Coupling Force Research Articles

Analytical modeling on the vibration response of a beam‐stiffened Mindlin thick plate with free boundary conditions

AbstractThis paper presents a new analytical solution for the vibration response of a beam‐stiffened Mindlin plate having a completely free boundary condition by utilizing a finite cosine integral transform. In the solution, the unknown coupling force and moments at the beam/plate interface and the unknown modal constants from the integral transform are determined by the continuity and compatibility conditions at the interface as well as the boundary conditions. It provides an easily implemented tool for exploring complex edge value problems for a class of higher‐order partial differential equations represented by fully free‐stiffened Mindlin thick plates. The validity of the model is evaluated by comparing the calculated free and forced vibration responses of the beam‐stiffened plate with those calculated using a beam‐stiffened thin plate and those from finite element analysis.

Depinning in the quenched Kardar-Parisi-Zhang class. II. Field theory.

There are two main universality classes for depinning of elastic interfaces in disordered media: quenched Edwards-Wilkinson (qEW) and quenched Kardar-Parisi-Zhang (qKPZ). The first class is relevant as long as the elastic force between two neighboring sites on the interface is purely harmonic and invariant under tilting. The second class applies when the elasticity is nonlinear or the surface grows preferentially in its normal direction. It encompasses fluid imbibition, the Tang-Leschorn cellular automaton of 1992 (TL92), depinning with anharmonic elasticity (aDep), and qKPZ. While the field theory is well developed for qEW, there is no consistent theory for qKPZ. The aim of this paper is to construct this field theory within the functional renormalization group (FRG) framework, based on large-scale numerical simulations in dimensions d=1, 2, and 3, presented in a companion paper [Mukerjee et al., Phys. Rev. E 107, 054136 (2023)10.1103/PhysRevE.107.054136]. In order to measure the effective force correlator and coupling constants, the driving force is derived from a confining potential with curvature m^{2}. We show, that contrary to common belief, this is allowed in the presence of a KPZ term. The ensuing field theory becomes massive and can no longer be Cole-Hopf transformed. In exchange, it possesses an IR attractive stable fixed point at a finite KPZ nonlinearity λ. Since there is neither elasticity nor a KPZ term in dimension d=0, qEW and qKPZ merge there. As a result, the two universality classes are distinguished by terms linear in d. This allows us to build a consistent field theory in dimension d=1, which loses some of its predictive powers in higher dimensions.

Coupled Excitation Strategy for Crack Initiation at the Adhesive Interface of Large-Sized Ultra-Thin Chips

The initial excitation of interface crack of large-size ultra-thin chips is one of the most complicated technical challenges. To address this issue, the reversible fracture characteristics of a silicon-based chip (chip size: 1.025 mm × 0.4 mm × 0.15 mm) adhesive layer interface was examined by scanning electron microscope (SEM) tests, and the characteristics of a cohesive zone model (CZM) unit were obtained through peel testing. The fitting curve of the elastic bilinear model was in high agreement with the experimental data, with a correlation coefficient of 0.98. The maximum energy release rate required for stripping was GC = 10.3567 N/m. Subsequently, a cohesive mechanical model of large-size ultra-thin chip peeling was established, and the mechanical characteristics of crack initial excitation were analyzed. The findings revealed that the larger deflection peeling angle in the peeling process resulted in a smaller peeling force and energy release rate (ERR), which made the initial crack formation difficult. To mitigate this, a coupling control method of structure and force surface was proposed. In this method, through structural coupling, the change in chip deflection was greatly reduced through the surface coupling force, and the peeling angle was greatly improved. It changed the local stiffness of the laminated structure, made the action point of fracture force migrate from the center of the chip to near the edge of the chip, the peeling angle was increased, and the energy release rate was locally improved. Finally, combined with mechanical analysis and numerical simulation of the peeling process, the mechanical characteristics of peeling were analyzed in detail. The results indicated that during the initial crack germination process, the ERR of the peel interface is significantly increased, the maximum stress value borne by the chip is significantly reduced, and the peel safety and reliability are greatly improved.

Unified integral transform solution for vibration analysis of ribbed plate

This paper presents a unified integral transform solution for the analysis of free and forced vibration of ribbed rectangular plate with arbitrary classical boundary conditions, whereas previous integral transform techniques have mainly focused on the analysis of the mechanical behavior of bare plates. The one- and two-dimensional integral transform techniques are applied to the higher-order partial differential governing equations of the beams and the plates, respectively, which are transformed into a system of linear algebraic equations after a rigorous derivation. The unknown coupling force and moment are determined by the compatibility conditions at the beam-plate coupling interface to obtain a unified solution scheme for ribbed plates with arbitrary classical boundary conditions. Good agreements are found between the results of analytical solution, finite element analysis and literature. Moreover, experiments on vibration analysis of a ribbed plate with completely free boundary conditions are conducted to further verify the validity and accuracy of the unified solution scheme. The effect of rib on the vibration response of rectangular plates is also investigated. It is shown that the vibration is controlled by the plate stiffness when the rib plays as a mass loading. The proposed unified analytical solution can be widely used to provide theoretical guidance for the vibration prediction of various structures with ribbed plates, such as offshore platforms, high-speed carriages, and aircraft wings.

Method for calculating pressure losses in the pipelines of slurry shield tunneling based on coupled simulation of computational fluid dynamics and discrete element method

AbstractHydraulic mucking/transport or slurry pipelining are widely used in dredging, trenching, (deep sea) mining, tunnel boring, and many other applications. Slurry pipelining during slurry shield tunneling is a classic instance of complex hydraulic mucking systems, which is characterized by the complex rheological behavior of the slurry and the inclusion of large and irregular particles. These characteristics make it difficult to estimate the pressure losses along slurry pipelines, compared to other hydraulic mucking systems. This study established a powerful method for predicting the pressure losses in long‐distance slurry pipelining of slurry shield tunneling based on computational fluid dynamics–discrete element method (CFD‐DEM)‐coupled simulations. Rheological tests were carried out to provide reliable slurry flow parameters for CFD calculations. Irregular pebbles with different sizes were digitally scanned using 3D scanning technology, and the scanned models were applied to the DEM. This method was successfully applied to a slurry shield tunnel project in Beijing, China. The mechanical properties of the fluid phase and particle phase were revealed by modeling a typical slurry pipeline. A comparison of the pressure losses along slurry pipelines was made between the proposed method and field data, indicating the validity of the established method. The simulation results indicate that when the slurry flows through the elbow, a secondary flow will be formed due to centrifugal force. Pebbles of different sizes show different motion responses under the combined action of gravity and slurry coupling force. The turbulent flow of particles will increase the frictional pressure losses in the elbow area, compared to the straight section. This work provides a valuable reference for the layout of the slurry circulation system of similar projects.

Analysis of Sliding Contact of Armature Inside the Vertical Curved Rails in Electromagnetic Railgun

In previous studies, the armature–rail sliding contact interface is usually considered to be an ideal slide in which both rails are parallel and symmetric. However, due to the influence of structural deformation of the barrel affected by boundary constraints and the manufacturing errors of rails and armature, it often leads to a variety of nonideal the armature–rail matching such as space curved or twisted rails, offset or deflected armature, and so on. This article focuses on the common vertical curved rail in electromagnetic railgun. By introducing centrifugal force effects and coupling electromagnetic force, the armature–rail contact pressure is analyzed theoretically. According to the 3-D finite-element simulation results, the effect of centrifugal force on sliding contact pressure should not be ignored. The effects of different curved radii, velocities, and densities of armature on the contact pressure are compared and analyzed. The influence law on the contact pressure is obtained, which provides a theoretical basis for the design of the railgun.

Computing hydrodynamic interactions in confined doubly periodic geometries in linear time.

We develop a linearly scaling variant of the force coupling method [K. Yeo and M. R. Maxey, J. Fluid Mech. 649, 205-231 (2010)] for computing hydrodynamic interactions among particles confined to a doubly periodic geometry with either a single bottom wall or two walls (slit channel) in the aperiodic direction. Our spectrally accurate Stokes solver uses the fast Fourier transform in the periodic xy plane and Chebyshev polynomials in the aperiodic z direction normal to the wall(s). We decompose the problem into two problems. The first is a doubly periodic subproblem in the presence of particles (source terms) with free-space boundary conditions in the z direction, which we solve by borrowing ideas from a recent method for rapid evaluation of electrostatic interactions in doubly periodic geometries [Maxian et al., J. Chem. Phys. 154, 204107 (2021)]. The second is a correction subproblem to impose the boundary conditions on the wall(s). Instead of the traditional Gaussian kernel, we use the exponential of a semicircle kernel to model the source terms (body force) due to the presence of particles and provide optimum values for the kernel parameters that ensure a given hydrodynamic radius with at least two digits of accuracy and rotational and translational invariance. The computation time of our solver, which is implemented in graphical processing units, scales linearly with the number of particles, and allows computations with about a million particles in less than a second for a sedimented layer of colloidal microrollers. We find that in a slit channel, a driven dense suspension of microrollers maintains the same two-layer structure as above a single wall, but moves at a substantially lower collective speed due to increased confinement.

Influence of Coupling Forces and Body Posture on the Rotational Hand–Arm Impedance in yh Direction

This manuscript investigates the rotational mechanical impedance of the human hand–arm system with respect to vibration excitation around the gripping axis of the hand under the influence of body posture, gripping force, and push force. Knowledge of rotational mechanical impedance is required for deriving models of hand–arm biodynamics. These models are used in the validation of power tools to predict further vibrational human–machine interactions. In the current state of research, such models exist for translational but not rotational vibration excitation. Consequently, this study investigates the properties of a hand–arm system with respect to rotational vibration excitation. In the study, the rotational impedance of the hand–arm systems of 13 adults was measured at various gripping and push forces applied in different body postures. The setup of the test used in this study consisted of a shaker that applied rotational vibrations at certain frequencies to the subjects’ hand–arm systems via a cylindrical handle. The results of the study indicate a spring–damper dynamic of the hand–arm system. The gripping force strongly influences the magnitude of rotational impedance across the frequency spectrum. Regarding push force and posture, no corresponding influence could be determined. The results suggest that the frictional contact between the hand and handle might confer a damping effect.

Enhanced optoelectronic performances of FePS3/ReS2 Van der Waals heterostructures with type-II band alignment

FePS3, as a typical represent of newly emerged transition metal chalcogenophosphates (TMCPs) with antiferromagnetic properties, has been considered as a splendid candidate for ultraviolet (UV) photodetectors. However, the limited response spectra band and photoresponsivity has seriously restricted its applications. As a typical representative of transition metal Re-based chalcogenides, ReS2 has an adjustable absorption band gap in the visible light band and extremely weak interlayer coupling force, which makes the material have higher absorbance and exciton transition probability, thereby greatly enhancing PL. Herein, we construct a high performance photodetector based on FePS3/ReS2 van der Waals (vdWs) heterostructure with excellent optical and optoelectronic properties. The in-plane optical anisotropic ratio of ReS2 nanoflake is significantly enhanced owing to the strong vdWs interlayer couplings, which is confirmed by the linear-polarized photoluminescence (PL) spectra. The photodetector exhibits broadband response spectrum ranging from UV to near-infrared (NIR) region, high photoresponsivity upto 102.5 A/W at 305 nm and 41.8 A/W at 638 nm, and fast response speed with rising/decaying times about 0.22/1.22 ms, which displays excellent superiority over other FePS3-based photodetectors. The high performances of FePS3/ReS2 are primarily attributed to the high electron mobility, strong light-matter interactions and built-in electric field at the heterointerface with type-II band alignment. The eminent and novel optoelectronic properties of the heterostructure pave promising platforms for the further development and applications of TMCPs in high-performance photodetections.

Mechano‐Triboelectric Transduction of Sliding‐Mode Nanogenerators with Magnetic Pre‐Stress

AbstractStudies on the enhancement of output performance are widely presented based on the theory of output characteristics for sliding‐mode triboelectric nanogenerators (TENGs). However, few studies are reported to investigate the electromechanical coupling of the external force onto the S‐TENG due to its fuzzy influence on electrical performance. In order to study the effect of the pre‐stress on S‐TENGs, in this work, a novel strategy of adding flexible magnet layers in the S‐TENG is first proposed to study the electrification and coupling effect induced by magnetic pre‐stress (or magnetically stresses triboelectric nanogenerator, MS‐TENG) both theoretically and experimentally. The electromechanical characteristic of the MS‐TENG is theoretically studied by introducing the magnetic pre‐stress coefficient. Considering the effect of the magnetic pre‐stress, load resistances, and sliding frequency on MS‐TENG at a low sliding speed, the relevant output performance of the MS‐TENG is derived through the equivalent circuit model. Furthermore, the corresponding experiments are conducted and the experimental results present a good agreement with the theoretical calculations, which effectively reveal the principle of the magnetic pre‐stress on the MS‐TENG. This work is aimed at providing a theoretical description with validations on the effect of external pre‐stresses on the performance enhancement of S‐TENGs.

Organic Cation Design of Manganese Halide Hybrids Glass toward Low‐Temperature Integrated Efficient, Scaling, and Reproducible X‐Ray Detector

AbstractZero‐dimensional (0D) structure‐based manganese metal halides (MHs) are believed to be the most promising candidates for the next‐generation X‐ray scintillators due to their intense radioluminescence and environmental friendliness. However, low‐temperature (<180 °C), large‐area integration with more efficient X‐ray detection remains a tremendous challenge. Herein, from the perspective of cation (ionic liquids) structure design, the basic physical parameters of 0D MHs are regulated. And the calculations and experimental results demonstrate larger‐size cations that induce lower melting temperatures, larger exciton‐binding energies, larger ion migration energy, and tunable hardness, which are most desirable for MHscintillators. As a result, the champion materialHTP2MnBr4is achieved as glassy transparency wafer by low‐temperature (165 °C) melt‐quenching. Its application to X‐ray imaging features high spatial resolution (17.28 lp mm−1), scalability (>30 × 30 cm2), and integration with strong coupling force. Furthermore, HTP2MnBr4 glass with reproducible properties demonstrates a high light yield (38 000 photon MeV−1), excellent irradiation stability, and low detection limit (0.13 µGy s−1). The authors believe this work will provide guidance for MHscintillators to further commercial applications.

Multi-scale synergic optimization strategy for dielectric energy storage ceramics

Dielectric capacitors, serving as the indispensable components in advanced high-power energy storage devices, have attracted ever increasing attention with the rapid development of science and technology. Among various dielectric capacitors, ceramic capacitors with perovskite structure show unique advantages in actual application, such as excellent adaptability in high temperature environments. And the optimization of their energy storage performances has become a hot research topic recently. This review presents the basic principles of energy storage in dielectric ceramics and introduces multi-scale synergic optimization strategies according to the key factors for superior energy storage performance. By summarizing the common points in numerous works, several universal modification strategies are reviewed and future research on fatigue fracture of ceramic capacitors under multi-field including but not limited to force, electric and thermal coupling conditions is also anticipated.

Novel constraints on fifth forces and ultralight dark sector with asteroidal data

We study for the first time the possibility of probing long-range fifth forces utilizing asteroid astrometric data, via the fifth force-induced orbital precession. We examine nine Near-Earth Object (NEO) asteroids whose orbital trajectories are accurately determined via optical and radar astrometry. Focusing on a Yukawa-type potential mediated by a new gauge field (dark photon) or a baryon-coupled scalar, we estimate the sensitivity reach for the fifth force coupling strength and mediator mass in the mass range m ≃ (10-21-10-15) eV, near the “fuzzy” dark matter region. Our estimated sensitivity is comparable to leading limits from equivalence principle tests, potentially exceeding these in a specific mass range. The fifth force-induced precession increases with the orbital semi-major axis in the small m limit, motivating the study of objects further away from the Sun. We also demonstrate that precession tests are particularly strong in probing long-range forces which approximately conserve the equivalence principle. We discuss future prospects for extending our study to more than a million asteroids, including NEOs, main-belt asteroids, Hildas, and Jupiter Trojans, as well as trans-Neptunian objects and exoplanets.

Dynamic modeling and analysis of the spline joint-flexible coupling-rotor system with misalignment

In the field of aviation and navigation, the spline joint-flexible coupling-rotor system has been widely used. However, the installation of the spline joint and the drive shaft is easy to introduce misalignment, then affecting the safe operation of the system. To solve this problem, this paper studies the dynamic modeling and analysis of the system with misalignment. The finite element dynamic model of the system is established. In this paper, the shaft misalignment is equivalent to the spline static misalignment and the misalignment excitation force of the flexible coupling. And a general model of the spline joint is established, which introduces the static misalignment caused by the installation of the spline joint and the drive shaft, the dynamic misalignment caused by the spline joint vibration, and the tooth surface friction. By solving the dynamic equation, the effect of the misalignment on the system's dynamic characteristics is analyzed, and some suggestions and methods for health monitoring of the system are given. The accuracy of the analysis method proposed in this paper is verified by experiment. The dynamic model and the method proposed in this paper have important theoretical significance for the dynamic design and analysis of rotor systems.

Frequency‐tunable resonant hybrid vibration energy harvester using a piezoelectric cantilever with electret‐based electrostatic coupling

AbstractHybrid vibration energy harvesting technology converts vibration energy into electricity using multiple transduction mechanisms to improve output power. A frequency‐tunable resonant hybrid vibration energy harvester using a piezoelectric cantilever with electret‐based electrostatic coupling is proposed in this article. The electrostatic coupling including electrostatic force coupling and electrical damping coupling is introduced by an electret film placed below the cantilever, where the electrostatic force acting on the cantilever realises a tunable resonant frequency and additional electrical damping boosts power output. A coupling electromechanical model is derived using Euler–Bernoulli beam theory and Kirchhoff's law. By investigating the static and dynamic stability of cantilever, the maximum electret surface potential is defined to prevent the pull‐in phenomenon. The damping of the device is evaluated, and the optimal electret surface potential is determined to obtain the matching of the electrical and mechanical damping for maximum power output. The resonant frequency of hybrid vibration energy harvester can be adjusted in range of 176.1 rad/s by changing the electret surface potential and resistive load. The experimental output power of hybrid vibration energy harvester was 5.2 μW, 27.4 times higher than that of the individual piezoelectric generator. The proposed hybrid vibration energy harvester exhibits a promising potential to power microelectronic devices and wireless sensor network node.

Investigation on White Layer Formation in Dry High-Speed Milling of Nickel-Based Superalloy GH4169

To investigate the formation mechanism of the white layer on the machined surface during high-speed milling of nickel-based superalloy GH4169, several cutting parameters were selected for milling experiments. Energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and electron backscattered diffraction (EBSD) were employed to characterize element distribution, phase transformation, and microstructure changes in the machined surface of the superalloy and then reveal the formation mechanism of the white layer on the machined surface. The results show that the white layer appears on the machined surface of GH4169, which is dense and has no obvious structural features. The total amount of elements in the white layer remains unchanged, but the distribution of elements such as C, N, O, Fe, and Ni changes due to phase change. The formation mechanism of the white layer is due to the dynamic recovery and dynamic recrystallization caused by the heat–force coupling effect, which leads to the grain refinement of the material and thus forms the white layer. This investigation can provide theoretical support to improve the service life of the parts in actual machining.

Identification and suppression of driving force misalignment angle for a MEMS gyroscope using parametric excitation

We report for the first time an implementable method to identify and suppress the driving force misalignment angle for a MEMS gyroscope working either in amplitude modulated (AM) or Lissajous frequency modulated (LFM) mode using parametric excitation. By introducing driving force misalignment angle into gyroscope dynamic equations, we illustrate that gyroscope angular rate output is affected by driving force misalignment angle and cross-axis damping jointly. We propose parametric excitation as a way to both identify and calculate the driving force misalignment angle. The identification results for a gyroscope working in both AM and LFM mode are similar, which indicates the effectiveness of the proposed identification method. Instead of using traditional amplitude control loop by adjusting the driving force, we do the automatic gain control by adjusting the parametric pump voltage so that a fixed drive voltage can be used, which also indicates fixed force coupling. Experimental results show that after suppression, the bias instability (BI) of AM mode is improved from 4.7° h−1 to 2.3° h−1 and the BI of LFM mode is improved from 1.4° h−1 to 0.9° h−1 which is the lowest result reported for LFM gyroscope.

Influence of coupling forces on the mechanical impedance of the hand-arm system during rotational vibration excitation around the xh-axis

The research presented in this paper focuses on the determination of the rotational mechanical impedance of the human hand-arm system under rotational vibration excitation, applied via the knob-shaped handle. During the development of power tools, the interaction between the power tool and the hand-arm system must be simulated. This requires accurate models of the hand-arm system's biodynamics. The current state of research provides such models for translational vibrations, but are limited when also considering rotational vibrations. To enable the development of such models, the study investigates the biodynamics of the hand-arm system for rotational vibration excitation. Therefore, the rotational impedance of 21 subjects was measured in a study. In the study, a knob-shaped measuring handle, whereby the subjects applied different combinations of gripping and push forces to the handle, vibrated the hand-arm system of the subjects rotationally. The results show that a higher gripping force results in a higher magnitude of rotational mechanical impedance, while the push force does not seem to influence the rotational impedance. The missing influence of the push force on the rotational impedance may be caused by the alignment between hand position, force direction, and excitation axis. The findings of this study extend the overall knowledge of rotational mechanical impedance for simulating the hand-arm system in power tool development. In regards to the rotational vibration exposure when performing sanding tasks, the results suggest that a frictional connection between the hand and the power tool handle reduces the vibration exposure of the hand-arm system.

Longitudinal and lateral coupling vehicle stability controller designed based on piecewise T-S fuzzy model

Due to tire force coupling and load transfer coupling during the stability control process, the vehicle longitudinal and lateral dynamics shows particularly obvious nonlinear coupling characteristics, which will deteriorate the performance of the stability controller. This paper proposes a Vehicle Stability Controller considering the vehicle longitudinal and lateral coupling characteristics. First, a piecewise guidance method, including the Adaptive Linear Regression Algorithm and Dimensionless Performance Evaluation Weighting Function, is developed to ensure the Takagi-Sugeno fuzzy model piecewise approaches the nonlinear characteristics of the original system and obtains the multiple linear fuzzy subsystems. Then, an H∞ robust controller with dynamic output feedback is used in each fuzzy subsystem based on the identification result of the driving intention, and the Linear Matrix Inequality is applied to obtain the controller gains. Subsequently, the Parallel Distributed Compensation architecture is adopted to integrate the outputs of all fuzzy subsystems, and vehicle stability controller is realized by using a rule-based control distribution strategy. The proposed controller is evaluated by simulations and hardware in the loop tests, and the results demonstrate satisfactory longitudinal following ability and lateral stability.

EMG-informed neuromuscular model assesses the effects of varied bodyweight support on muscles during overground walking

Bodyweight supported walking is a common gait rehabilitation method that can be used as an experimental approach to better understand walking biomechanics. Neuromuscular modeling can provide an analytical means to gain insight into how muscles coordinate to produce walking and other movements. To better understand how muscle length and velocity affect muscle force during overground walking with bodyweight support, we used an electromyography (EMG)-informed neuromuscular model to investigate changes in muscle parameters (muscle force, activation and fiber length) at varying bodyweight support levels: 0%, 24%, 45% and 69% bodyweight. Coupled constant force springs provided a vertical support force while we collected biomechanical data (EMG, motion capture and ground reaction forces) from healthy, neurologically intact participants walking at 1.20 ± 0.06 m/s. The lateral and medial gastrocnemius demonstrated a significant decrease in muscle force (lateral: p = 0.002 and medial: p < 0.001) and activation (lateral: p = 0.007 and medial: p < 0.001) through push-off at higher levels of support. The soleus, in contrast, had no significant change in muscle activation through push-off (p = 0.652) regardless of bodyweight support level even though soleus muscle force decreased with increasing support (p < 0.001). During push-off, the soleus had shorter muscle fiber lengths and faster shortening velocities as bodyweight support levels increased. These results provide insight into how muscle force can be decoupled from effective bodyweight during bodyweight supported walking due to changes in muscle fiber dynamics. The findings contribute evidence that clinicians and biomechanists should not expect a reduction in muscle activation and force when using bodyweight support to assist gait during rehabilitation.