Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stre...Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics(FVDAM). Compared with the results calculated by failure criterion based on macro-stress field(the maximum stress criteria and Hashin criteria) and micro-stress field(Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.展开更多
The present paper presents an algorithm and a program for plotting the clarifying curves and for determination of the specific amount of settled material during the initial period based on data obtained from sedimenta...The present paper presents an algorithm and a program for plotting the clarifying curves and for determination of the specific amount of settled material during the initial period based on data obtained from sedimentation experiments in stationary column of aqueous suspensions of solids particles with different concentrations. The algorithm and program have been developed for an interactive, rapid and convenient processing of the data obtained from sedimentation experiments in stationary column of aqueous suspensions of solids particles and allow obtaining with accuracy of precise and expressive graphs which characterize the behaviour of aqueous suspensions to sedimentation in stationary column. Sedimentation study of different aqueous suspensions of solids particles in stationary column is of great importance for experimentally determining the important parameters required to design and exploitation clarifiers and sludge thickeners from waste water treatment plants.展开更多
The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigati...The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigation and theoretical analysis were made on the law of deflection development and stiffness degradation, as well as the influence of fatigue load ranges. Test results indicate that the law of three-stage change under fatigue loading is followed by both midspan deflection and permanent deflection, which also have positive correlation with fatigue load amplitude. Fatigue stiffness of composite strengthened beams degrades gradually with the increasing of number of cycles. Based on the experimental results, a theoretical model by effective moment of inertia method is developed for calculating the sectional stiffness of such composite strengthened beams under fatigue loading, and the calculated results are in good agreement with the experimental results.展开更多
The excessive moisture has an adverse effect on the building materials structure. Most standard construction materials are characterized by porous structure, resulting in the ability to absorb water in liquid and gase...The excessive moisture has an adverse effect on the building materials structure. Most standard construction materials are characterized by porous structure, resulting in the ability to absorb water in liquid and gaseous phases in the inner pores. Under certain conditions, water fills the pores within the structure of building material and then moves back to its surrounding. Many technical studies have shown that monitoring the moisture transport is mainly based on experimental methods. This work is based on models of transport of moisture in building physics, i.e., the description of the moisture behaviour of building materials based on physical laws models (KRISCHER, KIESSL). The aim of this work is to obtain the parameters of distribution of moisture for calculation capillary conductivity coefficient for practical using by means of non-destructive method. The authors have now developed all the software required to perform a boundary element analysis of problems in potential flow. The examples which the authors can analyse will, however, be restricted to homogenous domains.展开更多
Off-center impurity effects in a spherical quantum dot are theoretically studied by degenerate perturbationmethod in strong confinement.The energy levels and binding energies are computed for the typical GaAs material...Off-center impurity effects in a spherical quantum dot are theoretically studied by degenerate perturbationmethod in strong confinement.The energy levels and binding energies are computed for the typical GaAs material asfunction of the donor position.The numerical results show the quantum size effect.We note that the energy levels andbinding energies are not only related to the position of donor and the strength of confinement,but also related to thefold of degenerate states.We can see obviously that gaps will appear among the degenerate states and the splitting ofenergy levels and binding energies will appear as the position of the impurity is shifted away off the center.展开更多
The yield criterion parameters of the soil material change with different values of the cohesion and the angle of friction because of sustained rainfall infiltration. Based on the Mohr-Coulomb(M-C) and Drucker-Prager(...The yield criterion parameters of the soil material change with different values of the cohesion and the angle of friction because of sustained rainfall infiltration. Based on the Mohr-Coulomb(M-C) and Drucker-Prager(D-P) yield criteria, some reasonable yield criteria selections were discussed for quantitative analysis of unsaturated soil slope stability. Moreover, a critical point was found at the effective angle of friction equaling to 16.5° by transformation of parameters related to unsaturated soil under sustained rainfall. When the effective angle of friction more than 16.5° through parameter transformation of different yield criteria under natural condition, the calculation result of the safety factor was such that: f(DP1) > f(M-C) > f(equivalent M-C) > f(DP2) > f(DP3). While the effective angle of friction less than 16.5°, through parameter transformation, the safety factors were in the following order: f(DP1) > f(M-C) > f(DP2) > f(equivalent M-C) > f(DP3). The calculated results from a case study showed that the equivalent M-C yield criterion should be the best at evaluating soil slope stability before rainfall; the DP2 yield criterion should be selected to calculate the soil slope stability at the effective angle of friction less than 16.5° under sustained rainfall. The yield criterion should be selected or adjusted reasonably to calculate the safety factor of unsaturated soil slopes before and during sustained rainfall.展开更多
In order to improve the anchoring force of anchors for carbon fiber reinforced polymer(CFRP) tendons further, a new wedge-bond-type anchor for CFRP tendons was developed. The increment in anchoring force induced by th...In order to improve the anchoring force of anchors for carbon fiber reinforced polymer(CFRP) tendons further, a new wedge-bond-type anchor for CFRP tendons was developed. The increment in anchoring force induced by the clamping segment of anchor was studied. Taking the deformation of all parts in clamping segment in the transverse direction into consideration, the calculation formula for the increment of anchoring force was proposed based on the linear elastic hypotheses. The proposed model is verified by experiments and conclusions are drawn that the anchoring force is influenced mainly by the inclination angle of clamping pieces, the length of clamping part and the thickness of bonding medium. Especially, the thickness of bonding medium should be lowered in design to improve the synergistic effect of anchors.展开更多
Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforc...Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforcing layers on the compressive deformation behavior of porous composites was investigated through micro-computed tomography(Micro-CT)and finite element method(FEM)analyses.The results indicate that the addition of reinforcement layers to sandwich structures can significantly enhance the compressive yield strength and energy absorption capacity of porous metal structures;Micro-CT in-situ observation shows that the strain of the porous structure without the reinforcing layer is concentrated in the middle region,while the strain of the porous structure with the reinforcing layer is uniformly distributed;FEM analysis reveals that the reinforcing layers can alter stress distribution and reduce stress concentration,thereby promoting uniform deformation of the porous structure.The addition of reinforcing layer increases the compressive yield strength of sandwich-structured composite materials by 124%under the condition of limited reduction of porosity,and the yield strength increases from 4.6 to 10.3 MPa.展开更多
The sound absorbing performance of the sintered fibrous metallic materials is investigated by employing a dynamic flow resistivity based model,in which the porous material is modeled as randomly distributed parallel f...The sound absorbing performance of the sintered fibrous metallic materials is investigated by employing a dynamic flow resistivity based model,in which the porous material is modeled as randomly distributed parallel fibers specified by two basic physical parameters:fiber diameter and porosity.A self-consistent Brinkman approach is applied to the calculation of the dynamic resistivity of flow perpendicular to the cylindrical fibers.Based on the solved flow resistivity,the sound absorption of single layer fibrous material can be obtained by adopting the available empirical equations.Moreover,the recursion formulas of surface impedance are applied to the calculation of the sound absorption coefficient of multi-layer fibrous materials.Experimental measurements are conducted to validate the proposed model,with good agreement achieved between model predictions and tested data.Numerical calculations with the proposed model are subsequently performed to quantify the influences of fiber diameter,porosity and backed air gap on sound absorption of uniform(single-layer)fibrous materials.Results show that the sound absorption increases with porosity at higher frequencies but decreases with porosity at lower frequencies.The sound absorption also decreases with fiber diameter at higher frequencies but increases at lower frequencies.The sound absorption resonance is shifted to lower frequencies with air gap.For multi-layer fibrous materials,gradient distributions of both fiber diameter and porosity are introduced and their effects on sound absorption are assessed.It is found that increasing the porosity and fiber diameter variation improves sound absorption in the low frequency range.The model provides the possibility to tailor the sound absorption capability of the sintered fibrous materials by optimizing the gradient distributions of key physical parameters.展开更多
Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistanc...Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistance and durability of the infrastructures. In this paper, it is proposed to use ECC as the matrix of frame columns for improving its load carrying capacity, ductility, and avoiding the brittleness of concrete. Based on the assumption of plane remaining plane and constitutive models of materials, theoretical models for calculating the load-carrying capacity of the steel reinforced ECC columns under small and large eccentric compression are proposed. With the parameters of the constitutive models from the existing experimental data, the relationship between ultimate axial load and moment capacities is also derived with the proposed models. To verify the validity of the proposed theoretical models, finite element analysis with the software of ATENA is conducted to simulate the mechanical behavior of the steel reinforced ECC columns under eccentric compressive loading. The calculation results from the theoretical models show good consistency with the simulated results, indicating that the proposed models are feasible and reliable for design. Finally, based on the theoretical models, the effect of the ultimate tensile strain and compressive strength of ECC, longitudinal reinforcement ratio on the load carrying capacity of the steel reinforced ECC column are comprehensively studied.展开更多
Cocrystal has been discovered and studied for more than 170 years since 1844, while the applications to optoelectronics only begin in the last decade. Several general questions that chemists and materials scientists c...Cocrystal has been discovered and studied for more than 170 years since 1844, while the applications to optoelectronics only begin in the last decade. Several general questions that chemists and materials scientists currently seek to answer are: can we design and control the molecular self-assembly and cocrystal growth, what’s the packing-property correlations, as well as how can we improve device parameters for real applications in industry. In this contribution, we review our and other groups’ recent advances in the cocrystal research field sequentially including:(1) nucleation and growth mechanisms for selective preparation of cocrystals with different donor/acceptor ratio and morphology;(2) charge transport and electronic devices, particularly field-effect transistor(FET) and photo-response device. We discuss the in-situ single crystal device fabrication method, ambipolar charge transport, and molecular packingcharge separation correlation;(3) photonic and optical property, focusing on optical waveguide, photonic logic computation, and nonlinear optics(NLO). We present unusual optical properties revealed by advanced instruments and general structure-function relations for future study. Importantly, the extensive investigations described herein yield in-depth and detailed understandings of molecular cocrystals,and show that such bi-component material systems together with the developed instrument measurement methodologies have the potential to initiate unconventional electronic and photonic science and technology.展开更多
基金Project(51075204)supported by the National Natural Science Foundation of ChinaProjects(2012ZB52026,2014ZB52024)supported by the Aeronautical Science Foundation of ChinaProject(NS2014024)supported by the Fundamental Research Funds for the Central Universities,China
文摘Based on parameter design language, a program of progressive failure analysis in composite structures is proposed. In this program, the relationship between macro- and micro-mechanics is established and the macro stress distribution of the composite structure is calculated by commercial finite element software. According to the macro-stress, the damaged point is found and the micro-stress distribution of representative volume element is calculated by finite-volume direct averaging micromechanics(FVDAM). Compared with the results calculated by failure criterion based on macro-stress field(the maximum stress criteria and Hashin criteria) and micro-stress field(Huang model), it is proven that the failure analysis based on macro- and micro-mechanics model is feasible and efficient.
文摘The present paper presents an algorithm and a program for plotting the clarifying curves and for determination of the specific amount of settled material during the initial period based on data obtained from sedimentation experiments in stationary column of aqueous suspensions of solids particles with different concentrations. The algorithm and program have been developed for an interactive, rapid and convenient processing of the data obtained from sedimentation experiments in stationary column of aqueous suspensions of solids particles and allow obtaining with accuracy of precise and expressive graphs which characterize the behaviour of aqueous suspensions to sedimentation in stationary column. Sedimentation study of different aqueous suspensions of solids particles in stationary column is of great importance for experimentally determining the important parameters required to design and exploitation clarifiers and sludge thickeners from waste water treatment plants.
基金Project(51108355)supported by the National Natural Science Foundation of ChinaProject(2011CDB269)supported by the Natural Science Foundation of Hubei Province,China
文摘The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigation and theoretical analysis were made on the law of deflection development and stiffness degradation, as well as the influence of fatigue load ranges. Test results indicate that the law of three-stage change under fatigue loading is followed by both midspan deflection and permanent deflection, which also have positive correlation with fatigue load amplitude. Fatigue stiffness of composite strengthened beams degrades gradually with the increasing of number of cycles. Based on the experimental results, a theoretical model by effective moment of inertia method is developed for calculating the sectional stiffness of such composite strengthened beams under fatigue loading, and the calculated results are in good agreement with the experimental results.
文摘The excessive moisture has an adverse effect on the building materials structure. Most standard construction materials are characterized by porous structure, resulting in the ability to absorb water in liquid and gaseous phases in the inner pores. Under certain conditions, water fills the pores within the structure of building material and then moves back to its surrounding. Many technical studies have shown that monitoring the moisture transport is mainly based on experimental methods. This work is based on models of transport of moisture in building physics, i.e., the description of the moisture behaviour of building materials based on physical laws models (KRISCHER, KIESSL). The aim of this work is to obtain the parameters of distribution of moisture for calculation capillary conductivity coefficient for practical using by means of non-destructive method. The authors have now developed all the software required to perform a boundary element analysis of problems in potential flow. The examples which the authors can analyse will, however, be restricted to homogenous domains.
文摘Off-center impurity effects in a spherical quantum dot are theoretically studied by degenerate perturbationmethod in strong confinement.The energy levels and binding energies are computed for the typical GaAs material asfunction of the donor position.The numerical results show the quantum size effect.We note that the energy levels andbinding energies are not only related to the position of donor and the strength of confinement,but also related to thefold of degenerate states.We can see obviously that gaps will appear among the degenerate states and the splitting ofenergy levels and binding energies will appear as the position of the impurity is shifted away off the center.
基金sponsored by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY13E080008)the Natural Science Foundation of China(Grant No.51108293)the Science and Technology Fund of Yunnan Provincial Communication Department of China(Grant No.2010(A)06-b)
文摘The yield criterion parameters of the soil material change with different values of the cohesion and the angle of friction because of sustained rainfall infiltration. Based on the Mohr-Coulomb(M-C) and Drucker-Prager(D-P) yield criteria, some reasonable yield criteria selections were discussed for quantitative analysis of unsaturated soil slope stability. Moreover, a critical point was found at the effective angle of friction equaling to 16.5° by transformation of parameters related to unsaturated soil under sustained rainfall. When the effective angle of friction more than 16.5° through parameter transformation of different yield criteria under natural condition, the calculation result of the safety factor was such that: f(DP1) > f(M-C) > f(equivalent M-C) > f(DP2) > f(DP3). While the effective angle of friction less than 16.5°, through parameter transformation, the safety factors were in the following order: f(DP1) > f(M-C) > f(DP2) > f(equivalent M-C) > f(DP3). The calculated results from a case study showed that the equivalent M-C yield criterion should be the best at evaluating soil slope stability before rainfall; the DP2 yield criterion should be selected to calculate the soil slope stability at the effective angle of friction less than 16.5° under sustained rainfall. The yield criterion should be selected or adjusted reasonably to calculate the safety factor of unsaturated soil slopes before and during sustained rainfall.
基金Project(BK20140553)supported by Jiangsu Province Science Foundation for Youths,ChinaProject(51478209)supported by the National Natural Science Foundation of China
文摘In order to improve the anchoring force of anchors for carbon fiber reinforced polymer(CFRP) tendons further, a new wedge-bond-type anchor for CFRP tendons was developed. The increment in anchoring force induced by the clamping segment of anchor was studied. Taking the deformation of all parts in clamping segment in the transverse direction into consideration, the calculation formula for the increment of anchoring force was proposed based on the linear elastic hypotheses. The proposed model is verified by experiments and conclusions are drawn that the anchoring force is influenced mainly by the inclination angle of clamping pieces, the length of clamping part and the thickness of bonding medium. Especially, the thickness of bonding medium should be lowered in design to improve the synergistic effect of anchors.
基金the Hunan Young Scientific Innovative Talents Program,China(No.2020RC3040)Outstanding Youth Fund of Hunan Natural Science Foundation,China(Nos.2021JJ20011,2021JJ40600,2021JJ40590)the National Natural Science Foundation of China(Nos.52001030,52204371)..
文摘Beta Ti−35Nb sandwich-structured composites with various reinforcing layers were designed and produced using additive manufacturing(AM)to achieve a balance between light weight and high strength.The impact of reinforcing layers on the compressive deformation behavior of porous composites was investigated through micro-computed tomography(Micro-CT)and finite element method(FEM)analyses.The results indicate that the addition of reinforcement layers to sandwich structures can significantly enhance the compressive yield strength and energy absorption capacity of porous metal structures;Micro-CT in-situ observation shows that the strain of the porous structure without the reinforcing layer is concentrated in the middle region,while the strain of the porous structure with the reinforcing layer is uniformly distributed;FEM analysis reveals that the reinforcing layers can alter stress distribution and reduce stress concentration,thereby promoting uniform deformation of the porous structure.The addition of reinforcing layer increases the compressive yield strength of sandwich-structured composite materials by 124%under the condition of limited reduction of porosity,and the yield strength increases from 4.6 to 10.3 MPa.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2011CB610300)the National Natural Science Foundation of China(Grant Nos.11102148,11321062 and 51134003)the Fundamental Research Funds for Central Universities of China(Grant No.xjj2011005)
文摘The sound absorbing performance of the sintered fibrous metallic materials is investigated by employing a dynamic flow resistivity based model,in which the porous material is modeled as randomly distributed parallel fibers specified by two basic physical parameters:fiber diameter and porosity.A self-consistent Brinkman approach is applied to the calculation of the dynamic resistivity of flow perpendicular to the cylindrical fibers.Based on the solved flow resistivity,the sound absorption of single layer fibrous material can be obtained by adopting the available empirical equations.Moreover,the recursion formulas of surface impedance are applied to the calculation of the sound absorption coefficient of multi-layer fibrous materials.Experimental measurements are conducted to validate the proposed model,with good agreement achieved between model predictions and tested data.Numerical calculations with the proposed model are subsequently performed to quantify the influences of fiber diameter,porosity and backed air gap on sound absorption of uniform(single-layer)fibrous materials.Results show that the sound absorption increases with porosity at higher frequencies but decreases with porosity at lower frequencies.The sound absorption also decreases with fiber diameter at higher frequencies but increases at lower frequencies.The sound absorption resonance is shifted to lower frequencies with air gap.For multi-layer fibrous materials,gradient distributions of both fiber diameter and porosity are introduced and their effects on sound absorption are assessed.It is found that increasing the porosity and fiber diameter variation improves sound absorption in the low frequency range.The model provides the possibility to tailor the sound absorption capability of the sintered fibrous materials by optimizing the gradient distributions of key physical parameters.
基金supported by the National Natural Science Foundation of China(Grant No.51278118)the Natural Science Foundation of Jiangsu Province(Grant No.BK2012756)the Scientific Research Project of Ministry of Education of China(Grant No.113029A)
文摘Fiber reinforced cementitious composites(ECC) are a class of advanced composites with strain hardening and multiple cracking behaviors. Substitution of concrete with ECC can significantly improve the seismic resistance and durability of the infrastructures. In this paper, it is proposed to use ECC as the matrix of frame columns for improving its load carrying capacity, ductility, and avoiding the brittleness of concrete. Based on the assumption of plane remaining plane and constitutive models of materials, theoretical models for calculating the load-carrying capacity of the steel reinforced ECC columns under small and large eccentric compression are proposed. With the parameters of the constitutive models from the existing experimental data, the relationship between ultimate axial load and moment capacities is also derived with the proposed models. To verify the validity of the proposed theoretical models, finite element analysis with the software of ATENA is conducted to simulate the mechanical behavior of the steel reinforced ECC columns under eccentric compressive loading. The calculation results from the theoretical models show good consistency with the simulated results, indicating that the proposed models are feasible and reliable for design. Finally, based on the theoretical models, the effect of the ultimate tensile strain and compressive strength of ECC, longitudinal reinforcement ratio on the load carrying capacity of the steel reinforced ECC column are comprehensively studied.
基金This work was supported by the National Key R&D Program(2017YFA0204503,2016YFB0401100)the National Natural Science Foundation of China(91833306,21875158,51633006,51703159,and 51733004)。
文摘Cocrystal has been discovered and studied for more than 170 years since 1844, while the applications to optoelectronics only begin in the last decade. Several general questions that chemists and materials scientists currently seek to answer are: can we design and control the molecular self-assembly and cocrystal growth, what’s the packing-property correlations, as well as how can we improve device parameters for real applications in industry. In this contribution, we review our and other groups’ recent advances in the cocrystal research field sequentially including:(1) nucleation and growth mechanisms for selective preparation of cocrystals with different donor/acceptor ratio and morphology;(2) charge transport and electronic devices, particularly field-effect transistor(FET) and photo-response device. We discuss the in-situ single crystal device fabrication method, ambipolar charge transport, and molecular packingcharge separation correlation;(3) photonic and optical property, focusing on optical waveguide, photonic logic computation, and nonlinear optics(NLO). We present unusual optical properties revealed by advanced instruments and general structure-function relations for future study. Importantly, the extensive investigations described herein yield in-depth and detailed understandings of molecular cocrystals,and show that such bi-component material systems together with the developed instrument measurement methodologies have the potential to initiate unconventional electronic and photonic science and technology.