Passive Parts Research Articles

A Multi-Functional Reactive Power Compensation Device with the Capability of Grounding Fault Regulation and Its Parameter Design Method

Aiming at the problems of low equipment utilization and the high-capacity requirements of existing arc-suppression devices, a multi-functional reactive power compensation device with the capability of grounding fault regulation (MF-RPCD) is proposed. Firstly, the topology and operation mechanism of MF-RPCD are introduced in this paper. MF-RPCD works in a reactive power compensation mode when a power grid is under normal operation to ensure the unit power factor operation of the power-grid side. When a single line-to-ground fault occurs in the power grid, MF-RPCD works in a fault-regulation mode to effectively suppress the ground-fault current. Secondly, the parameters of the active and passive parts of MF-RPCD are optimally designed to ensure the stable operation of MF-RPCD. Finally, the correctness, feasibility and effectiveness of the proposed topology and functions are verified using simulations and experiments.

Mechanical modeling and parameter analysis of the docking process for probe-drogue docking mechanisms

The on-orbit probe-drogue berthing docking of two spacecraft can effectively reduce impact force and adjust for initial deviations. However, its dynamic response and influence behaviors of design parameters are extremely concerning but difficult to obtain because of its complicated structure. In this paper, a fast mechanical modeling (FMM) method is proposed to obtain the dynamic response of probe-drogue docking mechanisms during spacecraft berthing missions. Regarding the quasi-static docking process, complex dynamic docking behaviors are simplified and decoupled. The FMM method divides docking into three contact processes based on the scene of contact; it analyzes the deviation adaptive docking principle of this type of docking mechanism by establishing the kinematics and mechanics models of active and passive parts. The finite element simulations and experiments of probe-drogue berthing docking were used to compare with the proposed FMM. The comparison results of different initial deviation conditions indicate that the FMM method guarantees computation accuracy and increases computation speed by two orders of magnitude, which greatly reduces computation costs. Then this efficient FMM method was utilized to analyze the influence of key parameters, such as friction coefficient and cone angle, on the contact force and driving force of the docking mechanism. The conclusions of the parameter analysis of probe-drogue berthing docking can be used to reduce contact force and accelerate iterative design as a reference for the design of this kind of docking mechanisms, making the docking process optimized and reliable.

Неотектоника зоны перехода океан-континент в районе Кот д’Ивуара (Западная Африка)

Structural and geophysical indicators of neotectonics in the area of the continental margin of Côte d'Ivoire are represented in three interacting zones: oceanic, continental and transitional. Together with the time-varying gravitational field, they form a system in which neotectonic processes are enhanced due to their equatorial position. Seismicity is represented by dense clusters of events in the areas of junction of the Strakhov, Sao Paulo and Romansh oceanic transform faults with the continent and their overland continuation. Seismicity and gravity variations show the relationship of deep density changes to stress discharge in the area and the effect of volumetric forces on lithospheric blocks. Free air and isostasy anomalies along the shelf are segmented by the effects of vertical motions. Pull-apart depressions near the passive parts of transform faults indicate basement deformations in the interfault blocks and activation of shear displacements of dextral kinematics near the bend of the passive parts of the faults to the northeast from main oceanic azimuth. Segments with isostasy maxima on the shelf correspond to areas with coarser grain size granulometric composition, indicating leaching of fine sedimentary fraction from the bottom material.

An electromechanically driven dielectric elastomer based tunable reflector

Deformable optics offer numerous advantages over conventional optical assemblies, including compactness, cost-effectiveness, efficiency, and flexibility. This study focuses on a reflector based on dielectric elastomer actuators (DEAs) with an internal fluid (air) coupling. DEAs are a class of electroactive materials adept at accommodating substantial actuation strains and rapid responses. Fluid distributed between the active and passive parts remains entirely enclosed by the device and transmits actuation pneumatically. Dynamic maneuvers conducted through a series of controlled electrical signals demonstrate proper control over optical characteristics. However, DEs exhibit inherent flaws in dynamic actuation, referred to as instabilities, which are mitigated by applying an initial pre-stretch. The study identifies optimal parameters that confer stability to the reflector: minimum to no creep, zero residual vibrations, and low viscous losses. An analytical framework is developed to assess device performance, focusing on the spherical curvature assumption that closely resembles the behavior of tunable spherical reflectors. Additionally, an optical bench setup is employed to demonstrate the relationship between focal length and applied pressure. Notably, this paper underscores the potential of a DE-based variable focal length reflector to function effectively within a dynamic environment.

Theoretical and experimental studies of gas preparation system for pressurization and reactive control system of launch vehicle

A new gas preparation system (GasPS-RCS) is proposed to solve two tasks: (A) to heat helium gas for tank pressurization; (B) to prepare gas for the Launch Vehicle (LV) Reactive Control System (RCS) at the LV orientation and stabilization sections of the LV on passive parts of the flight trajectory, to provide conditions for launching the Liquid Rocket Engine (LRE). The system includes a gas generator based on hydrogen peroxide, a separator for water separation, heat exchangers independent of the LRE, and gas-jet nozzles. The proposed new system allowed to reduce the length of pressurizing gas lines and reduce the increased helium gas consumption during the heat exchanger warm-up interval of the LRE during its launch. A special advantage of the proposed system is the possibility of ground testing of heat exchangers without an operating LRE. A mathematical model based on the first law of thermodynamics was used to perform a comparative analysis of GasPS-RCS with traditional pressurization and RCS systems. To validate the mathematical model, the experimental studies of helium pressurizing of a liquid nitrogen tank were conducted. The results show that the deviation of experimental and calculated values for pressure is 1.1% and for temperature up to 2%. According to the results of comparative analysis, the GasPS-RCS is 259 kg lighter for the first stage and 80 kg lighter for the second stage of the LV.

The method for design of combined electromagnetic shield for overhead power lines magnetic field

Aim. Development of the method of designing a combined electromagnetic shield, consisting of active and passive parts, to improve the effectiveness of reduction of industrial frequency magnetic field created by two-circuit overhead power lines in residential buildings. Methodology. The problem of design of combined electromagnetic shield including robust system of active shielding and electromagnetic passive shield of initial magnetic field solved based on of the multi-criteria two-player antagonistic game. The game payoff vector calculated based on the finite element calculations system COMSOL Muliphysics. The game solution calculated based on the particles multiswarm optimization algorithms. During the design of combined electromagnetic shields spatial location coordinates of shielding winding, the currents and phases in the shielding winding of active shielding, geometric dimensions and thickness of the electromagnetic passive shield are calculated. Results. The results of theoretical and experimental studies of combined electromagnetic passive and active shielding of magnetic field in residential building from power transmission line with a «Barrel» type arrangement of wires presented. Originality. For the first time the method of designing a combined electromagnetic shield, consisting of active and passive parts, for more effective reduction of the magnetic field of industrial frequency created by two-circuit overhead power lines in residential buildings is developed. Practical value. Based on results of calculated and experimental study the shielding efficiency of the initial magnetic field determined that shielding factors whith only electromagnetic passive shield is more 2 units, whith only active shield is more 4 units and with combined electromagnetic passive and active shield is more 10 units. It is shown the possibility to reduce the level of magnetic field induction in residential building from power transmission line with a «Barrel» type arrangement of wires by means of a combined electromagnetic passive and active shielding with single compensating winding to 0.5 μT level safe for the population. References 53, figures 15.

Effects of spot size on the operation mode of GaAs photoconductive semiconductor switch employing extrinsic photoconductivity

To guide the illuminating design to improve the on-state performances of gallium arsenide (GaAs) photoconductive semiconductor switch (PCSS), the effect of spot size on the operation mode of GaAs PCSS based on a semi-insulating wafer with a thickness of 1 mm, triggered by a 1064-nm extrinsic laser beam with the rectangular spot, has been investigated experimentally. It is found that the variation of the spot size in length and width can act on the different parts of the output waveform integrating the characteristics of the linear and nonlinear modes, and then significantly boosts the PCSS toward different operation modes. On this basis, a two-channel model containing the active and passive parts is introduced to interpret the relevant influencing mechanisms. Results indicate that the increased spot length can peak the amplitude of static domains in the active part to enhance the development of the nonlinear switching, while the extended spot width can change the distribution of photogenerated carriers on both parts to facilitate the linear switching and weaken the nonlinear switching, which have been proved by comparing the domain evolutions under different spot sizes.

Design and Study the Performance of a CMOS-Based Ring Oscillator Architecture for 5G Mobile Communication

Oscillator circuits are used to make accurate and reliable clock signals for systems as simple as a wristwatch and as complicated as satellites, which are important for long-distance communication. There are many ways to build an oscillator circuit, using either passive or active parts. Each option has pros and cons, but at the current level of mobile communication development, the most important things are interoperability and low power use. This need has driven the development of compact, battery-operated electronics, and Very Large-Scale Integration (VLSI)-based ring oscillators provide the ideal solution. These oscillators ought to dissipate less power, have a large tuning range, and be compact. The paper presents a novel Complementary Metal Oxide Silicon (CMOS) ring oscillator that serves as a Voltage Controlled Oscillator. The suggested architecture utilizes the advantages of both a current-starved ring oscillator and a negative-skewed delay by combining their constituent parts. The proposed architecture has a control voltage of 1.15 V and a supply voltage of 2 V, generating a 9.35 GHz dominant frequency with a 13.82% harmonic distortion between the inputs and outputs. The proposed architecture can implement 5G-based applications that require high frequency and low power by carefully selecting the passive components within the design. Doi: 10.28991/ESJ-2024-08-01-020 Full Text: PDF

Viscoelastic Dynamics of Photothermal‐Responsive Liquid Crystal Elastomer Fibers

AbstractLiquid crystal elastomers (LCEs) with photo‐responsive properties, typically driven by either photochemical or photothermal mechanisms, have found extensive applications as, for example, actuators in soft robots. However, intricate temperature‐dependent viscoelasticity of LCEs poses a challenge, leading to a notable gap in the domain of dynamic models for photothermal‐responsive LCE (PTR‐LCE) fibers. Here, a fundamental framework is proposed for accurate modeling and real‐time simulations of PTR‐LCE fiber dynamics. The PTR‐LCE fiber is described as a one‐dimensional (1D) string model that decomposes the fiber deformation into active and passive parts, which are characterized by an order parameter and a temperature‐dependent linear viscoelasticity model, respectively. Then, independent experimental measurements of model parameters are conducted, and a numerical algorithm is developed to solve the model, which is validated for convergence, time efficiency, and accuracy. Finally, the model is employed to simulate both open‐loop and Proportional‐Integral‐Derivative (PID) control of actuators made of PTR‐LCE fibers. The results confirm the advantages of this model over previous models. This work not only reveals the physical mechanisms underlying the PTR‐LCE fiber dynamic behaviors but also provides inspirations for more efficient and precise soft robotic applications.

Electromagnetic Shielding of Two-Circuit Overhead Power Lines Magnetic Field

The purpose of the work is to design an electromagnetic shield to reduce the level of the magnetic field generated by double-circuit overhead power lines to increase the shielding efficiency of the initial magnetic field in residential buildings to the level of sanitary standards and reduce the sys-tem's sensitivity to changes in system parameters. To achieve this goal, the structure of the electro-magnetic shield is determined, which consists of a single-circuit active and multi-circuit passive parts and is characterized by an increased efficiency of reducing the magnetic field of industrial frequency. The design of an electromagnetic shield is reduced to solving a minimax vector optimization problem, in which the vector objective function is calculated based on solutions of Maxwell's equations in a quasi-stationary approximation using the COMSOL Multiphysics software package. The solution of the minimax vector optimization problem is calculated on the basis of optimization algorithms by a multiswarm of particles from Pareto-optimal solutions. The most important results are theoretical and experimental studies of the effectiveness of the designed electromagnetic shield of the magnetic field generated by double-circuit overhead power lines. The significance of the results obtained lies in the fact that practical recommendations are given on the reasonable choice of the spatial arrangement of the contours of the multi-circuit passive screen and the shielding winding of the robust system of elec-tromagnetic shielding of the magnetic field generated by double-circuit overhead power lines. The possibility of reducing the induction of the initial magnetic field to the level of sanitary standards has been shown as well.

Transformation of Political Perceptions in the Age of Information Technologies: Analyzing the Impact on Political Beliefs

The dynamism of social development dictates new rules for the transmission of political ideas and communication in the political space. Society has gained qualitatively new opportunities for obtaining political information, so political actors are forced to work not only on disseminating information but also on creating demanded political content. The purpose of the article is to highlight a new paradigm of perception of political activity by different clusters of the socio-cultural space. The tasks of scientific research are to differentiate the impact of innovative information and digital resources on individual and social consciousness. The methodology of the article involves general scientific methods that provide analysis and structuring of political activity and offer consideration of effective models of political perception. Content analysis, comparative analysis, and analytical monitoring determine the level of At the same time, philosophical and synergistic principles highlight pluralism, interdisciplinarity, and self-organisation as relevant methods for optimising the informational support of the political activity. The results of the study propose algorithms for the influence of political ideas on the socially active, passive, and neutral parts of society. The specifics of informative influence on political life in general and on representatives of the political audience in particular, which forms the peculiarities of information activity in the political space, are considered. The results of the study offer a description of the functions of ICTs in enhancing the perception of political content. Innovation is a key leitmotif of political activity in the information and digital sphere, as it is accessible and understandable to people who actively use technological and digital resources in everyday life. A promising area of research is the consideration of potential indicators of political perception in the context of the transition from traditional telecommunication resources to the information and digital segment. Thus, political perception in the modern political space is shaped by various information support that has both a universal impact on the audience and is specifically targeted at certain clusters of society.

Measuring magnetic 1/f noise in superconducting microstructures and the fluctuation-dissipation theorem

The performance of superconducting devices like qubits, superconducting quantum interference devices (SQUIDs), and particle detectors is often limited by finite coherence times and noise. Various types of slow fluctuators in the Josephson junctions and the passive parts of these superconducting circuits can be the cause, and devices usually suffer from a combination of different noise sources, which are hard to disentangle and therefore hard to eliminate. One contribution is magnetic noise caused by fluctuating magnetic moments of magnetic impurities or dangling bonds in superconducting inductances, surface oxides, insulating oxide layers, and adsorbates. In an effort to further analyze such sources of noise, we have developed an experimental set-up to measure both the complex impedance of superconducting microstructures, and the overall noise picked up by these structures. This allows for important sanity checks by connecting both quantities via the fluctuation-dissipation theorem. Since these two measurements are sensitive to different types of noise, we are able to identify and quantify individual noise sources. Furthermore, our measurements are not limited by the quantum noise limit of front-end SQUIDs, allowing us to measure noise caused by just a few ppm of impurities in close-by materials. We present measurements of the insulating layers of our devices, and magnetically doped noble metal layers in the vicinity of the pickup coils at and .

Hybrid Active-Passive Shielding of Magnetic Field of Overhead Power Lines with Triangular Phase Conductors Arrangements

The aim of the work is to design a robust hybrid active-passive magnetic field shielding system created by overhead power lines with a triangular arrangement of phase wires, designed to increase the shielding efficiency of the initial magnetic field in residential premises to the level of sanitary standards and reduce the system's sensitivity to changes in system parameters. To achieve this goal, the following tasks were solved: the structure of a hybrid system of active-passive shielding was developed, and the synthesis of a system consisting of a double-circuit active and multi-circuit passive parts was performed. The synthesis of the system is reduced to solving a vector game, in which the vector payoff is calculated based on the solutions of the Maxwell equations in the quasi-stationary approximation using the COMSOL Multiphysics software. The solution of a multicriteria game is found on the basis of algorithms for optimizing a multi-swarm of particles from Pareto optimal solutions, taking into account binary preference relations. The most important results are theoretical and experimental studies of the effectiveness of the synthesized hybrid active-passive shielding system for the magnetic field created by overhead power lines with a triangular arrangement of phase wires in the shielding zone. The significance of the results obtained lies in the fact that in the course of designing a hybrid active and multiloop passive screens, the parameters of passive and active screens were calculated; as well as practical recommendations are given on the reasonable choice of the spatial arrangement of a multi-loop passive shield and two shielding windings of a robust system of hybrid shielding of the magnetic field created by overhead power lines with a triangular arrangement of phase wires.

Fracture Zones of the Doldrams Megatrasform System (Equatorial Atlantic)

This article presents results of the structural and morphological analysis of the fracture zones which are part of Doldrums Megatransform System (MTS), located in the northern part of the Equatorial Atlantic (6.5°–9° N) that include Vernadskiy and Bogdanov transform faults and the Doldrums and Pushcharovskiy megatransforms. Bathymetric map, based on the multibeam echo sounding data, collected during 45 cruise of the R/V Akademik Nikolaj Strakhov was used for this analysis. It was established that large-scale variations in the width of fracture zone valleys are determined by the distribution of stresses perpendicular to the fracture zone. In the areas with compressive stresses, the fracture zone valleys are narrower, and the in extension areas are wider. The difference in geodynamic settings within the MTS is due to the difference in spreading directions, which change from \(\perp \)89° to \(\perp \)93° when moving from south to north. The depth of fracture zone valleys consistently increases from the periphery of the MTS (Bogdanov and Doldrums faults) to the center (Pushcharovskiy fracture zone) in accordance with a decrease in the upper mantle temperature. In each fracture zone, the valley depth decreases from the rift- fracture zone intersections towards the center of the active part to a certain background depth. It is assumed that this phenomenon is the result of the uplift of the valley bottom, which occurred due to the decompaction of the lithosphere, caused by the serpentinization of ultramafic rocks. The violation of the revealed variations in the width and depth of fracture zone valley patterns occurs as a result of various ridges and uplifts formation in the fracture zone. In the axial zones of the active parts of the fracture zone valleys median ridges are widespread, extending parallel to the fracture zone and representing serpentinite diapirs squeezed out above the bottom surface. Transversal ridges which were formed 10‒11 million years ago as a result of the lithospheric plate edge flexural bending under extensional conditions are now located in the western passive parts on the southern sides of the of Doldrums and Pushcharovskiy fracture zone valleys. The transverse ridge on the northern side of the Vernadskiy fracture zone, which includes Mount Peyve, was formed between 3.65‒2.4 Ma. Due to the frequent jumps of the spreading axis in this region, it was divided into three segments. There are interfracture zone ridges in megatransforms, which in the active part consist of two fracture zone valleys. Time of their formation: in Pushcharovskiy megatransform ‒ 30‒32 million years ago and in Doldrums megatransform ‒ about 4 million years ago. Due to the curvilinearity of the outlines and under the pressure of moving lithospheric plates, the interfracture zone ridges experience longitudinal (along the fault) compressive and tensile stresses, which are compensated by vertical uplifts of their separate blocks and the formation of depressions, pull apart depressions, and spreading centers (the latter are only in Pushcharovskiy megatransform). Structure-forming processes that determine pattern and morphology of the fracture zones as a part of the MTS are related by their origin to the spreading and transform geodynamic systems.

Forecast of a qualitative renewal of the active part of fixed assets in agro-industrial complex

The renewal of fixed assets means the process of replacing obsolete means of labor with new, most perfect and modernized ones. In market economy and fierce competition between various manufacturers, one of the most important factors in increasing the profitability of production and economic activities of enterprises is the provision of their produced assets in the required quantity. Only with a good technical condition of production base, timely technical and technological re-equipment of production processes of economic entities, it is possible to have their stable growth. The goal is to analyze the theoretical and practical aspects of restoring the active part of the fixed production assets (hereinafter referred to as APFA) in crop production of the republic on the basis of economic and mathematical modeling. Methods – economic-mathematical, statistical, comparison, analysis and synthesis. Results – methodological provisions for the effective management of APFA are proposed. A system of standards was built and implemented, substantiating the indicators of economic efficiency of production (hereinafter referred to as IEEP). The main directions, tendencies and regularities of reproduction of the active part of fixed production assets are investigated. The criteria for the implementation of the method of planning and forecasting the pace of their reconstruction are shown. The set of normative IEEP is oriented to be used as a tool for decision-making by the country's authorities, allows to increase the volume of agricultural production over the forecast period (20 years). The calculation of the ratios of the shares of the APFA in the base and prospective periods, their productivity for five-year plans in the future, a comparison of the need for domestic investment by the state and the investment investments of large associations in the optimal mode of their recovery are presented. Conclusions – the ratio of active and passive parts is of great interest, since the capital productivity, capital profitability and financial condition of enterprises largely depend on their optimal combination. When analyzing the qualitative state of the active part of fixed assets, the completeness and timeliness of scheduled preventive repairs, their compliance with technical characteristics and operating conditions are checked.

Reconfigurable Intelligent Surface Enabled Over-the-Air Uplink NOMA

Innovative reconfigurable intelligent surface (RIS) technologies are rising and recognized as promising candidates to enhance 6G and beyond wireless communication systems. RISs acquire the ability to manipulate electromagnetic signals, thus, offering a degree of control over the wireless channel and the potential for many more benefits. Furthermore, active RIS designs have recently been introduced to combat the critical double fading problem and other impairments passive RIS designs may possess. In this paper, the potential and flexibility of active RIS technology are exploited for uplink systems to achieve virtual non-orthogonal multiple access (NOMA) through power disparity over-the-air rather than controlling transmit powers at the user side. Specifically, users with identical transmit power, path loss, and distance can communicate with a base station sharing time and frequency resources in a NOMA fashion with the aid of the proposed hybrid RIS system. Here, the RIS is partitioned into active and passive parts and the distinctive partitions serve different users aligning their phases accordingly while introducing a power difference to the users’ signals to enable NOMA. First, the end-to-end system model is presented considering two users. Furthermore, outage probability calculations and theoretical error probability analysis are discussed and reinforced with computer simulation results.

КОРРЕКТИРОВАНИЕ ПЕРИОДИЧНОСТИ ОПЕРАЦИЙ ТЕХНИЧЕСКОГО СЕРВИСА МОБИЛЬНЫХ МАШИН С УЧЕТОМ ЖЕСТКОСТИ КЛИМАТА

Based on the analysis of the main operational factors, among which, for specific areas of equipment supply, one of the main ones is the climatic factor, as well as the main damaging degradation processes during the operation of machines, an effective mechanism for planning the frequency of maintenance operations is proposed, which helps to ensure a high level of technical readiness of machines. The operability potential was analyzed, its active, reserve and passive parts were considered, which made it possible to present a model for changing and restoring the operability potential of a mobile machine. Mathematical dependences are given for certain models of machines of the same functional purpose, as well as characterizing processes of reducing the potential of their performance in a certain external environment, their transformation is noted when changing natural and climatic operating conditions. The construction of a priori diagram of the ranks of climatic factors made it possible to note that the most significant adverse effect is exerted by temperature, humidity and solar radiation in the operating area. Taking into account the distribution of zones of technical rigidity of the climate, its score and the coefficient of continentality, a method is proposed for correcting the frequency of operations of technical service of transport-technological machines for the zone of their actual operation.

Discontinuous conduction mode approach of ultra-lift DC-DC converter based on three windings coupled inductor

These days, DC-DC boost converters play an essential role in a variety of applications. Therefore, a variety of techniques were proposed in the literature to achieve the highest voltage gain. A large number of passive elements are typically used in high-voltage DC-DC converters. Increasing the order of the system would make modeling and controlling the output voltage of the converter more complex. This paper examines an ultra-lift DC–DC converter using a three-winding inductor and a super-lift construction in discontinuous conduction mode (DCM). This converter provides substantial voltage gain by utilizing the three-winding coupling inductor topology without increasing the duty cycle or passive circuit parts. Because the DCM operation mode occurs in the converter, it is necessary to investigate and analyze it. The DCM operation mode of an Ultra-Lift converter is examined in this study, and then simulation results are shown to validate the equations.

Dynamic resonance frequency control for a resonant-type smooth impact drive mechanism actuator

Multimodal piezoelectric actuators combine multiple vibration modes to achieve specific motions for precise actuation, or to enhance the output performance. For such a combination, the operating frequency ratio is necessarily an integer constraint. However, the resonance frequencies of target modes can be mismatched in assembly, and shift easily during operation, limiting the actuator applications. Therefore, we proposed a dynamic resonance frequency control method for multimodal piezoelectric actuators and applied it to a resonant-type smooth impact drive mechanism actuator. Passive piezoelectric parts were deployed on a Langevin transducer and connected with a field effect transistor (FET) switch. As a pulse width modulation (PWM) signal continuously adjusting the electrical boundary of these passive parts, the first longitudinal L1 mode’s resonance frequency was dynamically controlled to match the third L3 mode’s frequency with a ratio of two, generating a quasi-sawtooth displacement to drive a rotor. Experimental results indicated that the prototype’s L1 frequency can be continuously tuned from 25.715 to 24.76 kHz at 27 ℃, and the corresponding frequency ratio was adjusted from 1.953 to 2.028. Multimodal resonance frequency static matching was confirmed by changing the switching signal’s duty ratio. The L1 and L3 mode driving voltages were 50 Vp-p, and 23 Vp-p, respectively, and the speed of the rotor was 133.7 r/min. Dynamic resonance frequency control was realized with a feedback control system. As the driving PZT temperature increased to 70.5 ℃, both modes were matched and maintained resonance for 400 s. The results demonstrate that this method is conducive to improving actuator performance.

Modeling fracture in polymeric material using phase field method based on critical stretch criterion

In this work, the phase field method (PFM) is applied for modeling fracture in the polymeric type of materials. Considering the large extensibility of polymer chains before fracture, a crack initiation criteria based on a critical stretch value is proposed. The tensile stretches in the material contribute to the active strain energy, which is responsible for driving fracture. Additive decomposition of strain energy into active and passive parts is adopted based on the critical stretch value of polymer chains in a phase-field setting. This critical value is determined by assuming an equivalent uniaxial tensile state of stress in front of the crack tip at the onset of fracture. The stretch of individual polymeric chains is determined by using a polymer network model. The critical fracture toughness of the polymer is kept constant up to the onset of fracture and a gradually reducing value of it is adopted in front of the crack tip beyond the critical stretch. A hybrid phase-field formulation with a staggered solver is used owing to its numerical efficiency and robustness. The effectiveness and applicability of the present model are demonstrated through various numerical examples.