Structural Coupling Effects Research Articles

An Analytical Study on the Effects of Non-Uniform Vane Spacing on Forced Response Reduction in a Mistuned Blisk Rotor in a Multistage Axial Compressor

Abstract Stators with non-uniform vane spacing (NUVS) have been sought as an effective way to reduce the rotor-forced response at certain resonance crossing of concern. A comprehensive experimental study has been conducted in Purdue three-stage axial research compressor to evaluate the effectiveness of the NUVS stator on reducing the forced response of the downstream rotor using strain gauge measurement. The experimental results showed that the classical estimation method failed to predict the reduction factor correctly, mainly due to the lack of consideration for the damping and mistuning effects. To better understand the experimental results, and to provide an efficient and more accurate analysis tool for the rotor forced response under NUVS stator excitation, a detailed analytical study was conducted in this paper. The blade-forced response was solved using an efficient, steady-state linearized approach. A single-blade analysis was done first to study the effect of damping. The case studies show that higher damping causes more overlap of the blade forced response from adjacent engine order excitations and, thus, increases the total normalized blade response under NUVS stator excitation. A mistuned blisk aeroelastic model was introduced next, with the mistuning effect modeled using the fundamental mistuning model. Both structural coupling and aerodynamic coupling effects can be included in the aeroelastic model. Similar to the experimental results, the mistuned blisk case study shows a large blade-to-blade variation in the blade-forced response under both symmetric and asymmetric NUVS stator excitation, even at a low, non-intentional mistuning level. A statistical study with 100 randomly generated mistuned blisks shows that the forced response reduction effect of a specific NUVS design could vary significantly with a small change of the mistuning pattern, which suggests that mistuning has to be carefully considered in the design, evaluation, and optimization of the NUVS stator.

An impact-damping model of collision body with multi-point contact and external load, and its application in gear transmission

The damping term is an important component of the calculation model of the contact force of collision bodies because it simulates the energy dissipation of collision bodies during the contact-impact process. Therefore, an impact-damping model of a collision body with multi-point contact and external load is established by considering the restitution coefficient. The algorithm for solving this model is proposed based on iterative methods. Then, the accuracy of the established model is verified by the consistency between the calculated and tested results. The effect of multi-point contact and external load on the contact-impact process of the collision body is studied. The results show that the hysteresis damping factor increases from small to large when the collision body enters a stable state through repeated impacts. Further, the established damping model is applied to the dynamics model of a spur gear pair with backlash, extended teeth contact, and structure coupling effect of the gear body. The nonlinear dynamic characteristics, multi-state mesh, and teeth impact of the system are studied through the root-mean-square of transmission error, bifurcation diagrams with multi-mapping sections, and contact forces. The calculation results of the gear dynamics model with the impact-damping model are more consistent with the tested results than the calculation results of the gear dynamics model with the traditional damping model. Meanwhile, the connection between system resonance, response coexistence, teeth disengagement, and teeth impact is revealed.

Free Vibration of Thermally Loaded FG-GPLRC Nanoplates Integrated with Magneto-Electro-Elastic Layers in Contact with Fluid

This work investigates the free vibrations of innovative thermally loaded nanoplates constructed by integrating magneto-electro-elastic (MEE) layers with functionally-graded graphene platelet-reinforced composite cores (FG-GPLRC) and accounting for viscous fluid interactions. An advanced multiphysics model is developed using the Navier–Stokes equations to capture fluid structure coupling effects, Halpin–Tsai, and the rule of mixtures micromechanics to predict the non-uniform effective properties, third-order shear deformation plates theory (TSDPT) to incorporate thickness stretching, and the nonlocal strain gradient theory (NSGT) to characterize size dependencies. The Galerkin technique is used to solve the governing equations, which are derived from the Hamilton’s principle. Parametric analyses quantify the influences of fluid depth, temperature fluctuations, temperature profiles, nonlocal and strain gradient parameters, electric and magnetic potentials, graphene distribution patterns, graphene weight fractions, and boundary conditions on the vibration response. The outcomes of this study provide design guidelines and predictive tools enabling active vibration control systems for next-generation thermally-loaded nanocomposite structures with widespread applications from aerospace vehicles to nanoelectronics.

Mechanical response analysis of the wide-chord hollow fan blade considering the fluid–structure interaction

The aero-engine wide-chord hollow fan blade with a cavity stiffener structure can effectively reduce the weight and greatly increase the rotational speed. However, during the high-speed rotation process of the hollow fan, there is a strong coupling effect between the solid domain of the blade and the incoming air. This effect leads to a certain deformation of the rotor blade, which has a large impact on the structural strength of the blade. Aiming at the problem of the fluid–structure interaction in its operation, the finite-element method was used to simulate the two-layer structure of the TC4 titanium alloy wide-chord hollow fan blade. The centrifugal force and fluid–structure coupling effect were considered when carrying out the research on the structural mechanical characteristics of the blade. The results show that the maximum equivalent stress of the blade considering the fluid–structure coupling effect is 508 MPa at the rotational speed of 2,900 r/min, which is approximately 18% higher than the maximum stress when only the centrifugal force is considered. This phenomenon indicates that the effect of aerodynamic force on the blade stress cannot be ignored. The stress concentration area of the blade is located in the third stiffener from the leading edge and near the root of the blade, and the aerodynamic force has a more significant effect on the radial stress distribution of the blade. Further analysis of the equivalent stress distribution along the blade tip direction shows a trend of first increasing and then decreasing. The maximum equivalent stress appears at a distance of 30 mm up to the bottom of the stiffener.

Investigation of Effect of the Tooth Profile Modification on the Engagement Characteristics of the Gear Pair

As a vital component in the electric vehicle, the higher requirements for the gear precision are urgently needed in the service environment with high speed and heavy load. The tooth profile modification can greatly improve the accuracy and strength of the gear transmissions. Therefore, accurately obtaining the optimum modification parameters of the gear system under the action of specific loads is the premise of the research of gear vibration and noise reduction. The time-varying mesh stiffness calculation model is established in this paper considering the coupling effect of the tooth profile errors and structural coupling effect. The minimum variations of the loaded static transmission error are selected as the objective function to obtain the optimum modification parameters of gear pair. In addition, the effect of torque, modification amount and modification length on the engagement characteristics of the gear pair are studied. The research can provide some references for the design and optimization for the gear transmission system in the electric vehicle.

Analytical method for gear body-induced tooth deflections of hybrid metal-composite gears

Hybrid metal-composite gears are designed for weight optimization and vibration/noise control in gear transmission systems. However, it is time-consuming and expensive to analyze the meshing characteristics of hybrid gears based on the finite element method (FEM) and experiment. Therefore, this work presents an efficient analytical method (AM) for calculating gear body-induced tooth deflections of hybrid gears. Based on the multi-scale modeling method, mechanical properties of the two-dimensional triaxial braided composite (2DTBC) web are predicted by integrating micro yarn properties, meso braiding structures, and macro configuration. Subsequently, boundary problems of isotropic and anisotropic planar elastic rings are investigated to deduce analytical formulas for gear body-induced tooth deflections of hybrid gears considering structure coupling effect. The comparison with the FEM demonstrates that the proposed AM can accurately and effectively estimate gear body-induced tooth deflections. More results show that periodic variation exists in gear body-induced tooth deflections within one rotation cycle, while the rim thickness contributes more to weight reduction and the amplitude and fluctuation of tooth deflections than the braiding angle. This work provides beneficial guidance for the meshing behavior and weight reduction design of hybrid gears.

Study on Earthquake Failure Mechanism and Failure Mode of Cable-Stayed Pipeline Bridge Considering Fluid–Structure Coupling

To investigate the failure mode of the cable-stayed pipeline bridge under seismic loading, this study focuses on an oil and gas cable-stayed pipeline bridge as the research subject. A full-scale finite element calculation model of the structural system is established using ANSYS Workbench 14.0 software, considering the stress characteristics and structural properties of the oil and gas pipeline. Additionally, a fluid–structure coupling effect finite element model is developed to account for the influence of medium within the pipeline. The analysis includes evaluating deformation, stress, strain, and other responses of the oil and gas pipeline subjected to seismic waves from different directions. The results indicate that the overall damage in the pipeline is consistent with maximum deformation, stress, and strain, concentrated at both the inlet/outlet ends and side spans; however, variations exist in terms of seismic damage depending on wave directionality. Furthermore, by considering interactions between various components within the oil and gas cable-stayed pipeline bridge’s structural system during strong earthquakes, this study analyzes failure mechanisms caused by the support–pipeline interaction as well as excessive displacement-induced failure patterns in bridge towers. Finally, a proposed failure mode for pipe bridge systems resulting from longitudinal slip between supports and pipelines, along with excessive displacement of bridge towers, is presented.

Flexible plasmonic nanoparticle-on-a-mirror metasurface-enabled substrates for high-quality surface-enhanced Raman spectroscopy detection

Surface-enhanced Raman scattering (SERS) technology with the advantages of ultra-high sensitivity, non-destructive analysis, and quick measurement for molecular detection applications is receiving increasing attention. However, traditional rigid SERS substrates face challenges in in-suit conformal detection and weak structure coupling effect for real-life applications. Here we report a flexible polydimethylsiloxane (PDMS) substrate loaded with plasmonic nanoparticle-on-a-mirror (NPOM) metasurface for SERS detection that featured outstanding sensitivity, uniformity, repeatability, and excellent mechanical flexibility. The upper multilayered NPOM metasurface can be fabricated in a single-step process by ion beam sputtering of various targets. This NPOM configuration consists of dense silver nanoparticles over a silver mirror, separated by a SiO2 spacer layer, which can realize near-total power absorption and exhibits superior SERS ability. The bottom PDMS layer for support can provide excellent mechanical properties. In the test, the as-prepared NPOM/PDMS substrates show high SERS performance in detecting crystal violet and chlorpyrifos molecules. This flexible metasurface SERS substrate promises to provide an in-suit and efficient approach for trace substance detection.

Taking Advantage of Potential Coincidence Region: Advanced Self-Activated/Propelled Hydrazine-Assisted Alkaline Seawater Electrolysis and Zn-Hydrazine Battery.

Hydrazine-assisted water electrolysis presents a promising energy conversion technology for highly efficient hydrogen production. Owing to the potential coincidence region between hydrogen evolution reaction (HER) and hydrazine electro-oxidation, hydrazine oxidation reaction (HzOR) exhibits specific advantages on strategy combination, device construction, and application expansion. Herein, we report a bifunctional electrocatalyst of porous Ni foam-supported interfacial heterogeneous Ni2P/Co2P microspheres (denoted NiCoP/NF), which takes full advantage of this potential coincidence region. Thanks to the 3D microsphere structure and strong interfacial coupling effects between Ni2P and Co2P, NiCoP/NF demonstrates excellent bifunctional electrocatalytic performance, requiring ultralow overpotentials of 70 and 230 mV at 10 mA cm-2 for HER and HzOR, respectively. When using NiCoP/NF as both electrodes, HzOR-assisted water electrolysis exhibits considerably decreased potentials compared with the electro-oxidation of other chemical substrates. Furthermore, the potential coincidence region of 0.1 V makes the application of self-activated/propelled hydrazine-assisted alkaline seawater electrolysis, hydrazine-containing wastewater treatment, and Zn-hydrazine (Zn-Hz) battery realistic. The concept of potential coincidence region provided in this work has significant implications for water electrolysis and other related applications.

Local instability in GdBa2Cu3O7-x/La0.7Sr0.3MnO3 superconducting bilayer: Temperature-dependent EXAFS study

This study investigated the effect of local structural coupling between the buffer and the superconducting layers on the superconductivity of a GdBa2Cu3O7-x (GdBCO)/La0.7Sr0.3MnO3 (LSMO) bilayer. Epitaxial bilayers consisting of GdBCO with varying thicknesses (100, 300, and 500 nm), with and without LSMO (100 nm), were fabricated on a (001) SrTiO3 substrate. To investigate the local structural distortion within the GdBCO/LSMO system, the temperature-dependent extended X-ray absorption fine structure (EXAFS) spectra were measured at the Mn- and Cu–K absorption edges. The EXAFS analyses revealed local structural non-uniformity, which manifested as anomalies in the temperature dependence of both the Mn–O and Cu–O bond distributions. A strong correlation exists between the local structural distortion of the Mn–O bond and the degree of lattice instability in the CuO2 plane, which exhibits a strong thickness dependence. The inter-atomic potential of oxygen oscillations with an anharmonic approximation was adopted to interpret the structural anomalies. As a result, a double-well potential was obtained near Tc, owing to the occurrence of longer Cu–O bonds in the CuO2 plane. The difference in the degree of structural anomalies depending on the GdBCO thickness manifested as a difference in the distance between the two wells, which closely correlates with the appearance of a superconducting state. These experimental results demonstrate the role of local lattice fluctuations in the superconducting mechanism of the GdBCO/LSMO bilayer.

Phase engineering of nickel-based sulfides toward robust sodium-ion batteries

Nickel-based sulfides are considered promising materials for sodium-ion batteries (SIBs) anodes due to their abundant resources and attractive theoretical capacity. However, their application is limited by slow diffusion kinetics and severe volume changes during cycling. Herein, we demonstrate a facile strategy for the synthesis of nitrogen-doped reduced graphene oxide (N-rGO) wrapped Ni3S2 nanocrystals composites (Ni3S2-N-rGO-700 °C) through the cubic NiS2 precursor under high temperature (700 ℃). Benefitting from the variation in crystal phase structure and robust coupling effect between the Ni3S2 nanocrystals and N-rGO matrix, the Ni3S2-N-rGO-700 °C exhibits enhanced conductivity, fast ion diffusion kinetics and outstanding structural stability. As a result, the Ni3S2-N-rGO-700 °C delivers excellent rate capability (345.17 mAh g−1 at a high current density of 5 A g−1) and long-term cyclic stability over 400 cycles at 2 A g−1 with a high reversible capacity of 377 mAh g−1 when evaluated as anodes for SIBs. This study open a promising avenue to realize advanced metal sulfide materials with desirable electrochemical activity and stability for energy storage applications.

DC ice-melting operation of the ground wire based on the characteristic investigation of the thermal structure coupling effect

DC ice-melting operation of the ground wire based on the characteristic investigation of the thermal structure coupling effect

Enhanced sound insulation performance by a staggered phononic crystal with fins

Noise is associated with physical and mental health and well-being. Sound insulation materials allowing ventilation are in demand. A staggered phononic crystal with fins (SPCF), which is a combination of staggered structures and fins, is proposed to improve the sound insulation performance and meanwhile allow ventilation. The maximum peak value (5.2 dB) of the experimentally measured transmission loss of the SPCF is higher than the peak values of the reference samples. The improved sound insulation performance of the SPCF compared with reference samples is attributed to the frequency shift effect and structural coupling effect. The dissipated energy caused by the thermal effect in the SPCF accounts for about 20 %-26 % of the total dissipated energy, suggesting that the thermal effect must be considered to obtain an accurate total dissipated energy. The SPCF sets up a new strategy for the next-generation sound insulation materials allowing ventilation.

A fluid–structure interaction model for large wind turbines based on flexible multibody dynamics and actuator line method

With higher demand of affordable electricity and rapid development of wind turbine technology, scale of wind turbines has been upsizing. As a consequence, blades grow longer and slender. Large geometrically nonlinear deformation and vibration of the blades lead to more challenges in the structural design. In the aerodynamic analysis, traditional blade element momentum theory cannot predict the complicated behavior of these modern blades while fully resolved Navier–Stokes equation methods cost much time modeling and refinement. To overcome these challenges, this paper proposes a new numerical method to analyze turbine aeroelastic performance and fluid–structure interaction based on flexible multibody dynamics and large eddy simulation with anisotropic actuator line method. By comparing the results with various existing numerical methods, we show that the newly proposed method can effectively predict the performance of the wind turbine, such as deformation and power output. We find that blade flexibility poses noticeable impact on the performance of large scale turbines in normal working conditions. The location of nascent vortex is postponed by blade deflection. The max difference between rigid and flexible blades in downstream velocity distributions reaches 10% and occurs at a radial distance around 0.55D. The new method also takes the fluid–structure coupling effect and momentum interaction into consideration and eliminates the non-physical oscillations caused by uncoupled methods. Also, blades deflection and vibration are found to accelerate momentum exchange, which facilitates the wake recovery process. Furthermore,compared to the rigid-blade model, the turbulent kinetic energy obtained by the newly developed flexible-blade model is higher in the low-frequency region, in which large-scale vortices develop and the turbulent mixing effect is strong. This paper is expected to provide a framework for researchers and technology developers to design or estimate the performance of modern large wind turbines.

Enhancing Performance of Triboelectric Nanogenerator via Surface Structure Coupling by Light-Cured 3-D Printing

Triboelectric nanogenerator (TENG) possesses great potential for applications in distributed energy supply and self-powered sensing due to high-power density, low cost, and simple preparation process. Since the output performance of TENG is directly related to its surface charge density, much work has been devoted to the preparation of micro–nano structures on the surface of the friction layer to increase its effective contact area, which usually obtains excellent output performance. However, these preparation methods are generally extremely complex or require expensive equipment, and the prepared micro–nano structures are extremely susceptible to damage. In this article, a method to prepare a TENG with a fully coupled surface structure is proposed for the first time. The ultraviolet curable resin layer with a special structure and the ecoflex layer with a corresponding structure were prepared by light-cured 3-D printing and template method, which transforms the traditional surface friction into body friction. The surface structure coupling effect achieves a significant improvement in the output performance of the TENG. At the same time, this preparation method can also be used to improve the measuring sensitivity of the triboelectric nanogenerator as a pressure sensor.

Dynamic characteristics of large permanent magnet direct‐drive generators considering electromagnetic–structural coupling effects

AbstractDynamic characteristics of large permanent magnet direct‐drive generators (PMDGs) considering electromagnetic–structural coupling effects are analyzed in this study. Using the conformal mapping method, the scalar magnetic potential of the air gap magnetic field considering the slot effect is calculated. On the basis of the discrete current element and magnetic equivalent circuit model, the local magnetic saturation effect of the stator and rotor is quantitatively simulated and the air gap magnetic field intensity distribution is obtained via numerical simulation. A series of uniformly distributed equivalent electromagnetic springs are introduced to develop an electromagnetic–structural coupling finite element PMDG model. The proposed air gap field analysis method is verified by the finite element analysis results. On the basis of the test platform for the Goldwind 1.5 MW PMDG, both modal and dynamic response tests for the stator/rotor coupling system are conducted, and the results are compared with the natural frequencies, mode shapes, and vibration responses obtained using the numerical model. The effects of the air gap length and rotor speed on the natural frequencies of the coupling system are analyzed. The proposed model has the potential to accurately evaluate the PMDG vibration energy, avoiding resonance points, and maintaining stable operations of the unit.

Magnetoelectric coupling property of 0-3 type CoFe2O4-BaTiO3 nanocomposites

The 0-3 type CoFe2O4-BaTiO3 nanocomposites have been prepared by co-precipitation sintering process in this work. The structure, dielectric, magnetic properties and magnetoelectric (ME) coupling effect of nanocomposites are studied. It finds that the 0-3 connectivity in nanocomposites results in BaTiO3 hindering the merger and growth of CoFe2O4 leading to smaller particle size (in the range 52–55 nm), creating large interface area between CoFe2O4 and BaTiO3 in composites. Creating the space charge polarization dominant thereby the dielectric constant decreased sharply with increasing frequency. Magnetization data show typical ferromagnetic behavior. Nanocomposites have strong ME coupling effect, among which C40s (CoFe2O4 content is 40 wt%) sample has a maximum ME coupling coefficient of 587.3 mV/cm∙Oe at 1.8 kHz.

Seismic Response of Cable-Stayed Spanning Pipeline Considering Medium-Pipeline Fluid–Solid Coupling Dynamic Effect

With the aim of determining the influence of the fluid–structure coupling dynamic effect of the oil and gas transmission medium and pipeline on the seismic response, an oil pipeline supported by a cable-stayed spanning structure was taken as the study object. Kinetic equations taking into account the action of oil and gas medium were studied, and a finite element model structure considering the additional-mass method and the fluid–structure coupling effect were established separately. In addition, the mechanism of the oil–gas–pipeline coupling action on the seismic response of pipeline structure was analyzed, and the results were obtained. The results show that the pipeline has a minimal seismic response at the abutment location, the seismic response gradually increases along the abutment to the main tower, and the seismic response reach is maximized at about one-fifth of the bridge platform. The seismic response of the oil and gas pipeline model structure using the additional-mass method is generally more significant than that based on the fluid–solid coupled dynamic model; moreover, the maximum displacement response differs by about 24%, and the maximum acceleration response differs by approximately 30%, indicating that the oil and gas medium has a certain viscoelastic damping effect on the seismic response of the oil pipeline, which provides a reference for the seismic response calculation theory and analysis method of cable-stayed spanning oil pipelines.

Aerodynamic Damping of the Tubed Vortex Reducer in an Axial Compressor Disk Cavity

The tubed vortex reducer in the axial compressor can destroy the vortex in the disk cavity, by a thin-walled tube, to reduce the total pressure loss. The tube may suffer from vibration problems, such as flutter and forced vibration, which are closely related to aerodynamic damping. In this paper, the energy method and the influence coefficient method are used to study the aerodynamic damping of the tube. Based on the modal characteristics, steady and unsteady flow characteristics of the tube, the first and second modes with lower frequencies and greater vibration risk are selected as the analysis objects. The energy method is used to calculate the aerodynamic damping of the tube with different amplitudes, which shows that the results approximately meet the linear assumption and are accurate. The results obtained by the influence coefficient method show that the aerodynamic influence between adjacent tubes is very small, and the effect of inter-tube phase angle on the aerodynamic damping can be ignored. Finally, it is found that the effect of structural coupling caused by the support ring on the aerodynamic damping of the tube is mainly reflected in two aspects: frequency reduction and tube mode coupling.

Numerical Simulation of Plasma Plume With Gas–Surface Interaction and Chemical Reaction Coupling Effect Based on DSMC-PIC Parallel Algorithm

The spatio-temporal evolution of plasma plumes is accompanied by a series of complex chemical reactions and gas–surface interactions that crucially affect the working characteristics and performance of plasma devices. The direct simulation Monte Carlo (DSMC) and particle-in-cell (PIC) hybrid parallel algorithm is often used to numerically simulate such phenomena. This article discusses the gas–surface interaction models of neutral molecules as elucidated by the parallel DSMC-PIC program. These models include the Maxwell model, the Cercignani–Lampis–Lord model, the complete diffuse reflection (CDR) gas–surface reflection model, and coupling with H combined reactions at the wall. Meanwhile, we consider the ion gas–surface interaction models, which include the CDR model and coupling of the four wall chemical reactions of ions. In addition, the dissociation reactions of H2 and recombination reactions of H are considered in the flow field. For various combinations of models, the simulations reveal the structural characteristics, number density, and coupling effects of gas–surface reflections, gas–surface chemical reactions, chemical reactions in the flow field and electric field, and spatio-temporal evolution of H2, H, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}_{2}^{+}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}^{+}$ </tex-math></inline-formula> , which are shown by the structural characteristics of the number-density contours for different model combinations and analyzed in detail. The gas–surface interaction critically influences the number-density distribution near the wall and in the main flow. It also strongly affects the number-density distribution of light neutral molecules but not heavy neutral molecules and ions and produces the wall stacking effect. Apart from the stacking area, it has an indirect influence on the number-density distribution. The chemical reactions of ions on the wall affect the number-density distribution of all particles in the flow field and decisively affect the ions near the wall. Acceleration by the electric field intensifies the ion diffusion. The effect of coupling of gas–surface interaction and acceleration by the electric field is obvious. Via the number density and temperature, the chemical reactions in the flow field strongly affect the distribution of neutral molecules at the inlet; further, from the inlet, this effect weakens. Neutral particles and ions interact mainly through collisions.