Dynamic Stability Criteria Research Articles

Static and dynamic stabilities of modified gradient elastic Kirchhoff–Love plates

The static and dynamic stabilities of modified gradient elastic Kirchhoff–Love plates (MGEKLPs), which incorporate two length-scale parameters related to strain gradient and rotation gradient effects, are comprehensively analyzed under various load forms and boundary conditions (BCs). The study of static stability employs static balance method and an improved energy method by introducing higher-order deformation gradients and corresponding energy terms. Utilizing the variational method, a sixth-order fundamental buckling differential equation for MGEKLPs under both transverse and in-plane loads is derived, serving as the foundation for the static balance method. The static stability analysis of MGEKLPs examines the combined effects of strain and rotation gradients on size-dependent critical buckling loads. Building on generalized strain energy with higher-order deformation energy, the energy method of classical elastic thin plate model is enhanced and applied to the static stability analysis of MGEKLPs. This approach enables the investigation of static stability without being constrained by the need to solve complex differential equations, making it applicable to various BCs and load scenarios. While static stability provides a description of stable state of an elastic system, dynamic stability offers a more scientific and rigorous analysis. The dynamic stability of simplified gradient elastic Kirchhoff–Love plates (SGEKLPs) with curved edges and different BCs is further investigated by combining the generalized strain energy with Lyapunov’s second stability method, presenting the dynamic stability criterion in the form of norms. A strict description of the dynamic stability of a SGEKLP over the entire time domain is provided for different supporting conditions, including case where all edges are supported and case with free edges. The analysis of size-dependent static and dynamic stabilities offers theoretical guidance for designing elastic thin plates with microstructures.

Dynamics of axially moving spinning microbeams composed of tri-directional graded porous materials with axisymmetric cross-sections and piezoelectric layers in complex fields

The current article appraises the vibration and stability of tri-directional functionally graded porous microscale beams with rectangular cross-sections integrated with piezoelectric layers under spinning and axial movements in complex environments. The microbeam is surrounded by a three-parameter Winkler-Pasternak-Hetenyi medium, and its material characteristics are graded in thickness, width, and longitudinal spatial directions by considering non-uniform and uniform porosity models. Dynamic equations, vibration frequencies, and stability criteria of the system are determined with the aid of the Galerkin approach and Laplace transform. The Campbell diagram and stability maps are drawn. Frequency and stability analyses, as well as comparison and parametric analyses, are conducted. The impacts of piezoelectric voltage, magneto-hygro-thermal fields, axial and tangential distributed follower forces, substrate characteristics, scale parameter, aspect ratio, porosity factor, and material gradation on flutter and divergence instability boundaries are assessed in detail. It is deduced that instability regions are condensed, and the instability threshold is enhanced by fine-adjusting the porosity and material gradient. It is discovered that destructive environmental effects can be alleviated by regulating the piezoelectric voltage. In addition, compared with the case of a square cross-section, the divergence/flutter instability region of the microbeam with a rectangular cross-section is smaller/larger. The outcomes of the present research can be helpful in the design of next-generation bi-gyroscopic systems.

Research on dynamic stability of rolling missiles employing direct/aerodynamic force compound control

The direct/aerodynamic force compound control can enhance the maneuverability and response characteristics of missiles, and the dynamic stabilization is the precondition of normal operation for rolling missiles. Aiming at the stability problem caused by the cross-coupling effect of rolling missiles employing direct/aerodynamic force compound control, proposing a typical topological control system structure described by the complex coefficient theory, and deducing the dynamic stability conditions. Firstly, the mathematic model is established based on the kinematics and dynamics theories of rotating airframes and the direct/aerodynamic force compound control mechanism. Then, a three-loop autopilot and the direct/aerodynamic force ratio distribution method are designed to establish the complex summation model of the compound control system by selecting suitable complex variables. Furthermore, deducing the dynamic stability conditions and verifying them by numerical simulations. Finally, the stable regions of the rolling missile in different cases are obtained and found to be influenced by many factors, such as parameters of the autopilot, hybrid force distribution proportion and rolling rate. The derived dynamic stability criterion is effective for evaluating the stability of rolling missiles employing direct/aerodynamic force compound control and the research method used in this paper can provide reference for the stability study of strongly coupled nonlinear systems.

Ba2MgXO6 (X = S, Se), Chalcogenide‐Based Double Perovskite Materials for Green Optoelectronics and Thermoelectric Applications

Chalcogenide‐based double perovskite materials have recently attracted attention of researchers because of their excellent properties and eco‐friendly nature. These compounds have proven to comprise better oxidation resistance, high‐temperature stability, and lower processing cost. In this report, the first‐principles study on chalcogenides double perovskites Ba2MgXO6 (X = S, Se) is described. It is shown that these perovskites can be synthesized, as they satisfy the structural, dynamical, and thermodynamical stability criteria. It is revealed that these double perovskites are inherently semiconductors in nature with low bandgap values, 0.33 eV for Ba2MgSO6 and 0.66 eV for Ba2MgSeO6 along Γ symmetry point. The absorption coefficient ≈105 cm−1 and the reflectivity below 12% in visible region are calculated. Therefore, the Ba2MgXO6 for solar cell applications is recommended. Also, on the basis of calculated larger values of figure of merit, these perovskites are proposed for thermoelectric applications at high temperatures.

The radius variations of accreting main-sequence stars and mass transfer instability

ABSTRACT Many previous works studied the dynamical time-scale mass transfer stability criteria based on the donor response with neglecting the stellar structure of the accretor. In this letter, we investigate the radial response of accretors with mass accumulation and its effect on the binary mass transfer stability. We perform a series of detailed stellar evolution simulations with different types of accretors and obtain the radial variations of stars accreting at different rates. Since the time within which the donor loses half of the original mass has a correlation with the donor mass, we approximately obtain the mean mass transfer rate as a function of mass ratio. Assuming that the common envelope (CE) phase occurs if the accretor radius exceeds the outer Roche lobe radius, we obtain the critical mass ratio of dynamically unstable mass transfer. We find the critical mass ratios for donors filling their Roche lobes at the Main Sequence (MS) and Hertzsprung Gap (HG) stages are smaller than that derived from the radial response of the donor in the traditional way. Our results may suggest that the binary is easier to enter into the CE phase for a donor star at the MS or HG stage than previously believed.

Model and Dynamic Analysis of a Three-Body Tethered Satellite System in Three Dimensions

The three-body tethered satellite system is a new potential technology for the purposes of orbital transportation. In contrast to conventional orbit transfer methods, this system is expected to transport space supplies to a predetermined orbital altitude without consuming fuel; however, the unwanted libration resulting from the Coriolis force acting on moving subsatellites may induce tumbling within the system. In order to analyze the strongly coupled characteristics of the libration motion and the variable-length tethers, a six-DOF dynamic model of the system based on Newton’s law is established. By utilizing the dynamic equations and stability criterion for linear systems, three equilibrium configurations of the satellite system with two constant-length tethers are given. The coupling characteristics of the libration angles are analyzed based on mechanical features and simulations. The results demonstrate that part of the libration energy can transfer from out-of-plane motion to in-plane motion during out-of-plane libration, but not vice versa or when in-plane libration occurs alone. Furthermore, the dynamic characteristic of this system with a predesigned deployment strategy is surveyed. This investigation reveals that such a strategy can rapidly suppress the out-of-plane libration motion while maintaining purely sinusoidal oscillations in the in-plane motion.

Photovoltaic properties of novel quaternary chalcogenides based on high-throughput screening and first-principles calculations

<sec>In recent decades, the demand for clean energy has promoted extensive research on solar cells as a key renewable energy source. Among the various emerging absorber layer materials, Kesterite-type semiconductors have aroused significant interest. Especially, Kesterite Cu<sub>2</sub>ZnSnS<sub>4 </sub>(CZTS) stands out as a promising candidate for low-cost thin-film solar cells due to its direct bandgap, high optical absorption coefficient, suitable bandgap (1.39–1.52 eV), and abundance of constituent elements. However, the power conversion efficiency (PCE) of CZTS-based solar cells currently lags behind that of Cu(In,Ga)Se<sub>2</sub> (CIGS) cells, mainly due to insufficient open-circuit voltage caused by a large number of disordered cations and defect clusters, resulting in non-radiative recombination and band-tail states.</sec><sec>To address these challenges, partial or complete cation substitution has become a viable strategy for altering the harmful defects in CZTS. This study proposes a heterovalent substitution of Zn in CZTS and explores the potential of novel quaternary chalcogenide compound <i>A</i><sub>2</sub><i>M</i><sub>2</sub><i>M'Q</i><sub>4</sub> (<i>A</i> = Na, K, Rb, Cs, In, Tl; <i>M</i> = Cu, Ag, Au; <i>M'</i> = Ti, Zr, Hf, Ge, Sn; <i>Q</i> = S, Se, Te) as absorbers for solar cells. By substituting elements in five prototype structures, a comprehensive material database comprising 1350 <i>A</i><sub>2</sub><i>M</i><sub>2</sub><i>M'Q</i><sub>4</sub> compounds is established.</sec><sec>High-throughput screening and first-principles calculations are used to evaluate the thermodynamic stabilities, band gaps, spectroscopic limited maximum efficiencies (SLMEs), and phonon dispersions of these compounds. Our research results indicate that 543 compounds exhibit thermodynamic stability (<i>E</i><sub>hull</sub> < 0.01 eV/atom), 202 compounds possess suitable band gaps (1.0–1.5 eV), and 10 compounds meet all the criteria for thermodynamic and dynamic stability, suitable band gaps, and high optical absorption performance (10<sup>4</sup>–10<sup>6</sup> cm<sup>–1</sup>), with theoretical SLME values exceeding 30%.</sec><sec>Notably, <i>Ibam</i>-Rb<sub>2</sub>Ag<sub>2</sub>GeTe<sub>4</sub> exhibits the highest SLME (31.8%) in these candidates, featuring a band gap of 1.27 eV and a small carrier effective mass (< <i>m</i><sub>0</sub>). The electronic structures and optical properties of these compounds are comparable to those of CZTS, which makes them suitable for highly efficient single-junction thin-film solar cells.</sec><sec>All the data presented in this work can be found at <ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.doi.org/10.57760/sciencedb.j00213.00006">https://www.doi.org/10.57760/sciencedb.j00213.00006</ext-link>.</sec>

Dynamic mechanical mechanism and optimization approach of roadway surrounding coal water infusion for dynamic disaster prevention

Roadway surrounding coal water infusion is a most significant technical means for the dynamic disasters prevention. To evaluate its efficiency in dynamic mechanical environment, the damage distribution and mechanical parameters were analyzed before and after water infusion. And the relationship among damage distribution, dynamic mechanical parameters, and stress wave propagation were established. With the medium of the wave impedance, the stress wave transmission process was characterized, and the dynamic stability criterion was established from the perspectives of energy and stress, respectively. On this basis, the optimization approaches were further proposed and validated in practice. The results demonstrate that water infusion can effectively enlarge the wave impedance difference among each adjacent circumferential coal segment and damage range in the surrounding coal. It will enhances the stress wave attenuation, thereby protecting the roadway from dynamic failure. To better play its role, the optimization approaches should focus on increasing the damage degree and range of the microscopic fracture zone in surrounding coal. These findings provide valuable insights into the design and implementation of surrounding coal water infusion for dynamic disasters prevention.

Structural stability and physical properties of MAX phases M2SX (M=Sc, Y, X=B, C, N) via first-principles calculations

The structural, mechanical, lattice-dynamic, anisotropic, electronic and thermal properties of M2SX (M=Sc, Y; X=B, C, N) are investigated based on density functional theory. The calculated results indicate that all the phases satisfy the thermodynamic, mechanical and dynamic stability criteria. The mechanical properties are in good agreement with the reported values, and the results show that Sc2SN exhibits the highest bulk modulus B (145.7 GPa), shear modulus (103.0 GPa) and Young’s modulus E (250.0 GPa) with brittle behavior. The elastic anisotropy of M2SX indicates that Sc2SC is the most isotropic among the 6 phases. The electronic structure reveals that Sc2SC and Y2SC are indirect-bandgap semiconductors with 0.927 eV and 1.260 eV bandgap, and the other phases exhibit metallic characteristics. The Debye temperature, lattice thermal conductivity, minimum thermal conductivity, heat capacity and entropy have also been calculated for M2SX phases. The tendency for lattice thermal conductivity in high temperature: K lat (M2SN) > K lat (M2SC) > K lat (M2SB). All the present calculated data will provide useful guidance for development and research on the novel S-based MAX phases in the future.

Pressure effect on the physical, mechanical, and thermal properties of ternary halide perovskite AgCaCl3: a first-principles study.

As an inorganic halide perovskite material, AgCaCl3, characterized by its high stability and environmental friendliness, is considered a potential candidate for major applications in optoelectronics and lens manufacturing. This work aimed to determine the electronic properties such as density of state (DOS) and band structure (BS) of AgCaCl3. The results showed that the material has an indirect band gap almost invariably at 1.5eV in the pressure range studied. The dielectric function [Formula: see text], absorption coefficient [Formula: see text], optical conductivity [Formula: see text], reflectivity [Formula: see text], and the refractive index [Formula: see text] showed clearly that the perovskite AgCaCl3 preserved its optical characteristics within the chosen pressure range investigated. The calculated elastic constants C11, C12, and C14 as dynamic stability criteria for the elastic moduli such as bulk modulus (B), shear modulus (G), Young's modulus (Y), Poisson's ratio ([Formula: see text]), and anisotropy factor (A) showed that the material is a ductile plastic. Debye temperature ([Formula: see text]), isobaric and isochoric heat capacities (CP, CV), coefficient of the thermal expansion (α), Gibbs free energy (G), and entropy (S) were also studied. The results obtained provide a theoretical basis for experimental work and offer the possibility of future industrial applications of AgCaCl3. Density functional theory (DFT) calculations as implemented in the Wien2K code were used to study the mechanical and thermal properties of AgCaCl3 perovskite over a pressure range. Lattice parameters, electronic, and optical properties are optimized with the approximation of the generalized gradient of the Perdew-Burke-Ernzerhof function (PBE-GGA) function. The mechanical and thermodynamic properties were calculated using ElaStic and Gibbs2 codes, and the properties of AgCaCl3 over the pressure range investigated were predicted.

An ab initio DFT perspective on experimentally synthesized CuBi2O4.

Here we present a comprehensive density functional theory (DFT) based ab initio study of copper bismuth oxide CuBi2O4 (CBO) in combination with experimental observations. The CBO samples were prepared following both solid-state reaction (SCBO) and hydrothermal (HCBO) methods. The P4/ncc phase purity of the as-synthesized samples was corroborated by Rietveld refinement of the powdered X-ray diffraction measurements along with Generalized Gradient Approximation of Perdew-Burke-Ernzerhof (GGA-PBE) and the Hubbard interaction U corrected GGA-PBE+U relaxed crystallographic parameters. Scanning and field emission scanning electron micrographs confirmed the particle size of the SCBO and HCBO samples to be ∼250 and ∼60 nm respectively. The GGA-PBE and GGA-PBE+U derived Raman peaks are in better agreement with that of the experimentally observed ones when compared to local density approximation based results. The DFT derived phonon density of states conforms with the absorption bands in Fourier transform infrared spectra. Both structural and dynamic stability criteria of the CBO are confirmed by elastic tensor and density functional perturbation theory-based phonon band structure simulations respectively. The CBO band gap underestimation of GGA-PBE as compared to UV-vis diffuse reflectance derived 1.8 eV was eliminated by tuning the U and the Hartree-Fock exact-exchange mixing parameter αHF in GGA-PBE+U and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functionals respectively. The HSE06 with αHF = 14% yields the optimum linear optical properties of CBO in terms of the dielectric function, absorption, and their derivatives as compared to that of GGA-PBE and GGA-PBE+U functionals. Our as-synthesized HCBO shows ∼70% photocatalytic efficiency in degrading methylene blue dye under 3 h optical illumination. This DFT-guided experimental approach to CBO may help to gain a better understanding of its functional properties.

Biomechanical criterion of dynamic stability based on ZMP formula and Flash-Hogan principle of minimum jerk

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Dynamical Disruption Timescales and Chaotic Behavior of Hierarchical Triple Systems

We examine the stability of hierarchical triple systems using direct N-body simulations without adopting a secular perturbation assumption. We estimate their disruption timescales in addition to the mere stable/unstable criterion, with particular attention to the mutual inclination between the inner and outer orbits. First, we improve the fit to the dynamical stability criterion by Mardling & Aarseth widely adopted in the previous literature. Especially, we find that that the stability boundary is very sensitive to the mutual inclination; coplanar retrograde triples and orthogonal triples are much more stable and unstable, respectively, than coplanar prograde triples. Next, we estimate the disruption timescales of triples satisfying the stability condition up to 109 times the inner orbital period. The timescales follow the scaling predicted by Mushkin & Katz, especially at high e out where their random walk model is most valid. We obtain an improved empirical fit to the disruption timescales, which indicates that the coplanar retrograde triples are significantly more stable than the previous prediction. We furthermore find that the dependence on the mutual inclination can be explained by the energy transfer model based on a parabolic encounter approximation. We also show that the disruption timescales of triples are highly sensitive to tiny changes of the initial parameters, reflecting the genuine chaotic nature of the dynamics of those systems.

The Sub and Super-Tangential Nonconservative Load in Stability Problem of Nanobeams with Sprung Masses

In this study, the critical load and natural vibration frequency of Euler–Bernoulli single nanobeams based on Eringen’s nonlocal elasticity theory are investigated. Cantilever nanobeams with attached sprung masses were subjected to compressed concentrated and distributed follower forces. The parameter that determines the direction of nonconservative follower forces was given the positive and negative values, therefore, sub-tangential and super-tangential load were analyzed. The stability analysis is based on dynamical stability criterion and was carried out using a numerical algorithm for solving segmental nanobeams with many boundary conditions. The presented algorithm is based on the exact solutions of motion equations which are derived from equilibrium conditions for each separated segment of the nanobeam. Two comparison studies are conducted to ensure the validity and accuracy of the presented algorithm. The excellent agreement of critical load for Beck’s nano-column on Winkler foundation observed was confirmed as reported by other researchers. The effect of different values of the nonlocality parameter, tangency coefficient, spring stiffness coefficient, location of sprung mass and the greater number of attached sprung masses on a critical load of nanobeams compressed by nonconservative load are discussed. One of the presented results shows that significant differences between local and nonlocal theory appear when the beam subjected to follower forces loses its stability by flutter.

Effect of pressure on structural, elastic and mechanical properties of cubic perovskites XCoO3 (X = Nd, Pr) from first-principles investigations

In this current research article, the structural elasto-mechanical and thermal properties of cubic perovskites XCoO3 (X = Nd, Pr) have been studied theoretically under different pressures. The structure is optimized and calculated optimized data is in well agreement of available literature. All these calculations are performed by considering Perdew Burke Ernzerhof Generalized Gradient Approximation type exchange and correlation functional within Wien2k-code. The second order cubic independent elastic constants C11, C12 and C44 are computed by using this optimized data. The dynamical stability criteria is checked by computed constants and used to find the elastic moduli; shear, Young's and Bulk modulus. The other mechanical properties like Poisson's ratio, anisotropic factor, Pugh's ratio, shear constant, Cauchy pressure, Lame's constants, Kleinmann parameter are quantified and discussed. The results portray the ductility of XCoO3 (X = Nd, Pr) perovskites and utility in high temperature devices.

Application of Dynamic Stability Criterion in Evaluating Field Rutting of Asphalt Pavements Using the Wheel Tracking Test

Application of Dynamic Stability Criterion in Evaluating Field Rutting of Asphalt Pavements Using the Wheel Tracking Test

Efficient assessment for the pitchpoling risks of a generic wave energy converter based on first passage statistics

Of the rapidly emerging wave energy converter (WEC) designs, many can be essentially categorized as moored, floating, cylindrical structures. Their capsizing risks under random waves (i.e. dynamic instability) haven't been investigated adequately. The stochastic averaging proves to be an efficient approach providing quantitative assessments of dynamic instabilities. This study has adapted stochastic averaging to assess the pitchpoling risks of a generic moored floating WEC under random waves. Studies reveal that the statistics from stochastic averaging can be correlated reasonably with the statistics from the time domain simulations. Without requiring numerous simulations, the obtained first passage statistics could formulate a semi-analytical dynamic stability criterion for WEC designs. Sensitivity analysis have been performed with respect to various parameters, including wave period, mooring setup, initial condition and geometry modification.

Investigating a novel magnetic MAX phase nitride and its (001)-surfaces

Magnetic MAX phases including their surfaces exhibit promising functional properties for magneto-electronic devices and self-monitoring smart coatings. By employing an integrated ab-initio approach, here we investigate a new member of the MAX phase, Mn2AuN. This compound satisfies the chemical, mechanical and dynamical stability criteria, leading to a possibility of its synthesis, and exhibits electronic and elastic anisotropy. The identified ferromagnetic configuration (with high Curie temperature) is the most energetically favorable among the five different spin configurations i.e., non-magnetic, ferromagnetic, and three anti-ferromagnetic. From the coatings perspective, the surface properties of Mn2AuN(001) terminations are investigated considering the four possible surface termination models. Remarkably, the magnetism does not get vanished even after cleaving the bulk unit cell into the (001)-surfaces. While evaluating the surface energetics in different chemical potentials, the N-001 terminated surface comes out to be the most stable termination contrasting with carbide MAX phases and is the only termination that exhibits the magnetic characteristics.

Dynamic stability of thin-walled FML columns including delamination

This paper presents a numerical analysis of Fiber Metal Laminate thin-walled column behaviour under dynamic pulse loading. Structural resistance to dynamic pulse loading was assessed by applying two types of criteria: dynamic stability and failure criteria. The FE model was created to take into consideration delamination failure between laminate layers. Contact elements were implemented to solve this problem within the frame of a three-dimensional model. Therefore, it was possible to analyse the FML column dynamic stability by considering all failure mechanisms at the meso-mechanical level, i.e. aluminium yielding, fiber and matrix failure modes, and layer debonding.

An Integrative Analysis of the HD 219134 Planetary System and the Inner solar system: Extending DYNAMITE with Enhanced Orbital Dynamical Stability Criteria

Abstract Planetary architectures remain unexplored for the vast majority of exoplanetary systems, even among the closest ones, with potentially hundreds of planets still “hidden” from our knowledge. Dynamite is a powerful software package that can predict the presence and properties of these yet-undiscovered planets. We have significantly expanded the integrative capabilities of Dynamite, which now allows for (i) planets of unknown inclinations alongside planets of known inclinations, (ii) population statistics and model distributions for the eccentricity of planetary orbits, and (iii) three different dynamical stability criteria. We demonstrate the new capabilities with a study of the HD 219134 exoplanet system consisting of four confirmed planets and two likely candidates, where five of the likely planets and candiates are Neptune-sized or below with orbital periods less than 100 days. By integrating the known data for the HD 219134 planetary system with contextual and statistical exoplanet population information, we tested different system architecture hypotheses to determine their likely dynamical stability. Our results provide support for the planet candidates, and we predict at least two additional planets in this system. We also deploy Dynamite on analogs of the inner solar system by excluding Venus or Earth from the input parameters to test Dynamite's predictive power. Our analysis finds that the system remains stable while also recovering the excluded planets, demonstrating the increasing capability of Dynamite to accurately and precisely model the parameters of additional planets in multiplanet systems.