In order to study the critical load position that causes cavities beneath the continuously reinforced concrete pavement（ CRCP） slab under vehicle loading, the elliptical load is translated into the square load based...In order to study the critical load position that causes cavities beneath the continuously reinforced concrete pavement（ CRCP） slab under vehicle loading, the elliptical load is translated into the square load based on the equivalence principle.The CRCP slab is analyzed to determine the cavity position beneath the slab under vehicle loading. The influences of cavity size on the CRCP slab＇s stress and vertical displacement are investigated. The study results showthat the formation of the cavity is unavoidable under traffic loading, and the cavity is located at the edge of the longitudinal crack and the slab corner.The cavity size exerts an obvious influence on the largest horizontal tensile stress and vertical displacement. The slab corner is the critical load position of the CRCP slab. The results can be used to assist the design of CRCP in avoiding cavities beneath slabs subject to vehicle loading.展开更多
The current acid deposition critical loads in Guangdong, China were calculated using the PROFILE model with a 3 km × 3 km resolution. Calculations were carded out for critical loads of potential acidity, actual a...The current acid deposition critical loads in Guangdong, China were calculated using the PROFILE model with a 3 km × 3 km resolution. Calculations were carded out for critical loads of potential acidity, actual acidity, sulfur and nitrogen, with values in extents of 0-3.5, 0-14.0, 0-26.0 and 0-3.5 kmol/（hrnE.year）, respectively. These values were comparable to previously reported results and reflected the influences of vegetation and soil characteristics on the soil acid buffering capacity. Simulations of SO2 emission and sulfur deposition in this study showed that sulfur deposition core areas mirrored SO2 emission centers. The prediction of sulfur deposition after 20% and 40% reduction of SO2 emission suggested that the reduction of area sources contributed greatly to the decrease of sulfur deposition. Thus, abatement of area source emissions could be the primary way to mitigate sulfur deposition in Guangdong to meet both the provincial and national regulations of air pollution control.展开更多
In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematica...In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematical model predicting the critical load is proposed for calculating critical load as determined byscratch testing. The factors for correctly evaluating adhesion of coatings according to the experimental data arediscussed.展开更多
This paper presents a newly developed proximity indicator for voltage stability assessment which can be used to predict critical real system load and voltages at various load buses at critical loading point.The proxim...This paper presents a newly developed proximity indicator for voltage stability assessment which can be used to predict critical real system load and voltages at various load buses at critical loading point.The proximity indicator varies almost parabolic with total real load demand and reaches orthogonally to real load axis.This relation has been utilized to predict critical loading point.It has been shown that two operating points are needed for estimating critical point and proper selection of operating points and variation of proximity indicator near collapse point highly affect the accuracy of estimation.Simulation is based on load flow equations and system real and reactive loadings have been increased in proportion with base case scenario for IEEE 14 and IEEE 25 bus test systems to demonstrate the behaviour of proposed proximity indicator.CPF has been used as benchmark to check the accuracy of estimation.展开更多
In this paper, a set of variational formulas of solving nonlinear instability critical loads are established from the viewpoint of variational principle. The paper shows that it is very convenient to solve nonlinear i...In this paper, a set of variational formulas of solving nonlinear instability critical loads are established from the viewpoint of variational principle. The paper shows that it is very convenient to solve nonlinear instability critical load by using the variational formulas suggested in this paper.展开更多
Advanced design based on the concept of orthotropic structure includes better use of materials, less weight compared to the equivalent isotropic construction and controlled effectively reserve resistance in all its se...Advanced design based on the concept of orthotropic structure includes better use of materials, less weight compared to the equivalent isotropic construction and controlled effectively reserve resistance in all its segments. In this case a calculation of critical load is exposed using the FDM （Finite Difference Method） concept of thin plates subjected to complex loads due to forces in the middle-plane. Results of calculation model, discussed in this paper, are given in graphic form. Presented results should serve as an indicator of the expansion of theoretical base of similar models, which can be reasonably use by researchers and engineers in their practices, and by students for educational purposes.展开更多
The promotion of recent critical load securing of power system research has been directed towards centralized commands and control functions.This paper presents a multi-agent based critical load securing in a PV based...The promotion of recent critical load securing of power system research has been directed towards centralized commands and control functions.This paper presents a multi-agent based critical load securing in a PV based microgrid.For the trustworthy operation of critical buildings,the reliability,efficiency and security of the power system should be guaranteed.At present,to increase the security and reliability of electricity supply there is a need to design a distributed and autonomous subset of a larger grid or a microgrid.This work also clearly discusses the modelling and simulation of specialized microgrid called an Intelligent Distributed Autonomous Power Systems(IDAPS).The IDAPS microgrid plays a crucial role in constructing power grid that facilitate use of renewable energy technologies.IDAPS microgrid comprising of solar photovoltaic as distributed energy resources,different loads and their control algorithms,has been developed.Several case studies have been simulated to evaluate the operation of the IDAPS microgrid during parallel,islanded mode operation and securing critical loads during emergency.展开更多
A method described is to produce critical load maps of acid deposition for soils in China. Critical loads were assigned to the most sensitive soil in each 0.1°×0.1° grid square of China based on the Sko...A method described is to produce critical load maps of acid deposition for soils in China. Critical loads were assigned to the most sensitive soil in each 0.1°×0.1° grid square of China based on the Skokloster classification [1] and adjusted for temperature and land use. The map shows that soils with small critical load (<0.5keq·ha -1 ·a -1 ) i.e., highly sensitive to acid deposition, dominate in the south and northeast China. As a result of the adjustment, much of the acid sensitive area in the south estimated by the Skokloster method is lost. This reflects the decreased sensitivity as a result of agricultural activities and increased weathering rate in response to high temperature. Based on the 0.1°×0.1° map, a series of percentile critical load maps at 1°×1° scale were compiled for integrated assessments, as well as a critical load map using the minimum critical load for each grid. Comparison of critical loads with sulphur deposition in 1995 led to the critical load exceedance maps for sulphur deposition, which show that high exceedance areas do not correlate well with the low critical load areas, and almost one fourth of the land area, mainly in the southeast, is subject to the risk of acidification.展开更多
By means of the theory of universal unfolding, the influence of multi-imperfections upon the critical load of structure in engineering is analysed in this paper. For the pitchfork problem, a lower bound of increments ...By means of the theory of universal unfolding, the influence of multi-imperfections upon the critical load of structure in engineering is analysed in this paper. For the pitchfork problem, a lower bound of increments of the critical loads caused by imperfections of the structures is given. A simple and available numerical method for computing the lower bound is described.展开更多
In this paper, after taking th e effect of axis force on bending into consideration, the general potential ener gy for the circular double articulated arch is established undergoing vertical d istributive load g 0/...In this paper, after taking th e effect of axis force on bending into consideration, the general potential ener gy for the circular double articulated arch is established undergoing vertical d istributive load g 0/ cos 2θ . With sufficient engineering precision, the fourth approximations to the destabilizing critical load of the arch under t his load are obtained by Ritz method. The approximations to the critical load ta ble are listed for various center angles of arch, and are contrasted with the cr itical load circular arch undergoing radial uniform load. Some reference results have been obtained.展开更多
Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance i...Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.展开更多
Dynamical responses, such as motion and destruction of hyper-elastic cylindrical shells subject to periodic or suddenly applied constant load on the inner surface, are studied within a framework of finite elasto-dynam...Dynamical responses, such as motion and destruction of hyper-elastic cylindrical shells subject to periodic or suddenly applied constant load on the inner surface, are studied within a framework of finite elasto-dynamics. By numerical computation and dynamic qualitative analysis of the nonlinear differential equation, it is shown that there exists a certain critical value for the internal load describing motion of the inner surface of the shell. Motion of the shell is nonlinear periodic or quasi-periodic oscillation when the average load of the periodic load or the constant load is less than its critical value. However, the shell will be destroyed when the load exceeds the critical value. Solution to the static equilibrium problem is a fixed point for the dynamical response of the corresponding system under a suddenly applied constant load. The property of fixed point is related to the property of the dynamical solution and motion of the shell. The effects of thickness and load parameters on the critical value and oscillation of the shell are discussed.展开更多
According to the Mohr-Coulomb yield criterion, the stress field of the infinite slope is derived under a vertical uniform load q on the top of the slope. It is indicated that elastic and elasto-plastic states would oc...According to the Mohr-Coulomb yield criterion, the stress field of the infinite slope is derived under a vertical uniform load q on the top of the slope. It is indicated that elastic and elasto-plastic states would occur in the slope. When q is smaller than the critical load, q(p), the slope is in the elastic state. If q equals q(p), the slope is in the critical state, and the plastic deformation would occur along the critical angle. With the increase of q, the plastic zone would extend, and the slope is in the elasto-plastic State. If q equals limit load, the slope is in the limit equilibrium state. The slope may be divided into three zones. Some charts of the critical angle, the critical and limit load coefficients are presented in this paper.展开更多
In this paper, the averaged value of the strain energy density （SED） over a control volume is used to predict the critical load of V-notched specimens made of functionally graded steels （FGSs） under mixed-mode loa...In this paper, the averaged value of the strain energy density （SED） over a control volume is used to predict the critical load of V-notched specimens made of functionally graded steels （FGSs） under mixed-mode loading. The studied FGSs contain ferritic and austenite phases in addition to bainitic layer produced by electroslag remelting. The mechanism- based strain gradient plasticity theory is used to determine the flow stress （yield stress or ultimate stress） of each layer. The Young＇s modulus and the Poisson＇s ratio have been assumed to be constant, while other mechanical properties vary exponentially along the specimen width. The control volume is centered in relation to the maximum principal stress present on the notch edge and assumes a crescent shape. The points belonging to the volume perimeter are obtained numerically. In the present contribution, the effects of notch radius and notch depth on the SED and the critical load are studied. The notch radius varies from 0.2 to 2.0 mm, and the notch depth varies from 5 to 7 ram. By using the SED approach and finite element simulations, the critical load is determined, and the obtained results show a sound agreement with the experimental results.展开更多
Kirigami, the ancient Japanese paper cutting technique, has been applied to achieve high stretchability and low energy loss of designed metallic glass. Despite the exploration of the underlying deformation mechanism o...Kirigami, the ancient Japanese paper cutting technique, has been applied to achieve high stretchability and low energy loss of designed metallic glass. Despite the exploration of the underlying deformation mechanism of kirigami-inspired structures from the energy point of view, the morphable responses of the kirigami patterns and the origin of the kirigami response are yet to be fully understood. This study reveals the mechanical driven-forms of the kirigami structure with the corresponding deformation stages. Based on the beam deflection theory, the elastic buckling behavior of kirigami metallic glass is manifested and a critical force prediction model is developed. Moreover, a force concentration parameter is introduced in the rigid-plastic deformation stage, predicting the nominal ultimate force. The kirigami-inspired facture force is firstly proposed. The findings of these models are in good agreement with the experimental sizedependent kirigami responses, and expected to provide significant insights into the understanding of the deformation behavior and the design of kirigami metallic glasses.展开更多
Based on von Karman plate theory, the issue about nonlinear vibration for circular sandwich plates under circumjacent load with the loosely clamped boundary condition was researched. Nonlinear differential eigenvalue ...Based on von Karman plate theory, the issue about nonlinear vibration for circular sandwich plates under circumjacent load with the loosely clamped boundary condition was researched. Nonlinear differential eigenvalue equations and boundary conditions of the problem were formulated by variational method and then their exact static solution can be got. The solution was derived by modified iteration method, so the analytic relations between amplitude and nonlinear oscillating frequency for circular sandwich plates were obtained. When circumjacent load makes the lowest natural frequency zero, critical load is obtained.展开更多
The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory sy...The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory system is used to calculate the critical load of the trigonometrically varied inertia column. In doing so, the equilibrium equation of the column is theoretically studied using the perturbation method. Accuracy of the calculated results is evaluated by comparing the solution with numerical results. Effect of improving the initial guess on the solution accuracy is investigated. Effects of varying parameters of the trigonometrically varied inertia and the uniformly tapered columns on their stability behavior are studied. Finally, using the so-called ＂perfectibility＂ parameter, two design goals, i.e., being lightweight and being strong, are studied for the discussed columns.展开更多
Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service li...Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service life of tunnel.Considering the main environmental loads and mechanical loads of subsea tunnel,the durability properties of lining concrete under combined action of compressive load and carbonation has been studied through the critical compressive load test,accelerated carbonation test,natural carbonation test and capillary suction test.The tests results show that critical compressive load apparently accelerates the carbonation and deteriorates the anti-permeability of concrete.Under the combined action of critical compressive load and carbonation,the durability of lining concrete decreases.Based on the carbonization life criteria and research results,for the high-performance concrete with proposed mix ratio,the predicted service life of lining concrete for Jiaozhou bay subsea tunnel is about 80 years which fails to reach the required service life.It is necessary to adopt other measurements simultaneously to improve the durability of lining concrete.展开更多
The nonlinear analysis with an analytical approach on dynamic torsional buckling of stiffened functionally graded thin toroidal shell segments is investigated. The shell is reinforced by inside stiffeners and surround...The nonlinear analysis with an analytical approach on dynamic torsional buckling of stiffened functionally graded thin toroidal shell segments is investigated. The shell is reinforced by inside stiffeners and surrounded by elastic foundations in a thermal environment and under a time-dependent torsional load. The governing equations are derived based on the Donnell shell theory with the yon Karman geometrical nonlinearity, the Stein and McElman assumption, the smeared stiffeners technique, and the Galerkin method. A deflection function with three terms is chosen. The thermal parameters of the uniform temperature rise and nonlinear temperature conduction law are found in an explicit form. A closed-form expression for determining the static critical torsional load is obtained. A critical dynamic torsional load is found by the fourth-order Runge-Kutta method and the Budiansky-Roth criterion. The effects of stiffeners, foundations, material, and dimensional parameters on dynamic responses of shells are considered.展开更多
基金The Science Foundation of Ministry of Transport of the People's Republic of China(No.200731822301-7)
文摘In order to study the critical load position that causes cavities beneath the continuously reinforced concrete pavement（ CRCP） slab under vehicle loading, the elliptical load is translated into the square load based on the equivalence principle.The CRCP slab is analyzed to determine the cavity position beneath the slab under vehicle loading. The influences of cavity size on the CRCP slab＇s stress and vertical displacement are investigated. The study results showthat the formation of the cavity is unavoidable under traffic loading, and the cavity is located at the edge of the longitudinal crack and the slab corner.The cavity size exerts an obvious influence on the largest horizontal tensile stress and vertical displacement. The slab corner is the critical load position of the CRCP slab. The results can be used to assist the design of CRCP in avoiding cavities beneath slabs subject to vehicle loading.
基金supported by Guangdong Provincial Natural Science Foundation (No. 02-38100-4202003 and 06202438)New Century Excellent Talents Program of Ministry of Education of the People’s Republic of China(No. NCET-04-0790)
文摘The current acid deposition critical loads in Guangdong, China were calculated using the PROFILE model with a 3 km × 3 km resolution. Calculations were carded out for critical loads of potential acidity, actual acidity, sulfur and nitrogen, with values in extents of 0-3.5, 0-14.0, 0-26.0 and 0-3.5 kmol/（hrnE.year）, respectively. These values were comparable to previously reported results and reflected the influences of vegetation and soil characteristics on the soil acid buffering capacity. Simulations of SO2 emission and sulfur deposition in this study showed that sulfur deposition core areas mirrored SO2 emission centers. The prediction of sulfur deposition after 20% and 40% reduction of SO2 emission suggested that the reduction of area sources contributed greatly to the decrease of sulfur deposition. Thus, abatement of area source emissions could be the primary way to mitigate sulfur deposition in Guangdong to meet both the provincial and national regulations of air pollution control.
文摘In this paper based on the experiment principle of evaluating adhesion property by scratch testing, the peeling mechanism of thin films is discussed by applying contact theory and surface physics theory. A mathematical model predicting the critical load is proposed for calculating critical load as determined byscratch testing. The factors for correctly evaluating adhesion of coatings according to the experimental data arediscussed.
文摘This paper presents a newly developed proximity indicator for voltage stability assessment which can be used to predict critical real system load and voltages at various load buses at critical loading point.The proximity indicator varies almost parabolic with total real load demand and reaches orthogonally to real load axis.This relation has been utilized to predict critical loading point.It has been shown that two operating points are needed for estimating critical point and proper selection of operating points and variation of proximity indicator near collapse point highly affect the accuracy of estimation.Simulation is based on load flow equations and system real and reactive loadings have been increased in proportion with base case scenario for IEEE 14 and IEEE 25 bus test systems to demonstrate the behaviour of proposed proximity indicator.CPF has been used as benchmark to check the accuracy of estimation.
文摘In this paper, a set of variational formulas of solving nonlinear instability critical loads are established from the viewpoint of variational principle. The paper shows that it is very convenient to solve nonlinear instability critical load by using the variational formulas suggested in this paper.
文摘Advanced design based on the concept of orthotropic structure includes better use of materials, less weight compared to the equivalent isotropic construction and controlled effectively reserve resistance in all its segments. In this case a calculation of critical load is exposed using the FDM （Finite Difference Method） concept of thin plates subjected to complex loads due to forces in the middle-plane. Results of calculation model, discussed in this paper, are given in graphic form. Presented results should serve as an indicator of the expansion of theoretical base of similar models, which can be reasonably use by researchers and engineers in their practices, and by students for educational purposes.
文摘The promotion of recent critical load securing of power system research has been directed towards centralized commands and control functions.This paper presents a multi-agent based critical load securing in a PV based microgrid.For the trustworthy operation of critical buildings,the reliability,efficiency and security of the power system should be guaranteed.At present,to increase the security and reliability of electricity supply there is a need to design a distributed and autonomous subset of a larger grid or a microgrid.This work also clearly discusses the modelling and simulation of specialized microgrid called an Intelligent Distributed Autonomous Power Systems(IDAPS).The IDAPS microgrid plays a crucial role in constructing power grid that facilitate use of renewable energy technologies.IDAPS microgrid comprising of solar photovoltaic as distributed energy resources,different loads and their control algorithms,has been developed.Several case studies have been simulated to evaluate the operation of the IDAPS microgrid during parallel,islanded mode operation and securing critical loads during emergency.
基金Supported by the National Natural Science Foundation of China!(No.59678016)
文摘A method described is to produce critical load maps of acid deposition for soils in China. Critical loads were assigned to the most sensitive soil in each 0.1°×0.1° grid square of China based on the Skokloster classification [1] and adjusted for temperature and land use. The map shows that soils with small critical load (<0.5keq·ha -1 ·a -1 ) i.e., highly sensitive to acid deposition, dominate in the south and northeast China. As a result of the adjustment, much of the acid sensitive area in the south estimated by the Skokloster method is lost. This reflects the decreased sensitivity as a result of agricultural activities and increased weathering rate in response to high temperature. Based on the 0.1°×0.1° map, a series of percentile critical load maps at 1°×1° scale were compiled for integrated assessments, as well as a critical load map using the minimum critical load for each grid. Comparison of critical loads with sulphur deposition in 1995 led to the critical load exceedance maps for sulphur deposition, which show that high exceedance areas do not correlate well with the low critical load areas, and almost one fourth of the land area, mainly in the southeast, is subject to the risk of acidification.
文摘By means of the theory of universal unfolding, the influence of multi-imperfections upon the critical load of structure in engineering is analysed in this paper. For the pitchfork problem, a lower bound of increments of the critical loads caused by imperfections of the structures is given. A simple and available numerical method for computing the lower bound is described.
文摘In this paper, after taking th e effect of axis force on bending into consideration, the general potential ener gy for the circular double articulated arch is established undergoing vertical d istributive load g 0/ cos 2θ . With sufficient engineering precision, the fourth approximations to the destabilizing critical load of the arch under t his load are obtained by Ritz method. The approximations to the critical load ta ble are listed for various center angles of arch, and are contrasted with the cr itical load circular arch undergoing radial uniform load. Some reference results have been obtained.
基金Project supported by the National Natural Science Foundation of China(No.11672265)。
文摘Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.
基金the National Natural Science Foundation of China(Nos.10772104 and10402018)the Shanghai Leading Academic Discipline Project(No.Y0103)
文摘Dynamical responses, such as motion and destruction of hyper-elastic cylindrical shells subject to periodic or suddenly applied constant load on the inner surface, are studied within a framework of finite elasto-dynamics. By numerical computation and dynamic qualitative analysis of the nonlinear differential equation, it is shown that there exists a certain critical value for the internal load describing motion of the inner surface of the shell. Motion of the shell is nonlinear periodic or quasi-periodic oscillation when the average load of the periodic load or the constant load is less than its critical value. However, the shell will be destroyed when the load exceeds the critical value. Solution to the static equilibrium problem is a fixed point for the dynamical response of the corresponding system under a suddenly applied constant load. The property of fixed point is related to the property of the dynamical solution and motion of the shell. The effects of thickness and load parameters on the critical value and oscillation of the shell are discussed.
文摘According to the Mohr-Coulomb yield criterion, the stress field of the infinite slope is derived under a vertical uniform load q on the top of the slope. It is indicated that elastic and elasto-plastic states would occur in the slope. When q is smaller than the critical load, q(p), the slope is in the elastic state. If q equals q(p), the slope is in the critical state, and the plastic deformation would occur along the critical angle. With the increase of q, the plastic zone would extend, and the slope is in the elasto-plastic State. If q equals limit load, the slope is in the limit equilibrium state. The slope may be divided into three zones. Some charts of the critical angle, the critical and limit load coefficients are presented in this paper.
文摘In this paper, the averaged value of the strain energy density （SED） over a control volume is used to predict the critical load of V-notched specimens made of functionally graded steels （FGSs） under mixed-mode loading. The studied FGSs contain ferritic and austenite phases in addition to bainitic layer produced by electroslag remelting. The mechanism- based strain gradient plasticity theory is used to determine the flow stress （yield stress or ultimate stress） of each layer. The Young＇s modulus and the Poisson＇s ratio have been assumed to be constant, while other mechanical properties vary exponentially along the specimen width. The control volume is centered in relation to the maximum principal stress present on the notch edge and assumes a crescent shape. The points belonging to the volume perimeter are obtained numerically. In the present contribution, the effects of notch radius and notch depth on the SED and the critical load are studied. The notch radius varies from 0.2 to 2.0 mm, and the notch depth varies from 5 to 7 ram. By using the SED approach and finite element simulations, the critical load is determined, and the obtained results show a sound agreement with the experimental results.
基金fully supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.PolyU 15222017)。
文摘Kirigami, the ancient Japanese paper cutting technique, has been applied to achieve high stretchability and low energy loss of designed metallic glass. Despite the exploration of the underlying deformation mechanism of kirigami-inspired structures from the energy point of view, the morphable responses of the kirigami patterns and the origin of the kirigami response are yet to be fully understood. This study reveals the mechanical driven-forms of the kirigami structure with the corresponding deformation stages. Based on the beam deflection theory, the elastic buckling behavior of kirigami metallic glass is manifested and a critical force prediction model is developed. Moreover, a force concentration parameter is introduced in the rigid-plastic deformation stage, predicting the nominal ultimate force. The kirigami-inspired facture force is firstly proposed. The findings of these models are in good agreement with the experimental sizedependent kirigami responses, and expected to provide significant insights into the understanding of the deformation behavior and the design of kirigami metallic glasses.
文摘Based on von Karman plate theory, the issue about nonlinear vibration for circular sandwich plates under circumjacent load with the loosely clamped boundary condition was researched. Nonlinear differential eigenvalue equations and boundary conditions of the problem were formulated by variational method and then their exact static solution can be got. The solution was derived by modified iteration method, so the analytic relations between amplitude and nonlinear oscillating frequency for circular sandwich plates were obtained. When circumjacent load makes the lowest natural frequency zero, critical load is obtained.
文摘The aim of this study is to calculate the critical load of variable inertia columns. The example studied in this paper can be used as a paradigm for other non-uniform columns. The wavelength of equivalent vibratory system is used to calculate the critical load of the trigonometrically varied inertia column. In doing so, the equilibrium equation of the column is theoretically studied using the perturbation method. Accuracy of the calculated results is evaluated by comparing the solution with numerical results. Effect of improving the initial guess on the solution accuracy is investigated. Effects of varying parameters of the trigonometrically varied inertia and the uniformly tapered columns on their stability behavior are studied. Finally, using the so-called ＂perfectibility＂ parameter, two design goals, i.e., being lightweight and being strong, are studied for the discussed columns.
基金Funded by the National Key Basic Research and Development Plans-973 Plans(2009CB623203)the Key Project of National Natural Science Foundation of China (50739001)+2 种基金the National Natural Science Foundation of China (50878109)the National Key Technology R & D Program (2007BAB27B03)the Education Ministry Doctor Foundation of China (20070429001)
文摘Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service life of tunnel.Considering the main environmental loads and mechanical loads of subsea tunnel,the durability properties of lining concrete under combined action of compressive load and carbonation has been studied through the critical compressive load test,accelerated carbonation test,natural carbonation test and capillary suction test.The tests results show that critical compressive load apparently accelerates the carbonation and deteriorates the anti-permeability of concrete.Under the combined action of critical compressive load and carbonation,the durability of lining concrete decreases.Based on the carbonization life criteria and research results,for the high-performance concrete with proposed mix ratio,the predicted service life of lining concrete for Jiaozhou bay subsea tunnel is about 80 years which fails to reach the required service life.It is necessary to adopt other measurements simultaneously to improve the durability of lining concrete.
基金supported by the Vietnam National Foundation for Science and Technology Development(No.107.02-2015.11)
文摘The nonlinear analysis with an analytical approach on dynamic torsional buckling of stiffened functionally graded thin toroidal shell segments is investigated. The shell is reinforced by inside stiffeners and surrounded by elastic foundations in a thermal environment and under a time-dependent torsional load. The governing equations are derived based on the Donnell shell theory with the yon Karman geometrical nonlinearity, the Stein and McElman assumption, the smeared stiffeners technique, and the Galerkin method. A deflection function with three terms is chosen. The thermal parameters of the uniform temperature rise and nonlinear temperature conduction law are found in an explicit form. A closed-form expression for determining the static critical torsional load is obtained. A critical dynamic torsional load is found by the fourth-order Runge-Kutta method and the Budiansky-Roth criterion. The effects of stiffeners, foundations, material, and dimensional parameters on dynamic responses of shells are considered.
