The hot working behaviors of Mg-9Y-1MM-0.6Zr （WE91） magnesium alloy were researched in a temperature range of 653 773 K and strain rate range of 0.001 1 s 1 on Gleeble 1500D hot simulator under the maximum deformati...The hot working behaviors of Mg-9Y-1MM-0.6Zr （WE91） magnesium alloy were researched in a temperature range of 653 773 K and strain rate range of 0.001 1 s 1 on Gleeble 1500D hot simulator under the maximum deformation degree of 60%. A mathematical model was established to predict the stress—strain curves of this alloy during deformation. The experimental results show that the relationship between stress and strain is obviously affected by the strain rates and deformation temperatures. The flow stress of WE91 magnesium alloy during high temperature deformation can be represented by Zener-Hollomon parameter in the hyperbolic Arrhenius-type equation, and the stress—strain curves obtained by the established model are in good agreement with the experimental results,which prove that the model reflects the real deformation characteristics of the WE91 alloy. The average deformation activation energy is 220 kJ/mol at strain of 0.1. The microstructures of WE91 during deformation processing are influenced by temperature and strain rates.展开更多
Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolut...Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al-l.lMn-0.3Mg-0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440-450 ℃ and strain rate of 0.01 s-1.展开更多
A face recognition system based on Support Vector Machine (SVM) and Hidden Markov Model (HMM) has been proposed. The powerful discriminative ability of SVM is combined with the temporal modeling ability of HMM. The ou...A face recognition system based on Support Vector Machine (SVM) and Hidden Markov Model (HMM) has been proposed. The powerful discriminative ability of SVM is combined with the temporal modeling ability of HMM. The output of SVM is moderated to be probability output, which replaces the Mixture of Gauss (MOG) in HMM. Wavelet transformation is used to extract observation vector, which reduces the data dimension and improves the robustness.The hybrid system is compared with pure HMM face recognition method based on ORL face database and Yale face database. Experiments results show that the hybrid method has better performance.展开更多
To describe the relationship between the whole material deformation behavior and each grain deformation behavior inmicro-forming,experimental and numerical modelling methods were employed.Tensile test results reveal t...To describe the relationship between the whole material deformation behavior and each grain deformation behavior inmicro-forming,experimental and numerical modelling methods were employed.Tensile test results reveal that contrary to the valueof flow stress,the scatter of flow stress decreases with the increase of thickness-to-grain diameter(T/d)ratio.Microhardnessevaluation results show that each grain owns unique deformation behavior and randomly distributes in each specimen.The specimenwith less number of grains would be more likely to form an easy deformation zone and produce the concentration of plasticdeformation.Based on the experiment results,a size-dependent model considering the effects of grain size,geometry size,and thedeformation behavior of each grain was developed.And the effectiveness and practicability of the size-dependent model wereverified by experimental results.展开更多
A brief review of the former studies on the mechanisms of soil rheology and microstructure is presented. Then a microstructure model and a set of rheological constitutive relations for sott clays, which describe how t...A brief review of the former studies on the mechanisms of soil rheology and microstructure is presented. Then a microstructure model and a set of rheological constitutive relations for sott clays, which describe how the rheological consolidation settlement develops, are established in the framework of the catastrophe theory. The validity of this model is verified by a series of rheological consolidation experiments with different loading rates. The experimental data show that creep deformation can be clearly observed in these tests, and the consolidation settlement is loading rate dependent. The characteristics of the deformation can be explained and reproduced successfully using the model. It can be concluded that only the biggest set of voids would collapse for one load increment. Parameters in the model, k and η, are gained by curve fitting. With only two free parameters, good fits of the data are achieved.展开更多
Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure f...Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure formed at grain boundaries with no precipitates inside the grains.In partially melted zone(PMZ),symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-likeθ′phases appeared in the secondary heated zone.In over aged zone(OAZ),the coarsening and dissolution ofθ′phases occurred and mostθ′phases transformed intoθphases.In general heat affected zone(HAZ),θ′phases coarsened.Factors such as the strengthening phases,the grain size,the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint.Moreover,a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates,the average diameter of precipitates and the concentration of soluble elements was proposed.展开更多
Hot deformation behaviors and microstructure evolution of Ti-3Al-5Mo-4Cr-2Zr-1Fe(Ti-35421)alloy in theβsingle field are investigated by isothermal compression tests on a Gleeble-3500 simulator at temperatures of 820-...Hot deformation behaviors and microstructure evolution of Ti-3Al-5Mo-4Cr-2Zr-1Fe(Ti-35421)alloy in theβsingle field are investigated by isothermal compression tests on a Gleeble-3500 simulator at temperatures of 820-900°C and strain rates of 0.001-1 s^(-1).The research results show that discontinuous yield phenomenon and rheological softening are affected by the strain rates and deformation temperatures.The critical conditions for dynamic recrystallization and kinetic model of Ti-35421 alloy are determined,and the Arrhenius constitutive model is constructed.The rheological behaviors of Ti-35421 alloys aboveβphase transformation temperature are predicted by the constitutive model accurately.The EBSD analysis proves that the deformation softening is controlled by dynamic recovery and dynamic recrystallization.In addition,continuous dynamic recrystallization is determined during hot deformation,and the calculation model for recrystallization grain sizes is established.Good linear dependency between the experimental and simulated values of recrystallized grain sizes indicates that the present model can be used for the prediction of recrystallized grain size with high accuracy.展开更多
In this paper, we extend the mapping transformation method through introducing variable coefficients.By means of the extended mapping transformation method, many explicit and exact general solutions with arbitrary fun...In this paper, we extend the mapping transformation method through introducing variable coefficients.By means of the extended mapping transformation method, many explicit and exact general solutions with arbitrary functions for some nonlinear partial differential equations, which contain solitary wave solutions, trigonometric function solutions, and rational solutions, are obtained.展开更多
Kinetics of color change in tomato purees dried using microwave and conventional method were investigated. For this purpose, the color parameters of Hunter L,a,b and browning index （A42o）, and estimated values of ch...Kinetics of color change in tomato purees dried using microwave and conventional method were investigated. For this purpose, the color parameters of Hunter L,a,b and browning index （A42o）, and estimated values of chroma, hue angle, AE, Hunter a/b and a ~ b were examined. The changes in color of tomato samples followed both zero and first order kinetic models to describe visual color changes, and ＆E parameters followed first order kinetic. It was concluded that Hunter axb parameters can be used adequately to follow up the color change of tomato samples during the drying.展开更多
The mesoscopic modeling developed rapidly in the past three decades is a promising tool for predicting and understanding the microstructure evolution at grain scale.In this paper,the recent development of mesoscopic m...The mesoscopic modeling developed rapidly in the past three decades is a promising tool for predicting and understanding the microstructure evolution at grain scale.In this paper,the recent development of mesoscopic modeling and its application to microstructure evolution in steels is reviewed.Firstly,some representative computational models are briefly introduced,e.g.,the phase field model,the cellular automaton model and the Monte Carlo model.Then,the emphasis is put on the application of mesoscopic modeling of the complex features of microstructure evolution,including solidification,solid-state phase transformation,recrystallization and grain growth.Finally,some issues in the present mesoscopic modeling and its perspective are discussed.展开更多
基金Projects(2007CB613704,2007CB613705)supported by the National Basic Research Program of China
文摘The hot working behaviors of Mg-9Y-1MM-0.6Zr （WE91） magnesium alloy were researched in a temperature range of 653 773 K and strain rate range of 0.001 1 s 1 on Gleeble 1500D hot simulator under the maximum deformation degree of 60%. A mathematical model was established to predict the stress—strain curves of this alloy during deformation. The experimental results show that the relationship between stress and strain is obviously affected by the strain rates and deformation temperatures. The flow stress of WE91 magnesium alloy during high temperature deformation can be represented by Zener-Hollomon parameter in the hyperbolic Arrhenius-type equation, and the stress—strain curves obtained by the established model are in good agreement with the experimental results,which prove that the model reflects the real deformation characteristics of the WE91 alloy. The average deformation activation energy is 220 kJ/mol at strain of 0.1. The microstructures of WE91 during deformation processing are influenced by temperature and strain rates.
基金Project(31115014)supported by the of Open Research Fund Program of State Key Laboratory of Advanced Design and Manufacture forVehicle Body(Hunan University)Project(12JJ9017)supported by the Natural Science Foundation of Hunan Province,China
文摘Hot compression tests of an extruded Al-1.1Mn-0.3Mg-0.25RE alloy were performed on Gleeble-1500 system in the temperature range of 300-500 ℃ and strain rate range of 0.01-10 s-l. The associated microstructural evolutions were studied by observation of optical and transmission electron microscopes. The results show that the peak stress level decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon parameter in the hyperbolic-sine equation with the hot deformation activation energy of 186.48 kJ/mol. The steady flow behavior results from dynamic recovery whereas flow softening is associated with dynamic recrystallization and dynamic transformation of constituent particles. The main constituent particles are enriched rare earth phases. Positive purifying effects on impurity elements of Fe and Si are shown in the Al-l.lMn-0.3Mg-0.25RE alloy, which increases the workability at high temperature. Processing map was calculated and an optimum processing was determined with deformation temperature of 440-450 ℃ and strain rate of 0.01 s-1.
基金This project is supported by the National Natural Science Foundation of China (No. 69889050)
文摘A face recognition system based on Support Vector Machine (SVM) and Hidden Markov Model (HMM) has been proposed. The powerful discriminative ability of SVM is combined with the temporal modeling ability of HMM. The output of SVM is moderated to be probability output, which replaces the Mixture of Gauss (MOG) in HMM. Wavelet transformation is used to extract observation vector, which reduces the data dimension and improves the robustness.The hybrid system is compared with pure HMM face recognition method based on ORL face database and Yale face database. Experiments results show that the hybrid method has better performance.
文摘To describe the relationship between the whole material deformation behavior and each grain deformation behavior inmicro-forming,experimental and numerical modelling methods were employed.Tensile test results reveal that contrary to the valueof flow stress,the scatter of flow stress decreases with the increase of thickness-to-grain diameter(T/d)ratio.Microhardnessevaluation results show that each grain owns unique deformation behavior and randomly distributes in each specimen.The specimenwith less number of grains would be more likely to form an easy deformation zone and produce the concentration of plasticdeformation.Based on the experiment results,a size-dependent model considering the effects of grain size,geometry size,and thedeformation behavior of each grain was developed.And the effectiveness and practicability of the size-dependent model wereverified by experimental results.
基金Project(51079126) supported by the National Natural Science Foundation of ChinaProject(Y1090971) supported by the Natural Science Foundation of Zhejiang Province, China
文摘A brief review of the former studies on the mechanisms of soil rheology and microstructure is presented. Then a microstructure model and a set of rheological constitutive relations for sott clays, which describe how the rheological consolidation settlement develops, are established in the framework of the catastrophe theory. The validity of this model is verified by a series of rheological consolidation experiments with different loading rates. The experimental data show that creep deformation can be clearly observed in these tests, and the consolidation settlement is loading rate dependent. The characteristics of the deformation can be explained and reproduced successfully using the model. It can be concluded that only the biggest set of voids would collapse for one load increment. Parameters in the model, k and η, are gained by curve fitting. With only two free parameters, good fits of the data are achieved.
基金Project(U1637601)supported by the Joint Funds of the National Natural Science Foundation of China。
文摘Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure formed at grain boundaries with no precipitates inside the grains.In partially melted zone(PMZ),symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-likeθ′phases appeared in the secondary heated zone.In over aged zone(OAZ),the coarsening and dissolution ofθ′phases occurred and mostθ′phases transformed intoθphases.In general heat affected zone(HAZ),θ′phases coarsened.Factors such as the strengthening phases,the grain size,the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint.Moreover,a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates,the average diameter of precipitates and the concentration of soluble elements was proposed.
基金the financial supports from the National Natural Science Foundation of China (Nos. 52001163, 52075237)the Primary Research and Development Plan of Jiangsu Province, China (No. BE2019119)
文摘Hot deformation behaviors and microstructure evolution of Ti-3Al-5Mo-4Cr-2Zr-1Fe(Ti-35421)alloy in theβsingle field are investigated by isothermal compression tests on a Gleeble-3500 simulator at temperatures of 820-900°C and strain rates of 0.001-1 s^(-1).The research results show that discontinuous yield phenomenon and rheological softening are affected by the strain rates and deformation temperatures.The critical conditions for dynamic recrystallization and kinetic model of Ti-35421 alloy are determined,and the Arrhenius constitutive model is constructed.The rheological behaviors of Ti-35421 alloys aboveβphase transformation temperature are predicted by the constitutive model accurately.The EBSD analysis proves that the deformation softening is controlled by dynamic recovery and dynamic recrystallization.In addition,continuous dynamic recrystallization is determined during hot deformation,and the calculation model for recrystallization grain sizes is established.Good linear dependency between the experimental and simulated values of recrystallized grain sizes indicates that the present model can be used for the prediction of recrystallized grain size with high accuracy.
文摘In this paper, we extend the mapping transformation method through introducing variable coefficients.By means of the extended mapping transformation method, many explicit and exact general solutions with arbitrary functions for some nonlinear partial differential equations, which contain solitary wave solutions, trigonometric function solutions, and rational solutions, are obtained.
文摘Kinetics of color change in tomato purees dried using microwave and conventional method were investigated. For this purpose, the color parameters of Hunter L,a,b and browning index （A42o）, and estimated values of chroma, hue angle, AE, Hunter a/b and a ~ b were examined. The changes in color of tomato samples followed both zero and first order kinetic models to describe visual color changes, and ＆E parameters followed first order kinetic. It was concluded that Hunter axb parameters can be used adequately to follow up the color change of tomato samples during the drying.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50871109 and 51001096)
文摘The mesoscopic modeling developed rapidly in the past three decades is a promising tool for predicting and understanding the microstructure evolution at grain scale.In this paper,the recent development of mesoscopic modeling and its application to microstructure evolution in steels is reviewed.Firstly,some representative computational models are briefly introduced,e.g.,the phase field model,the cellular automaton model and the Monte Carlo model.Then,the emphasis is put on the application of mesoscopic modeling of the complex features of microstructure evolution,including solidification,solid-state phase transformation,recrystallization and grain growth.Finally,some issues in the present mesoscopic modeling and its perspective are discussed.
