Significant advances in battery and fuel cell technologies over the past decade have catalyzed the transition toward electrified transportation systems and large-scale renewable energy integration.Concurrent with thes...Significant advances in battery and fuel cell technologies over the past decade have catalyzed the transition toward electrified transportation systems and large-scale renewable energy integration.Concurrent with these developments,the interdisciplinary role of mechanics has emerged as a critical research frontier.展开更多
In this research,we introduce an innovative approach that combines the Continuum Damage Mechanics-Finite Element Method(CDM-FEM)with the Particle Swarm Optimization(PSO)-based technique,to predict the Medium-Low-Cycle...In this research,we introduce an innovative approach that combines the Continuum Damage Mechanics-Finite Element Method(CDM-FEM)with the Particle Swarm Optimization(PSO)-based technique,to predict the Medium-Low-Cycle Fatigue(MLCF)life of perforated structures.First,fatigue tests are carried out on three center-perforated structures,aiming to assess their fatigue life under various strengthening conditions.These tests reveal significant variations in fatigue life,accompanied by an examination of crack initiation through the analysis of fatigue fracture surfaces.Second,an innovative fatigue life prediction methodology is applied to perforated structures,which not only forecasts the initiation of fatigue cracks but also traces the progression of damage within these structures.It leverages an elastoplastic constitutive model integrated with damage and a damage evolution model under cyclic loads.The accuracy of this approach is validated by comparison with test results,falling within the three times error band.Finally,we explore the impact of various strengthening techniques,including cross-sectional reinforcement and cold expansion,on the fatigue life and damage evolution of these structures.This is achieved through an in-depth comparative analysis of both experimental data and computational predictions,which provides valuable insights into the behavior of perforated structures under fatigue conditions in practical applications.展开更多
The integration of physics-based modelling and data-driven artificial intelligence(AI)has emerged as a transformative paradigm in computational mechanics.This perspective reviews the development and current status of ...The integration of physics-based modelling and data-driven artificial intelligence(AI)has emerged as a transformative paradigm in computational mechanics.This perspective reviews the development and current status of AI-empowered frameworks,including data-driven methods,physics-informed neural networks,and neural operators.While these approaches have demonstrated significant promise,challenges remain in terms of robustness,generalisation,and computational efficiency.We delineate four promising research directions:(1)Modular neural architectures inspired by traditional computational mechanics,(2)physics informed neural operators for resolution-invariant operator learning,(3)intelligent frameworks for multiphysics and multiscale biomechanics problems,and(4)structural optimisation strategies based on physics constraints and reinforcement learning.These directions represent a shift toward foundational frameworks that combine the strengths of physics and data,opening new avenues for the modelling,simulation,and optimisation of complex physical systems.展开更多
In this review, acritical look at the research progress ofexperimentalsolid mechanics in China for the past years is presented. Issues are discussed of the discovery and development of new fundamental methods and tech...In this review, acritical look at the research progress ofexperimentalsolid mechanics in China for the past years is presented. Issues are discussed of the discovery and development of new fundamental methods and techniques versus performance benchmarking for many of their applications. Included herein are photoelasticity and various forms of modern photomechanics, acoustical techniques, image processing and videometrics, radial and spectrum techniques, and experimental mechanics on micro/nano scale. It is also noticed that both the ever developed instrumentation and specialized synthetical techniques have played important roles in advancing experimental mechanics in scientific researches and industrial applications. Finally, an attempt is made to look into the future of experimental solid mechanics with personal opinions offered on what the future trends will be for the researches in the field.展开更多
This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements, including nanoparticles, nanowires, nanobeams, and nanofilms, and heterogeneous materials containing na...This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements, including nanoparticles, nanowires, nanobeams, and nanofilms, and heterogeneous materials containing nanoscale inhomogeneities. It begins with the fundamental formulations of surface mechanics of solids, including the definition of surface stress as a surface excess quantity, the surface constitutive relations, and the surface equilibrium equations. Then, it depicts some theoretical and experimental studies of the mechanical properties of nanostructured elements, as well as the static and dynamic behaviour of cantilever sensors caused by the surface stress which is influenced by adsorption. Afterwards, the article gives a summary of the analytical elasto-static and dynamic solutions of a single as well as multiple inhomogeneities embedded in a matrix with the interface stress prevailing. The effect of surface elasticity on the diffraction of elastic waves is elucidated. Due to the difficulties in the analytical solution of inhomogeneities of complex shapes and configurations, finite element approaches have been developed for heterogeneous materials with the surface stress. Surface stress and surface energy are inherently related to crack propagation and the stress field in the vicinity of crack tips. The solutions of crack prob- lems taking into account surface stress effects are also included. Predicting the effective elastic and plastic responses of heterogeneous materials while taking into account surface and interface stresses has received much attention. The advances in this topic are inevitably delineated. Mechanics of rough surfaces appears to deserve special attention due to its theoretical and practical implications. Some most recent work is reviewed. Finally, some challenges are pointed out. They include the characterization of surfaces and interfaces of real nanomaterials, experimental mea- surements and verification of mechanical parameters of complex surfaces, and the effects of the physical and chemical processes on the surface properties, etc.展开更多
The Micro- and Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives, trends, and directions in mechanics of heterogeneous materials in ...The Micro- and Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives, trends, and directions in mechanics of heterogeneous materials in January 2010. The international journal, Acta Mechanica Solida Sinica, is de- voted to all fields of solid mechanics and relevant disciplines in science, technology, and engineering, with a balanced coverage on analytical, experimental, numerical and applied investigations. On the occasion of the 30TM anniversary of Acta Mechanica Solida Sinica, its editor-in-chief, Professor Q.S. Zheng invited some of the forum participants to review the state-of-the-art of mechanics of heterogeneous solids, with a particular emphasis on the recent research development results of Chinese scientists. Their reviews are organized into five research areas as reported in different sections of this paper. ~I firstly brings in fo- cus on micro- and nano-mechanics, with regards to several selective topics, including multiscale coupled models and computational methods, nanocrystal superlattices, surface effects, micromechanical damage mechanics, and microstructural evolution of metals and shape memory alloys. ~II shows discussions on multifield coupled mechanical phenomena, e.g., multi-fields actuations of liquid crystal polymer networks, mechanical behavior of materials under radiations, and micromechanics of heterogeneous materials. In ~III, we mainly address the multiscale mechanics of biological nanocomposites, biological adhesive surface mechanics, wetting and dewetting phenomena on microstructured solid surfaces. The phononic crystals and manipulation of elastic waves were elaborated in ~IV. Finally, we conclude with a series of perspectives on solid mechanics. This review will set a primary goal of future science research and engineering application on solid mechanics with the effort of social and economic development.展开更多
To consider fiber random distribution at the microscale for the multiscale model based on the micro-mechanics failure(MMF)theory,clustering method is used for the extraction of amplification factors.As the clustering ...To consider fiber random distribution at the microscale for the multiscale model based on the micro-mechanics failure(MMF)theory,clustering method is used for the extraction of amplification factors.As the clustering method is a kind of unsupervised machine learning method,the elements with similar mechanical behavior under external loading can be included in a cluster automatically at the microscale.With this modification,the fiber random distribution model can be used for multiscale damage analysis in the framework of MMF theory.To validate the modified multiscale analysis method,progressive damage analysis of a kind of 2D twill woven composites is conducted based on different microscale models.The stress values for microscale models with fiber hexagonal and random distribution patterns are compared first.Much higher stress concentration is generated in the fiber random distribution model due to the smaller inter-fiber distance especially under longitudinal shear loading.The obtained cluster distribution results exhibit the characters of the stress distribution in the two microscale models.Thereafter,tensile and compressive responses of the 2D twill woven composite are predicted with the modified multiscale analysis method and accuracy of the method is verified through comparison with published experimental results.From the simulation results,it can be found that the matrix damage initiation from the model based on the fiber random distribution model is premature compared with that from the model based on the fiber hexagonal distribution model.Besides,under tensile loading,the damage all initiates from the fill tows and propagates to the wrap tows.However,under compressive loading,the matrix damage initiates from the wrap tows in the model based on the fiber random distribution model.展开更多
The effects of microstructure and its evolution on the macroscopic superelastic stress-strain response of polycrystalline Shape Memory Alloy(SMA)are studied by a microstructure-based constitutive model developed in th...The effects of microstructure and its evolution on the macroscopic superelastic stress-strain response of polycrystalline Shape Memory Alloy(SMA)are studied by a microstructure-based constitutive model developed in this paper.The model is established on the following basis:(1)the transformation conditions of the unconstrained single crystal SMA microdomain(to be distinguished from the bulk single crystal),which serve as the local criterion for the derivation of overall transfor- mation yield conditions of the polycrystal;(2)the micro-to macro-transition scheme by which the connection between the polycrystal aggregates and the single crystal microdomain is established and the macroscopic transformation conditions of the polycrystal SMA are derived;(3)the quantitative incorporation of three microstruc- ture factors(i.e.,nucleation,growth and orientation distribution of martensite)into the modeling.These microstructural factors are intrinsic of specific polycrystal SMA systems and the role of each factor in the macroscopic constitutive response is quan- titatively modeled.It is demonstrated that the interplay of these factors will result in different macroscopic transformation kinematics and kinetics which are responsible for the observed macroscopic stress-strain hardening or softening response,the latter will lead to the localization and propagation of transformation bands in TiNi SMA.展开更多
Classical continuum mechanics which leads to a local continuum model,encounters challenges when the discontinuity appears,while peridynamics that falls into the category of nonlocal continuum mechanics suffers from a ...Classical continuum mechanics which leads to a local continuum model,encounters challenges when the discontinuity appears,while peridynamics that falls into the category of nonlocal continuum mechanics suffers from a high computational cost.A hybrid model coupling classical continuum mechanics with peridynamics can avoid both disadvantages.This paper describes the hybrid model and its adaptive coupling approach which dynamically updates the coupling domains according to crack propagations for brittle materials.Then this hybrid local/nonlocal continuum model is applied to fracture simulation.Some numerical examples like a plate with a hole,Brazilian disk,notched plate and beam,are performed for verification and validation.In addition,a peridynamic software is introduced,which was recently developed for the simulation of the hybrid local/nonlocal continuum model.展开更多
Continuum mechanics, just as the name implies, deals with the mechanics problems of all continua, whose physical （or mechanical） properties are assumed to vary continuously in the spaces they occupy. Continuum mecha...Continuum mechanics, just as the name implies, deals with the mechanics problems of all continua, whose physical （or mechanical） properties are assumed to vary continuously in the spaces they occupy. Continuum mechanics may be seen as the symbol of modem mechanics, which differs greatly from current physics, the two often being mixed up by people and even sci- entists. In this short paper, I will first try to give an illustration on the differences between （modem） mechanics and physics, in my personal view, and then focus on some important current research activities in continuum mechanics, attempting to identify its path to the near future. We can see that continuum mechanics, while having a dominating impact on engineering design in the 20th century, also plays a pivotal role in modem science, and is much closer to physics, chemistry, biology, etc. than ever before.展开更多
The mechanical properties of metallic thin films deposited on a substrate play a crucial role in the performance of micro/nano-electromechanical systems(MEMS/NEMS)and flexible electronics. This article reviews ongoing...The mechanical properties of metallic thin films deposited on a substrate play a crucial role in the performance of micro/nano-electromechanical systems(MEMS/NEMS)and flexible electronics. This article reviews ongoing study on the mechanics of substrate-supported thin films, with emphasis on the experimental characterization techniques,such as the rule of mixture and X-ray tensile testing. In particular, the determination of interfacial adhesion energy, film deformation, elastic properties and Bauschinger effect are discussed.展开更多
In this paper, by capturing the atomic information and reflecting the behaviour governed by the nonlinear potential function, an analytical molecular mechanics approach is proposed. A constitutive relation for single-...In this paper, by capturing the atomic information and reflecting the behaviour governed by the nonlinear potential function, an analytical molecular mechanics approach is proposed. A constitutive relation for single-walled carbon nanotubes （SWCNT＇s） is established to describe the nonlinear stress-strain curve of SWCNT＇s and to predict both the elastic properties and breaking strain of SWCNT＇s during tensile deformation. An analysis based on the virtual internal bond （VIB） model proposed by P. Zhang et al. is also presented for comparison. The results indicate that the proposed molecular mechanics approach is indeed an acceptable analytical method for analyzing the mechanical behavior of SWCNT＇s.展开更多
In the present paper, continuum fracture mechanics is used to analyze the Smart-Cut process, a recently established ion cut technology which enables highly efficient fabrication of various silicon-on-insulator （SOI）...In the present paper, continuum fracture mechanics is used to analyze the Smart-Cut process, a recently established ion cut technology which enables highly efficient fabrication of various silicon-on-insulator （SOI） wafers of high uniformity in thickness. Using integral transform and Cauchy singular integral equation methods, the mode-I and mode-II stress intensity factors, energy release rate, and crack opening displacements are derived in order to examine several important fracture mechanisms involved in the Smart-Cut process. The effects of defect interaction and stiffening wafer on defect growth are investigated. The numerical results indi- cate that a stiffener/handle wafer can effectively prevent the donor wafer from blistering and exfoliation, but it slows down the defect growth by decreasing the magnitudes of SIF＇s. Defect interaction also plays an important role in the splitting process of SOI wafers, but its contribution depends strongly on the size, interval and internal pressure of defects. Finally, an analytical formula is derived to estimate the implantation dose required for splitting a SOI wafer.展开更多
Epithelial monolayers act as a vital player in a variety of physiological activities,such as wound healing and embryonic development.The mechanical behavior of epithelial monolayers has been increasingly studied with ...Epithelial monolayers act as a vital player in a variety of physiological activities,such as wound healing and embryonic development.The mechanical behavior of epithelial monolayers has been increasingly studied with the recent rapid development of techniques.Under dynamic loadings,the creep response of epithelial monolayers shows a power-law dependence on the time with an exponent larger than that of a single cell.Under static loadings,the elastic modulus of epithelial monolayers is nearly two orders of magnitude higher than that of a single cell.To date,there is a lack of a mechanical model that can describe both the dynamic and static mechanical responses of epithelial monolayers.Here,based on the structural features of cells,we establish a multi-scale structural model of cell monolayers.It is found that the proposed model can naturally capture the dynamic and static mechanical properties of cell monolayers.Further,we explore the effects of the cytoskeleton and the membrane moduli on the dynamical power-law rheological responses and static stress-strain relations of a single cell and cell monolayers,respectively.Our work lays the foundation for subsequent studies of the mechanical behavior of more complex epithelial tissues.展开更多
In Part 2 of the paper on the Smart-Cut process, the effects of bonding flaws characterized by the size and internal pressure before and after splitting are studied by using fracture mechanics models. It is found that...In Part 2 of the paper on the Smart-Cut process, the effects of bonding flaws characterized by the size and internal pressure before and after splitting are studied by using fracture mechanics models. It is found that the bonding flaws with large size are prone to cause severe deviation of defect growth, leading to a non-transferred area of thin layer when splitting. In a practical Smart-Cut process where the internal pressure of bonding flaws is very small, large interfacial defects always promote defect growth in the splitting process. Meanwhile, increasing the internal pressure of the bonding flaws decreases the defect growth and its deviation before splitting. The mechanism of relaxation of stiffener constraint is proposed to clarify the effect of bonding flaws. Moreover, the progress of the splitting process is analyzed when bonding flaws are present. After splitting, those bonding flaws with large size and high internal pressure are vulnerable for the blistering of the thin film during high-temperature annealing.展开更多
Phonons are the quantum mechanical descriptions of vibrational modes that manifest themselves in many physical properties of condensed matter systems. As the size of electronic devices continues to decrease below mean...Phonons are the quantum mechanical descriptions of vibrational modes that manifest themselves in many physical properties of condensed matter systems. As the size of electronic devices continues to decrease below mean free paths of acoustic phonons, the engineering of phonon spectra at the nanoscale becomes an important topic. Phonon manipulation allows for active control and management of heat fow, enabling functions such as regulated heat transport. At the same time, phonon transmission, as a novel signal transmission method, holds great potential to revolutionize modern industry like microelectronics technology, and boasts wide-ranging applications. Unlike fermions such as electrons, polarity regulation is difficult to act on phonons as bosons, making the development of effective phonon modulation methods a daunting task.This work reviews the development of phonon engineering and strategies of phonon manipulation at different scales, reports the latest research progress of nanophononic devices such as thermal rectifiers, thermal transistors, thermal memories, and thermoelectric devices,and analyzes the phonon transport mechanisms involved. Lastly, we survey feasible perspectives and research directions of phonon engineering. Thermoelectric analogies, external field regulation, and acousto-optic co-optimization are expected to become future research hotspots.展开更多
Flexoelectricity is a fascinating electromechanical phenomenon that occurs in non-homogeneously deformed dielectric materials.Unlike piezoelectricity,the flexoelectric effect is highly dependent on both the material s...Flexoelectricity is a fascinating electromechanical phenomenon that occurs in non-homogeneously deformed dielectric materials.Unlike piezoelectricity,the flexoelectric effect is highly dependent on both the material scale and the deformation gradient.Although several theoretical models have been proposed to explain the mechanism of flexoelectricity,these models can be rather complicated for those who are interested in studying the topic.This paper aims to simplify the understanding of flexoelectricity by focusing on the bending behavior of a prismatic dielectric beam from a mechanics of material perspective.We avoid using complicated mathematical formulations based on continuum mechanics,including advanced tensor algebra and calculus of variations.Our formulation clearly explains how inhomogeneous deformations and material size affect the electromechanical coupling,changing the effective bending stiffness,deflection,and rotation angles of a bending beam.We hope this paper can help undergraduate students and researchers,who are unfamiliar with the electromechanical coupling in flexoelectricity,to develop an understanding of this phenomenon and encourage further research in this area.展开更多
Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sam- ple material and molecular dynamic simulations, ...Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sam- ple material and molecular dynamic simulations, we demon- strate that strain engineering can serve as an effective way to control the surface wettability. The contact angles 0 of water droplets on a graphene vary from 72.5° to 106° under biaxial strains ranging from -10% to 10% that are applied on the graphene layer. For an intrinsic hydrophilic surface （at zero strain）, the variation of 0 upon the applied strains is more sensitive, i.e., from 0° to 74.8°. Overall the cosines of the contact angles exhibit a linear relation with respect to the strains. In light of the inherent dependence of the contact an- gle on liquid-solid interfacial energy, we develop an analytic model to show the cos 0 as a linear function of the adsorption energy Eads of a single water molecule over the substrate sur- face. This model agrees with our molecular dynamic results very well. Together with the linear dependence of Eads on bi- axial strains, we can thus understand the effect of strains on the surface wettability. Thanks to the ease of reversibly ap- plying mechanical strains in micro/nano-electromechanical systems, we believe that strain engineering can be a promis- ing means to achieve the reversibly control of surface wetta- bility.展开更多
Fluid-filled closed-cell porous media could exhibit distinctive features which are influenced by initial fluid pressures inside the cavities.Based on the equivalent farfield method,micromechanics-based solutions for t...Fluid-filled closed-cell porous media could exhibit distinctive features which are influenced by initial fluid pressures inside the cavities.Based on the equivalent farfield method,micromechanics-based solutions for the local elastic fields of porous media saturated with pressurized fluid are formulated in this paper.In the present micromechanics model,three configurations are introduced to characterize the different state the closed-cell porous media.The fluid-filled cavity is assumed to be a compressible elastic solid with a zero shear modulus,and the pressures in closed pores are represented by eigenstrains introduced in fluid domains.With the assumption of spheroidal fluidfilled pores,the local stress and strain fields in solid matrix of porous media are derived by using the Exterior-Point Eshelby tensors,which are dependent of the Poisson’s ratio of solid matrix and the locations of the investigated material points outside the spheroidal fluid domain.The reliability and accuracy of the analytical elastic solutions are verified by a classical example.Moreover,for finite volume fraction of the fluid inclusions,the local elastic fields of the porous media subjected to the initial fluid pressure and external load are obtained.The results show that the present micromechanics model provides an effective approach to characterize the local elastic fields of the materials with closed-cell fluid-filled pores.展开更多
文摘Significant advances in battery and fuel cell technologies over the past decade have catalyzed the transition toward electrified transportation systems and large-scale renewable energy integration.Concurrent with these developments,the interdisciplinary role of mechanics has emerged as a critical research frontier.
基金support from the National Natural Science Foundation of China(No.12472072)the Fundamental Research Funds for the Central Universities,China.
文摘In this research,we introduce an innovative approach that combines the Continuum Damage Mechanics-Finite Element Method(CDM-FEM)with the Particle Swarm Optimization(PSO)-based technique,to predict the Medium-Low-Cycle Fatigue(MLCF)life of perforated structures.First,fatigue tests are carried out on three center-perforated structures,aiming to assess their fatigue life under various strengthening conditions.These tests reveal significant variations in fatigue life,accompanied by an examination of crack initiation through the analysis of fatigue fracture surfaces.Second,an innovative fatigue life prediction methodology is applied to perforated structures,which not only forecasts the initiation of fatigue cracks but also traces the progression of damage within these structures.It leverages an elastoplastic constitutive model integrated with damage and a damage evolution model under cyclic loads.The accuracy of this approach is validated by comparison with test results,falling within the three times error band.Finally,we explore the impact of various strengthening techniques,including cross-sectional reinforcement and cold expansion,on the fatigue life and damage evolution of these structures.This is achieved through an in-depth comparative analysis of both experimental data and computational predictions,which provides valuable insights into the behavior of perforated structures under fatigue conditions in practical applications.
基金supported by the Australian Research Council(Grant No.IC190100020)the Australian Research Council Indus〓〓try Fellowship(Grant No.IE230100435)the National Natural Science Foundation of China(Grant Nos.12032014 and T2488101)。
文摘The integration of physics-based modelling and data-driven artificial intelligence(AI)has emerged as a transformative paradigm in computational mechanics.This perspective reviews the development and current status of AI-empowered frameworks,including data-driven methods,physics-informed neural networks,and neural operators.While these approaches have demonstrated significant promise,challenges remain in terms of robustness,generalisation,and computational efficiency.We delineate four promising research directions:(1)Modular neural architectures inspired by traditional computational mechanics,(2)physics informed neural operators for resolution-invariant operator learning,(3)intelligent frameworks for multiphysics and multiscale biomechanics problems,and(4)structural optimisation strategies based on physics constraints and reinforcement learning.These directions represent a shift toward foundational frameworks that combine the strengths of physics and data,opening new avenues for the modelling,simulation,and optimisation of complex physical systems.
基金Project supported by the NSFC (Nos.10472112,19232020,10627201,10972113, 90916010 and 10732080)the National Basic Research Program of China (Nos.2007CB936803 and 2010CB631005)SRFDP (Nos.20070003053 and 20090002110048)
文摘In this review, acritical look at the research progress ofexperimentalsolid mechanics in China for the past years is presented. Issues are discussed of the discovery and development of new fundamental methods and techniques versus performance benchmarking for many of their applications. Included herein are photoelasticity and various forms of modern photomechanics, acoustical techniques, image processing and videometrics, radial and spectrum techniques, and experimental mechanics on micro/nano scale. It is also noticed that both the ever developed instrumentation and specialized synthetical techniques have played important roles in advancing experimental mechanics in scientific researches and industrial applications. Finally, an attempt is made to look into the future of experimental solid mechanics with personal opinions offered on what the future trends will be for the researches in the field.
基金the support of the National Natural Science Foundation of China (NSFC) through grants Nos.10032010,10072002,10372004,10525209,10872003 and 10932001the Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD,Grant No.2007B2)+5 种基金Research Fund for the New Teacher Program of the State Education Ministry of China (Grant No.200800011011)Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry of Chinathe support of NSFC (Grants Nos.10772093 and 10732050)the support of NSFC (Nos.11072186,10902081 and 11021202)973-Program (Nos.2007CB936803 and 2010CB631005)973-Program (No.2007CB707702)
文摘This review article summarizes the advances in the surface stress effect in mechanics of nanostructured elements, including nanoparticles, nanowires, nanobeams, and nanofilms, and heterogeneous materials containing nanoscale inhomogeneities. It begins with the fundamental formulations of surface mechanics of solids, including the definition of surface stress as a surface excess quantity, the surface constitutive relations, and the surface equilibrium equations. Then, it depicts some theoretical and experimental studies of the mechanical properties of nanostructured elements, as well as the static and dynamic behaviour of cantilever sensors caused by the surface stress which is influenced by adsorption. Afterwards, the article gives a summary of the analytical elasto-static and dynamic solutions of a single as well as multiple inhomogeneities embedded in a matrix with the interface stress prevailing. The effect of surface elasticity on the diffraction of elastic waves is elucidated. Due to the difficulties in the analytical solution of inhomogeneities of complex shapes and configurations, finite element approaches have been developed for heterogeneous materials with the surface stress. Surface stress and surface energy are inherently related to crack propagation and the stress field in the vicinity of crack tips. The solutions of crack prob- lems taking into account surface stress effects are also included. Predicting the effective elastic and plastic responses of heterogeneous materials while taking into account surface and interface stresses has received much attention. The advances in this topic are inevitably delineated. Mechanics of rough surfaces appears to deserve special attention due to its theoretical and practical implications. Some most recent work is reviewed. Finally, some challenges are pointed out. They include the characterization of surfaces and interfaces of real nanomaterials, experimental mea- surements and verification of mechanical parameters of complex surfaces, and the effects of the physical and chemical processes on the surface properties, etc.
文摘The Micro- and Nano-mechanics Working Group of the Chinese Society of Theoretical and Applied Mechanics organized a forum to discuss the perspectives, trends, and directions in mechanics of heterogeneous materials in January 2010. The international journal, Acta Mechanica Solida Sinica, is de- voted to all fields of solid mechanics and relevant disciplines in science, technology, and engineering, with a balanced coverage on analytical, experimental, numerical and applied investigations. On the occasion of the 30TM anniversary of Acta Mechanica Solida Sinica, its editor-in-chief, Professor Q.S. Zheng invited some of the forum participants to review the state-of-the-art of mechanics of heterogeneous solids, with a particular emphasis on the recent research development results of Chinese scientists. Their reviews are organized into five research areas as reported in different sections of this paper. ~I firstly brings in fo- cus on micro- and nano-mechanics, with regards to several selective topics, including multiscale coupled models and computational methods, nanocrystal superlattices, surface effects, micromechanical damage mechanics, and microstructural evolution of metals and shape memory alloys. ~II shows discussions on multifield coupled mechanical phenomena, e.g., multi-fields actuations of liquid crystal polymer networks, mechanical behavior of materials under radiations, and micromechanics of heterogeneous materials. In ~III, we mainly address the multiscale mechanics of biological nanocomposites, biological adhesive surface mechanics, wetting and dewetting phenomena on microstructured solid surfaces. The phononic crystals and manipulation of elastic waves were elaborated in ~IV. Finally, we conclude with a series of perspectives on solid mechanics. This review will set a primary goal of future science research and engineering application on solid mechanics with the effort of social and economic development.
基金the support of the National Natural Science Foundation of China(No.11572086)the Fundamental Research Funds for the Central Universities+2 种基金the Scientific Research Innovation Program of Jiangsu Province College of China(No.KYLX16_0185)the Scientific Research Foundation of Graduate School of Southeast University of China(No.YBJJ1760)the China Scholarship Council of China(No.201706090076)。
文摘To consider fiber random distribution at the microscale for the multiscale model based on the micro-mechanics failure(MMF)theory,clustering method is used for the extraction of amplification factors.As the clustering method is a kind of unsupervised machine learning method,the elements with similar mechanical behavior under external loading can be included in a cluster automatically at the microscale.With this modification,the fiber random distribution model can be used for multiscale damage analysis in the framework of MMF theory.To validate the modified multiscale analysis method,progressive damage analysis of a kind of 2D twill woven composites is conducted based on different microscale models.The stress values for microscale models with fiber hexagonal and random distribution patterns are compared first.Much higher stress concentration is generated in the fiber random distribution model due to the smaller inter-fiber distance especially under longitudinal shear loading.The obtained cluster distribution results exhibit the characters of the stress distribution in the two microscale models.Thereafter,tensile and compressive responses of the 2D twill woven composite are predicted with the modified multiscale analysis method and accuracy of the method is verified through comparison with published experimental results.From the simulation results,it can be found that the matrix damage initiation from the model based on the fiber random distribution model is premature compared with that from the model based on the fiber hexagonal distribution model.Besides,under tensile loading,the damage all initiates from the fill tows and propagates to the wrap tows.However,under compressive loading,the matrix damage initiates from the wrap tows in the model based on the fiber random distribution model.
基金The project supported by the Research Grant Committee(RGC)of Hong Kong SARthe National Natural Science Foundation of China and the Provincial Natural Foundation of Jiangxi Province of China
文摘The effects of microstructure and its evolution on the macroscopic superelastic stress-strain response of polycrystalline Shape Memory Alloy(SMA)are studied by a microstructure-based constitutive model developed in this paper.The model is established on the following basis:(1)the transformation conditions of the unconstrained single crystal SMA microdomain(to be distinguished from the bulk single crystal),which serve as the local criterion for the derivation of overall transfor- mation yield conditions of the polycrystal;(2)the micro-to macro-transition scheme by which the connection between the polycrystal aggregates and the single crystal microdomain is established and the macroscopic transformation conditions of the polycrystal SMA are derived;(3)the quantitative incorporation of three microstruc- ture factors(i.e.,nucleation,growth and orientation distribution of martensite)into the modeling.These microstructural factors are intrinsic of specific polycrystal SMA systems and the role of each factor in the macroscopic constitutive response is quan- titatively modeled.It is demonstrated that the interplay of these factors will result in different macroscopic transformation kinematics and kinetics which are responsible for the observed macroscopic stress-strain hardening or softening response,the latter will lead to the localization and propagation of transformation bands in TiNi SMA.
基金The authors gratefully acknowledge the financial support received from KAUST baseline,the National Natural Science Foundation(11872016)the Fundamental Research Funds of Dalian University of Technology(Grant No.DUT17RC(3)092)for the completion of this work.
文摘Classical continuum mechanics which leads to a local continuum model,encounters challenges when the discontinuity appears,while peridynamics that falls into the category of nonlocal continuum mechanics suffers from a high computational cost.A hybrid model coupling classical continuum mechanics with peridynamics can avoid both disadvantages.This paper describes the hybrid model and its adaptive coupling approach which dynamically updates the coupling domains according to crack propagations for brittle materials.Then this hybrid local/nonlocal continuum model is applied to fracture simulation.Some numerical examples like a plate with a hole,Brazilian disk,notched plate and beam,are performed for verification and validation.In addition,a peridynamic software is introduced,which was recently developed for the simulation of the hybrid local/nonlocal continuum model.
基金Project supported by the National Natural Science of Foundation of China(Nos.11321202 and 11272281)
文摘Continuum mechanics, just as the name implies, deals with the mechanics problems of all continua, whose physical （or mechanical） properties are assumed to vary continuously in the spaces they occupy. Continuum mechanics may be seen as the symbol of modem mechanics, which differs greatly from current physics, the two often being mixed up by people and even sci- entists. In this short paper, I will first try to give an illustration on the differences between （modem） mechanics and physics, in my personal view, and then focus on some important current research activities in continuum mechanics, attempting to identify its path to the near future. We can see that continuum mechanics, while having a dominating impact on engineering design in the 20th century, also plays a pivotal role in modem science, and is much closer to physics, chemistry, biology, etc. than ever before.
基金supported by the National Natural Science Foundation of China (Grants 11472186 and 11602083)the Natural Science Foundation of Hunan Province, China (Grant 2016JJ6044)
文摘The mechanical properties of metallic thin films deposited on a substrate play a crucial role in the performance of micro/nano-electromechanical systems(MEMS/NEMS)and flexible electronics. This article reviews ongoing study on the mechanics of substrate-supported thin films, with emphasis on the experimental characterization techniques,such as the rule of mixture and X-ray tensile testing. In particular, the determination of interfacial adhesion energy, film deformation, elastic properties and Bauschinger effect are discussed.
基金the National Natural Science Foundation of China(10121202,90305015 and 10328203)the Key Grant Project of Chinese Ministry of Education (0306)+1 种基金the Research Grants Council of the Hong Kong Special Administrative RegionChina(HKU7195/04E)
文摘In this paper, by capturing the atomic information and reflecting the behaviour governed by the nonlinear potential function, an analytical molecular mechanics approach is proposed. A constitutive relation for single-walled carbon nanotubes （SWCNT＇s） is established to describe the nonlinear stress-strain curve of SWCNT＇s and to predict both the elastic properties and breaking strain of SWCNT＇s during tensile deformation. An analysis based on the virtual internal bond （VIB） model proposed by P. Zhang et al. is also presented for comparison. The results indicate that the proposed molecular mechanics approach is indeed an acceptable analytical method for analyzing the mechanical behavior of SWCNT＇s.
基金the Australian Research Council (ARC),the National Natural Science Foundation of China (10525210 and 10732050) 973 Project (2004CB619303)
文摘In the present paper, continuum fracture mechanics is used to analyze the Smart-Cut process, a recently established ion cut technology which enables highly efficient fabrication of various silicon-on-insulator （SOI） wafers of high uniformity in thickness. Using integral transform and Cauchy singular integral equation methods, the mode-I and mode-II stress intensity factors, energy release rate, and crack opening displacements are derived in order to examine several important fracture mechanisms involved in the Smart-Cut process. The effects of defect interaction and stiffening wafer on defect growth are investigated. The numerical results indi- cate that a stiffener/handle wafer can effectively prevent the donor wafer from blistering and exfoliation, but it slows down the defect growth by decreasing the magnitudes of SIF＇s. Defect interaction also plays an important role in the splitting process of SOI wafers, but its contribution depends strongly on the size, interval and internal pressure of defects. Finally, an analytical formula is derived to estimate the implantation dose required for splitting a SOI wafer.
基金supported by the National Natural Science Foundation of China(Grant Nos.12072252 and 12122210)the Natural Science Basic Research Plan in Shanxi Province of China(Grant No.2019JC-02).
文摘Epithelial monolayers act as a vital player in a variety of physiological activities,such as wound healing and embryonic development.The mechanical behavior of epithelial monolayers has been increasingly studied with the recent rapid development of techniques.Under dynamic loadings,the creep response of epithelial monolayers shows a power-law dependence on the time with an exponent larger than that of a single cell.Under static loadings,the elastic modulus of epithelial monolayers is nearly two orders of magnitude higher than that of a single cell.To date,there is a lack of a mechanical model that can describe both the dynamic and static mechanical responses of epithelial monolayers.Here,based on the structural features of cells,we establish a multi-scale structural model of cell monolayers.It is found that the proposed model can naturally capture the dynamic and static mechanical properties of cell monolayers.Further,we explore the effects of the cytoskeleton and the membrane moduli on the dynamical power-law rheological responses and static stress-strain relations of a single cell and cell monolayers,respectively.Our work lays the foundation for subsequent studies of the mechanical behavior of more complex epithelial tissues.
基金supported by the Australian Research Council (ARC), the National Natural Science Foundation of China (10525210 and 10732050) 973 Project (2004CB619303)
文摘In Part 2 of the paper on the Smart-Cut process, the effects of bonding flaws characterized by the size and internal pressure before and after splitting are studied by using fracture mechanics models. It is found that the bonding flaws with large size are prone to cause severe deviation of defect growth, leading to a non-transferred area of thin layer when splitting. In a practical Smart-Cut process where the internal pressure of bonding flaws is very small, large interfacial defects always promote defect growth in the splitting process. Meanwhile, increasing the internal pressure of the bonding flaws decreases the defect growth and its deviation before splitting. The mechanism of relaxation of stiffener constraint is proposed to clarify the effect of bonding flaws. Moreover, the progress of the splitting process is analyzed when bonding flaws are present. After splitting, those bonding flaws with large size and high internal pressure are vulnerable for the blistering of the thin film during high-temperature annealing.
基金supported by the National Natural Science Foundation of China Grant Nos. 52276072 and 51976096。
文摘Phonons are the quantum mechanical descriptions of vibrational modes that manifest themselves in many physical properties of condensed matter systems. As the size of electronic devices continues to decrease below mean free paths of acoustic phonons, the engineering of phonon spectra at the nanoscale becomes an important topic. Phonon manipulation allows for active control and management of heat fow, enabling functions such as regulated heat transport. At the same time, phonon transmission, as a novel signal transmission method, holds great potential to revolutionize modern industry like microelectronics technology, and boasts wide-ranging applications. Unlike fermions such as electrons, polarity regulation is difficult to act on phonons as bosons, making the development of effective phonon modulation methods a daunting task.This work reviews the development of phonon engineering and strategies of phonon manipulation at different scales, reports the latest research progress of nanophononic devices such as thermal rectifiers, thermal transistors, thermal memories, and thermoelectric devices,and analyzes the phonon transport mechanisms involved. Lastly, we survey feasible perspectives and research directions of phonon engineering. Thermoelectric analogies, external field regulation, and acousto-optic co-optimization are expected to become future research hotspots.
基金supported by the National Natural Science Foundation of China(12202249)the Fundamental Research Funds for the Central Universities of China(2024JCG001).
文摘Flexoelectricity is a fascinating electromechanical phenomenon that occurs in non-homogeneously deformed dielectric materials.Unlike piezoelectricity,the flexoelectric effect is highly dependent on both the material scale and the deformation gradient.Although several theoretical models have been proposed to explain the mechanism of flexoelectricity,these models can be rather complicated for those who are interested in studying the topic.This paper aims to simplify the understanding of flexoelectricity by focusing on the bending behavior of a prismatic dielectric beam from a mechanics of material perspective.We avoid using complicated mathematical formulations based on continuum mechanics,including advanced tensor algebra and calculus of variations.Our formulation clearly explains how inhomogeneous deformations and material size affect the electromechanical coupling,changing the effective bending stiffness,deflection,and rotation angles of a bending beam.We hope this paper can help undergraduate students and researchers,who are unfamiliar with the electromechanical coupling in flexoelectricity,to develop an understanding of this phenomenon and encourage further research in this area.
基金supported by the National Natural Science Foundation of China(11172149)the financial support from the IBM World Community Grid project "Computing for Clean Water"+2 种基金the Boeing-Tsinghua Joint Research Project "New Air Filtration Materials"grant 2012 from engineering faculty of Monash Universitysupported by an award under the Merit Allocation Scheme on the Australia NCI National Facility at the ANU
文摘Reversible control of surface wettability has wide applications in lab-on-chip systems, tunable optical lenses, and microfluidic tools. Using a graphene sheet as a sam- ple material and molecular dynamic simulations, we demon- strate that strain engineering can serve as an effective way to control the surface wettability. The contact angles 0 of water droplets on a graphene vary from 72.5° to 106° under biaxial strains ranging from -10% to 10% that are applied on the graphene layer. For an intrinsic hydrophilic surface （at zero strain）, the variation of 0 upon the applied strains is more sensitive, i.e., from 0° to 74.8°. Overall the cosines of the contact angles exhibit a linear relation with respect to the strains. In light of the inherent dependence of the contact an- gle on liquid-solid interfacial energy, we develop an analytic model to show the cos 0 as a linear function of the adsorption energy Eads of a single water molecule over the substrate sur- face. This model agrees with our molecular dynamic results very well. Together with the linear dependence of Eads on bi- axial strains, we can thus understand the effect of strains on the surface wettability. Thanks to the ease of reversibly ap- plying mechanical strains in micro/nano-electromechanical systems, we believe that strain engineering can be a promis- ing means to achieve the reversibly control of surface wetta- bility.
基金The supports from the National Natural Science Foundation of China(Grant No.11572109)the Hebei Natural Science Foundation of China(Grant No.A2016201198)+1 种基金the Key project of science and technology research in Colleges and Universities of Hebei Province(Grant No.ZD2017006)the China Scholarship Council are gratefully acknowledged.
文摘Fluid-filled closed-cell porous media could exhibit distinctive features which are influenced by initial fluid pressures inside the cavities.Based on the equivalent farfield method,micromechanics-based solutions for the local elastic fields of porous media saturated with pressurized fluid are formulated in this paper.In the present micromechanics model,three configurations are introduced to characterize the different state the closed-cell porous media.The fluid-filled cavity is assumed to be a compressible elastic solid with a zero shear modulus,and the pressures in closed pores are represented by eigenstrains introduced in fluid domains.With the assumption of spheroidal fluidfilled pores,the local stress and strain fields in solid matrix of porous media are derived by using the Exterior-Point Eshelby tensors,which are dependent of the Poisson’s ratio of solid matrix and the locations of the investigated material points outside the spheroidal fluid domain.The reliability and accuracy of the analytical elastic solutions are verified by a classical example.Moreover,for finite volume fraction of the fluid inclusions,the local elastic fields of the porous media subjected to the initial fluid pressure and external load are obtained.The results show that the present micromechanics model provides an effective approach to characterize the local elastic fields of the materials with closed-cell fluid-filled pores.
