Kai Zhang

Northwestern Polytechnical University | NWPU · School of Mechanics, Civil Engineering and Architecture

This study introduces a novel underground subwavelength seismic metamaterial (SM) designed to attenuate ultra-low-frequency surface waves. The SM comprises a three-component column featuring rubber embedded within a steel resonator. Through calculations utilizing the Bloch theorem and the sound cone method, we investigate the dispersion relations a...

Mechanical metamaterials are highly versatile structures capable of achieving unconventional mechanical properties. Of particular interest are mechanical metamaterials with the ability to tune bandgaps, offering potential applications in vibration control tailored to specific requirements. In this study, a new type of metamaterial is introduced to...

A recent topic of interest in dynamics research is bi-stable negative stiffness (NS) mechanical metamaterials that allow for the efficient control of wave propagation and bandgap (BG) tuning. In this study, a three-dimensional (3D) bi-stable NS mechanical metamaterial based on fan-shaped inclined beams was developed. It has BGs in multiple directio...

Higher-order topological insulators (HOTIs) have attracted considerable attention because of their topological properties of low-dimensional topological corner states and edge states that exist in bandgaps. High-frequency edge states and corner states can be realized by controlling the interface configuration. However, most studies on HOTI focus on...

By introducing the concept of a graded structure to seismic metamaterials, a new type of graded seismic metamaterial assembled using four steel sections with different graded levels is proposed to investigate its attenuation performance for surface waves. The dispersion curves and vibration modes are obtained using the finite element method and the...

This paper studies the dynamic properties of a 3D chiral mechanical metamaterial, which largely depend on tacticity describing the connection forms of the chiral unit. Based on the finite element theory and Bloch's theorem, a dynamic model of the 3D chiral mechanical metamaterial is established to analyze the band structures and transmission respon...

Negative-stiffness mechanical metamaterials that can achieve bandgap tuning are a novel area of intense interest, enabling vibration control as well as a wide range of mechanical properties. In this paper, a negative-stiffness mechanical metamaterial consists of beam elements that can be reconfigured for large deformations and the bandgap can be tu...

This paper aims to study the effect of the interaction of adjacent unit-cells in coupled mass-in-mass metamaterial on wave behaviors, which enables us to achieve a wavy dispersion relationship. Elastic wave propagation in a coupled mass-in-mass metamaterial is investigated to clarify the effect of the interaction of adjacent unit-cells on the dispe...

The spider web is a multifunctional structure with vibration transmission performance and excellent mechanical properties. In this study, a spider web-inspired resonator is designed to adjust the band gaps of periodic lattices with different topologies. The spider web-inspired resonator can increase the relative density of periodic lattice and gene...

This work investigates the elastic wave propagation in origami-inspired lattice which is a space network established by the beams at the mountain lines and valley lines in Miura-origami. The eigenvalue equation describing the dispersion relation is established by the finite element method and Bloch theorem, and the band structure is obtained by usi...

This study describes the wave propagation in a periodic lattice which is formed by a spring-mass two-dimensional structure with local Duffing nonlinear resonators. The wave propagation characteristics of the system are evaluated by using the perturbation method to determine the dispersion relationships and wave propagation characteristics in the no...

In this study, we propose valley phononic crystals that consist of a hexagonal aluminum plate with six chiral arrangements of ligaments. Valley phononic crystals were introduced into a topological insulator (TI) system to produce topologically protected edge waves (TPEWs) along the topological interfaces. The implementation of chiral topological ed...

Periodic lattices have unusual physical and mechanical properties that can be used to control elastic wave propagation and design smart wave devices. In this study, a lattice design strategy is proposed that considers chirality and tacticity to realize a low-frequency band gap. The design of elastic wave logic gates is also investigated. In the des...

Fractal lattice is a kind of lattices with multifunctional physical characteristics and superior mechanical properties. The wave propagation of the triangular lattice with Koch fractal is calculated by the finite element method and Bloch theorem. The effects of the iteration number on the band gaps and the band edge modes are studied. The finite el...

In this study, the band structure and directional characteristics of the hexagonal lattice with Koch snowflake are investigated. The finite element method and Bloch theorem are used to analyze the wave propagation in hexagonal lattice with Koch snowflake for different fractal orders. The effects of the geometric parameters on band structures are di...

In this study, wave propagation characteristics of the Star-3/6 structures are studied, and the effects of geometric parameters on the wave propagation are analyzed. Especially, Poisson’s ratio is studied based on the long wavelength approximation of band structure. The Star-3/6 structures are assembled to be hexagonal and triangular topologies wit...

The mechanical properties of micro-scale materials are different from their macroscopic counterparts. This study investigates the impact of the size effect on the band structure of a one-dimensional periodic microstructure. The equation of motion for the Euler–Bernoulli beam model considering the size effect is derived based on the modified coupled...

This study investigates the propagation of Lamb waves in seismic metamaterials (SMs) assembled using periodically arranged cross-like and square steel sections in a soil medium to assess the feasibility of their use for seismic wave attenuation. Four types of SMs with different steel sections were considered. The finite element method was used to c...

This paper presents the effects of manufacturing micro-structure on the elastic properties of FFF (fused filament fabrication) 3D printing material and the vibration characteristics of FFF 3D printing plates. According to the results of scanning electron microscopy, three different material directions are defined to describe the orthotropy of FFF 3...

This study describes the wave propagation in a periodic lattice which is formed by a spring-mass two-dimensional structure with local Duffing nonlinear resonators. The wave propagation characteristics of the system is evaluated by using the perturbation method and Floquet-Bloch theorem to determine the dispersion relationships and wave propagation...

In this study, multi-resonator coupled metamaterials (MRCMs) with local resonators are proposed to obtain the multiple and wide band gaps. Kinetic models of the MRCMs are established, and the boundary conditions of the unit cell are obtained with Bloch’s theorem. The effects of structural parameters, including the mass of the resonator and the spri...

In this study, we introduce a tunable topological insulator (TI) system consisting of a hexagonal aluminum plate with rotatable droplet-shaped holes to produce topologically protected edge waves (TPEWs) along a topological interface. By rotating the round plate in the unit cells to break the unit cells' mirror symmetry while preserving C3 symmetry,...

The creep behavior caused by the viscous mechanical effect of biodegradable polylactic acid (PLA‐max) material is of great significance to its application. To better understand the creep properties of PLA‐max materials processed by fused filament fabrication, the effects of printing parameters including printing angle and layer thickness on them ar...

In this study, we design a type of rotationally symmetric lattice with curved beams and investigate the wave propagation properties of the structure. The analytical model of the structure is established to obtain the mass and stiffness matrices first. Because the dimensions of the mass and stiffness matrices will become very large if the structure...

In this study, the wave propagation properties of lattice metamaterials with Koch fractal structures are investigated in terms of band structures and directional wave propagation. The analytical models of lattice metamaterials are established using the finite element method, and the dispersion relation is solved using the Bloch’s theorem. The band...

As an inherent defect of Fused Filament Fabrication 3D printing materials, the occurrence of inter-layer failure reduces the tensile failure strength significantly. To better understand this defect and improve the mechanical properties of FFF 3D printing materials and structures, the distribution and basic mechanical principles of inter-layer failu...

In this study, the wave propagation properties in terms of the band gap and directions of wave propagation of the auxetic chiral structure are analyzed. The mechanism of generation of the band gap are carefully investigated. The auxetic chiral structure are assembled with the repeat unit cells and the unit cell contains a number of rigidly connecte...

This work is devoted to study the mechanical behaviors of polylactic acid (PLA) materials from additive manufacturing, and an orthotropic model is established to predict the mechanical properties under arbitrary printing orientation. Firstly, the morphology of PLA material is analyzed by using scanning electron microscopy, from which the orthotropi...

It is discovered in this investigation that there exist two different failure modes and a special separation angle which is the demarcation point of the two different failure modes when FDM (Fused Deposition Modelling) 3D printing materials fail under a tensile load. In order to further understand the mechanical properties of FDM 3D printing materi...

This study focuses on temperature-dependent wave propagation in hexagonal and square lattices, which has potential application in the design of programmable lattices. To obtain the thermal effect on the wave behaviors of the lattices, temperature fields are applied to the structures and the thermal responses of the structures are analyzed. Furtherm...

This paper aims to investigate the wave behavior of the octa-chiral lattices with local resonators and tunable wave propagation properties with different chiral geometrical dimensions. The octa-chiral lattices are assembled with the repeat unit cells and the unit cell contains a ring and eight slender elastic massless ligaments which are rigidly co...

A unified rigid-flexible coupled modeling method for large flexible space structures is proposed based on absolute nodal coordinate formulation (ANCF). The explicit formulas of gravitational potential energy and generalized gravitational force are developed, which are simple to use and apply to all ANCF elements. First, the shape functions of all k...

The aim of this paper is to investigate the effect of the applied pre-load on wave propagating behaviors of hexagonal lattices in terms of band structures, band gap distributions and phase/group velocities. The structure is composed of the repeat elementary unit cell, and the elementary unit cell is assembled with the axial pre-loaded elastic Timos...

Free vibration and mode damping loss factor of the finite periodic beam structure with viscoelastic damping material are investigated in this paper based on wave component method. A simple iterative operation for the natural vibration modes of the beam structure is firstly proposed by considering that the mode shape can be formed through superposit...

The aim of this work is to provide closed-form expressions of the effective elastic constants of hexagonal and re-entrant hexagonal structures, which contain the variable dimensional parameters, such as the relative density, aspect ratio, length ratio and the cell wall angle. We also numerically investigate the dynamic properties of the sandwich pl...

A molecular structural mechanics model for the numerical simulation of phonon dispersion relations of graphene is developed by relating the C-C bond molecular potential energy to the strain energy of the equivalent beam-truss space frame. With the stiffness matrix known and further based on the periodic structure characteristics, the Bloch theorem...

The in-plane dynamic crushing behavior of re-entrant honeycomb is analyzed and compared with the conventional hexagon topology. Detailed deformation modes along two orthogonal directions are examined, where a parametric study of the effect of impact velocity and cell wall aspect ratio is performed. An analytical formula of the dynamic crushing stre...

Purpose – The purpose of this paper is to provide an efficient numerical solution for dynamic properties of sandwich tubes with honeycomb cores and investigate the effects of material distribution and relative density on the dynamic properties of the structure. Design/methodology/approach – By introducing dual variables and applying the variationa...

The purpose of this paper is to investigate the plane wave propagation in two-dimensional hexagonal lattices with plateau borders and analyze the effects of the dimensional parameters on the dynamic properties of hexagonal lattices. Based on the Bloch’s theorem and the finite element method, the dispersion relations of this structure are analyzed....

A new type of hexagonal honeycomb sandwich tube with plateau borders are introduced in this work and the Symplectic analysis with its high computational efficiency and high accuracy is applied to obtain the structural dynamic properties. The effects of material distribution ( ) and relative density ( ) on the dynamic properties of the structure are...

In this paper, star-shaped honeycombs are analyzed in terms of their equivalent mechanical behaviors and band gap properties. Firstly, by applying Castigliano’s second theorem, the effective Young’s modulus and Poisson’s ratio are derived by an analytical method used in structural mechanics. On the basis of Bloch’s theorem, the dispersion character...

Wave propagation in infinitely long hollow sandwich cylinders with prismatic cores is analyzed by the extended Wittrick-Williams (W-W) algorithm and the precise integration method (PIM). The effective elastic constants of prismatic cellular materials are obtained by the homogenization method. By applying the variational principle and introducing th...

Abstract Wave propagation in two-dimensional hierarchical honeycomb structures with two-order hierarchy is investigated by using the symplectic algorithm. By applying the variational principle to the dual variables, the wave propagation problem is transformed into a two-dimensional symplectic eigenvalue problem. The band gaps and spatial filtering...

Under the condition that the strain energy of the periodic representative volume element (RVE) is equivalent to the elastic solid RVE, we improve the method for calculating the equivalent elastic constants by considering the in-plane shear effect of a functional prismatic sandwich panel. The prismatic core is equalized to the anisotropic and homoge...

In this paper, the transient temperature distribution and the thermomechanical response of sandwich tubes with prismatic cores are analyzed considering active cooling. The effective thermal conductivities of prismatic cores with active cooling are derived. By using the effective thermal conductivities, the transient temperature fields of the tubes...

Hollow cylindrical tubes with a prismatic sandwich lining designed to replace the solid cross-sections are studied in this paper. The sections are divided by a number of revolving periodic unit cells and three topologies of unit cells (Square, Triangle and Kagome) are proposed. Some types of multiple-topology designed materials are also studied. Th...

Hollow cylindrical tubes with a prismatic sandwich lining designed to replace the solid cross-sections are studied in this paper. The sections are divided by a number of revolving periodic unit cells and three topologies of unit cells (Square, Triangle and Kagome) are proposed. Some types of multiple-topology designed materials are also studied. Th...

The actively cooled performance of a particular cylindrical sandwich shell with cellular materials was analyzed, and the thermal performance indexes of cellular materials with different heat transfer boundary conditions were derived respectively. The particular cylindrical sandwich shell with cellular materials has an equal cell number, a consisten...