Ch. Zhang

University of Siegen

Direct methods to manipulate internal heat conduction in solids remain nearly elusive. In this work, we propose a two-dimensional (2D) gradient thermal metamaterial lens designed to control the internal non-Fourier heat conduction. This gradient thermal metamaterial comprises cylindrical structures made of dermis immersed in a stratum background wi...

A special kind of elastic metamaterials with periodic unit-cells composed of two layers with internal crack-like voids situated at the interfaces between two neighboring sub-layers is studied. To investigate experimentally guided waves propagation in EMMs with arrays of voids, several specimens with periodic arrays of crack-like voids have been man...

The bandgap properties of elastic metamaterials can be efficiently utilized to tailor the propagation characteristics of elastic and acoustic waves, which have promising applications in noise and vibration reduction and isolation. In this paper, an elastic metamaterial with a multilayered honeycomb structure (EMHS) is proposed to enlarge the bandga...

The frictionless contact problem between a conducting triangular or cylindrical punch and a thermoelectric strip is analyzed in this paper. When designing and optimizing thermoelectric devices for energy harvesting and temperature control applications, the interaction between the punch geometry and the thermoelectric strip is crucial. By the Fourie...

Elastic metamaterials (EMMs) have been developed for more than two decades, but their practical applications have been scarcely reported due to their narrow bandgaps, relatively high working frequency ranges, poor loadbearing capabilities, and other implementation-related issues. As an attempt to solve some of these problems, in this work, a novel...

Nuclide transport in fractured media involves advection, dispersion, adsorption, etc. The adsorption and diffusion properties of rock matrix have spatial variability, which results in an anomalous transport of nuclides. In this study, a time-fractional advection-diffusion equation (t-FADE) model is utilized to capture the sub-diffusion transport be...

With the increase in car ownership, traffic noise pollution has increased considerably and is one of the most severe types of noise pollution that affects living standards. Noise reduction by sound barriers is a common protective measure used in this country and abroad. The acoustic performance of a sound barrier is highly dependent on its shape an...

The phase field modeling of viscoelastic fracture can effectively predict complex crack behavior and offer valuable insights for analyzing time-dependent failure mechanisms. However, its application in nearly incompressible viscoelastic materials presents several numerical challenges, including the volumetric locking and inhibition of crack opening...

In this paper, we make the first attempt to apply the boundary integrated neural networks (BINNs) for the numerical solution of two-dimensional (2D) elastostatic and piezoelectric problems. BINNs combine artificial neural networks with the well-established boundary integral equations (BIEs) to effectively solve partial differential equations (PDEs)...

Elastic metamaterials have been developed for more than two decades, but their applications have been scarcely reported due to their narrow bandgaps, relatively high working frequency ranges, poor load-bearing capabilities, and other issues. As an attempt to solve these problems, in this work, a kind of tunable metamaterial beam is proposed to isol...

This paper investigates the frictionless contact problem of a functionally graded thermoelectric (FGTE) layered half-plane under the action of a rigid flat punch. The punch is an electrical and thermal conductor. The electro-thermo-elastic properties of the FGTE materials vary exponentially with thickness. Especially, the imperfect interface condit...

The study of artificially structured materials to control waves is ongoing, owing to their unprecedented properties. However, their narrow working frequency ranges significantly hinder their applications. In this study, a kind of tunable zigzag metamaterial beams with wider working frequency ranges are proposed by incorporating springs and damping...

The control and manipulation of acoustic and elastic waves is an important research topic in engineering sciences. In acoustics, an adequate combination of different materials can contribute to an efficient and broadband sound isolation. The realization of a vibration‐free environment for high‐precision mechanical systems in laboratories and measur...

Existing solid composite structures composed of several viscoelastic materials and metals mainly exploit diverse resonances, damping, and scattering to realize underwater acoustic wave functionalities. However, low-frequency broadband underwater sound absorption and insulation are still hard to capture with an acoustic coating possessing subwavelen...

A novel slit-perforated multi-layered porous metamaterial (SMPM) is proposed in this paper, which exhibits a broadband and low-frequency sound absorption characteristic. The proposed SMPM is composed of periodic porous matrix layers and periodically distributed adjacent second-type porous layers containing slits. The theoretical model is establishe...

An advanced semi-analytical hybrid approach for simulating the dynamic behaviour of guided waves-based SHM system is proposed here. The proposed numerical method simulates wave excitation, scattering and sensing in a multi-layered elastic waveguide with a system of internal delaminations and piezoelectric/elastic inhomogeneities mounted on the surf...

Terahertz elastic waves travelling in piezoelectric semiconductors (PSs) with the deformation-polarization-carrier coupling have a huge potential application in elastic wave-based devices. To reveal wave propagation characteristics of terahertz elastic waves in rod-like PS structures, we present three typical rod models based on the Hamilton princi...

A novel kind of acoustic metamaterials (AMMs) with unit cells composed of two layers made of dissimilar materials with a crack-like void situated at the interface between bars is considered. Recently, the authors showed numerically that this novel kind of AMMs can provide unidirectional propagation of guided waves. Several AMM specimens (the finite...

The boundary integral equation method and the finite element method (FEM) are employed to simulate elastic wave propagation in layered acoustic metamaterials with two-layered unit-cells and multiple periodic arrays of planar strip-like cuts. The results of numerical analysis (transmission coefficients and sensor voltage) demonstrate that band-gaps...

The propagation of acoustic waves in periodic structures, also known as phononic crystals or PCs, is prohibited in certain frequency ranges, which are referred to as the frequency band-gaps. The existence, the location and the width of the frequency band-gaps are mainly determined by the geometrical parameters and the material properties of the PCs...

Thin-walled structural problems have been a longstanding computational challenge. The research bottleneck in applying the standard numerical methods for such problems arises from their special geometrical configurations in which the thickness-to-length ratio of the thin-structures is usually up to the order of 10⁻⁶ or even smaller. In this paper, w...

In this paper, the band structure analysis of the thermoelastic wave propagation in a phononic crystal (PC), which it is reinforced by graphene platelets (GPLs) and carbon nanotubes (CNTs), is presented. The reinforced PC beam is made of periodic unit-cells including a metal section and a GPLs/CNTs-reinforced epoxy section. The Green-Naghdi theory...

In this work, cyclic tension-unloading tests with different peak strains (10%-18%) in the temperature range from 313K to 393K are performed to investigate the effects of temperature and loading level on the cyclic deformation behavior of NiTi shape memory alloy (SMA) wires. Experimental results demonstrate that the superelasticity degradation occur...

In recent years the periodic structures and materials, such as the photonic or the phononic crystals, are becoming increasingly popular due to their exceptional wave propagation properties. For example the phononic crystals or the phononic structures are able to manipulate the elastic and acoustic wave propagation characteristics by exhibiting the...

Topological states of classic waves are fascinating for both fundamental and practical purposes due to their unprecedented wave characteristics. In this paper, we realize the one-dimensional topological insulators for electromagnetic and mechanical waves simultaneously based on phoxonic crystal (PxC) cavity chains. The proposed PxC cavity chains ar...

By the stiffness matrix method based on the nonlocal elastic continuum theory, the transmission spectra of the transverse elastic waves propagating normally in nanoscaled periodic piezoelectric laminates with defects are investigated in detail in this paper. Defect is introduced by replacing a constituent layer or inserting another layer in a unit-...

In this paper, the photo-thermoelastic wave propagation analysis in a semiconductor nanorod resonator under laser excitation employing the strain-gradient Moore–Gibson–Thompson (MGT) and Love–Bishop theories is presented, which is for the first time to the authors’ knowledge. The governing equations of the photo-thermoelastic wave propagation are d...

Conventional two-dimensional (2D) re-entrant auxetic honeycomb is one of the earliest examples of auxetic metamaterials. Recently, plenty of 2D re-entrant honeycomb variants are developed to enhance their stiffness. However, the stiffness enhancement for most of the existing designs is generally obtained with compromising the conjugated auxeticity....

Missing rib auxetics with a reinforced central core may have tunable negative Poisson's ratios (NPRs) and other mechanical parameters. In analogy with the other enhanced missing rib configurations (e.g., enhanced hexa-, anti-tri- and anti-tetra-missing rib honeycombs), a novel enhanced tetra-missing rib honeycomb metamaterial is proposed in this wo...

Time fractional differential model is an effective tool to characterize anomalous diffusion phenomena in hydrology and environmental science. Efficient numerical method is necessary to overcome the bottleneck of expensive computational cost for real-world application. Therefore, this paper proposes a scale-dependent hybrid algorithm to numerically...

This paper proposes a new method based on the polynomial expansions for structural uncertainty analysis. A generalized finite difference method (GFDM) based on the Taylor expansion is adopted to compute the structural responses, which has good adaptabilities to the analysis domains due to its meshless property. With the help of the polynomial chaos...

A Lagrangian–Eulerian stabilized collocation method (LESCM) for the fluid–structure interaction problems involving free surface flow is presented in this work, in which the structure is modeled by a rigid body. This method is an evolution of the material point method and particle-in-cell methods which are based on the hybrid Lagrangian–Eulerian des...

Representative of the advanced engineering designs, hierarchical structures have attracted particular attention in academia and engineering. This study proposed a novel design strategy to obtain hierarchical structures with three layers. The macroscopic layer contained the structures to be optimized, which were periodically fashioned by multi-phase...

Stress concentration caused by reinforcements has very unfavorable effects on the metal matrix composites, which will inevitably induce localized strains and crack initiation. In this paper, an effective approach is presented to relieve stress concentrations near the reinforcements in metallic composites. The Ag-SnO2 contact materials with CuO addi...

Study on artificial structured-materials to control waves is a lasting hot topic due to their unprecedented properties. However, the narrow working frequency range highly hinders their applications. In this work, a tunable zigzag metamaterial beam with a wider working frequency range is proposed through incorporation of springs and damping elements...

In this paper, the general equations of plane strain problems are first summarized for three typical couple stress theories. Based on the constitutive relations, the general traction boundary integral equations (TBIEs) are then derived from the displacement BIEs (DBIEs) along with the explicit high-order fundamental solutions for the plane couple-s...

In this paper, a novel design concept for active auto-adaptive metamaterial (AAAMM) plates is proposed based on an active auto-adaptive (AAA) control strategy guided by the particle swarm optimization (PSO) technique. The AAAMM plates consist of an elastic base plate and two periodic arrays of piezoelectric patches. The periodic piezoelectric patch...

In this paper, a method based on the physics-informed neural networks (PINNs) is presented to model in-plane crack problems in the linear elastic fracture mechanics. Instead of forming a mesh, the PINNs is meshless and can be trained on batches of randomly sampled collocation points. In order to capture the theoretical singular behavior of the near...

In this work, we propose a method to design subwavelength metasurfaces for flexural waves in thin plates based on sinusoidally-shaped phononic beam structures. In the proposed method, the effective bending stiffness of sinusoidally-shaped phononic beam structures is tuned, and the effective phase velocity of the flexural waves is modulated subseque...

In this paper, a phononic crystal (PnC) Luneburg lens is designed for harvesting the mechanical energy of Rayleigh surface waves. The square-latticed PnC is formed by drilling holes periodically in an aluminum matrix. The PnC Luneburg lens for Rayleigh surface waves is constructed by spatially modulating the hole radius of each PnC unit-cell accord...

In this study, we propose the three-dimensional (3D) phononic crystal-based coupled resonator waveguides (PnCCRWs) for the guidance of acoustic waves along complex routes. The proposed 3D PnC exhibits a complete acoustic band-gap. The point defect mode with a frequency in the band-gap is achieved via the introduction of a point defect into the perf...

Sandwich structures (SSs) are widely deployed in engineering applications, such as for the low-frequency vibration or acoustic mitigation and isolation. However, it is challenging to enhance their low-frequency vibration mitigation and isolation performance while maintaining their multi-functionalities, such as lightweight, high bending stiffness,...

This study proposes a new method for the topological design of hierarchical structures with high performance in thermal insulation. Firstly, a three-layer design strategy including macro-, meso- and micro-layers is presented. The macroscopic structures are formed by periodically arranged mesoscopic structures, whose topological configurations are d...

Composite materials with multiple properties are important for a range of engineering applications. Hence, this study focuses on topological design of hierarchical materials with multiple performance in both thermal insulation and mechanics. First, a novel multi-objective optimization function is defined to find a solution from the Pareto frontier,...

Most existing mixed-mode I/II delamination growth criteria are purely empirical or semi-empirical fitting functions of the experimental fracture toughness, which limit their wide range applications. In this work, a novel delamination growth criterion is proposed for mixed-mode I/II delamination predictions considering the significant R-curve effect...

Unidirectional nonreciprocal wave propagation is an unprecedented phenomenon, which has attracted much research interest. Connecting a phononic crystal with an asymmetric structure to break the spatial inversion symmetry is a popular manner to realize this phenomenon using the wave mode transformation. In this paper, a new model is proposed based o...

PurposeFlexural wave propagation in non-homogeneous plates has wide engineering backgrounds, such as the out-of-plane vibration of the decks in buildings, and so on, and the corresponding research will provide some useful suggestions for the vibration control of the associated structures.Method Taking the out-of-plane vibration of the basal plate b...

Unlike their electromagnetic and acoustic counterparts, elastic waves involve different wave modes. The interplay and the coupling among them increase the complexity of the problem while also offering a larger space for wave manipulation. Elastic bulk wave conversion in an elastic metamaterial has recently shown great promise in medical ultrasound...

In this paper, we propose a kind of reflection-type broadband acoustic coding metasurfaces (BACMs), which are composed of two square helical channels and the connected air cavity at the end of the channels. This helical-cavity coupled structure is selected as a logical unit “1,” the pure air hole is set as a logical unit “0,” and the reflective pha...

Unlike conventional metamaterials with a periodic array of identical resonators, rainbow metamaterials consist of an array of discrete resonators with a spatially varying parameter, yielding a wide attenuation band gap. In this research, a particular kind of gradient zigzag metamaterial beam with rainbow effects is proposed with the gradual height...

The miniaturization of electronic devices is an important trend in the development of modern microelectronics information technology. However, when the size of the component or the material is reduced to the micro/nano scale, some size-dependent effects have to be taken into account. In this paper, the wave propagation in nano phononic crystals is...

Due to their limited number of units but outstanding ability to control rather complex wave-propagation phenomena, acoustic coding metasurfaces (ACMs) as two-dimensional metamaterials show a stronger competitiveness in metamaterial applications. However, hindered by their narrow-band modulation capability, the previously reported ACMs do not exhibi...

Metasurfaces, the ultrathin media with extraordinary wavefront modulation ability, have shown great promise for many potential applications. However, most of the existing metasurfaces are limited by narrow-band and strong dispersive modulation, which complicates their real-world applications, which usually require strict customized dispersion. To a...

Inspired by the electronic demultiplexer, acoustic/elastic demultiplexers have received much attention in recent years. An acoustic/elastic demultiplexer can split one input wave signal into several output wave signals based on their frequencies. However, little to no work has been reported on the acoustic/elastic demultiplexers by considering the...

Pre-stresses or axial loadings induced by deformations of adjacent structures, edge constraints or mounting inaccuracies and elastic supporting components attached to one side of the sandwich structures may affect the aerothermoelastic stability, which is an important subject in the design of supersonic aircraft. Therefore, the nonlinear flutter an...

Micro- and mesostructures of multiphase materials obtained from tomography and image acquisition are an ever more important database for simulation analyses. Huge data sets for reconstructed 3d volumes typically as voxel grids call for criteria and measures to find an affordable balance of accuracy and efficiency. The present work shows for a 3d me...