It has been ten years since 2011 when the first issue of Theoretical and Applied Mechanics Letters(TAML) came out. To date, TAML has published over 700 articles and 30 special issues covering a broad range of topics i...It has been ten years since 2011 when the first issue of Theoretical and Applied Mechanics Letters(TAML) came out. To date, TAML has published over 700 articles and 30 special issues covering a broad range of topics in mechanics. Such great achievements are even not possible without the continued dedication and support from authors, reviewers and editors. At this very special moment, I would like to express my sincere thanks to all of you, and hope you will continue to devote your time and effort s to the further advances of TAML.展开更多
Based on the concept of constitutive relation error along with the residual of both origin and dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed in this paper. It lea...Based on the concept of constitutive relation error along with the residual of both origin and dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed in this paper. It leads to high quality local error bounds in the problem of fracture mechanics simulation with extended finite element method （XFEM）, which involves enrichment to solve a stress singularity in the crack. Since goal-oriented error estimation with enriched degrees of freedom gives us a chance to evaluate the XFEM simulation, the stress intensity factor calculated by two kinds of XFEM programs developed by ourselves and by commercial code ABAQUS are compared in this work. By comparing the reliability of the stress intensity factor calculation, the accuracy of two programs in different cases is evaluated and the source of error is discussed. A 2-dimensional XFEM example is given to illustrate the computational procedure.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
This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens ...This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.展开更多
Driven by the trend of device miniaturization and high-density integration,the interaction between adjacent electrodes has become a critical factor affecting the interfacial reliability of thermoelectric(TE)structures...Driven by the trend of device miniaturization and high-density integration,the interaction between adjacent electrodes has become a critical factor affecting the interfacial reliability of thermoelectric(TE)structures.This study investigates the influence of adjoining electrode interactions on the interfacial response of a multi-electrode/TE substrate structure,including interfacial stresses and stress intensity factors at the electrode ends.To solve the corresponding boundary-value problem,the Fourier transforms are adopted to derive a governing integro-differential equation for the interfacial shear stress in multi-electrode systems,incorporating the TE effects as generalized forces on the right-hand side.The results show that both the interfacial tension and transverse stress in the electrodes are significantly affected by the presence of adjacent electrodes.The interaction between neighboring electrodes diminishes as their spacing increases or when an adhesive interlayer is introduced.Furthermore,the softer and thinner electrodes,the softer and thicker adhesive interlayer,and the smaller TE loads are found to be beneficial for improving the interfacial performance.These findings may contribute to the accurate measurement in surface sensors and layout design of multi-point health monitoring systems for TE structures.展开更多
Lattice materials have demonstrated promising potential in engineering applications owing to their exceptional lightweight,high specific strength,and tunable mechanical properties.However,the traditional homogenizatio...Lattice materials have demonstrated promising potential in engineering applications owing to their exceptional lightweight,high specific strength,and tunable mechanical properties.However,the traditional homogenization methods based on the classical elasticity theory struggle to accurately describe the non-classical mechanical behaviors of lattice materials,especially when dealing with complex unit-cell geometries featured by non-symmetric configurations or non-single central node connections.In response to this limitation,this study establishes a generalized homogenization model based on the micropolar theory framework,employing Hill's boundary conditions to precisely predict the equivalent moduli of complex lattice materials.By introducing the independent rotational degree of freedom(DOF)characteristic of the micropolar theory,the proposed model successfully overcomes the limitation of conventional methods in accurately describing the asymmetric deformation and scale effects.We initially calculate the constitutive relations of two-dimensional(2D)cross-shaped multi-node chiral lattices and subsequently extend the method to three-dimensional(3D)lattices,successfully predicting the mechanical properties of both traditional and eccentric body-centered cubic(BCC)lattices.The theoretical model is validated through the finite element numerical verification which shows excellent consistency with the theoretical predictions.A further parametric study investigates the influence of geometric parameters,revealing the underlying size-effect mechanism.This paper provides a reliable theoretical tool for the design and property optimization of complex lattice materials.展开更多
As an intriguing interdisciplinary research field, cell and molecular biomechanics is at the cutting edge of mechanics in general and biomechanics in particular. It has the potential to provide a quantitative understa...As an intriguing interdisciplinary research field, cell and molecular biomechanics is at the cutting edge of mechanics in general and biomechanics in particular. It has the potential to provide a quantitative understanding of how forces and deformation at tissue, cellular and molecular levels affect human health and disease. In this article, we review the recent advances in cell and molecular biomechanics, examine the available computational and experimental tools, and discuss important issues including protein deformation in mechanotransduction, cell deformation and constitutive behavior, cell adhesion and migration, and the associated models and theories. The opportunities and challenges in cell and molecular biomechanics are also discussed. We hope to provide readers a clear picture of the current status of this field, and to stimulate a broader interest in the applied mechanics community.展开更多
Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions.However,material identification is a challenging task,especially when the ch...Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions.However,material identification is a challenging task,especially when the characteristic of the material is highly nonlinear in nature,as is common in biological tissue.In this work,we identify unknown material properties in continuum solid mechanics via physics-informed neural networks(PINNs).To improve the accuracy and efficiency of PINNs,we develop efficient strategies to nonuniformly sample observational data.We also investigate different approaches to enforce Dirichlet-type boundary conditions(BCs)as soft or hard constraints.Finally,we apply the proposed methods to a diverse set of time-dependent and time-independent solid mechanic examples that span linear elastic and hyperelastic material space.The estimated material parameters achieve relative errors of less than 1%.As such,this work is relevant to diverse applications,including optimizing structural integrity and developing novel materials.展开更多
Rock salt has excellent properties for its use as underground leak‐proof containers for the storage of renewable energy.Salt solution mining has long been used for salt mining,and can now be employed in the construct...Rock salt has excellent properties for its use as underground leak‐proof containers for the storage of renewable energy.Salt solution mining has long been used for salt mining,and can now be employed in the construction of underground salt caverns for the storage of hydrogen gas.This paper presents a wide range of methods to study the mineralogy,geochemistry,microstructure and geomechanical characteristics of rock salt,which are important in the engineering of safe underground storage rock salt caverns.The mineralogical composition of rock salt varies and is linked to its depositional environment and diagenetic alterations.The microstructure in rock salt is related to cataclastic deformation,diffusive mass transfer and intracrystalline plastic deformation,which can then be associated with the macrostructural geomechanical behavior.Compared to other types of rock,rock salt exhibits creep at lower temperatures.This behavior can be divided into three phases based on the changes in strain with time.However,at very low effective confining pressure and high deviatoric stress,rock salt can exhibit dilatant behavior,where brittle deformation could compromise the safety of underground gas storage in rock salt caverns.The proposed review presents the impact of purity,geochemistry and water content of rock salt on its geomechanical behavior,and thus,on the safety of the caverns.展开更多
Any micromechanics model initially developed for predicting stiffness (elastic property) of a composite can be used to predict its strength with a reasonable accuracy,as long as the homogenized stresses in the matrix ...Any micromechanics model initially developed for predicting stiffness (elastic property) of a composite can be used to predict its strength with a reasonable accuracy,as long as the homogenized stresses in the matrix are converted into its true values. A critical assessment on the predictability of 14 famous micromechanics models for stiffness and strength of UD (unidirectional) composites was made in this work against the benchmark data provided in three world-wide failure exercises (WWFEs). Bridging Model exhibited the highest accuracy in both the stiffness and strength predictions. Moreover,it was the only consistent model in the internal stress calculation. Non-consistency implies that a full three-dimensional (3D)approach should be used to predict the effective property of the composite. The paper also showed that the smallest fiber volume in an RVE (representative volume element) led to the best approximation to a composite property.展开更多
Transmembrane water pores are crucial for substance transport through cell membranes via membrane fusion, such as in neural communication. However, the molecular mechanism of water pore formation is not clear. In this...Transmembrane water pores are crucial for substance transport through cell membranes via membrane fusion, such as in neural communication. However, the molecular mechanism of water pore formation is not clear. In this study, we apply all-atom molecular dynamics and bias-exchange metadynamics simulations to study the process of water pore formation under an electric field. We show that water molecules can enter a membrane under an electric field and form a water pore of a few nanometers in diameter. These water molecules disturb the interactions between lipid head groups and the ordered arrangement of lipids. Following the movement of water molecules, the lipid head groups are rotated and driven into the hydrophobic region of the membrane. The reorientated lipid head groups inside the membrane form a hydrophilic surface of the water pore. This study reveals the atomic details of how an electric field influences the movement of water molecules and lipid head groups, resulting in water pore formation.展开更多
Based on the concept of the constitutive relation error along with the residuals of both the origin and the dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed. It lead...Based on the concept of the constitutive relation error along with the residuals of both the origin and the dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed. It leads to the high quality locM error bounds in the problem of the direct-solution steady-state dynamic analysis with a frequency-domain finite element, which involves the enrichments with plural variable basis functions. The solution of the steady-state dynamic procedure calculates the harmonic response directly in terms of the physical degrees of freedom in the model, which uses the mass, damping, and stiffness matrices of the system. A three-dimensional finite element example is carried out to illustrate the computational procedures.展开更多
1 Introduction The purpose of this special issue“Computational Mechanics of Granular Materials and its Engineering Applications”is to introduce the latest research progress in computational mechanics and engineering...1 Introduction The purpose of this special issue“Computational Mechanics of Granular Materials and its Engineering Applications”is to introduce the latest research progress in computational mechanics and engineering applications of granular materials,with particular emphasis on the theoretical constructions of arbitrarily shaped particles,flow pattern transitions,bond-fracture model,neural network algorithm,CFD-DEM coupled method,and coarse-graining model,and to improve our understanding of the physical and mechanical properties of granular systems from the perspective of practical engineering applications.展开更多
The results of the tests for a friction pair “a cylindrical specimen made of 0.45% carbon steel—a counter specimen-liner made of polytetrafluoroethyleneF4-B” during sliding friction are presented. The test results ...The results of the tests for a friction pair “a cylindrical specimen made of 0.45% carbon steel—a counter specimen-liner made of polytetrafluoroethyleneF4-B” during sliding friction are presented. The test results at different levels of contact load are analyzed using the Archard’s equation and are presented as a friction fatigue curve. The concept of the frictional stress intensity factor during sliding friction is introduced, and an expression that relates the wear rate to this factor and is close in shape to the Paris equation in fracture mechanics is proposed.展开更多
An ongoing project at McGill University is aimed at developing an adapted seismic screening method for schools in the province of Qu6bec, Canada. As part of this project the ＂FEMA 154 Rapid Visual Screening of Buildi...An ongoing project at McGill University is aimed at developing an adapted seismic screening method for schools in the province of Qu6bec, Canada. As part of this project the ＂FEMA 154 Rapid Visual Screening of Buildings for Potential Seismic Hazard＂ and the ＂NRC92 Manual for Screening of Buildings for Seismic Investigation＂ were used to assess 102 school buildings located in the city of Montr6al. Results for both methods are in reasonable agreement, with 65% of the buildings requiring a detailed evaluation according to FEMAI54 and 50% according to NRC92. Findings highlighted the particular characteristics of educational facilities： they are low rise buildings with high incidence of structural irregularities. Accounting for them in the screening phase is essential, and is better achieved by NRC92. However, this method is largely based on expert opinion, which makes it difficult to update, while FEMA154 uses a rational methodology for calculating vulnerability scores based on the capacity spectrum approach. The FEMA154 analytical procedure allows updating and adapting the method to its use outside its intended scope.展开更多
Discovery of effect of force adaptation in mechanics is presented. The discovery is based on use of the mobile closed mechanical contour for force transfer from the mechanism input link to an output link, According to...Discovery of effect of force adaptation in mechanics is presented. The discovery is based on use of the mobile closed mechanical contour for force transfer from the mechanism input link to an output link, According to discovery the motion transfer can be carried out by Assur structural group in the form of the mobile closed contour, and the output link is the link with one degree of freedom. The received mechanical system includes an input link, an output link and the closed contour placed between them as fourth class Assur structural group. The kinematic chain has two degrees of freedom. However the closed contour imposes an additional constraint on relative motion of its links. The carried out discovery allows providing the variable transfer ratio only due to the variable external load. Mechanical properties of the closed contour allow providing the required transfer ratio independently, smart and automatically.展开更多
Focal adhesions(FAs)are large,mmltiprotein complexs that provides linkers between cytoskeleton to the extracellular matrix(ECM).Cells sense and respond to forces through FAs to regulate a broad range of processes,such...Focal adhesions(FAs)are large,mmltiprotein complexs that provides linkers between cytoskeleton to the extracellular matrix(ECM).Cells sense and respond to forces through FAs to regulate a broad range of processes,such as cell growth,migration,differen-tiation and apoptosis.Currently,the underlying mechanisms of the force dependent mechanical properties/features of FAs have not yetbeen fully understood.Fa example,strong mechanical forces(inchuding those developed in some cases by cells themselves)can,obvi-ously,disrupt cell-cell and cell-matrix adhesions.However,recent experiments also demonstrated the existence of force dependentadhesian growth(rather than dissociation).展开更多
Cells sense and respond to forces and extracellular environment through FAs to regulate a broad range of processes,such as cell growth,migration,differentiation and apoptosis.
The field of mechanics of biological and bio-inspired materials underwent an exciting development over the past several years, which made it stand at the cutting edge of both engineering mechanics and biomechanics. As...The field of mechanics of biological and bio-inspired materials underwent an exciting development over the past several years, which made it stand at the cutting edge of both engineering mechanics and biomechanics. As an intriguing interdisciplinary research field, it aims at elucidating the fundamental principles in nature＇s design of strong, multi-functional and smart Materials by focusing on the assembly, deformation, stability and failure of the materials.展开更多
A dimensionless load-displacement model based on the energy-density equivalence principle is proposed to obtain the stress-strain relationships of metallic materials under monotonic indentations with various diameters...A dimensionless load-displacement model based on the energy-density equivalence principle is proposed to obtain the stress-strain relationships of metallic materials under monotonic indentations with various diameters of spherical indenters.Finite element simulations are carried out to verify the constitutive relations from the new model,involving indentations made with various spherical indenters.For each indenter,some quasi-static spherical indentation tests are conducted on the materials with 40 preset constitutive relationships.The results indicate that the stress-strain curves predicted by the model align with the preset curves under 200 loading conditions.Moreover,the goodness-of-fit between the predicted stress-strain curves and the preset curves exceeds0.96 for all indenters and materials.In the end,the indentation tests are conducted by the spherical indenters with the diameters of 1.587 mm for fifteen metallic materials and1 mm for eight metallic materials.The results show that the stress-strain curves obtained by the spherical indentation based on the new model closely match those obtained from the uniaxial tensile tests.The relative errors for both the proof strength at 0.2%plastic extension and the tensile strength are below 5%.展开更多
文摘It has been ten years since 2011 when the first issue of Theoretical and Applied Mechanics Letters(TAML) came out. To date, TAML has published over 700 articles and 30 special issues covering a broad range of topics in mechanics. Such great achievements are even not possible without the continued dedication and support from authors, reviewers and editors. At this very special moment, I would like to express my sincere thanks to all of you, and hope you will continue to devote your time and effort s to the further advances of TAML.
基金Project supported by the National Natural Science Foundation of China(No.10876100)
文摘Based on the concept of constitutive relation error along with the residual of both origin and dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed in this paper. It leads to high quality local error bounds in the problem of fracture mechanics simulation with extended finite element method （XFEM）, which involves enrichment to solve a stress singularity in the crack. Since goal-oriented error estimation with enriched degrees of freedom gives us a chance to evaluate the XFEM simulation, the stress intensity factor calculated by two kinds of XFEM programs developed by ourselves and by commercial code ABAQUS are compared in this work. By comparing the reliability of the stress intensity factor calculation, the accuracy of two programs in different cases is evaluated and the source of error is discussed. A 2-dimensional XFEM example is given to illustrate the computational procedure.
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.
文摘This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.
基金Project supported by the National Natural Science Foundation of China(Nos.12502117,12272269,11972257)the Natural Science Foundation of Ningxia of China(No.2024AAC03018)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Shanghai Gaofeng Project for University Academic Program Development。
文摘Driven by the trend of device miniaturization and high-density integration,the interaction between adjacent electrodes has become a critical factor affecting the interfacial reliability of thermoelectric(TE)structures.This study investigates the influence of adjoining electrode interactions on the interfacial response of a multi-electrode/TE substrate structure,including interfacial stresses and stress intensity factors at the electrode ends.To solve the corresponding boundary-value problem,the Fourier transforms are adopted to derive a governing integro-differential equation for the interfacial shear stress in multi-electrode systems,incorporating the TE effects as generalized forces on the right-hand side.The results show that both the interfacial tension and transverse stress in the electrodes are significantly affected by the presence of adjacent electrodes.The interaction between neighboring electrodes diminishes as their spacing increases or when an adhesive interlayer is introduced.Furthermore,the softer and thinner electrodes,the softer and thicker adhesive interlayer,and the smaller TE loads are found to be beneficial for improving the interfacial performance.These findings may contribute to the accurate measurement in surface sensors and layout design of multi-point health monitoring systems for TE structures.
基金Project supported by the National Natural Science Foundation of China(No.12472077)the supports from Shanghai Gaofeng Project for University Academic Program Development,Fundamental Research Funds for the Central Universities(No.22120240353).
文摘Lattice materials have demonstrated promising potential in engineering applications owing to their exceptional lightweight,high specific strength,and tunable mechanical properties.However,the traditional homogenization methods based on the classical elasticity theory struggle to accurately describe the non-classical mechanical behaviors of lattice materials,especially when dealing with complex unit-cell geometries featured by non-symmetric configurations or non-single central node connections.In response to this limitation,this study establishes a generalized homogenization model based on the micropolar theory framework,employing Hill's boundary conditions to precisely predict the equivalent moduli of complex lattice materials.By introducing the independent rotational degree of freedom(DOF)characteristic of the micropolar theory,the proposed model successfully overcomes the limitation of conventional methods in accurately describing the asymmetric deformation and scale effects.We initially calculate the constitutive relations of two-dimensional(2D)cross-shaped multi-node chiral lattices and subsequently extend the method to three-dimensional(3D)lattices,successfully predicting the mechanical properties of both traditional and eccentric body-centered cubic(BCC)lattices.The theoretical model is validated through the finite element numerical verification which shows excellent consistency with the theoretical predictions.A further parametric study investigates the influence of geometric parameters,revealing the underlying size-effect mechanism.This paper provides a reliable theoretical tool for the design and property optimization of complex lattice materials.
基金supported by the National Heart,Lung,and Blood Institute,National Institutes of Health,as a Program of Excellence in Nanotechnology Award,N01 HV-08234,to Gang Baothe support from the National Natural Science Foundation of China through Grant Nos.10872115,11025208 and 10732050
文摘As an intriguing interdisciplinary research field, cell and molecular biomechanics is at the cutting edge of mechanics in general and biomechanics in particular. It has the potential to provide a quantitative understanding of how forces and deformation at tissue, cellular and molecular levels affect human health and disease. In this article, we review the recent advances in cell and molecular biomechanics, examine the available computational and experimental tools, and discuss important issues including protein deformation in mechanotransduction, cell deformation and constitutive behavior, cell adhesion and migration, and the associated models and theories. The opportunities and challenges in cell and molecular biomechanics are also discussed. We hope to provide readers a clear picture of the current status of this field, and to stimulate a broader interest in the applied mechanics community.
基金funded by the Cora Topolewski Cardiac Research Fund at the Children’s Hospital of Philadelphia(CHOP)the Pediatric Valve Center Frontier Program at CHOP+4 种基金the Additional Ventures Single Ventricle Research Fund Expansion Awardthe National Institutes of Health(USA)supported by the program(Nos.NHLBI T32 HL007915 and NIH R01 HL153166)supported by the program(No.NIH R01 HL153166)supported by the U.S.Department of Energy(No.DE-SC0022953)。
文摘Material identification is critical for understanding the relationship between mechanical properties and the associated mechanical functions.However,material identification is a challenging task,especially when the characteristic of the material is highly nonlinear in nature,as is common in biological tissue.In this work,we identify unknown material properties in continuum solid mechanics via physics-informed neural networks(PINNs).To improve the accuracy and efficiency of PINNs,we develop efficient strategies to nonuniformly sample observational data.We also investigate different approaches to enforce Dirichlet-type boundary conditions(BCs)as soft or hard constraints.Finally,we apply the proposed methods to a diverse set of time-dependent and time-independent solid mechanic examples that span linear elastic and hyperelastic material space.The estimated material parameters achieve relative errors of less than 1%.As such,this work is relevant to diverse applications,including optimizing structural integrity and developing novel materials.
文摘Rock salt has excellent properties for its use as underground leak‐proof containers for the storage of renewable energy.Salt solution mining has long been used for salt mining,and can now be employed in the construction of underground salt caverns for the storage of hydrogen gas.This paper presents a wide range of methods to study the mineralogy,geochemistry,microstructure and geomechanical characteristics of rock salt,which are important in the engineering of safe underground storage rock salt caverns.The mineralogical composition of rock salt varies and is linked to its depositional environment and diagenetic alterations.The microstructure in rock salt is related to cataclastic deformation,diffusive mass transfer and intracrystalline plastic deformation,which can then be associated with the macrostructural geomechanical behavior.Compared to other types of rock,rock salt exhibits creep at lower temperatures.This behavior can be divided into three phases based on the changes in strain with time.However,at very low effective confining pressure and high deviatoric stress,rock salt can exhibit dilatant behavior,where brittle deformation could compromise the safety of underground gas storage in rock salt caverns.The proposed review presents the impact of purity,geochemistry and water content of rock salt on its geomechanical behavior,and thus,on the safety of the caverns.
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.11832014 and 11472192)
文摘Any micromechanics model initially developed for predicting stiffness (elastic property) of a composite can be used to predict its strength with a reasonable accuracy,as long as the homogenized stresses in the matrix are converted into its true values. A critical assessment on the predictability of 14 famous micromechanics models for stiffness and strength of UD (unidirectional) composites was made in this work against the benchmark data provided in three world-wide failure exercises (WWFEs). Bridging Model exhibited the highest accuracy in both the stiffness and strength predictions. Moreover,it was the only consistent model in the internal stress calculation. Non-consistency implies that a full three-dimensional (3D)approach should be used to predict the effective property of the composite. The paper also showed that the smallest fiber volume in an RVE (representative volume element) led to the best approximation to a composite property.
基金supported by the National Natural Science Foundation of China (Grants 11372042, 11221202, 11532009, and 11202026)
文摘Transmembrane water pores are crucial for substance transport through cell membranes via membrane fusion, such as in neural communication. However, the molecular mechanism of water pore formation is not clear. In this study, we apply all-atom molecular dynamics and bias-exchange metadynamics simulations to study the process of water pore formation under an electric field. We show that water molecules can enter a membrane under an electric field and form a water pore of a few nanometers in diameter. These water molecules disturb the interactions between lipid head groups and the ordered arrangement of lipids. Following the movement of water molecules, the lipid head groups are rotated and driven into the hydrophobic region of the membrane. The reorientated lipid head groups inside the membrane form a hydrophilic surface of the water pore. This study reveals the atomic details of how an electric field influences the movement of water molecules and lipid head groups, resulting in water pore formation.
基金Project supported by the National Natural Science Foundation of China (No. 10876100)
文摘Based on the concept of the constitutive relation error along with the residuals of both the origin and the dual problems, a goal-oriented error estimation method with extended degrees of freedom is developed. It leads to the high quality locM error bounds in the problem of the direct-solution steady-state dynamic analysis with a frequency-domain finite element, which involves the enrichments with plural variable basis functions. The solution of the steady-state dynamic procedure calculates the harmonic response directly in terms of the physical degrees of freedom in the model, which uses the mass, damping, and stiffness matrices of the system. A three-dimensional finite element example is carried out to illustrate the computational procedures.
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFA1500302,2018YFA0605902)the National Natural Science Foundation of China(Grant Nos.20212024,42176241).
文摘1 Introduction The purpose of this special issue“Computational Mechanics of Granular Materials and its Engineering Applications”is to introduce the latest research progress in computational mechanics and engineering applications of granular materials,with particular emphasis on the theoretical constructions of arbitrarily shaped particles,flow pattern transitions,bond-fracture model,neural network algorithm,CFD-DEM coupled method,and coarse-graining model,and to improve our understanding of the physical and mechanical properties of granular systems from the perspective of practical engineering applications.
文摘The results of the tests for a friction pair “a cylindrical specimen made of 0.45% carbon steel—a counter specimen-liner made of polytetrafluoroethyleneF4-B” during sliding friction are presented. The test results at different levels of contact load are analyzed using the Archard’s equation and are presented as a friction fatigue curve. The concept of the frictional stress intensity factor during sliding friction is introduced, and an expression that relates the wear rate to this factor and is close in shape to the Paris equation in fracture mechanics is proposed.
文摘An ongoing project at McGill University is aimed at developing an adapted seismic screening method for schools in the province of Qu6bec, Canada. As part of this project the ＂FEMA 154 Rapid Visual Screening of Buildings for Potential Seismic Hazard＂ and the ＂NRC92 Manual for Screening of Buildings for Seismic Investigation＂ were used to assess 102 school buildings located in the city of Montr6al. Results for both methods are in reasonable agreement, with 65% of the buildings requiring a detailed evaluation according to FEMAI54 and 50% according to NRC92. Findings highlighted the particular characteristics of educational facilities： they are low rise buildings with high incidence of structural irregularities. Accounting for them in the screening phase is essential, and is better achieved by NRC92. However, this method is largely based on expert opinion, which makes it difficult to update, while FEMA154 uses a rational methodology for calculating vulnerability scores based on the capacity spectrum approach. The FEMA154 analytical procedure allows updating and adapting the method to its use outside its intended scope.
文摘Discovery of effect of force adaptation in mechanics is presented. The discovery is based on use of the mobile closed mechanical contour for force transfer from the mechanism input link to an output link, According to discovery the motion transfer can be carried out by Assur structural group in the form of the mobile closed contour, and the output link is the link with one degree of freedom. The received mechanical system includes an input link, an output link and the closed contour placed between them as fourth class Assur structural group. The kinematic chain has two degrees of freedom. However the closed contour imposes an additional constraint on relative motion of its links. The carried out discovery allows providing the variable transfer ratio only due to the variable external load. Mechanical properties of the closed contour allow providing the required transfer ratio independently, smart and automatically.
文摘Focal adhesions(FAs)are large,mmltiprotein complexs that provides linkers between cytoskeleton to the extracellular matrix(ECM).Cells sense and respond to forces through FAs to regulate a broad range of processes,such as cell growth,migration,differen-tiation and apoptosis.Currently,the underlying mechanisms of the force dependent mechanical properties/features of FAs have not yetbeen fully understood.Fa example,strong mechanical forces(inchuding those developed in some cases by cells themselves)can,obvi-ously,disrupt cell-cell and cell-matrix adhesions.However,recent experiments also demonstrated the existence of force dependentadhesian growth(rather than dissociation).
基金supported by grants from the National Natural Science Foundation of China,Nos 10628205,10732050,and 10872115
文摘Cells sense and respond to forces and extracellular environment through FAs to regulate a broad range of processes,such as cell growth,migration,differentiation and apoptosis.
文摘The field of mechanics of biological and bio-inspired materials underwent an exciting development over the past several years, which made it stand at the cutting edge of both engineering mechanics and biomechanics. As an intriguing interdisciplinary research field, it aims at elucidating the fundamental principles in nature＇s design of strong, multi-functional and smart Materials by focusing on the assembly, deformation, stability and failure of the materials.
基金Project supported by the National Natural Science Foundation of China(Nos.11872320 and 12072294)。
文摘A dimensionless load-displacement model based on the energy-density equivalence principle is proposed to obtain the stress-strain relationships of metallic materials under monotonic indentations with various diameters of spherical indenters.Finite element simulations are carried out to verify the constitutive relations from the new model,involving indentations made with various spherical indenters.For each indenter,some quasi-static spherical indentation tests are conducted on the materials with 40 preset constitutive relationships.The results indicate that the stress-strain curves predicted by the model align with the preset curves under 200 loading conditions.Moreover,the goodness-of-fit between the predicted stress-strain curves and the preset curves exceeds0.96 for all indenters and materials.In the end,the indentation tests are conducted by the spherical indenters with the diameters of 1.587 mm for fifteen metallic materials and1 mm for eight metallic materials.The results show that the stress-strain curves obtained by the spherical indentation based on the new model closely match those obtained from the uniaxial tensile tests.The relative errors for both the proof strength at 0.2%plastic extension and the tensile strength are below 5%.
