In this study,a simply supported functionally graded material beam with a giant magnetostrictive thin film(GMF)was selected as an energy harvester.Based on the theory of large deformation and the Villari effect of GMF...In this study,a simply supported functionally graded material beam with a giant magnetostrictive thin film(GMF)was selected as an energy harvester.Based on the theory of large deformation and the Villari effect of GMF,piston theory was used to simulate the dynamic equation of the whole structure under supersonic aerodynamic pressure and in a thermal environment by using Hamilton^principle,and the energy harvesting effect of GMF was simulated by using a Runge-Kutta algorithm.Below the critical flutter velocity,the maximum voltage output and energy harvesting results were discussed as they were affected by external factors such as the geometric model of structure parameters,slenderness ratio,gradient index,number of turns of an electromagnetic coil,airflow velocity,and temperature.The electromechanical coupling coefficient/C33 was 71%.The results show that this proposed harvester can achieve an optimal harvesting effect by adjusting the parameters appropriately,and collect energy in thermal and supersonic environments using the GMF,which provides power to sensors of the health monitoring system of the aircraft’s own structure.展开更多
The current collector fracture failure of lithium-ion batteries(LIBs)occurs during its winding production process frequently,and the consequent damages are usually large,but little research has been conducted on this ...The current collector fracture failure of lithium-ion batteries(LIBs)occurs during its winding production process frequently,and the consequent damages are usually large,but little research has been conducted on this phenomenon.This work stems from the difficulty and obstacles in the winding process of actual production of LIBs.The fracture failure of the current collectors is easily caused by the evolution and mutation of the mechanical behavior during the winding process,resulting in safety hazards and poor efficiency.The purpose of this work is to reveal the evolution and distribution mechanism of circumferential strain of the current collectors on the fracture failure under the constraint of winding process.Experimental tests,finite element calculations and theoretical model are used to study the evolution and distribution of circumferential strain.The dynamic evolution process of circumferential strain is tested accurately,and the mechanism of fracture failure of current collectors is revealed.The criterion for current collector strength is proposed based on the results of strain analysis and SEM observation.展开更多
The transient response in a bi-material cylinder of soft ferromagnetic material under magnetic shock is investigated in this study.The analytical solutions for displacement and stress have been derived using the finit...The transient response in a bi-material cylinder of soft ferromagnetic material under magnetic shock is investigated in this study.The analytical solutions for displacement and stress have been derived using the finite Hankel transform and the Laplace transform.The numerical examples show that the displacement and stress fields respond dynamically in the bi-material cylinder under magnetic shock.The derived displacement at the center and radial stress on the surface of the cylinder satisfy the boundary conditions,showing the correctness of calculation.The displacement and stress waves propagate from the surface to the center of the cylinder when the magnetic field is loaded.The stress fields increase from the center to the surface of the cylinder and are much larger than the quasi-static state since the waves reflect,collide and concentrate in the body of the cylinder.The method of this paper can be used in the design of soft ferromagnetic structures.展开更多
Plasticized polyvinyl chloride(PVC)gel is a type of electroactive polymers,which has potentials to be applied as soft actuators.However,few studies have been performed to investigate the mechanical responses of PVC ge...Plasticized polyvinyl chloride(PVC)gel is a type of electroactive polymers,which has potentials to be applied as soft actuators.However,few studies have been performed to investigate the mechanical responses of PVC gels in cyclic loading conditions.In this work,we combined experiments and theory to characterize the mechanical responses of two plasticized PVC gels.The gels were subjected to different types of loading-unloading-reloading cycles.The experimental results showed that the plasticized PVC gels exhibited stress softening response(the Mullins effect)in the cyclic tests.Meanwhile,the gels regained some strength after annealing at room temperature for several hours,indicating the self-healing ability of gels.We further extended the eight-chain model with incorporation of the chain dissociation and reassociation mechanism.The developed constitutive model is able to reproduce the Mullins effect and the recovery of the Mullins effect observed in the experiments.Our results clearly show that understanding the complex mechanical response is crucial for the applications of plasticized PVC gels.展开更多
This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests.We propose simplified numerical modeling to examine the effects of particle size and coordination...This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests.We propose simplified numerical modeling to examine the effects of particle size and coordination number on particle breakage behavior.We validate the proposed modeling by comparing the numerical results with the experimental data reported in the literature,in terms of the variability of particle tensile strength and axial force-displacement responses.Based on the numerical results,it is clear that a larger particle size entails a higher tensile strength with a larger discreteness.In addition,the characteristic tensile strength increases linearly with an increasing coordination number.Moreover,smaller particles are more susceptible to the cushion effect than larger particles.The numerical results also indicate that an increasing coordination number induces a more ductile mode of failure.Based on these results,we propose an empirical equation for calculating tensile strength,incorporating both the cushion effect and the size effect.展开更多
Correction To:Acta Mechanica Solida Sinica https://doi.org/10.1007/s10338-019-00107-5 Unfortunately due to a typesetting mistake in the caption of Fig.1,fourth line,仏has been displayed wrongly as/2-The original artic...Correction To:Acta Mechanica Solida Sinica https://doi.org/10.1007/s10338-019-00107-5 Unfortunately due to a typesetting mistake in the caption of Fig.1,fourth line,仏has been displayed wrongly as/2-The original article has been corrected.展开更多
A new method for structural damage identification is presented based on perturbations of curvature mode shape and frequency.Firstly,the structure's mass and stiffness matrices are expressed as functions of its ele...A new method for structural damage identification is presented based on perturbations of curvature mode shape and frequency.Firstly,the structure's mass and stiffness matrices are expressed as functions of its elements'physical parameters,which reflect their damage states. According to differences in the curvature mode shape of the structure in undamaged and damaged states,possible damage equations and determined damage equations are established and used to solve for the elements'damage parameters.Then,to ensure the accuracy of the recognition result,a reasonable solution is substituted into a damage-checking equation based on the change of frequency of the damaged structure.Numerical examples are used to show that,to identify the damage,only one order mode needs to be tested.When the degree of damage is low, first-order perturbation equations can be used to recognize the damage with sufficient accuracy. If the extent of the damage is high,second-order perturbation equations can be used to provide more accurate identification results.展开更多
A multi-scale model is developed to link the continuum damage variable in macroscale to the number density of multiple pits and cracks in microscale for studying the corrosion fatigue of aluminum alloy from multi-scal...A multi-scale model is developed to link the continuum damage variable in macroscale to the number density of multiple pits and cracks in microscale for studying the corrosion fatigue of aluminum alloy from multi-scale viewpoint.The developed model is used to predict the coherent multi-scale corrosion fatigue process of aluminum alloy component in the 3.5 wt% NaC1water solution under constant stress amplitude at a nominal frequency of 5Hz, and the numerical prediction results are compared with the experimental results.It shows that the model is effective and can be used to study the corrosion fatigue mechanisms of alurninum alloy from both macro and microscale viewpoints.展开更多
Plain concrete is regarded as a two-phase material comprising randomly distributed aggregates and mortar matrix. A series of three-point bending concrete beams with symmetric or asymmetric double notches are modeled u...Plain concrete is regarded as a two-phase material comprising randomly distributed aggregates and mortar matrix. A series of three-point bending concrete beams with symmetric or asymmetric double notches are modeled using the modified random aggregate generation and packing algorithm. The cohesive zone model is used as the fracture criterion and the cohesive elements are inserted into both the mortar matrix and the aggregate-mortar interfaces as potential micro-cracking zones. The dead and alive crack phenomena are studied experimentally and numerically; and the influences of notch location, aggregate distribution and gradation on fracture are numerically evaluated. Some important conclusions are given.展开更多
To compensate for the imperfection of traditional bi-directional evolutionary structural optimization, material interpolation scheme and sensitivity filter functions are introduced. A suitable filter can overcome the ...To compensate for the imperfection of traditional bi-directional evolutionary structural optimization, material interpolation scheme and sensitivity filter functions are introduced. A suitable filter can overcome the checkerboard and mesh-dependency. And the historical information on accurate elemental sensitivity numbers are used to keep the objective function converging steadily. Apart from rational intervals of the relevant important parameters, the concept of distinguishing between active and non-active elements design is proposed, which can be widely used for improving the function and artistry of structures directly, especially for a one whose accurate size is not given. Furthermore, user-friendly software packages are developed to enhance its accessibility for practicing engineers and architects. And to reduce the time cost for large timeconsuming complex structure optimization, parallel computing is built-in in the MATLAB codes.The program is easy to use for engineers who may not be familiar with either FEA or structure optimization. And developers can make a deep research on the algorithm by changing the MATLAB codes. Several classical examples are given to show that the improved BESO method is superior for its handy and utility computer program software.展开更多
Through the Galerkin method the nonlinear ordinary differential equations(ODEs)in time are obtained from the nonlinear partial differential equations(PDEs) to describe the motion of the coupled structure of a suspende...Through the Galerkin method the nonlinear ordinary differential equations(ODEs)in time are obtained from the nonlinear partial differential equations(PDEs) to describe the motion of the coupled structure of a suspended-cable-stayed beam. In the PDEs, the curvature of main cables and the deformation of cable stays are taken into account. The dynamics of the structure is investigated based on the ODEs when the structure is subjected to a harmonic excitation in the presence of both high-frequency principle resonance and 1:2 internal resonance. It is found that there are typical jumps and saturation phenomena of the vibration amplitude in the structure. And the structure may present quasi-periodic vibration or chaos, if the stiffness of the cable stays membrane and frequency of external excitation are disturbed.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 understand...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
Two kinds of fractures can be observed in the SPH(smoothed particle hydrodynamics) simulations,which are the physical fracture and the numerical fracture.The physical one exists in reality,while the numerical one is f...Two kinds of fractures can be observed in the SPH(smoothed particle hydrodynamics) simulations,which are the physical fracture and the numerical fracture.The physical one exists in reality,while the numerical one is fictitious.This paper presents the effects of both fractures and proposes a simple adding particle technique to avoid the numerical fracture.The real physical fracture is then figured out by using an applicable fracture criterion.Firstly,the effect of the numerical fracture on the computational accuracy is investigated by introducing the artificial fracture in a model of wave propagation.Secondly,a simple adding particle technique is proposed and validated by a three dimensional bending test.Finally,the experiments of penetration on the skin of aircrafts are simulated by both the initial SPH method and the improved method with the adding particle technique.The results show that the improved SPH method can describe the physical fracture very well with better accuracy.展开更多
The free vibration analysis of cylindrical helical springs is carried out by means of an analytical study.In the governing equations of the motion of the springs,all displacement functions are defined at the centroid ...The free vibration analysis of cylindrical helical springs is carried out by means of an analytical study.In the governing equations of the motion of the springs,all displacement functions are defined at the centroid axis and also the effects of the rotational inertia,axial and shear deformations are included in the proposed model.Explicit analytical expressions which give the vibrating mode shapes are derived by rigorous application of the symbolic computing package MATHEMATICA and a process of searching is used to determine the exact natural frequencies.Numerical examples are provided for fixed-fixed boundary conditions.The free vibrational parameters are chosen as the number of coils(n=4 ～ 14),the helix pitch angle(α=5 ～ 30?) and as the ratio of the diameters of the cylinder and the wire(D/d=4 ～ 18) in a wide range.Validation of the proposed model has been achieved through comparison with a finite element model using two-node standard beam elements and the results available in published literature,which in these cases indicates a very good correlation.展开更多
Interaction between a screw dislocation dipole and a mode III interface crack is investigated. By using the complex variable method, the closed form solutions for complex potentials are obtained when a screw dislocati...Interaction between a screw dislocation dipole and a mode III interface crack is investigated. By using the complex variable method, the closed form solutions for complex potentials are obtained when a screw dislocation dipole lies inside a medium. The stress fields and the stress intensity factors at the tip of the interface crack produced by the screw dislocation dipole are given. The influence of the orientation, the dipole arm and the location of the screw dislocation dipole as well as the material mismatch on the stress intensity factors is discussed. The image force and the image torque acting on the screw dislocation dipole center are also calculated. The mechanical equilibrium position of the screw dislocation dipole is examined for various material property combinations and crack geometries. The results indicate that the shielding or anti-shielding effect on the stress intensity factor increases abruptly when the dislocation dipole approaches the tip of the crack. Additionally, the disturbation of the interface crack on the motion of the dislocation dipole is also significant.展开更多
According to the basic idea of classical Yin-Yang complementarity and modern dual-complementarity,in a simple and unified new way proposed by Luo,the unconventional Gurtin-type variational prinicples for finite deform...According to the basic idea of classical Yin-Yang complementarity and modern dual-complementarity,in a simple and unified new way proposed by Luo,the unconventional Gurtin-type variational prinicples for finite deformation elastodynamics can be established systemati-cally.In this paper,an important integral relation in terms of convolution is given,which canbe considered as the expression of the generalized principle of virtual work for finite deformationdynamics.Based on this relation,it is possible not only to obtain the principle of virtual work forfinite deformation dynamics,but also to derive systematically the complementary functionals forfive-field,three-field,two-field and one-field unconventional Gurtin-type variational principles bythe generalized Legendre transformations given in this paper.Furthermore,with this approach,the intrinsic relationship among various principles can be clearly explained.展开更多
By using the logarithmic strain, the finite deformation plastic theory, corresponding to the infinitesimal plastic theory, is established successively. The plastic consistent algorithm with first order accuracy for th...By using the logarithmic strain, the finite deformation plastic theory, corresponding to the infinitesimal plastic theory, is established successively. The plastic consistent algorithm with first order accuracy for the finite element method (FEM) is developed. Numerical examples are presented to illustrate the validity of the theory and effectiveness of the algorithm.展开更多
基金the National Natural Science Foundation of China(Grant Nos.12022213,11772205,11902203,and 12002217)Liaoning Revitalization Talents Program(XLYC1807172).
文摘In this study,a simply supported functionally graded material beam with a giant magnetostrictive thin film(GMF)was selected as an energy harvester.Based on the theory of large deformation and the Villari effect of GMF,piston theory was used to simulate the dynamic equation of the whole structure under supersonic aerodynamic pressure and in a thermal environment by using Hamilton^principle,and the energy harvesting effect of GMF was simulated by using a Runge-Kutta algorithm.Below the critical flutter velocity,the maximum voltage output and energy harvesting results were discussed as they were affected by external factors such as the geometric model of structure parameters,slenderness ratio,gradient index,number of turns of an electromagnetic coil,airflow velocity,and temperature.The electromechanical coupling coefficient/C33 was 71%.The results show that this proposed harvester can achieve an optimal harvesting effect by adjusting the parameters appropriately,and collect energy in thermal and supersonic environments using the GMF,which provides power to sensors of the health monitoring system of the aircraft’s own structure.
基金National Natural Science Foundation of China(12002183)Postdoctoral Science Foundation(2019TQ0171,2020M670304)Beijing Natural Science Foundation(Grant Nos.16L00001 and 2182065)are Rratefullv acknowledged.
文摘The current collector fracture failure of lithium-ion batteries(LIBs)occurs during its winding production process frequently,and the consequent damages are usually large,but little research has been conducted on this phenomenon.This work stems from the difficulty and obstacles in the winding process of actual production of LIBs.The fracture failure of the current collectors is easily caused by the evolution and mutation of the mechanical behavior during the winding process,resulting in safety hazards and poor efficiency.The purpose of this work is to reveal the evolution and distribution mechanism of circumferential strain of the current collectors on the fracture failure under the constraint of winding process.Experimental tests,finite element calculations and theoretical model are used to study the evolution and distribution of circumferential strain.The dynamic evolution process of circumferential strain is tested accurately,and the mechanism of fracture failure of current collectors is revealed.The criterion for current collector strength is proposed based on the results of strain analysis and SEM observation.
基金supported by the National Natural Science Foundation of China under Grant No.11802145Jiangsu Provincial Natural Science Foundation of China under Grant No.BK20191450.
文摘The transient response in a bi-material cylinder of soft ferromagnetic material under magnetic shock is investigated in this study.The analytical solutions for displacement and stress have been derived using the finite Hankel transform and the Laplace transform.The numerical examples show that the displacement and stress fields respond dynamically in the bi-material cylinder under magnetic shock.The derived displacement at the center and radial stress on the surface of the cylinder satisfy the boundary conditions,showing the correctness of calculation.The displacement and stress waves propagate from the surface to the center of the cylinder when the magnetic field is loaded.The stress fields increase from the center to the surface of the cylinder and are much larger than the quasi-static state since the waves reflect,collide and concentrate in the body of the cylinder.The method of this paper can be used in the design of soft ferromagnetic structures.
基金This work is supported by the National Natural Science Foundation of China(Grant No.12022204)the Fundamental Research Funds for the Central Universities(Grant No.2021FZZX001-16).
文摘Plasticized polyvinyl chloride(PVC)gel is a type of electroactive polymers,which has potentials to be applied as soft actuators.However,few studies have been performed to investigate the mechanical responses of PVC gels in cyclic loading conditions.In this work,we combined experiments and theory to characterize the mechanical responses of two plasticized PVC gels.The gels were subjected to different types of loading-unloading-reloading cycles.The experimental results showed that the plasticized PVC gels exhibited stress softening response(the Mullins effect)in the cyclic tests.Meanwhile,the gels regained some strength after annealing at room temperature for several hours,indicating the self-healing ability of gels.We further extended the eight-chain model with incorporation of the chain dissociation and reassociation mechanism.The developed constitutive model is able to reproduce the Mullins effect and the recovery of the Mullins effect observed in the experiments.Our results clearly show that understanding the complex mechanical response is crucial for the applications of plasticized PVC gels.
基金the National Natural Science Foundation of China(Grant Nos.51971188 and 51071134)the Science and Technology Major Project of Hunan Province(Grant No.2019GK 1012)+1 种基金Huxiang High-Level Talent Gathering Program of Hunan Province-In novative team(Grant No.2019RS1059)the Degree and Postgraduate Education Reform Project of Hunan Province(Grant No,CX20190493),All of this support is gratefully acknowledged.
文摘This paper uses the discrete element method to model the size and cushion effects during single-particle crushing tests.We propose simplified numerical modeling to examine the effects of particle size and coordination number on particle breakage behavior.We validate the proposed modeling by comparing the numerical results with the experimental data reported in the literature,in terms of the variability of particle tensile strength and axial force-displacement responses.Based on the numerical results,it is clear that a larger particle size entails a higher tensile strength with a larger discreteness.In addition,the characteristic tensile strength increases linearly with an increasing coordination number.Moreover,smaller particles are more susceptible to the cushion effect than larger particles.The numerical results also indicate that an increasing coordination number induces a more ductile mode of failure.Based on these results,we propose an empirical equation for calculating tensile strength,incorporating both the cushion effect and the size effect.
文摘Correction To:Acta Mechanica Solida Sinica https://doi.org/10.1007/s10338-019-00107-5 Unfortunately due to a typesetting mistake in the caption of Fig.1,fourth line,仏has been displayed wrongly as/2-The original article has been corrected.
基金National Natural Science Foundation of China (No.11402090)Key Scientific Research Projects in Colleges and Universities of Henan Province (No.17B130001,No.19A560014)Science and Technology Project of Henan Province (No.182102310890).
文摘A new method for structural damage identification is presented based on perturbations of curvature mode shape and frequency.Firstly,the structure's mass and stiffness matrices are expressed as functions of its elements'physical parameters,which reflect their damage states. According to differences in the curvature mode shape of the structure in undamaged and damaged states,possible damage equations and determined damage equations are established and used to solve for the elements'damage parameters.Then,to ensure the accuracy of the recognition result,a reasonable solution is substituted into a damage-checking equation based on the change of frequency of the damaged structure.Numerical examples are used to show that,to identify the damage,only one order mode needs to be tested.When the degree of damage is low, first-order perturbation equations can be used to recognize the damage with sufficient accuracy. If the extent of the damage is high,second-order perturbation equations can be used to provide more accurate identification results.
基金Fundamental Research Funds for the Central Universities,Natural Science Foundation of Jiangsu Province (BK20170655,BK20170677),and the National Program on Key Research Project (2016YFC0701301-02).
文摘A multi-scale model is developed to link the continuum damage variable in macroscale to the number density of multiple pits and cracks in microscale for studying the corrosion fatigue of aluminum alloy from multi-scale viewpoint.The developed model is used to predict the coherent multi-scale corrosion fatigue process of aluminum alloy component in the 3.5 wt% NaC1water solution under constant stress amplitude at a nominal frequency of 5Hz, and the numerical prediction results are compared with the experimental results.It shows that the model is effective and can be used to study the corrosion fatigue mechanisms of alurninum alloy from both macro and microscale viewpoints.
基金Project supported by the National Basic Research Program of China(973 Program:No.2011CB013800)Hubei Provincial Natural Science Foundation of China(No.2015CFB205)
文摘Plain concrete is regarded as a two-phase material comprising randomly distributed aggregates and mortar matrix. A series of three-point bending concrete beams with symmetric or asymmetric double notches are modeled using the modified random aggregate generation and packing algorithm. The cohesive zone model is used as the fracture criterion and the cohesive elements are inserted into both the mortar matrix and the aggregate-mortar interfaces as potential micro-cracking zones. The dead and alive crack phenomena are studied experimentally and numerically; and the influences of notch location, aggregate distribution and gradation on fracture are numerically evaluated. Some important conclusions are given.
基金supported by the National Natural Science Foundation of China(No.51078311)
文摘To compensate for the imperfection of traditional bi-directional evolutionary structural optimization, material interpolation scheme and sensitivity filter functions are introduced. A suitable filter can overcome the checkerboard and mesh-dependency. And the historical information on accurate elemental sensitivity numbers are used to keep the objective function converging steadily. Apart from rational intervals of the relevant important parameters, the concept of distinguishing between active and non-active elements design is proposed, which can be widely used for improving the function and artistry of structures directly, especially for a one whose accurate size is not given. Furthermore, user-friendly software packages are developed to enhance its accessibility for practicing engineers and architects. And to reduce the time cost for large timeconsuming complex structure optimization, parallel computing is built-in in the MATLAB codes.The program is easy to use for engineers who may not be familiar with either FEA or structure optimization. And developers can make a deep research on the algorithm by changing the MATLAB codes. Several classical examples are given to show that the improved BESO method is superior for its handy and utility computer program software.
基金supported by the National Natural Science Foundation of China(Nos.10672121 and 11072125)
文摘Through the Galerkin method the nonlinear ordinary differential equations(ODEs)in time are obtained from the nonlinear partial differential equations(PDEs) to describe the motion of the coupled structure of a suspended-cable-stayed beam. In the PDEs, the curvature of main cables and the deformation of cable stays are taken into account. The dynamics of the structure is investigated based on the ODEs when the structure is subjected to a harmonic excitation in the presence of both high-frequency principle resonance and 1:2 internal resonance. It is found that there are typical jumps and saturation phenomena of the vibration amplitude in the structure. And the structure may present quasi-periodic vibration or chaos, if the stiffness of the cable stays membrane and frequency of external excitation are disturbed.
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supported by the National Natural Science Foundation of China (No.10577016)the 111 Project (No. B07050)the program for 2008 New Century Excellent Talents in University (No.NCET080454)
文摘Two kinds of fractures can be observed in the SPH(smoothed particle hydrodynamics) simulations,which are the physical fracture and the numerical fracture.The physical one exists in reality,while the numerical one is fictitious.This paper presents the effects of both fractures and proposes a simple adding particle technique to avoid the numerical fracture.The real physical fracture is then figured out by using an applicable fracture criterion.Firstly,the effect of the numerical fracture on the computational accuracy is investigated by introducing the artificial fracture in a model of wave propagation.Secondly,a simple adding particle technique is proposed and validated by a three dimensional bending test.Finally,the experiments of penetration on the skin of aircrafts are simulated by both the initial SPH method and the improved method with the adding particle technique.The results show that the improved SPH method can describe the physical fracture very well with better accuracy.
基金supported by the National Natural Science Foundation of China (No.10572105)the Shanghai Leading Academic Discipline Project (No.B302)
文摘The free vibration analysis of cylindrical helical springs is carried out by means of an analytical study.In the governing equations of the motion of the springs,all displacement functions are defined at the centroid axis and also the effects of the rotational inertia,axial and shear deformations are included in the proposed model.Explicit analytical expressions which give the vibrating mode shapes are derived by rigorous application of the symbolic computing package MATHEMATICA and a process of searching is used to determine the exact natural frequencies.Numerical examples are provided for fixed-fixed boundary conditions.The free vibrational parameters are chosen as the number of coils(n=4 ～ 14),the helix pitch angle(α=5 ～ 30?) and as the ratio of the diameters of the cylinder and the wire(D/d=4 ～ 18) in a wide range.Validation of the proposed model has been achieved through comparison with a finite element model using two-node standard beam elements and the results available in published literature,which in these cases indicates a very good correlation.
基金Project supported by the National Natural Science Foundation of China (No. 10472030).
文摘Interaction between a screw dislocation dipole and a mode III interface crack is investigated. By using the complex variable method, the closed form solutions for complex potentials are obtained when a screw dislocation dipole lies inside a medium. The stress fields and the stress intensity factors at the tip of the interface crack produced by the screw dislocation dipole are given. The influence of the orientation, the dipole arm and the location of the screw dislocation dipole as well as the material mismatch on the stress intensity factors is discussed. The image force and the image torque acting on the screw dislocation dipole center are also calculated. The mechanical equilibrium position of the screw dislocation dipole is examined for various material property combinations and crack geometries. The results indicate that the shielding or anti-shielding effect on the stress intensity factor increases abruptly when the dislocation dipole approaches the tip of the crack. Additionally, the disturbation of the interface crack on the motion of the dislocation dipole is also significant.
基金Project supported by the National Natural Science Foundation of China (Nos. 50335030, 50505033 and 50575171)National Basic Research Program of China (No. 2005CB724106)Doctoral Program Foundation of University of China(No. 20040698026)
文摘在间隔(BSWI ) 上基于 B 花键小浪，截断的圆锥形的壳元素的二个班被构造解决 axisymmetric 问题，即 BSWI 薄截断的圆锥形的壳元素和 BSWI 有独立斜坡变丑插值的中等厚的截断的圆锥形的壳元素。在基于小浪的元素的构造，而不是传统的多项式插值， BSWI 的可伸缩的功能被采用经由变化原则通过构造元素的转变矩阵，然后构造 BSWI 元素形成形状功能。不同于把小浪 Galerkin 方法加在一起的直接小浪的进程，小浪扩大的系数代表的元素的排水量域经由构造转变矩阵被转变成边和内部模式。BSWI 元素为结构的分析联合 B 花键功能近似和各种各样的基于小浪的元素的精确性。圆锥形的壳的一些静态、动态的数字例子被学习比传统的元素与更高的效率和精确表明现在的元素。
基金Project supported by the National Science Fund of Distinguished Young Scholars (No.10025211) the NJTU Paper Foundation (No.PD250) and the China Postdoctoral Science Foundation.
基金Project supported by the National Natural Science Foundation of China(Nos.10172097,19902022 and 19672074)
文摘According to the basic idea of classical Yin-Yang complementarity and modern dual-complementarity,in a simple and unified new way proposed by Luo,the unconventional Gurtin-type variational prinicples for finite deformation elastodynamics can be established systemati-cally.In this paper,an important integral relation in terms of convolution is given,which canbe considered as the expression of the generalized principle of virtual work for finite deformationdynamics.Based on this relation,it is possible not only to obtain the principle of virtual work forfinite deformation dynamics,but also to derive systematically the complementary functionals forfive-field,three-field,two-field and one-field unconventional Gurtin-type variational principles bythe generalized Legendre transformations given in this paper.Furthermore,with this approach,the intrinsic relationship among various principles can be clearly explained.
文摘By using the logarithmic strain, the finite deformation plastic theory, corresponding to the infinitesimal plastic theory, is established successively. The plastic consistent algorithm with first order accuracy for the finite element method (FEM) is developed. Numerical examples are presented to illustrate the validity of the theory and effectiveness of the algorithm.
