The influence of glycol,the main composition of the most frequently used aircraft dicer,on the freeze-thaw durability of high performance concrete（HPC）is investigated.Freeze-thaw durability of HPC is tested by accel...The influence of glycol,the main composition of the most frequently used aircraft dicer,on the freeze-thaw durability of high performance concrete（HPC）is investigated.Freeze-thaw durability of HPC is tested by accelerated freeze-thaw test.Four kinds of the solution,i.e.,tap water,3.5% NaCl solution,glycol solutions,and a LBR-A type commercial aircraft deicer are employed.Results show that freeze-thaw durability of HPC exposed to glycol solutions is closely related to the solution concentrations.The failure of HPC exposed to 3.5% glycol solution is similar to that of those exposed to 3.5% NaCl solution,i.e.,serious surface scaling.While the damage of HPC exposed to 12.5%—25% glycol solutions is postponed.Compared with glycol solution,the commercial aircraft deicer has much more negative effects on HPC freeze-thaw durability compared with 3.5% NaCl solution.In the presence of commercial aircraft deicer for HPC subjected to freeze-thaw cycles,the deterioration is mainly due to scaling and spalling.展开更多
As a frequently-used roadbed filler,soil-rock mixture is often in the environment of freeze-thaw cycles and different confining pressures.In order to study the freeze-thaw damage mechanism of elastic modulus of soil-r...As a frequently-used roadbed filler,soil-rock mixture is often in the environment of freeze-thaw cycles and different confining pressures.In order to study the freeze-thaw damage mechanism of elastic modulus of soil-rock mixtures at different confining pressures,the concept of meso-interfacial freeze-thaw damage coefficient is put forward and the meso-interfacial damage phenomenon of soil-rock mixtures caused by the freeze-thaw cycle environment is concerned;a double-inclusion embedded model for elastic modulus of soil-rock mixtures in freezing-thawing cycle is proposed.A large triaxial test was performed and the influences of confining pressure and experimental factors on elastic modulus of soil-rock mixtures were obtained,and then the accuracy of the double-inclusion embedded model to predict the elastic modulus of soil-rock mixtures in freezing-thawing cycle is verified.Experiment results showed that as to soil-rock mixtures,with the increase of confining pressure,the elastic modulus increases approximately linearly.The most crucial factors to affect the elastic modulus are rock content and compaction degree at the same confining pressure;the elastic modulus increases with the increase of rock content and compactness;as the number of freeze-thaw cycles increases,the freeze-thaw damage coefficient of meso-structural interface and the elastic modulus decrease.展开更多
In order to study the seismic behavior of frame with specially shaped columns,the hysteretic curve was analyzed based on a quasi-static test of a two-span,three-story frame with specially shaped columns.The top layer ...In order to study the seismic behavior of frame with specially shaped columns,the hysteretic curve was analyzed based on a quasi-static test of a two-span,three-story frame with specially shaped columns.The top layer framework curve and the corresponding resilience model were obtained from the hysteretic curve.And the stiffness and strength degeneration were also investigated.The results indicated that the stiffness degeneration is not obvious,thus the frame with specially shaped columns has high earthquake-resistant behavior.The resilience model calculated from the test can provide reference for design and nonlinear finite element analysis.展开更多
Author researches a lot of the mathematical models and the related conventional material constants in the traditional and the modem mechanics; to adopt two types of variables a and D, for the fatigue-damage-fracture b...Author researches a lot of the mathematical models and the related conventional material constants in the traditional and the modem mechanics; to adopt two types of variables a and D, for the fatigue-damage-fracture behaviors to elastic-plastic steels contained flaws, to put forward several calculation models, which are the driving force and the life prediction expressions at each stage and in whole process; for the key parameters .A1 and ,A2 in two stages, there are functional relation with other conventional material constants σF,m1 and M2,λ2, they are defined as the new calculable comprehensive material constants, and indicate their physical and geometrical meanings. In addition, for conversion methods between two types of variables, relevant calculating example is provided. Thereby, make a linking between the fracture mechanics and the damage mechanics, communicating their relationships. This works for saving man powers and funds on fatigue-damage-fracture testing that will be having practical significance.展开更多
In order to investigate the springback performance of a cold-rolled transformation-induced plasticity （TRIP） steel sheet during cyclic bending, three-points bending experiments were performed. The specimen was first...In order to investigate the springback performance of a cold-rolled transformation-induced plasticity （TRIP） steel sheet during cyclic bending, three-points bending experiments were performed. The specimen was firstly forward bended and then reversed bended according to three basic punch strokes, 10 mm, 20 mm and 30 mm, respectively. The outlines of the deformed specimens, punch load and crosshead displacement were obtained. The experimental procedures and the method of determining the springback displacement were reported in detail. The contributi^m of the strain hardening and decrease of elastic modulus to the overall springback was explained. The results demonstrated that springback increases both with the cycles and with the punch stroke during the cyclic bending process. Furthermore, springback in forward bending is larger than that in the corresponding reverse bending. This may be helpful to understand the complex springback behavior of the complicated sheet metal pancls.展开更多
An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and exte...An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and extension tests were conducted to study the parameters of the model. Results showed that the relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain were nearly unique, when the initial octahedral shear stress ratios of specimens were equal to 0.3, 0.5 and 0.7. The relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain determined from the cyclic triaxial compression tests were basically the same as those determined from the cyclic triaxial extension tests. Furthermore, the relationships were not related to the initial stress condition, the test stress state and the octahedral cyclic shear stress ratio. The relationships determined from the cyclic triaxial tests under no deviatoric stress were basically the same as those determined from the cyclic triaxial tests under deviatoric stress. The change of the octahedral cyclic accumulative strain with the number of cycles was unique under different tests stress states. An equivalent visco-elastic constitutive model of saturated soft clay under UU condition was initially established.展开更多
This paper discusses the suitability of using TSA （thermoelastic stress analysis） as an advanced tool to detect damaged areas and highly stressed （hot spot） areas in structural components. Such components can be, ...This paper discusses the suitability of using TSA （thermoelastic stress analysis） as an advanced tool to detect damaged areas and highly stressed （hot spot） areas in structural components. Such components can be, for example, parts of large structural panels built of welded metallic or composite materials. Besides detecting hot spot areas, it is expected that stresses in these areas can be suitably quantified and processed in order to predict crack initiation and propagation due to in-service loads. The paper starts with references to selected review and application articles on the subject. Two simple laboratory experiments are presented which illustrate the quality of the results that can be achieved using TSA. In the first experiment, a stainless steel T-joint designed to model a welded structural component is analysed. The T-joint had a machine-notched crack-like flaw close to the component＇s weld toe. The qualitative and quantitative experimental results determined along four specified areas of the T-joint model showed that TSA can indeed be used as a tool to detect loaded cracks and hot spots in large metallic structures, and that stresses can be accurately evaluated. In the second experiment, a prismatic bar made of CFRE （carbon fibre-reinforced-epoxy） was tested to locate three subsurface areas of damage introduced beforehand into the component. Two of these inside damaged areas were detected to be 3.1 mm and 7.1 mm from the observed surface. The positive results achieved with the two lab experiments, along with a review of the selected research publications, indicate that TSA application can be extended to the real-world field of structural components. Topics to be addressed in this research field should have to do with components that work under random or quasi-cyclic service loading, problems where adiabatic conditions do not prevail, and reduction of the cost of infra-red cameras.展开更多
We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that whe...We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.展开更多
基金Supported by the National Basic Research Program of China("973"Program)(2009CB623203)the China Postdoctoral Science Foundation(20070421036)+1 种基金the Natural Science Foundation of Jiangsu Province(BK2005216)the Research Foundation of Nanjing University of Aeronautics and Astronautics(NS2010015)~~
文摘The influence of glycol,the main composition of the most frequently used aircraft dicer,on the freeze-thaw durability of high performance concrete（HPC）is investigated.Freeze-thaw durability of HPC is tested by accelerated freeze-thaw test.Four kinds of the solution,i.e.,tap water,3.5% NaCl solution,glycol solutions,and a LBR-A type commercial aircraft deicer are employed.Results show that freeze-thaw durability of HPC exposed to glycol solutions is closely related to the solution concentrations.The failure of HPC exposed to 3.5% glycol solution is similar to that of those exposed to 3.5% NaCl solution,i.e.,serious surface scaling.While the damage of HPC exposed to 12.5%—25% glycol solutions is postponed.Compared with glycol solution,the commercial aircraft deicer has much more negative effects on HPC freeze-thaw durability compared with 3.5% NaCl solution.In the presence of commercial aircraft deicer for HPC subjected to freeze-thaw cycles,the deterioration is mainly due to scaling and spalling.
基金Project(50908234)supported by the National Natural Science Foundation of China
文摘As a frequently-used roadbed filler,soil-rock mixture is often in the environment of freeze-thaw cycles and different confining pressures.In order to study the freeze-thaw damage mechanism of elastic modulus of soil-rock mixtures at different confining pressures,the concept of meso-interfacial freeze-thaw damage coefficient is put forward and the meso-interfacial damage phenomenon of soil-rock mixtures caused by the freeze-thaw cycle environment is concerned;a double-inclusion embedded model for elastic modulus of soil-rock mixtures in freezing-thawing cycle is proposed.A large triaxial test was performed and the influences of confining pressure and experimental factors on elastic modulus of soil-rock mixtures were obtained,and then the accuracy of the double-inclusion embedded model to predict the elastic modulus of soil-rock mixtures in freezing-thawing cycle is verified.Experiment results showed that as to soil-rock mixtures,with the increase of confining pressure,the elastic modulus increases approximately linearly.The most crucial factors to affect the elastic modulus are rock content and compaction degree at the same confining pressure;the elastic modulus increases with the increase of rock content and compactness;as the number of freeze-thaw cycles increases,the freeze-thaw damage coefficient of meso-structural interface and the elastic modulus decrease.
基金Supported by Fund of Specially Shaped Column Code of Ministry of Construction of China.
文摘In order to study the seismic behavior of frame with specially shaped columns,the hysteretic curve was analyzed based on a quasi-static test of a two-span,three-story frame with specially shaped columns.The top layer framework curve and the corresponding resilience model were obtained from the hysteretic curve.And the stiffness and strength degeneration were also investigated.The results indicated that the stiffness degeneration is not obvious,thus the frame with specially shaped columns has high earthquake-resistant behavior.The resilience model calculated from the test can provide reference for design and nonlinear finite element analysis.
文摘Author researches a lot of the mathematical models and the related conventional material constants in the traditional and the modem mechanics; to adopt two types of variables a and D, for the fatigue-damage-fracture behaviors to elastic-plastic steels contained flaws, to put forward several calculation models, which are the driving force and the life prediction expressions at each stage and in whole process; for the key parameters .A1 and ,A2 in two stages, there are functional relation with other conventional material constants σF,m1 and M2,λ2, they are defined as the new calculable comprehensive material constants, and indicate their physical and geometrical meanings. In addition, for conversion methods between two types of variables, relevant calculating example is provided. Thereby, make a linking between the fracture mechanics and the damage mechanics, communicating their relationships. This works for saving man powers and funds on fatigue-damage-fracture testing that will be having practical significance.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51175382)the Fundamental Research Funds for the Central Universities
文摘In order to investigate the springback performance of a cold-rolled transformation-induced plasticity （TRIP） steel sheet during cyclic bending, three-points bending experiments were performed. The specimen was firstly forward bended and then reversed bended according to three basic punch strokes, 10 mm, 20 mm and 30 mm, respectively. The outlines of the deformed specimens, punch load and crosshead displacement were obtained. The experimental procedures and the method of determining the springback displacement were reported in detail. The contributi^m of the strain hardening and decrease of elastic modulus to the overall springback was explained. The results demonstrated that springback increases both with the cycles and with the punch stroke during the cyclic bending process. Furthermore, springback in forward bending is larger than that in the corresponding reverse bending. This may be helpful to understand the complex springback behavior of the complicated sheet metal pancls.
基金Supported by National Natural Science Foundation of China ( No. 51179120)
文摘An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and extension tests were conducted to study the parameters of the model. Results showed that the relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain were nearly unique, when the initial octahedral shear stress ratios of specimens were equal to 0.3, 0.5 and 0.7. The relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain determined from the cyclic triaxial compression tests were basically the same as those determined from the cyclic triaxial extension tests. Furthermore, the relationships were not related to the initial stress condition, the test stress state and the octahedral cyclic shear stress ratio. The relationships determined from the cyclic triaxial tests under no deviatoric stress were basically the same as those determined from the cyclic triaxial tests under deviatoric stress. The change of the octahedral cyclic accumulative strain with the number of cycles was unique under different tests stress states. An equivalent visco-elastic constitutive model of saturated soft clay under UU condition was initially established.
文摘This paper discusses the suitability of using TSA （thermoelastic stress analysis） as an advanced tool to detect damaged areas and highly stressed （hot spot） areas in structural components. Such components can be, for example, parts of large structural panels built of welded metallic or composite materials. Besides detecting hot spot areas, it is expected that stresses in these areas can be suitably quantified and processed in order to predict crack initiation and propagation due to in-service loads. The paper starts with references to selected review and application articles on the subject. Two simple laboratory experiments are presented which illustrate the quality of the results that can be achieved using TSA. In the first experiment, a stainless steel T-joint designed to model a welded structural component is analysed. The T-joint had a machine-notched crack-like flaw close to the component＇s weld toe. The qualitative and quantitative experimental results determined along four specified areas of the T-joint model showed that TSA can indeed be used as a tool to detect loaded cracks and hot spots in large metallic structures, and that stresses can be accurately evaluated. In the second experiment, a prismatic bar made of CFRE （carbon fibre-reinforced-epoxy） was tested to locate three subsurface areas of damage introduced beforehand into the component. Two of these inside damaged areas were detected to be 3.1 mm and 7.1 mm from the observed surface. The positive results achieved with the two lab experiments, along with a review of the selected research publications, indicate that TSA application can be extended to the real-world field of structural components. Topics to be addressed in this research field should have to do with components that work under random or quasi-cyclic service loading, problems where adiabatic conditions do not prevail, and reduction of the cost of infra-red cameras.
基金supported by the Hong Kong Research Grant Council(RGC)(Grant No.619113)the National Natural Science Foundation of China(Grant No.11128204)the State Key Lab of Water Resources and Hydropower Engineering of WHU,China
文摘We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.
