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    Mass-spring model for elastic wave propagation in multilayered van der Waals metamaterials
    Yabin JING, Lifeng WANG, Yuqiang GAO
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (7): 1107-1118.   DOI: 10.1007/s10483-024-3153-9
    Abstract211)   HTML5)    PDF(pc) (5187KB)(189)       Save

    Multilayered van der Waals (vdW) materials have attracted increasing interest because of the manipulability of their superior optical, electrical, thermal, and mechanical properties. A mass-spring model (MSM) for elastic wave propagation in multilayered vdW metamaterials is reported in this paper. Molecular dynamics (MD) simulations are adopted to simulate the propagation of elastic waves in multilayered vdW metamaterials. The results show that the graphene/MoS2 metamaterials have an elastic wave bandgap in the terahertz range. The MSM for the multilayered vdW metamaterials is proposed, and the numerical simulation results show that this model can well describe the dispersion and transmission characteristics of the multilayered vdW metamaterials. The MSM can predict elastic wave transmission characteristics in multilayered vdW metamaterials stacked with different two-dimensional (2D) materials. The results presented in this paper offer theoretical help for the vibration reduction of multilayered vdW semiconductors.

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    A transfer learning enhanced physics-informed neural network for parameter identification in soft materials
    Jing'ang ZHU, Yiheng XUE, Zishun LIU
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (10): 1685-1704.   DOI: 10.1007/s10483-024-3178-9
    Abstract165)   HTML7)    PDF(pc) (11313KB)(181)       Save

    Soft materials, with the sensitivity to various external stimuli, exhibit high flexibility and stretchability. Accurate prediction of their mechanical behaviors requires advanced hyperelastic constitutive models incorporating multiple parameters. However, identifying multiple parameters under complex deformations remains a challenge, especially with limited observed data. In this study, we develop a physics-informed neural network (PINN) framework to identify material parameters and predict mechanical fields, focusing on compressible Neo-Hookean materials and hydrogels. To improve accuracy, we utilize scaling techniques to normalize network outputs and material parameters. This framework effectively solves forward and inverse problems, extrapolating continuous mechanical fields from sparse boundary data and identifying unknown mechanical properties. We explore different approaches for imposing boundary conditions (BCs) to assess their impacts on accuracy. To enhance efficiency and generalization, we propose a transfer learning enhanced PINN (TL-PINN), allowing pre-trained networks to quickly adapt to new scenarios. The TL-PINN significantly reduces computational costs while maintaining accuracy. This work holds promise in addressing practical challenges in soft material science, and provides insights into soft material mechanics with state-of-the-art experimental methods.

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    Tunable topological interface states via a parametric system in composite lattices with/without symmetric elements
    Jianguo CUI, Tianzhi YANG, Wenju HAN, Liang LI, Muqing NIU, Liqun CHEN
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (12): 2055-2074.   DOI: 10.1007/s10483-024-3194-9
    Abstract583)   HTML55)    PDF(pc) (2975KB)(175)       Save

    Over the past decades, topological interface states have attracted significant attention in classical wave systems. Generally, research on the topological interface states of elastic waves is conducted in the lattices with symmetric elements. This paper proposes composite lattices with/without symmetric elements, and demonstrates the realization of tunable topological interface states of elastic waves via parametric systems. To quantize the topological characteristics of the bands, a modified Zak phase is defined to calculate the topological invariant by the eigenstates for the lattices with/without symmetric elements. The numerical results show that the tunable frequencies of topological interface states can be realized in composite lattices with/without symmetric elements through the modulation of the parametric excitation frequency. The tunable topological interface states can be introduced into the vibration energy harvesting to design efficient and steady energy harvesting systems.

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    Near resonance vibration isolation on a levered-dual response (LEDAR) Coulomb-damped system by difierential preloads/ofisets in linear springs
    T. I. TOLUWALOJU, C. K. THEIN, D. HALIM
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (6): 1033-1050.   DOI: 10.1007/s10483-024-3123-6
    Abstract154)   HTML5)    PDF(pc) (7684KB)(173)       Save

    The levered-dual response (LEDAR) Coulomb-damped system attains near resonant vibration isolation by differential preloads/offsets in linear springs. It takes the advantages of both the preloads/offsets in linear springs and the guiderail friction for realizing different levels of vibration isolation. The isolation capacities are investigated on the strategies with both the horizontal and vertical guiderails, with the horizontal rail only, and without guiderails. The compressive preloads generally result in the consumption of most of the initial excitation energy so as to overcome the potential threshold. The isolation onsets at the frequency ratio of 1 0.095 on the left-hand side (LHS) and the right-hand side (RHS) of the lever are relative to the load plate connector. The observed near resonant isolation thus makes the LEDAR system a candidate for the isolation of the mechanical systems about resonance while opening a path for simultaneous harvester-isolation functions and passive functions at extreme frequencies.

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    Analytical modeling of piezoelectric meta-beams with unidirectional circuit for broadband vibration attenuation
    Jiawei MAO, Hao GAO, Junzhe ZHU, Penglin GAO, Yegao QU
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (10): 1665-1684.   DOI: 10.1007/s10483-024-3155-9
    Abstract189)   HTML22)    PDF(pc) (10252KB)(173)       Save

    Broadband vibration attenuation is a challenging task in engineering since it is difficult to achieve low-frequency and broadband vibration control simultaneously. To solve this problem, this paper designs a piezoelectric meta-beam with unidirectional electric circuits, exhibiting promising broadband attenuation capabilities. An analytical model in a closed form for achieving the solution of unidirectional vibration transmission of the designed meta-beam is developed based on the state-space transfer function method. The method can analyze the forward and backward vibration transmission of the piezoelectric meta-beam in a unified manner, providing reliable dynamics solutions of the beam. The analytical results indicate that the meta-beam effectively reduces the unidirectional vibration across a broad low-frequency range, which is also verified by the solutions obtained from finite element analyses. The designed meta-beam and the proposed analytical method facilitate a comprehensive investigation into the distinctive unidirectional transmission behavior and superb broadband vibration attenuation performance.

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    A vertical track nonlinear energy sink
    Meng LI, Hu DING
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (6): 931-946.   DOI: 10.1007/s10483-024-3127-6
    Abstract189)   HTML9)    PDF(pc) (8074KB)(163)       Save

    Eliminating the effects of gravity and designing nonlinear energy sinks (NESs) that suppress vibration in the vertical direction is a challenging task with numerous damping requirements. In this paper, the dynamic design of a vertical track nonlinear energy sink (VTNES) with zero linear stiffness in the vertical direction is proposed and realized for the first time. The motion differential equations of the VTNES coupled with a linear oscillator (LO) are established. With the strong nonlinearity considered of the VTNES, the steady-state response of the system is analyzed with the harmonic balance method (HBM), and the accuracy of the HBM is verified numerically. On this basis, the VTNES prototype is manufactured, and its nonlinear stiffness is identified. The damping effect and dynamic characteristics of the VTNES are studied theoretically and experimentally. The results show that the VTNES has better damping effects when strong modulation responses (SMRs) occur. Moreover, even for small-amplitude vibration, the VTNES also has a good vibration suppression effect. To sum up, in order to suppress the vertical vibration, an NES is designed and developed, which can suppress the vertical vibration within certain ranges of the resonance frequency and the vibration intensity.

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    Control and vibration analyses of a sandwich doubly curved micro-composite shell with honeycomb, truss, and corrugated cores based on the fourth-order shear deformation theory
    F. SHIRDELAN, M. MOHAMMADIMEHR, F. BARGOZINI
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (10): 1773-1790.   DOI: 10.1007/s10483-024-3175-6
    Abstract131)   HTML2)    PDF(pc) (1250KB)(148)       Save

    Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures, flexibility, and attractive appearance. However, the inability of controlling and regulating vibrations and destroying them afterward is a challenge to scientists. In this paper, the curve shell equations and a linear quadratic regulator are adopted for the state feedback design to manage the structure vibrations in state space forms. A five-layer sandwich doubly curved micro-composite shell, comprising two piezoelectric layers for the sensor and actuator, is modeled by the fourth-order shear deformation theory. The core (honeycomb, truss, and corrugated) is analyzed for the bearing of transverse shear forces. The results show that the honeycomb core has a greater effect on the vibrations. When the parameters related to the core and the weight percentage of graphene increase, the frequency increases. The uniform distribution of graphene platelets results in the lowest natural frequency while the natural frequency increases. Furthermore, without taking into account the piezoelectric layers, the third-order shear deformation theory (TSDT) and fourth-order shear deformation theory (FOSDT) align closely. However, when the piezoelectric layers are incorporated, these two theories diverge significantly, with the frequencies in the FOSDT being lower than those in the TSDT.

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    A vibration isolator with a controllable quasi-zero stiffness region based on nonlinear force design
    Xinyu LIAN, Bing LIU, Huaxia DENG, Xinglong GONG
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (8): 1279-1294.   DOI: 10.1007/s10483-024-3137-8
    Abstract138)   HTML7)    PDF(pc) (5999KB)(143)       Save

    To achieve stability optimization in low-frequency vibration control for precision instruments, this paper presents a quasi-zero stiffness (QZS) vibration isolator with adjustable nonlinear stiffness. Additionally, the stress-magnetism coupling model is established through meticulous theoretical derivation. The controllable QZS interval is constructed via parameter design and magnetic control, effectively segregating the high static stiffness bearing section from the QZS vibration isolation section. Furthermore, a displacement control scheme utilizing a magnetic force is proposed to regulate entry into the QZS working range for the vibration isolation platform. Experimental results demonstrate that the operation within this QZS region reduces the peak-to-peak acceleration signal by approximately 66.7% compared with the operation outside this region, thereby significantly improving the low frequency performance of the QZS vibration isolator.

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    Multi-layer quasi-zero-stiffness meta-structure for high-efficiency vibration isolation at low frequency
    Jiahao ZHOU, Jiaxi ZHOU, Hongbin PAN, Kai WANG, Changqi CAI, Guilin WEN
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (7): 1189-1208.   DOI: 10.1007/s10483-024-3157-6
    Abstract199)   HTML0)    PDF(pc) (10840KB)(135)       Save

    An easily stackable multi-layer quasi-zero-stiffness (ML-QZS) meta-structure is proposed to achieve highly efficient vibration isolation performance at low frequency. First, the distributed shape optimization method is used to design the unit cel, i.e., the single-layer QZS (SL-QZS) meta-structure. Second, the stiffness feature of the unit cell is investigated and verified through static experiments. Third, the unit cells are stacked one by one along the direction of vibration isolation, and thus the ML-QZS meta-structure is constructed. Fourth, the dynamic modeling of the ML-QZS vibration isolation meta-structure is conducted, and the dynamic responses are obtained from the equations of motion, and verified by finite element (FE) simulations. Finally, a prototype of the ML-QZS vibration isolation meta-structure is fabricated by additive manufacturing, and the vibration isolation performance is evaluated experimentally. The results show that the vibration isolation performance substantially enhances when the number of unit cells increases. More importantly, the ML-QZS meta-structure can be easily extended in the direction of vibration isolation when the unit cells are properly stacked. Hence, the ML-FQZS vibration isolation meta-structure should be a fascinating solution for highly efficient vibration isolation performance at low frequency.

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    A physics-informed neural network for simulation of finite deformation in hyperelastic-magnetic coupling problems
    Lei WANG, Zikun LUO, Mengkai LU, Minghai TANG
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (10): 1717-1732.   DOI: 10.1007/s10483-024-3174-9
    Abstract168)   HTML3)    PDF(pc) (7702KB)(126)       Save

    Recently, numerous studies have demonstrated that the physics-informed neural network (PINN) can effectively and accurately resolve hyperelastic finite deformation problems. In this paper, a PINN framework for tackling hyperelastic-magnetic coupling problems is proposed. Since the solution space consists of two-phase domains, two separate networks are constructed to independently predict the solution for each phase region. In addition, a conscious point allocation strategy is incorporated to enhance the prediction precision of the PINN in regions characterized by sharp gradients. With the developed framework, the magnetic fields and deformation fields of magnetorheological elastomers (MREs) are solved under the control of hyperelastic-magnetic coupling equations. Illustrative examples are provided and contrasted with the reference results to validate the predictive accuracy of the proposed framework. Moreover, the advantages of the proposed framework in solving hyperelastic-magnetic coupling problems are validated, particularly in handling small data sets, as well as its ability in swiftly and precisely forecasting magnetostrictive motion.

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    A coupled Legendre-Laguerre polynomial method with analytical integration for the Rayleigh waves in a quasicrystal layered half-space with an imperfect interface
    Bo ZHANG, Honghang TU, Weiqiu CHEN, Jiangong YU, L. ELMAIMOUNI
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (9): 1539-1556.   DOI: 10.1007/s10483-024-3145-8
    Abstract147)   HTML1)    PDF(pc) (3378KB)(125)       Save

    The Laguerre polynomial method has been successfully used to investigate the dynamic responses of a half-space. However, it fails to obtain the correct stress at the interfaces in a layered half-space, especially when there are significant differences in material properties. Therefore, a coupled Legendre-Laguerre polynomial method with analytical integration is proposed. The Rayleigh waves in a one-dimensional (1D) hexagonal quasicrystal (QC) layered half-space with an imperfect interface are investigated. The correctness is validated by comparison with available results. Its computation efficiency is analyzed. The dispersion curves of the phase velocity, displacement distributions, and stress distributions are illustrated. The effects of the phonon-phason coupling and imperfect interface coefficients on the wave characteristics are investigated. Some novel findings reveal that the proposed method is highly efficient for addressing the Rayleigh waves in a QC layered half-space. It can save over 99% of the computation time. This method can be expanded to investigate waves in various layered half-spaces, including earth-layered media and surface acoustic wave (SAW) devices.

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    Actively tunable sandwich acoustic metamaterials with magnetorheological elastomers
    Jinhui LIU, Yu XUE, Zhihong GAO, A. O. KRUSHYNSKA, Jinqiang LI
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (11): 1875-1894.   DOI: 10.1007/s10483-024-3186-9
    Abstract144)   HTML4)    PDF(pc) (3756KB)(123)       Save

    Sandwich structures are widespread in engineering applications because of their advantageous mechanical properties. Recently, their acoustic performance has also been improved to enable attenuation of low-frequency vibrations induced by noisy environments. Here, we propose a new design of sandwich plates (SPs) featuring a metamaterial core with an actively tunable low-frequency bandgap. The core contains magnetorheological elastomer (MRE) resonators which are arranged periodically and enable controlling wave attenuation by an external magnetic field. We analytically estimate the sound transmission loss (STL) of the plate using the space harmonic expansion method. The low frequency sound insulation performance is also analyzed by the equivalent dynamic density method, and the accuracy of the obtained results is verified by finite-element simulations. Our results demonstrate that the STL of the proposed plate is enhanced compared with a typical SP analog, and the induced bandgap can be effectively tuned to desired frequencies. This study further advances the field of actively controlled acoustic metamaterials, and paves the way to their practical applications.

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    Size-dependent thermomechanical vibration characteristics of rotating pre-twisted functionally graded shear deformable microbeams
    Songye JIN, Bo ZHANG, Wuyuan ZHANG, Yuxing WANG, Huoming SHEN, Jing WANG, Juan LIU
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (6): 1015-1032.   DOI: 10.1007/s10483-024-3121-8
    Abstract126)   HTML4)    PDF(pc) (4670KB)(123)       Save

    A three-dimensional (3D) thermomechanical vibration model is developed for rotating pre-twisted functionally graded (FG) microbeams according to the refined shear deformation theory (RSDT) and the modified couple stress theory (MCST). The material properties are assumed to follow a power-law distribution along the chordwise direction. The model introduces one axial stretching variable and four transverse deflection variables including two pure bending components and two pure shear ones. The complex modal analysis and assumed mode methods are used to solve the governing equations of motion under different boundary conditions (BCs). Several examples are presented to verify the effectiveness of the developed model. By coupling the slenderness ratio, gradient index, rotation speed, and size effect with the pre-twisted angle, the effects of these factors on the thermomechanical vibration of the microbeam with different BCs are investigated. It is found that with the increase in the pre-twisted angle, the critical slenderness ratio and gradient index corresponding to the thermal instability of the microbeam increase, while the critical material length scale parameter (MLSP) and rotation speed decrease. The sensitivity of the fundamental frequency to temperature increases with the increasing slenderness ratio and gradient index, and decreases with the other increasing parameters. Moreover, the size effect can suppress the dynamic stiffening effect and enhance the Coriolis effect. Finally, the mode transition is quantitatively demonstrated by a modal assurance criterion (MAC).

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    Modeling and analysis of an inextensible beam with inertial and geometric nonlinearities
    Zhanhuan YAO, Tieding GUO, Wanzhi QIAO
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (12): 2113-2130.   DOI: 10.1007/s10483-024-3198-9
    Abstract530)   HTML14)    PDF(pc) (1353KB)(116)       Save

    The present study focuses on an inextensible beam and its relevant inertia nonlinearity, which are essentially distinct from the commonly treated extensible beam that is dominated by the geometric nonlinearity. Explicitly, by considering a weakly constrained or free end (in the longitudinal direction), the inextensibility assumption and inertial nonlinearity (with and without an initial curvature) are introduced. For a straight beam, a multi-scale analysis of hardening/softening dynamics reveals the effects of the end stiffness/mass. Extending the straight scenario, a refined inextensible curved beam model is further proposed, accounting for both its inertial nonlinearity and geometric nonlinearity induced by the initial curvature. The numerical results for the frequency responses are also presented to illustrate the dynamic effects of the initial curvature and axial constraint, i.e., the end mass and end stiffness.

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    Numerical computations of magnetohydrodynamic mixed convective flow of Casson nanofluid in an open-ended cavity formed by earthquake-induced faults
    M. IBTESAM, S. NADEEM, J. ALZABUT
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (12): 2215-2230.   DOI: 10.1007/s10483-024-3190-9
    Abstract585)   HTML8)    PDF(pc) (9082KB)(114)       Save

    The numerical computations for the magnetohydrodynamic (MHD) mixed convective flow of a non-Newtonian Casson nanofluid (Cu/H$_2$O) within an open-ended cavity formed by earthquake-induced faults are analyzed, aiming to investigate the fluid dynamics and convection processes of geothermal systems. Such cavities, typically found in energy reservoirs, are primarily caused by tensional fault zones formed due to the accumulated energy from the disintegration of radioactive materials. These cavities play a crucial role in energy transmission, particularly in the form of heat. The focus of this paper is on the laminar, steady, and incompressible fluid flow. An inclined magnetic field is applied with an angle of inclination $z=30^{\circ}$. Additionally, a heated material with two vertical corrugated walls is placed at the center of the cavity. The governing nonlinear partial differential equations (PDEs) are transformed into the equations with a non-dimensional form. The Galerkin finite element method (FEM) is implemented to solve the dimensionless equations. The impacts of key variables, including the Reynolds number $Re$, the volume fraction $(0.01\leqslant \phi_{\rm p}\leqslant 0.05)$, the Hartmann number $Ha$, and the Casson parameter $(0.5\leqslant \gamma\leqslant 1.0)$, on the velocity and temperature distributions are studied. The analysis of the fluid flow and the heat transfer rate is conducted. The results indicate that the velocity increases as the volume fraction and the Reynolds number increase. Similarly, the heat transfer rate rises with the Reynolds number and the volume fraction, while decreases with the higher Hartmann number. The Nusselt number increases with the volume fraction and the Reynolds number but decreases with the Hartmann number.

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    Lattice Boltzmann method formulation for simulation of thermal radiation effects on non-Newtonian Al2O3 free convection in entropy determination
    M. NEMATI, M. SEFID, A. KARIMIPOUR, A. J. CHAMKHA
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (6): 1085-1106.   DOI: 10.1007/s10483-024-3117-8
    Abstract198)   HTML12)    PDF(pc) (20368KB)(113)       Save

    The simultaneous investigation on the parameters affecting the flow of electrically conductive fluids such as volumetric radiation, heat absorption, heat generation, and magnetic field (MF) is very vital due to its existence in various sectors of industry and engineering. The present research focuses on mathematical modeling to simulate the cooling of a hot component through power-law (PL) nanofluid convection flow. The temperature reduction of the hot component inside a two-dimensional (2D) inclined chamber with two different cold wall shapes is evaluated. The formulation of the problem is derived with the lattice Boltzmann method (LBM) by code writing via the FORTRAN language. The variables such as the radiation parameter (0-1), the Hartmann number (0-75), the heat absorption/generation coefficient (-5-5), the fluid behavioral index (0.8-1.2), the Rayleigh number (103-105), the imposed MF angle (0°-90°), the chamber inclination angle (-90°-90°), and the cavity cold wall shape (smooth and curved) are investigated. The findings indicate that the presence of radiation increases the mean Nusselt number value for the shear-thickening, Newtonian, and shear thinning fluids by about 6.2%, 4%, and 2%, respectively. In most cases, the presence of nanoparticles improves the heat transfer (HT) rate, especially in the cases where thermal conduction dominates convection. There is the lowest cooling performance index and MF effect for the cavity placed at an angle of 90°. The application in the design of electronic coolers and solar collectors is one of the practical cases of this numerical research.

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    Size-dependent vibration and buckling of porous functionally graded microplates based on modified couple stress theory in thermal environments by considering a dual power-law distribution of scale effects
    Feixiang TANG, Shaonan SHI, Siyu HE, Fang DONG, Sheng LIU
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (12): 2075-2092.   DOI: 10.1007/s10483-024-3196-7
    Abstract553)   HTML21)    PDF(pc) (1758KB)(112)       Save

    In this study, the thermodynamic behaviors of the intrinsic frequency and buckling temperature of rectangular plates of functionally graded materials (FGMs) are explored based on the modified couple stress theory (MCST) and the novel dual power-law scale distribution theory. The effects of linear, homogeneous, and non-homogeneous temperature fields on the frequency and buckling temperature of FGM microplates are evaluated in detail. The results show that the porosity greatly affects the mechanical properties of FGM plates, reducing their frequency and flexural temperature compared with non-porous plates. Different temperature profiles alter plate frequencies and buckling temperatures. The presence and pattern of scale effect parameters are also shown to be crucial for the mechanical response of FGM plates. The present research aims to provide precise guidelines for the micro-electro-mechanical system (MEMS) fabrication by elucidating the complex interplay between thermal, material, and structural factors that affect the performance of FGM plates in advanced applications.

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    Strong shock propagation for the finite-source circular blast in a confined domain
    Qihang MA, Kaileong CHONG, Bofu WANG, Quan ZHOU
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (6): 1071-1084.   DOI: 10.1007/s10483-024-3120-7
    Abstract133)   HTML9)    PDF(pc) (2968KB)(110)       Save

    The circular explosion wave produced by the abrupt discharge of gas from a high-temperature heat source serves as a crucial model for addressing explosion phenomena in compressible flow. The reflection of the primary shock and its propagation within a confined domain are studied both theoretically and numerically in this research. Under the assumption of strong shock, the scaling law governing propagation of the main shock is proposed. The dimensionless frequency of reflected shock propagation is associated with the confined distance. The numerical simulation for the circular explosion problem in a confined domain is performed for validation. Under the influence of confinement, the principal shock wave systematically undergoes reflection within the domain until it weakens, leading to the non-monotonic attenuation of kinetic energy in the explosion fireball and periodic oscillations of the fireball volume with a certain frequency. The simulation results indicate that the frequency of kinetic energy attenuation and the volume oscillation of the explosive fireball align consistently with the scaling law.

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    Low-frequency bandgap and vibration suppression mechanism of a novel square hierarchical honeycomb metamaterial
    Xingjian DONG, Shuo WANG, Anshuai WANG, Liang WANG, Zhaozhan ZHANG, Yuanhao TIE, Qingyu LIN, Yongtao SUN
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (10): 1841-1856.   DOI: 10.1007/s10483-024-3168-7
    Abstract147)   HTML3)    PDF(pc) (8866KB)(109)       Save

    The suppression of low-frequency vibration and noise has always been an important issue in a wide range of engineering applications. To address this concern, a novel square hierarchical honeycomb metamaterial capable of reducing low-frequency noise has been developed. By combining Bloch's theorem with the finite element method, the band structure is calculated. Numerical results indicate that this metamaterial can produce multiple low-frequency bandgaps within 500 Hz, with a bandgap ratio exceeding 50%. The first bandgap spans from 169. 57 Hz to 216. 42 Hz. To reveal the formation mechanism of the bandgap, a vibrational mode analysis is performed. Numerical analysis demonstrates that the bandgap is attributed to the suppression of elastic wave propagation by the vibrations of the structure's two protruding corners and overall expansion vibrations. Additionally, detailed parametric analyses are conducted to investigate the effect of θ, i. e., the angle between the protruding corner of the structure and the horizontal direction, on the band structures and the total effective bandgap width. It is found that reducing θ is conducive to obtaining lower frequency bandgaps. The propagation characteristics of elastic waves in the structure are explored by the group velocity, phase velocity, and wave propagation direction. Finally, the transmission characteristics of a finite periodic structure are investigated experimentally. The results indicate significant acceleration amplitude attenuation within the bandgap range, confirming the structure's excellent low-frequency vibration suppression capability.

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    Radiative heat transfer analysis of a concave porous fin under the local thermal non-equilibrium condition: application of the clique polynomial method and physics-informed neural networks
    K. CHANDAN, K. KARTHIK, K. V. NAGARAJA, B. C. PRASANNAKUMARA, R. S. VARUN KUMAR, T. MUHAMMAD
    Applied Mathematics and Mechanics (English Edition)    2024, 45 (9): 1613-1632.   DOI: 10.1007/s10483-024-3143-6
    Abstract105)   HTML2)    PDF(pc) (3214KB)(105)       Save

    The heat transfer through a concave permeable fin is analyzed by the local thermal non-equilibrium (LTNE) model. The governing dimensional temperature equations for the solid and fluid phases of the porous extended surface are modeled, and then are nondimensionalized by suitable dimensionless terms. Further, the obtained non-dimensional equations are solved by the clique polynomial method (CPM). The effects of several dimensionless parameters on the fin's thermal profiles are shown by graphical illustrations. Additionally, the current study implements deep neural structures to solve physics-governed coupled equations, and the best-suited hyperparameters are attained by comparison with various network combinations. The results of the CPM and physics-informed neural network (PINN) exhibit good agreement, signifying that both methods effectively solve the thermal modeling problem.

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