Shan Tang

Dalian University of Technology | DUT

Lithium metal batteries (LMBs) can double the energy density of lithium ion batteries. However, the notorious lithium dendrite growth and large volume change are not well addressed, especially under deep-cycling. Here, w e build an in-situ mechanical-electrochemical coupling system and find that tensile stress can induce smooth lithium deposition....

In this work, a three-dimensional explicit geometrically nonlinear topology optimization method is developed. Moving Morphable Voids (MMVs) are used to describe the optimized structures, which enjoy the advantages of fewer design variables and seamless integration with CAD system. Furthermore, attributing to the decoupling between the description o...

Developing appropriate analytic-function-based constitutive models for new materials with nonlinear mechanical behavior is demanding. For such kinds of materials, it is more challenging to realize the integrated design from the collection of the material experiment under the classical topology optimization framework based on constitutive models. Th...

Developing appropriate analytic-function-based constitutive models for new materials with nonlinear mechanical behavior is demanding. For such kinds of materials, it is more challenging to realize the integrated design from the collection of the material experiment under the classical topology optimization framework based on constitutive models. Th...

In this article, an efficient sequential linear programming algorithm (SLP) for uncertainty analysis-based data-driven computational mechanics (UA-DDCM) is presented. By assuming that the uncertain constitutive relationship embedded behind the prescribed data set can be characterized through a convex combination of the local data points, the upper...

Ductile fracture generally relates to microscopic voiding and to strain localization in metallic materials. When the void size is reduced to the nanoscale, size effects often lead to a different macroscopic plastic behavior from that established for the same material with larger voids. For example, irradiation of metallic materials can generate a l...

Hydrogels are nowadays widely used in various biomedical applications, and show great potential for the making of devices such as biosensors, drug- delivery vectors, carriers, or matrices for cell cultures in tissue engineering, etc. In these applications, due to the irregular complex surface of the human body or its organs/structures, the devices...

In this paper a multiscale data-driven approach is developed to model the effective macro-scale thermo-mechanical properties for isotropic, hyperelastic materials, subjected to finite deformation. Two independent artificial neural networks (ANNs) are designed to describe a stress–strain law with temperature dependence, and a heat-conduction law wit...

A mechanistically informed data-driven approach is proposed to simulate the complex plastic behavior of microstructured/homogenized solids subjected to cyclic loading, especially to simulate the Masing effect. Our proposed approach avoids the complicated mathematical construction of an appropriate yield surface, and does not require a large amount...

In this paper, a direct data-driven approach for the modeling of isotropic, tension–compression asymmetric, elasto-plastic materials is proposed. Our approach bypasses the conventional construction of explicit mathematical function-based elasto-plastic models, and the need for parameter-fitting. In it, stress update is driven directly by a set of s...

This work proposes a data-driven approach, G-MAP123, using discrete data directly for nonlinear elastic materials to solve boundary value problems, avoiding analytic-function based constitutive models. G-MAP123 is formulated in the current configuration in which the Cauchy stress and the left Cauchy–Green strain are adopted as the stress–strain mea...

This paper presents a mixed Graph-FEM (Finite Element Method) approach for the phase field modeling of fracture in plates and shells composed of nonlinearly elastic solids. In this approach, the finite element mesh is deemed equivalent to a typical graph in computer science. The equation for phase field evolution is thus discretized by a graph Lapl...

In this paper we propose a parameter-free grain boundary (GB) model for the meso-scale, employing it to effectively capture one-to-one twin pattern development across polycrystals (for the first time), by means of crystal plasticity finite element methods (CPFEM). Our model does not require higher-order mechanics, involve limiting length-scales, or...

In the present paper, a new uncertainty analysis-based framework for data-driven computational mechanics (DDCM) is established. Compared with its practical classical counterpart, the distinctive feature of this framework is that uncertainty analysis is introduced into the corresponding problem formulation explicitly. Instated of only focusing on a...

In this paper, a mechanistic data-driven approach is proposed to accelerate structural topology optimization, employing an in-house developed finite element convolutional neural network (FE-CNN). Our approach can be divided into two stages: offline training, and online optimization. During offline training, a mapping function is built between high...

Direct numerical simulation based on experimental stress–strain data without explicit constitutive models is an active research topic. In this paper, a mechanistic-based, data-driven computational framework is proposed for elastoplastic materials undergoing finite strain. Harnessing the physical insights from the existing model-based plasticity the...

Besides being ubiquitous in engineering applications such as Polyethylene terephthalate, materials with tension-compression asymmetry can also be found in lots of biological systems, e.g., muscle and brain tissue. However, the effect of tension-compression asymmetry at finite strains has not been well studied, especially lack of theoretical model a...

To understand the potential cytotoxicity of perfluoroalkyl substances (PFAS), we study their interactions with a model phospholipid bilayer membrane using molecular dynamics (MD) simulations. Four typical PFAS molecules are investigated, including perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorooctanesulfonic acid (PFOS), and...

In this paper, a mechanistic-based data-driven approach, MAP123-EP, is proposed for numerical analysis of elastoplastic materials. In this method, stress-update is driven by a set of one-dimensional stress–strain data generated by numerical or physical experiments under uniaxial loading. Numerical results indicate that combined with the classical s...

We have developed a highly efficient and portable fluid–structure interaction (FSI) simulation package, so-called OpenFSI. Within this package, the structure dynamics is accounted by a lattice model (LM) implemented in the framework of Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), demonstrating the same accuracy as finite elem...

The recently developed data-driven approach can establish the material law for nonlinear elastic composite materials (especially newly developed materials) by the generated stress-strain data under different loading paths. Generally, the displacement (or strain) fields can be obtained relatively easier using Digital Image Correlation (DIC) techniqu...

In this paper, a data-driven approach for constructing elastoplastic constitutive law of microstructured materials is proposed by combining the insights from plasticity theory and the tools of artificial intelligence (i.e., constructing yielding function through ANN) to reduce the required amount of data for machine learning. Illustrative examples...

Inorganic solid-state electrolyte (SSE) has offered a promising option for the safe rechargeable Li metal batteries. However, the solid-solid interfacial incompatibility greatly hampers the practical use. The interface becomes even worse during repeated Li plating/stripping, especially under high current density and long cycling operation. To promi...

There are two types of pop-in mode that have been widely observed in nanoindentation experiments: the single pop-in, and the successive pop-in modes. Here we employ the molecular dynamics (MD) modelling to simulate nanoindentation for three face-centred cubic (FCC) metals, including Al, Cu and Ni, and two body-centred cubic (BCC) metals, such as Fe...

Organic molecules and polymers have a broad range of applications in biomedical, chemical, and materials science fields. Traditional design approaches for organic molecules and polymers are mainly experimentally-driven, guided by experience, intuition, and conceptual insights. Though they have been successfully applied to discover many important ma...

We explore the cellular uptake process of PEGylated liposomes and bicelles by investigating their membrane wrapping process using large-scale molecular dynamics simulations. We find that due to the mobility of ligands on the liposome/bicelle, the membrane wrapping process of a PEGylated liposome/bicelle can be divided into two stages, whose transit...

A new data-driven method that generalizes experimentally measured and/or computational generated data sets under different loading paths to build three dimensional nonlinear elastic material law with objectivity under arbitrary loadings using neural networks is proposed. The proposed approach is first demonstrated by exploiting the concept of repre...

Mechanical science and engineering can use machine learning. However, data sets have remained relatively scarce; fortunately, known governing equations can supplement these data. This paper summarizes and generalizes three reduced order methods: self-consistent clustering analysis, virtual clustering analysis, and FEM-clustering analysis. These app...

This paper examines {10 1¯2} twin nucleation and growth under uniaxial tension at the prismatic/basal boundary through both molecular dynamics simulations and continuum mechanics modelling. Our results show that two disconnection dipoles exist on every intrinsic prismatic plane of the crystal which constructs the prismatic/basal boundary. Only one...

This paper outlines a single crystal plasticity theory for the mesoscale resolution of the diffusionless transformation process of deformation twinning. Unlike prevalent crystal plasticity models of lattice transformation that characterize volume fraction evolution of coexisting parent and product lattices at a material point, our model alternates...

In this paper, a phase field model with energy decomposition previously developed for rubber is extended for hydrogel. Predications of the extended model are qualitatively and quantitatively compared with our experimental results. To be consistent with the phase field model for rubber, we first reformulate the free energy of hydrogels with initial...

Solid state lithium metal batteries are the most promising next‐generation power sources owing to their high energy density and safety. Solid polymer electrolytes (SPE) have gained wide attention due to the excellent flexibility, manufacturability, lightweight, and low‐cost processing. However, fatal drawbacks of the SPE such as the insufficient io...

Phase-field models for fracture problems have attracted considerable attention in recent years, which are capable of tracking the discontinuities numerically, and also produce complex crack patterns in many applications. In this paper, a phase-field model for a general nonlinearly elastic material is proposed using a novel additive decomposition of...

In situ scanning electron microscope (SEM) investigation is carried out on high-entropy alloy (HEA) specimen with various geometries to realize the multi-axial stress states. The dimple structure on the fracture surface is quantified and the nucleation of void is examined. The deformation twins can provide more sites for void nucleation and constra...

Solid state electrolytes are the key components for high energy density lithium ion batteries and especially for lithium metal batteries where lithium dendrite growth is an inevitable obstacle in liquid electrolytes. Solid polymer electrolytes based on a complex of polymers and lithium salts are intrinsically advantageous over inorganic electrolyte...

The bilayered structure of hard thin film on soft substrate can lose stability and form specific patterns, such as wrinkles or creases, on the surface, induced by external stimuli. For bilayer hydrogels, the surface morphology caused by the instability is usually controlled by the solvent-induced swelling/shrinking and mechanical force. Here, two i...

Lithium has many challenges, especially its tendency to form dendrites. Under bending conditions in cylindrical or flexible cells, lithium-dendrite growth can be further aggravated due to local plastic deformation and pulverization of lithium filaments. In article number 1703891, Jiayan Luo and co-workers fabricate bending-tolerant lithium-metal an...

Bendable energy-storage systems with high energy density are demanded for conformal electronics. Lithium-metal batteries including lithium–sulfur and lithium–oxygen cells have much higher theoretical energy density than lithium-ion batteries. Reckoned as the ideal anode, however, Li has many challenges when directly used, especially its tendency to...

Na based batteries are proposed as promising energy storage candidates for beyond Li-ion technology due to the higher natural earth of Na metal. For its high capacity and low potential, Na metal may carve itself a niche when directly used as anodes. Similar to or even more problematic than Li, however, uneven plating/stripping of Na leads to dendri...

Stress-driven grain boundary (GB) migration is an important plastic deformation mechanism in nanopolycrystalline metals. Recently, Liu et al. (2014) and Zong et al. (2015) have shown a new mechanism for GB migration in a Hexagonal Close-packed (HCP) bicrystal with 90° GB misorientation under uniaxial stress loading conditions, which is different fr...

Controlling the morphologies and properties of the surface and/or interface of bi-materials consisting of soft polymers provides new opportunities in many engineering applications. Crease is a widely observed deformation mode in nature and engineering applications for soft polymers where the smooth surface folds into a region of self-contact with a...

This work combines experiments and finite element simulations to study the effect of pre-imposed cyclic loading on surface instability of silicon rubber under compression. We first fabricate cuboid blocks of silicon rubber and pinch them cyclicly a few times. Then, an in-house apparatus is set to apply uniaxial compression on the silicon rubber und...

Soft solids such as PDMS or silicone are widely needed in many advanced applications such as flexible electronics and medical engineering. The ability to control the structure and properties of the surface of soft solids provides new opportunities in these applications. In particular, mechanical loading induced elastic instability is a convenient m...

Developing supercapacitors with high energy density, good rate capability, and superior cycle life is crucial to the ever-increasing energy storage devices. However, how to design and develop a new type of faradaic electrode material with large surface area, low resistance, and stable microstructures is still a challenge work. Herein, we have succe...

This paper deals with the study of an internally pressurized void whose matrix,such as rock and poly-meric materials,exhibits pressure-sensitive yielding and plastic dilatancy. The macroscopic behaviors of porous solids are studied by numerical axisymmetric spherical and cylindrical unit cell analyses at finite strains subjected to Cauchy-type inte...

A hyperelastic constitutive model is proposed to predict the mechanical behavior of macroscopically transversely isotropic composites containing chain-structured particles. In this model, each particle chain is treated as a “virtual fiber” and the composite is modeled as a virtual fiber reinforced composite. When the particles and the matrix are bo...

This paper aims at studying the effect of sulci structures during tumor growth and cerebral edema in brain tissues. Motivated by the Intracranial Cerebral Pressure (ICP) monitoring during the brain surgery, a computational model has been created to study macroscopic behaviors of brain tissues with local volume expansion introduced by the tumor grow...

Recent experiments and molecular dynamics simulations have proven that polymer chains are less confined in layers near the free surfaces of submicron-nanosized pores. A recent model has incorporated this observed variable chain confinement at void surfaces in a mechanism-based hyperelastic model. This work employs that model to do two things: expla...

If a soft solid is compressible, its volume changes with imposed loading. The extent of the volume change depends on its Poisson's ratio. Here, we study the effect of the mechanical-driven volumetric change on buckling and post-buckling behaviors of a hard thin film perfectly bound on a compliant substrate through the theoretical analysis and finit...

It has been experimentally observed that wrinkles formed on the surface of electrospun polymer nanofibers when they are under uniaxial tension (Appl. Phys. Lett., 91, p. 151901 (2007)). Molecular dynamics (MD) simulations, finite element analyses (FEA), and continuum theory calculations have been performed to understand this interesting phenomenon....

A computational method is proposed for the analysis and prediction of instability (wrinkling or necking) of multilayered compressible plates and sheets made by metals or polymers under plane strain conditions. In previous works, a basic assumption (or a physical argument) that has been frequently made is that materials are incompressible to simplif...

Ductile fracture in alloys is a multiscale process in which primary voids formed at micron-scale particles coalesce by a zig-zag pattern of shear localization driven by finer-scale microvoiding at submicron-scale secondary particles. Employing the method of serial sectioning, unprecedented 3-D microstructural reconstructions of steel crack-tip proc...

Molecular dynamics and finite element simulations are performed to study the phenomenon of surface rippling in polymeric nanofibers under tension. Each nanofiber is modeled as a core–shell system that resembles most relevant features extracted from detailed molecular simulations and experiments. Accordingly, our model nanofiber consists of a dense...

In order to improve the piezoelectric properties of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), we added various amounts of silver nanowires (AgNWs) into PVDF-HFP and N,N-dimethylformamide (DMF) solution to prepare composite films. Stretching and poling were applied to the films to induce the formation of the polar β-phase and reor...

Recent experiments using nanoindentation and buckling-based metrology (Stafford C. M. et al., Nat. Mater., 3 (2004) 545) have shown the elastic modulus of submicron-nano porous polymers to be lower than that predicted by classical homogenization or finite element simulations, especially at high porosities. This letter presents a model that captures...

A multiresolution concurrent theory for heterogenous materials is proposed with novel macro scale and micro scale constitutive laws that include the plastic yield function at different length scales. In contrast to the conventional plasticity, the plastic flow at the micro zone depends on the plastic strain gradient. The consistency condition at th...

A modified-JIC test on CT (compact tension) specimens of an alloy (Ti-Modified 4330 steel) was carried out. The microstructure (primary and secondary inclusions) in the fracture process zone and fracture surface are reconstructed with a microtomography technique. The zig-zag fracture profile resulting from nucleation of microvoid sheets at the seco...

Existing and emerging methods in computational mechanics are rarely validated against problems with an unknown outcome. For this reason, Sandia National Laboratories, in partnership with US National Science Foundation and Naval Surface Warfare Center Carderock Division, launched a computational challenge in mid-summer, 2012. Researchers and enginee...