Fan Yang

Tongji University · School of Aerospace Engineering and Mechanics

A persistent challenge of the checkerboard lattice metamaterials has been the trade-off between the controllability in crushing process and the enhancement of mechanical properties, where high stability and customizability tend to yield relatively low energy absorption capacity. To breakthrough this challenge, a design strategy based on a multi-fea...

Lattice structures, characterized by their lightweight nature, high specific mechanical properties, and high design flexibility, have found widespread applications in fields such as aerospace and automotive engineering. However, the lightweight design of lattice structures often presents a trade-off between strength and stiffness. To tackle this is...

Topological phononic cavities, such as ring resonators with topological whispering gallery modes (TWGMs), offer a flexible platform for the realization of robust phononic circuits. However, the chiral mechanism governing TWGMs and their selective routing in integrated phononic circuits remain unclear. This work reveals, both experimentally and theo...

Based on the principle of local resonance and the strategy of hybrid design, in this paper we propose three truss-plate hybrid multifunctional lattice metamaterials featured by the cubic cell topology with a central truss-plate unit connected by the elastic beams to the eight corners. Finite element (FE) simulations were validated by experimental t...

Compared to acoustic cloak, elastic wave cloak is difficult to construct due to inapplicability of form invariance for the control equations. Traditional elastic wave cloak is limited to Willis material or Cosserat material. In this paper, a modified symmetric design method for elastic wave cloak is proposed for underground protective structures ba...

Lattice rotation mechanism plays an important role in the plastic deformation and the microstructure evolution of nanocrystalline metals. It assists the grain growth and the polycrystal texture formation. In this paper, the lattice rotation of quasi-3D Ni samples under uniaxial tension is investigated by molecular dynamics simulations. For this pur...

Topological structures are well known for their robust and unidirectional wave transportation in acoustic and elastic communities. The rainbow effect in metamaterials is also promising for applications such as buffers, filters, wavelength-division multiplexing devices, and etc. In this work, the combination of topology and rainbow effect, i.e., top...

Numerical methods have been extensively applied to fracture mechanics, while they cannot simulate the problems without the mechanical models or constitutive equations. Artificial neural networks (ANNs) can be utilized to predict complex fracture problems, but these approaches require large amounts of data for the training. Therefore, in this paper,...

A proper and reliable fracture fixation is important for fracture healing. The proximal femoral intramedullary nail (IN), such as proximal femoral nail anti-rotation (PFNA) or Gamma nail, is widely used for intertrochanteric fracture fixation. However, it still suffers considerable stress concentrations, especially at the junction between the nail...

Inspired by the hollow-tube architecture and chambers found in bamboo, we propose a design concept for mechanical metamaterials based on the hybridization of plate lattice and hollow-truss lattice (HPHL) to enhance the mechanical performance of lattice metamaterials in this paper. The design feasibility of HPHL is demonstrated through sample manufa...

It is a long‐standing challenge to break the tradeoffs between different mechanical property indicators such as the strength versus toughness in the design of lightweight lattice materials. To tackle this challenge, a hierarchical lattice metamaterial with modified face‐centered cubic (FCC) cell configuration, inspired by the glass sponge skeletal...

Auxetic structures with negative Poisson's ratio exhibit excellent performance in cushioning, shear resistance and energy absorption, but their load-bearing capacity is usually poor. To address this drawback of the conventional Auxetic structure, a star-rhombic honeycomb (SRH) design is proposed in this paper to improve its load-bearing capacity. A...

In this paper, the effect of the distribution pattern of the reinforcement phase on the mechanical properties was studied for the simple-cubic matrix dual-phase lattices given the same second phase proportion. Two reinforcement phases, the body centered cubic and the face centered cubic cells, were investigated. Specifically, a novel distribution p...

The back propagation (BP) is one of the most widely used algorithms in the feedforward neural network (FNN), but selecting the non-optimal weights and thresholds may induce the slow convergence and local optimization. In this work, we propose an improved BP algorithm in which the loss function is constructed based on a small scale of data to seek t...

One factor that plays an important role in the aerodynamic performance of aeroengines is the shape of the blades, which is vulnerable to change resulting from the plastic deformation and the residual stresses induced by the complex manufacturing processes, especially the shot peening. However, few studies were focused on the detailed strategies of...

In this paper, a hybrid octagonal simple-cubic (OSC) lattice structure is obtained by combining the cell configurations of the bending-dominated octagonal lattice and the stretching-dominated SC lattice. Finite element (FE) numerical models of the three lattice structures (octagonal, octet and OSC lattice) are established and the axial quasi-static...

In metal metallurgy, precipitation strengthening is widely used to increase material strength by utilizing the impediment effect of the second-phase particles on dislocation movements. Inspired by this mechanism, in this paper, novel multiphase heterogeneous lattice materials are developed with enhanced mechanical properties utilizing a similar hin...

Since most approximation functions in meshfree methods are rational functions which do not possess the Kronecker delta property, how to achieve exact integration and accurately impose the essential boundary conditions are two typical difficulties for meshfree methods. In this paper, a new stabilized Lagrange interpolation collocation method (SLICM)...

In this paper, a meshfree weighted radial basis collocation method associated with the Newton’s iteration method is introduced to solve the nonlinear inverse Helmholtz problems for identifying the parameter. All the measurement data can be included in the least-squares solution, which can avoid the iteration calculations for comparing the solutions...

Lattice materials possess excellent mechanical properties such as light weight, high specific stiffness and high energy absorption capacity. However, the commonly used lattice materials inspired by Bravais lattice often give rise to property anisotropy that is not desirable for engineering application such as bone implants. For this sake, a design...

The energy absorption potential of conventional thin-walled tubes is compromised by the long-wavelength folding lobes, which result in a mean crushing force that is much smaller than their yield strength. Here, inspired by the characteristics of the skeletal of the glass sponge, a new thin-walled multi-cell tubular structure with modified face-cent...

Acoustic cloaking is an important application of acoustic metamaterials. This article proposes a novel design scheme for acoustic cloaking based on the region partitioning and multi-origin coordinate transformation. The cloaked region is partitioned into multiple narrow strips. For each strip, a local coordinate system is established with the local...

The shape and deformation of the blades play important roles in the aerodynamic performance of aeroengines, which results from the plastic deformation and the residual stresses after complex manufacturing processes, especially the shot peening. However, few studies were focused on the detailed strategies of the shot peening on the complex profile a...

In this paper, we propose a new multicellular design of assembled multi-frusta with alternate orientations and varied taper angles for effective energy absorption applications. Extensive crush test experiments, comprehensive finite-element simulations and analytical modeling were carried out to evaluate the energy absorption performance of the newl...

Lattice structures have been widely used in biomedicine, transportation, infrastructure, and other engineering fields due to their high specific strength, strong energy absorption capacity, and tunable mechanical property. Existing researches mainly focus on the uniform lattice structure or gradient lattice structure with varying density, with the...

Hybridization is an effective approach to designing new lattice structures. In this paper, a novel hybrid lattice design is proposed with nested cell topology combining inner stretching-dominated struts and outer bending-dominated struts. Two hybrid lattices have been created, i.e., HS1 with inner G7 and outer octagonal cell topology, and HS2 with...

In both experiment and simulation, we demonstrate a graded array of Helmholtz resonators (HRs) with cross-linked polypropylene (IXPP) ferroelectret films on the inner walls of cavities, which can realize both sound absorption and energy harvesting within 300–800 Hz. This dual-function graded array contains nine HRs with different sizes, which can o...

Bicuspid aortic valve (BAV) is frequently associated with ascending thoracic aortic aneurysm (ATAA). Impact of cusp fusion patterns on biomechanics and microstructure of the ATAA remains unknown. This study aims to investigate biaxial mechanical properties of the ATAAs with right-left (RL) and right-noncoronary (RN) cusp fusion patterns. Fresh ATAA...

Bio-inspired lattices have been proved to possess better energy absorption capacity than conventional structures. Here, the two-dimensional deep-sea glass sponge structure is extended to three-dimensional and further topologically optimized to design a novel lattice called modified body-centered cubic (MBCC) lattice. The quasi-static compression be...

Our previous work reported a novel lattice structure composed of modified face-centered cubic (modified FCC) cells with crossing rods introduced at the center of each cell. In this work, the proposed modified FCC lattice is further investigated to ascertain its compression behaviors under different loading rates. For this purpose, numerical simulat...

In gradient nanocrystalline metals, the grain size variation usually comes with the compressive residual stress induced by mechanical surface treatments such as surface mechanical attrition and severe shot peening. This paper focused on the fracture of gradient nanocrystalline metals with the residual stress that is introduced during the mechanical...

In this paper, the problem of crack propagation in the gradient nano-grained (GNG) metals is studied through extensive quasi-3D molecular dynamic (MD) simulations. Numerical samples of GNG copper with initial central crack are established and simulations of uniaxial deformation are carried out. The effect of the grain size gradient on the crack pro...

Lattice structures have shown excellent mechanical properties, such as high energy absorption capacity. In this work, the extended body centered cubic lattice was proposed by offsetting the position of the body center. The pattern recognition method of nonlinear discriminant function was creatively used to classify the proposed eccentric body cente...

In this work, a new hierarchical lattice design is proposed by replacing the original straight beams of face-centered cubic (FCC) lattice with a string of higher-level circular beams from the perspective of forming more plastic hinges to improve the energy absorption capacity. The quasi-static compression behavior of our proposed lattice is thoroug...

The meshfree strong form direct collocation method (DCM) can address the domain integration issues involved in the Galerkin meshfree methods and outperform them in the efficiency. However, the accuracy and stability of the DCM may not match the Galerkin meshfree methods in solving the complex problems. Moreover, strong form demands the high order d...

Harvesting multi-frequency sound energy from environmental noise is a meaningful topic to supply energy for potential devices. In this work, we constructed an array of Helmholtz resonators (HRs) with cross-linked polypropylene (IXPP) ferroelectret films on the inner walls of HR cavities, whose resonant frequencies range from 300 to 800 Hz and quasi...

This study investigates the compression behaviors of body-centered cubic (BCC) lattice structures with three different constituent materials, i.e., polylactic acid (PLA), AlSi10Mg and polyamide 12 (PA12), fabricated by fused deposition modeling (FDM), selective laser melting (SLM) and multi-jet fusion (MJF) techniques, respectively. The numerical m...

In this paper, a novel lattice structure for energy absorption application is proposed that is modified from the traditional face-centered cubic (FCC) lattice by introducing a cross-rod at the center of the cell. A thorough study is carried out to investigate the quasi-static crushing behavior of the proposed lattice through theoretical modeling, n...

In this work, two typical interfaces are established for the antisymmetric plate wave by introducing linear defect in between phononic crystals with opposite valley Hall phases. The evolution of projected curves is demonstrated as the defect width increases, which magnifies the occurrence of multiple edge states on both interfaces. The mapping of t...

The reproducing kernel (RK) approximation based direct collocation method (DCM) requires the complex and time-consuming derivatives calculation of the approximation function, and the DCM has the poor accuracy and stability, which hinder the extensive application of this method. Therefore, in this work, we propose a gradient reproducing kernel (GRK)...

Inspired by the microstructure of the triclinic crystal material, in this work we designed triclinic lattice structures (TC) with twin boundaries for energy absorption application. The deformation mode and energy absorption capacity of TCs under the quasi-static compression are investigated by finite element method, which is validated by the experi...

In this paper, the mechanical behavior of gradient nano-grained copper under uniaxial deformation was investigated using molecular dynamics simulations. The stress response was found to be different in the regions with different grain sizes, which was attributed to the different dislocation activities due to the dislocation-grain boundary synergies...

The static and dynamic problems of thin functionally graded shells (FGSs) with in-plane material inhomogeneity are investigated in this work. Governing equations are derived based on the first-order shear deformation shell theory. A meshfree radial basis collocation method (RBCM) which employs infinitely continuous radial basis functions (RBFs) as...

Polycrystalline-like (PL) lattices are potential energy-absorbing structures composed of basic periodic mono-crystals arranged in different orientations. A series of numerical simulations were conducted to investigate the in-plane crushing resistance and energy absorption of different polycrystalline-like lattice structures. The finite element mode...

Lattice structures are widely used in many engineering fields due to their excellent mechanical properties such as high specific strength and high specific energy absorption (SEA) capacity. In this paper, square-cell lattice structures with different lattice orientations are investigated in terms of the deformation modes and the energy absorption (...

The dynamic crushing behaviors of FCC lattice structures with various rotation angles are explored by numerical simulations. According to the localization band formed by the cell collapse, several deformation modes are distinguished. The effects of the orientation angle and the crushing velocity on the mechanical properties of the lattice are inves...

Gradient nanocrystalline metal possesses gradually varied non-uniform mechanical properties as its grain size varies gradually from nano-scale at surface to macro-scale at center, leading to possibly different cracking behavior compared with the conventional uniform metals. In this paper, the J-integral of a mode I crack in the gradient nanocrystal...

Benefit from the gradient distribution of microstructure, gradient nanograined (GNG) metals have broad application prospect owing to their advantages of both high strength and good tensile ductility. Meanwhile, the fracture behavior of gradient nanograined metals is different from that of traditional homogeneous materials. Using molecular dynamics...

Introducing nonuniform thickness has shown promising potential in enhancing the energy absorption of thin-walled tubes. However, existing studies were focused on the axial loading, with little attention being paid to the oblique loading condition. In this paper, the energy absorption performance and the deformation modes of the circular tubes with...

Due to the outstanding performances in both strength and ductility, gradient nano‐grained (GNG) metals possess strong application potential. In this paper, a quasi‐three‐dimensional molecular dynamics model of GNG copper with initial central crack is established, and the effect of the grain size gradient on the crack evolution is investigated. The...

Effect of diabetes mellitus (DM) on the dissection properties of thoracic aortas remains largely unclear and relevant biomechanical analysis is lacking. In the present study forty adult rabbits (1.6-2.2 kg) were collected and type 1 diabetic rabbit model was induced by injection of alloxan. A total of 10 control and 30 diabetic (with different time...

Compared with the excellent energy absorption performance under axial loading, thin-walled tubes are vulnerable to instable global bending under oblique loading condition. In this paper, a novel design was developed to improve the energy absorption performance of the thin-walled circular tubes under oblique loading by introducing multiple circumfer...

Hierarchical topology is introduced to construct weight-efficient carbon fiber reinforced polymer (CFRP) tubular energy absorbers through filling small-diameter tubes into large-sized tubes. Crushing behaviors of the thin-walled tubes and the hierarchical tubes are investigated through quasi-static compression experiments and compared with each oth...

In this article, we extend our earlier analytical efforts of the progressive collapse of foam-filled conical frustum with the aid of a kinematically admissible folding mechanism. The instantaneous crushing force as well as the mean crushing force were derived from the principle of energy conservation accounting for the typically overlooked term of...

Energy absorbing efficiency of thin-walled tubular structures is restricted by the long-wave folding elements, which makes the mean crushing force (MCF) of the thin-walled tubular structure usually much smaller than its yielding strength. Hierarchical lattice topology increases the energy absorbing ability of tubular structure notably without incre...

In this paper, the progressive collapse of foam filled conical frusta is investigated analytically using four different kinematically admissible folding mechanisms with varied straight folds. Comparisons are made between these four kinematically admissible mechanisms; specifically, pure inward folding, pure outward folding, first inward followed by...

Diabetes has been recognized as a major risk factor to cause macrovascular diseases and plays a key role in aortic wall remodeling. However, the effects of diabetes on elastic properties of aortas remain largely unknown and quantitative mechanical data are lacking. Thirty adult rabbits (1.6–2.2 kg) were collected and the type 1 diabetic rabbit mode...

Gradient nano-grained (GNG) metals have great application potential due to its outstanding performance in both strength and ductility. In this paper, we investigate the uniaxial deformation response of GNG Cu utilizing the developed size-dependent crystal plasticity model with random initial grain lattice orientation implemented by the user-materia...

This paper is intended to quantify the relationship between the peen forming effectiveness and various involved parameters through a realistic numerical study. For this purpose, a new finite element (FE) model is proposed with full geometry representation, random shots generation, and rate-dependent material law of kinematic strain-hardening. The m...

In this paper, we examined the energy conservation for the current schemes of applying active deformation in molecular dynamics (MD) simulations. Specifically, two methods are examined. One is scaling the dimension of the simulation box and the atom positions via an affine transformation, suitable for the periodic system. The other is moving the ri...

Shock loads which are characterized by high intensity, short duration, and vibration at varied frequencies can lead to the failure of embedded electronics typically used to operate/ control numerous devices. Failure of electronics renders these devices ineffective, since they cannot carry out their intended function. It is therefore the objective o...