 78%, P = 0.366. In 63.2% AH jump was induced by both pacing modes; in 17.8% – only by burst pacing; in 14.8% – only by programmed pacing; in 4.2% there was no inducible jump. There was negative correlation between both pacing modes, ρ = –0.204, Р<0.001. ConclusionBurst and programmed atrial stimulation separately prove the presence of dual AV nodal physiology in 81 and 78% of the patients with AVNRT, respectively. There is negative correlation between the two pacing modes, allowing the combination of the two methods to prove diagnostic in 95.8% of the patients.

Parameters of radiation processes in the microwave resonant plasma

This work presents results of experimental studies of the spectral and photometric characteristics of optical radiation generated by a pulse-periodic microwave discharge close to ECR (2.45 GHz, average power of up to 200 W, argon pressure of 10–4–10–1 Torr). Under these conditions, dense (n e = 1010–4 × 1011 cm–3) low-temperature (T e = 3–5 eV) plasma is produced in the working volume at an ionization rate of 10–3–5 × 10–5. It is shown that the increase in the electron density near the upper boundary of the pressure range at a constant level of the input power leads to a drastic change in the type and spectral composition of plasma radiation and a jumplike increase in the light flux. The results of probe and optical measurements made it possible to determine the range of the operating parameters defining the character and parameters of the radiation processes under study.

Properties of strained TaS3 samples in the state of charge density wave and in the normal state

The uniaxial strain of quasi-one-dimensional conductor whiskers of orthorhombic TaS3 at a strain higher than e c ~ 0.8% leads to a sharp increase in the coherence of the properties of a charge density wave (CDW), which manifests itself in its motion in fields higher than threshold field E t . During uniaxial elongation, TaS3 is shown to exhibit the following unusual properties even in weak fields: Peierls transition temperature T P depends nonmonotonically on e, one-dimensional fluctuations weaken near T P , and the coherence length of a charge density increases at T < T P . Investigations in fields higher than E t show that the ultracoherent properties of CDW exist in a wide temperature range and are retained when temperature increases up to T P . These properties of CDW make it possible to observe a sharp increase in E t near T P and an almost jumplike increase in E t at T < 90 K. The increase in E t at T P is explained by a decrease in the coherence volume of CDW because of a fluctuational suppression of the Peierls gap.

Carbon-oxygen-neon mass nuclei in superstrong magnetic fields

The properties of $^{12}\mathrm{C},\phantom{\rule{0.16em}{0ex}}^{16}\mathrm{O}$, and $^{20}\mathrm{Ne}$ nuclei in strong magnetic fields $B\ensuremath{\simeq}{10}^{17}$ G are studied in the context of strongly magnetized neutron stars and white dwarfs. The sky3d code is extended to incorporate the interaction of nucleons with the magnetic field and is utilized to solve the time-independent Hartree-Fock equations with a Skyrme interaction on a Cartesian three-dimensional grid. The numerical solutions demonstrate a number of phenomena, which include a splitting of the energy levels of spin-up and -down nucleons, spontaneous rearrangement of energy levels in $^{16}\mathrm{O}$ at a critical field, which leads to jump-like increases of magnetization and proton current in this nucleus, and evolution of the intrinsically deformed $^{20}\mathrm{Ne}$ nucleus toward a more spherical shape under increasing field strength. Many of the numerical features can be understood within a simple analytical model based on the occupation by the nucleons of the lowest states of the harmonic oscillator in a magnetic field.

Structure induced anelasticity in Fe3Me (Me = Al, Ga, Ge) alloys

Neutron diffraction and mechanical spectroscopy techniques were combined in one study in order to interpret structure induced anelasticity of Fe-(25–27)Me alloys where Me is Al, Ga or Ge. The following sequences of phase transitions at continuous heating in the 20–850 °C temperature range were recorded: (i) in Fe-27Al the B2 (only in water quenched state) → D03 → B2 → A2, (ii) in Fe-27Ga: D03 → L12 → D019 → A2(B2), and (iii) in Fe-25Ge: D019 (+A2 very limited amount) → A3 (+A2 very limited amount). At continuous cooling from 850 °C, we recorded the following transitions: (i) in Fe-27Al A2 → B2 → D03, (ii) in Fe-27Ga: A2 → B2 → L12 (+ very limited amount of D019 and remaining A2 phases which underwent to D03 ordering), and (iii) in Fe-25Ge A3 (+A2 very limited amount) → D019 (+A2 very limited amount). These transition sequences determine different temperature dependencies of magnetic and anelastic properties in the studied alloys. In Fe-27Al and Fe-27Ga water quenched samples the bcc-born phases (A2, B2, D03) dominate at room temperature and a Snoek-type anelastic relaxation is recorded in both alloys. The Snoek relaxation is not recorded in Fe-25Ge alloy which has a close-packed D019 structure. Zener relaxation was recorded in all three systems Fe-Al, Fe-Ga and Fe-Ge both at heating and cooling. The first order irreversible D03 → L12 transition (in Fe-27Ga) at continuous heating generates internal stresses due to a huge jump-like increase of atomic volume with temperature and leads to a well-pronounced transient internal friction effect. The reversible D03 ↔ B2 transition (in Fe-27Al) also leads to a transient but much smaller anelastic effect. Much slower phase transition in Fe-25Ge alloy does not influence temperature dependent anelasticity in this alloy.

Changes in the Electrical Parameters of CdTe-based Crystals During Isothermal Annealing

We observed a novel unanticipated effect in CdTe, ${\bf Cd}_{1-{\bf x}}{\bf Zn}_{\bf x}{\bf Te}$ and ${\bf Cd}_{1-{\bf x}}{\bf Mn}_{\bf x}{\bf Te}$ crystals whilst we were measuring the dependences of several electrical properties (e.g., specific conductivity and free-carrier density) over time. During isothermal annealing under constant thermodynamic conditions (temperatures of 450- $500^\circ {\rm C}$ and under maximal cadmium-vapor pressure), we recorded a jump-like increase in the conductivity after some $\sim 1 - 2$ hours of heating required to stabilize the sample’s electric parameters. The values of specific conductivity and free-carrier density suddenly increased by up to tenfold, and they persisted at those levels during further ageing. At the same time, the sample’s conductivity became insensitive to stoichiometric changes in the crystal. We explain this effect as reflecting a sudden reformatting of the sample’s native/foreign point-defect structure. This transformation is evaluated and mathematically approximated within the framework of our model of the melting of Te-containing second-phase particles; this process releases impurities from within the particles. The respective diffusion “clouds” grow, and at the moment of their mutual percolation (infiltration), a peculiar “short circuit” is observed with striking changes in the crystals’ electrical parameters.

On the Properties of a Bose gas in Spaces with Dimensions n = 1, 2, 4 Within the Framework of the General Theory of a Space with n Dimensions

An ideal Bose gas is considered within the framework of the general case of a space with n dimensions with a different technique for obtaining the well-known result of the absence of its condensed phase in spaces of lower dimensions n = 1, 2. It is also shown that, as in the case n = 3, at the degeneracy temperature there is a jump in the temperature derivative of the heat capacity in spaces with n > 3, and the curve of the heat capacity itself has a maximum with a break at this temperature with a specific character for n = 4 that is different than for the other values. Taking interaction effects into account, this leads to the appearance of a second-order phase transition for all n = 3… with a jump-like increase in the heat capacity at the transition from one symmetric phase of matter to another, less symmetric phase, which can be of interest in the context of models of the early Multi-Universe. Possible applications of the results of this paper in the realm of cosmology are discussed; in particular, a possible variant of the solution of the problem of dark matter is proposed.

The natural tiling approach to cation conductivity in KAlO2 polymorphs

A detailed analysis of correlations between structural features and cation conductivity is performed for KAlO(2) polymorphs in a wide temperature range of 300-1023 K. To explore the migration maps of K(+) cations we have used neutron diffraction data for low- and high-temperature KAlO(2) polymorphs and applied for the first time a novel algorithm based on the natural tiling concept and implemented it into the program package TOPOS. Five independent elementary channels for the K(+) cation migration have been revealed whose cross-sections were found to be essentially different in the low-temperature form, indicating a high anisotropy of the cation conductivity. During the transition to the cubic high-temperature phase all five channels become equivalent with sharply increased cross-sections that account for the jump-like increase of the cation conductivity and gives rise to its three-dimensional character.

Ionization transition in low-density plasma

Ionization equilibrium in low-density low-temperature plasma is considered. It is demonstrated using hydrogen and cesium as examples that the Saha equation predicts an almost jump-like change in the electron density on isochors in a narrow temperature range. Thus, in contrast to a smooth rise in the degree of ionization with increasing temperature at high plasma densities, an increase in the temperature in low-density plasma should result in a sharp transition from a neutral state to a fully ionized plasma. This transition is accompanied by a jump-like increase in the electric conductivity. The relation of these effects to the recombination transition in the model of the early Universe is discussed. The possibility of observing such a transition experimentally and the problems concerning the time of plasma relaxation into an equilibrium state at long free path lengths of plasma particles are considered.