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The Dynamic Behaviors of a Shape Memory Polymer Membrane

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Acta Mechanica Solida Sinica 2018年第5期31卷 635-651页

作者： Yauxin Li Ruoxuan liu zishun liu International Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace Xi'an Jiaotong University Xi'an 710049 China

As a kind of popular smart materials, shape memory polymers （SMPs） have a great potential for applications in deployable aerospace structures and other engineering struc- tures. However, the vibration analysis of shape memory polymer structures, which would play an important role in engineering, has not gained much attention. In this study, we propose a dynamic model and establish the governing equations for characterizing the dynamic behavior of a shape memory polymer membrane subjected to time-dependent forces. The derivation of governing equations is based on a well-developed constitutive model of SMPs combined with the Euler-Lagrange equation. With the proposed model, two different loading cases are stud- ied： the equal-biaxial sinusoidal force and the uniaxial sinusoidal force. To analyze the dynamic response of a shape memory polymer membrane and find some effective ways to control vibra- tion, the isothermal amplitude-frequency response, the time-dependent behavior of vibration and the vibration in a variable temperature process are investigated in the numerical simulation. It is observed that temperature, mechanical force and heating rate have significant effects on the dynamic performances of a shape memory polymer membrane. We also investigate the shape memory behavior of SMP membrane involving the dynamic response. The influence of dynamics on shape fixation and shape recovery is discussed. These results and discussion may provide guidance for exploring the vibration and dynamic performances of shape memory polymer in deployable aerospace structures.

关键词： Shape memory polymer Nonlinear vibration Dynamic model Thermo mechanical behavior

The inhomogeneous diffusion of chemically crosslinked polyacrylamide hydrogel based on poroviscosity theory

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Science China(Technological Sciences) 2019年第8期62卷 1375-1384页

作者： ZHENG ShouJing LI ZiQian liu zishun International Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructuresXi’an Jiaotong University

The diffusion of hydrogels is a phenomenon not only profound in novel applications of mechanical engineering but also very common in nature. Comprehensive studies of the swelling properties under stable states have been carried out in the past several years;however, ambiguities in the understanding of the kinetic behaviour of the diffusion phenomenon of hydrogels still *** potential applications of hydrogels are confined due to the lack of perceptiveness of the kinetic behaviour of diffusion in hydrogels. Based on our previous work, in this study, we initiate the theoretical kinetic study of the inhomogeneous diffusion of hydrogels. With poroviscosity introduced, we develop a theory for the inhomogeneous diffusion of hydrogels. After implementing this theory into the finite element solution, we could predict the water content in the hydrogel as a function of time and location. The quantitative prediction of the inhomogeneous diffusion and the formulas are given in the numerical ***, the corresponding experiments are carried out to substantiate this theory. It can be observed that the theoretical prediction meets fairly well with our experimental data. Finally, we carry out a systematic parameter study to discuss the effect of three important parameters on the diffusion property. The increase of the interaction parameter is seen to constrain the diffusion while increase of the chemical potential is seen to facilitate the process. The change of the diffusion coefficient D, on the other hand, does not affect the process much. By comparing the conclusions above with the experimental data, we can narrow down the range of the values of χ and D.

关键词： inhomogeneous diffusion hydrogel poroviscosity kinetic behaviour

Recent advances of hydrogel network models for studies on mechanical behaviors

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Acta Mechanica Sinica 2021年第3期37卷 367-386,I0001页

作者： Jincheng Lei Ziqian Li Shuai Xu zishun liu International Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructuresXi'an Jiaotong UniversityXi'an 710049China

Current constitutive theories face challenges when predicting the extremely large deformation and fracture of hydrogels,which calls for the demands to reveal the fundamental mechanism of the various mechanical behaviors of hydrogels from bottom *** hydrogel network model provides a better approach to bridge the gap between the micro-structure and the macroscopic mechanical *** work summarizes the theoretical and numerical researches on the hydrogel network models,aiming to provide new insights into the effect of microstructure on the swelling-deswelling process,hyperelasticity,viscoelasticity and fracture of *** network models are divided into full-atom network models,realistic network models and abstract network ***-atom network models have detailed atomic structure but small *** network models with different coarse-graining degree have large model size to explain the swelling-deswelling process,hyperelasticity and *** network models abstract polymer chains into analytical interactions,leading to the great leap of model *** shows advantages to reproduce the crack initiation and propagation in hydrogels by simulating chain *** research directions on the network modeling are *** hope this work can help integrate the merits of network modeling methods and continuum mechanics to capture the various mechanical behaviors of hydrogels.

关键词： Hydrogel Polymer network Mechanical behavior Fracture

Novel mechanical behavior of periodic structure with the pattern transformation

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Theoretical & Applied Mechanics Letters 2013年第5期3卷 35-38页

作者： Jianying Hu Yuhao He Jincheng Lei zishun liu Inter Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructureXi'an Jiaotong University

Abstract In periodic cellular structures, novel pattern transformations are triggered by a reversible elastic instability under the axial compression. Based on the deformation-triggered new pattern, periodic cellular structures can achieve special mechanical properties. In this paper, the designed architecture materials which include elastomer matrixes containing empty holes or filled holes with hydrogel material are modeled and simulated to investigate the mechanical property of the periodic materials. By analyzing the relationship between nominal stress and nominal strain of periodic material, and the corresponding deformed patterns, the influence of geometry and shapes of the holes on the mechanical property of architecture material is studied in more details. We hope this study can provide future perspectives for the deformation-triggered periodic structures.

关键词： pattern transformation periodic structures composite gel material mechanical property

Ultrastable Viologen Ionic Liquids-Based Ionogels for Visible Strain Sensor Integrated with Electrochromism,Electrofluorochromism,and Strain Sensing

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CCS Chemistry 2023年第8期5卷 1917-1930页

作者： Yueyan Zhang Mengying Guo Guoping Li Xiaoliang Chen zishun liu Jinyou Shao YongAn Huang Gang He Frontier Institute of Science and Technology Xi’an Jiaotong UniversityXi’an 710054 Micro-/Nano-technology Research Center State Key Laboratory for Manufacturing Systems EngineeringXi’an Jiaotong UniversityXi’an 710054 International Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructuresXi’an Jiaotong UniversityXi’an 710049 State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074

Flexible electronics play a key role in the development of human society and our daily *** they are expected to revolutionize personal health ***,it remains challenging to fabricate smart sensors with high robustness,reliability,and visible ***,high-performance electrochromic(EC),electro-fluorochromic(EFC),and double-network ionogels with excellent transmissivity,high mechanical robustness,and ultrastable reversibility are prepared by combination of thienoviologen-containing ionic liquids with poly(ethyl acrylate)*** ionogels exhibit good mechanical properties(1000%stretchability and 3.2 kJ m^(−2) fracture energy).The ionogel-based EC devices have a significantly simplified device fabrication process as well as superior cycling stability in which 88%of the contract ratio is maintained at 88%at 500 cycles,even after being stored for 2 years under ambient atmosphere(relative humidity:30%∼40%,25°C).The conductivity of ionogels showed a fast and reproducible response to strain,and the conductivity decreased with increased *** virtue of the EC and EFC properties of the thienoviologen component,the EC and EFC efficiency decreased with the increased strain loaded on the ionogels,and almost no EC or EFC phenomena were observed when the strain was above 300%.This feasible strategy provides an opportunity for the development of visible strain sensors to monitor the body’s movements through color and fluorescence emission.

关键词： ionogels flexible electronics viologen electrochromism strain sensor

Molecular dynamics simulation on the rotation mechanical mechanism of the twinned nanowires

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Molecular dynamics simulation on the rotation mechanical mec...

中国计算力学大会2014暨第三届钱令希计算力学奖颁奖大会

作者： Ying Wang zishun liu Int.Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructuresXi’an Jiaotong University

There have been a few studies on mechanical mechanism of the periodic twinned nanowires in recent *** purpose of this work is to investigate the behavior of twinned Au nanowires under the torsion *** this study,the Molecular Dynamics(MD)software LAMMPS is adopted to carry out simulation of the twinned nanowires *** parameter of Common Neighbor Analysis is used to mark the different atoms which have different local crystal structures around *** results show that the Common Neighbor Analysis of some atoms on three main regions have been changed a lot in the rotation process of twinned *** local crystal structures of some atoms on the two regions near the ends of nanowires have been altered,but have gradually recovered during the rotation *** found that some fcc planes of the middle area have become the hcp planes with the deformation increasing,and the hcp lattice represents twin *** middle plane of the nanowire is also a plane of the middle area,which has changed from twin plane into grain boundary,then fcc plane.

关键词： molecular dynamics twin rotation mechanical mechanism nanowire

Novel mechanical behavior of composite gel structures with the pattern transformation

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Novel mechanical behavior of composite gel structures with t...

中国力学大会——2013

作者： Hu Jianying He Yuhao liu zishun Int.Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructureXi’an Jiaotong University

In this study,we develop a novel elastomeric porous matrix material with arrays of rectangular and/or circular gel inclusions. The designed material can achieve special mechanical ***,the new mechanical behaviors of this composite material with pattern transformation have been investigated through numerical *** to the obtained nominal stress *** strain curves,the Poisson’s ratio and corresponding deformed structure patterns,we explore the effects

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Modeling and Simulation of Deformation Behavior for Temperature Sensitive Shape Memory Polymer

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Modeling and Simulation of Deformation Behavior for Temperat...

中国计算力学大会2014暨第三届钱令希计算力学奖颁奖大会

作者： Yuhao He Siusiu Guo zishun liu Int.Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical StructureXi’an Jiaotong University

In this study,a standard linear viscoelastic three-dimensional(3D)constitutive model was developed for shape memory polymers(SMPs)to reproduce their thermo-mechanical *** 3D constitutive model has been implemented into commercial software ABAQUE by adopting user material subroutine(UMAT)for finite element *** validate robustness of the subroutine,numerical simulations of a rectangular bar under axial tension and torsion were *** results of the bar under axial te nsion were compared with the experimental data reported in the previous literature,and good agreement can be observed between the simulated results and *** results for torsional test,which is rarely analyzed,could play an important ro le in the characterization of SMP applications.S imulated results of the thermal-mechanical experiments also verify the efficiency of the 3D viscoelastic constitutive *** proposed 3D viscoelastic model will serve as a modeling tool for the design o f more complex SMP-based structures and devices.

关键词： Shape Memory Polymer Temperature sensitive Viscoelastic Model UMAT

Atomic Understanding of Nanoindentation and Wear of the γTi-Al

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Atomic Understanding of Nanoindentation and Wear of the γTi...

中国计算力学大会2014暨第三届钱令希计算力学奖颁奖大会

作者： Shuai Xu Zhendong Sha zishun liu International Center for Applied Mechanics State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an Jiaotong University

SinceγTi-Al intermetallic compounds displays outstanding mechanical and physical properties,especially the high specific strength and excellent performance at high temperature,it makeγTi-Al has a great potential in the application in aerospace engineering and weapon *** thus the research onγTi-Al mechanical properties has caught much attention in the last ***,it is imperative to understand the fundamental mechanical and physical properties ofγ*** present study,we have performed large-scale molecular dynamics(MD)simulations onγTi-Al to study the mechanical properties and wear mechanism at *** nanoindentation test onγTi-Al materials is carried out by using MD simulation in which the diamond tip was assumed to be *** simulation result shows that the Young’s modulus ofγTi-Al materials is 153.9GPa,which is quite close to the experimental value of 165 *** wear simulation results show that material loss during sliding is linearly proportional to sliding distance and indentation *** should be noticed that material loss is always smaller than the number of atoms the tip slides over,which we think is caused by both elastic and plastic deformation.

关键词： γTi-Al molecular dynamic simulation nanoindentation wear