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
The hot deformation behavior of AA2014forging aluminum alloy was investigated by isothermal compression tests attemperatures of350-480°C and strain rates of0.001-1s-1on a Gleeble-3180simulator.The corresponding m...The hot deformation behavior of AA2014forging aluminum alloy was investigated by isothermal compression tests attemperatures of350-480°C and strain rates of0.001-1s-1on a Gleeble-3180simulator.The corresponding microstructures of thealloys under different deformation conditions were studied using optical microscopy(OM),electron back scattered diffraction(EBSD)and transmission electron microscopy(TEM).The processing maps were constructed with strains of0.1,0.3,0.5and0.7.The results showed that the instability domain was more inclined to occur at strain rates higher than0.1s-1and manifested in theform of local non-uniform deformation.At the strain of0.7,the processing map showed two stability domains:domain I(350-430°C,0.005-0.1s-1)and domain II(450-480°C,0.001-0.05s-1).The predominant softening mechanisms in both of the twodomains were dynamic recovery.Uniform microstructures were obtained in domain I,and an extended recovery occurred in domainII,which would lead to the potential sub-grain boundaries progressively transforming into new high-angle grain boundaries.Theoptimum hot working parameters for the AA2014forging aluminum alloy were determined to be370-420°C and0.008-0.08s-1.展开更多
Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300-420°C and strain rate range of 0.01-10 s-1.A physically-bas...Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300-420°C and strain rate range of 0.01-10 s-1.A physically-based model was developed to accurately predict the flow stress.Meanwhile,processing maps were established to optimize hot working parameters.It is found that decreasing the strain rate or increasing the deformation temperature reduces the flow stress.The high activation energy is closely related to the pinning of dislocations from Si-containing dispersoids.Moreover,the deformed grains and the Si-containing dispersoids in the matrix are elongated perpendicular to the compression direction,and incomplete dynamic recrystallization(DRX)is discovered on the elongated boundaries in domain with peak efficiency.The flow instability is mainly attributed to the flow localization,brittle fracture of eutectic Si phase,and formation of adiabatic shear band.The optimum hot working window is 380-420°C and 0.03-0.28 s-1.展开更多
The apparent activation energy for deformation(Q)and strain rate sensitivity(m)of GH4586 superalloy are calculated and the variation trend is reasonably explained by the microstructure observations.Constitutive modell...The apparent activation energy for deformation(Q)and strain rate sensitivity(m)of GH4586 superalloy are calculated and the variation trend is reasonably explained by the microstructure observations.Constitutive modelling of this superalloy is established and the processing maps at different strains are constructed.The results show that the Q value is in the range of 751.22−878.29 kJ/mol.At a temperature of 1060°C,strain rate of 0.001 s^(−1),and strain of 0.65,the m value of GH4586 superalloy reaches a maximum of 0.42.The optimal processing parameter of GH4586 superalloy is at a deformation temperature of 1050°C and a strain rate of 0.001 s^(−1).The domains of flow instability notably expand with increasing strain during high temperature deformation of GH4586 superalloy.展开更多
The hot deformation behaviors of Cr5 steel were investigated.The hot compression tests were conducted in the temperature range of 900-1150 °C under strain rates of 0.01,0.1 and 1 s^(-1).The constitutive equation ...The hot deformation behaviors of Cr5 steel were investigated.The hot compression tests were conducted in the temperature range of 900-1150 °C under strain rates of 0.01,0.1 and 1 s^(-1).The constitutive equation and material constants(Q,n,α ln A) are obtained according to the hyperbolic sine function and Zener-Hollomon parameter.Besides,dynamic recrystallization(DRX) grain size model and critical strain model are acquired.The processing maps with the strain of 0.1,0.3 and 0.5 are obtained on the basis of dynamic materials model.It has been observed that DRX occurs at high temperature and low strain rate.According to the processing map,the safety region exists in the temperature range of 920-1150 °C with strain rate of 0.01-0.20 s^(-1).展开更多
[Objective] The aims was to construct peak sweet processing suitability evaluation model and determine the suitable varieties of peak sweet processing in chestnut. [Method] "Zaofeng", "Yah Long" etc. 15 chestnut v...[Objective] The aims was to construct peak sweet processing suitability evaluation model and determine the suitable varieties of peak sweet processing in chestnut. [Method] "Zaofeng", "Yah Long" etc. 15 chestnut varieties in Yan Shan area were taken as research objects and investigated the sensory, physicochemical nutrition and processing indexes. The correlation analysis, principal component analysis and cluster analysis were adopted to simplify and calculate the evaluation index, and set up the mathematical model. [Result] Obvious differences in different varieties of raw materials and products of each index and some indicators existed significant correlation relationship; principal component analysis determined the five principal components: hardness, b value, moisture content, total sugar, browning degree and edible rate or the core indicators of quality evaluation in peak sweet chestnut, and the establishment of products comprehensive value scoring model: Y=0.033 509 hardness +0.033 509 b value +0.f85 1'73 moisture content +0.208 983 total sugar +0.108 499 browning degree +0.430 327 ratio of feed, peak sweet chestnut quality and raw material associated model: Y=-1.109+0.015 ratio of good fruit -0.018 kernel hardness +0.008 starch, [Conclusion] Peak sweet chestnut processing suitability evaluation model can provide the basis for chestnut processing and the suitable processing of the chestnut breeding; "Yanguang", "Yan Long", "Yankui", are very suitable, and "Zibo", "Yah Ping" are more appropriate for peak sweet processing.展开更多
This research paper describes an SEE (Structural Engineering Encounter) Lab project. The paper reports on the development of a single-story, single-bay portal frame model as part of the AIMS2 (attract, inspire, men...This research paper describes an SEE (Structural Engineering Encounter) Lab project. The paper reports on the development of a single-story, single-bay portal frame model as part of the AIMS2 (attract, inspire, mentor and support students) grant supported through the US DOE (Department of Education) summer research program at California State University, Northridge. This research effort is part of a comprehensive program to develop laboratory models of structures commonly encountered in civil engineering practice, which can serve the dual purpose of accomplishing engineering education and research in the areas of structural and earthquake engineering. The objective of the present study was to construct a physical model of the aforementioned frame to experimentally collect data due to the application of vertical and lateral loadings through instrumentation such as strain gages and an LVDT (linear variable differential transformer) displacement transducer, and also to make comparisons with theoretical and numerical predictions.展开更多
Gravity dam is a typical structure that has been frequently used in the fields of water conservancy engineering, and the safety of the structure has received widespread attention recently. Due to earthquakes or other ...Gravity dam is a typical structure that has been frequently used in the fields of water conservancy engineering, and the safety of the structure has received widespread attention recently. Due to earthquakes or other reasons, gravity dams normally have damage such as cracks in practical service. Damage in the structures can alter the structural dynamic behavior and seriously affect structural performance. Maintaining safety and integrity of the gravity dam structures requires a better understanding of dynamic response of structure with damage and associated damage detection method. In order to study thoroughly the dynamic behavior of gravity dam with damage, the sweep vibration responses of the gravity dam with and without damage are investigated. The experimental results show that the peak-peak acceleration responses all increase for the structure is with crack. At the same time, a structural damage detection method, i.e., the local damage factor (LDF) method, is considered in the study of gravity dam damage detection when the dam is subjected to the base excitation. It is shown that the LDF method can be used as a damage index and is capable of evaluating both the presence and relative severity of structural damage, and it can be used as a viable condition assessment and damage identification technique to detect and quantify the damage in the gravity dam.展开更多
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Project(51301209) supported by the National Natural Science Foundation of China
文摘The hot deformation behavior of AA2014forging aluminum alloy was investigated by isothermal compression tests attemperatures of350-480°C and strain rates of0.001-1s-1on a Gleeble-3180simulator.The corresponding microstructures of thealloys under different deformation conditions were studied using optical microscopy(OM),electron back scattered diffraction(EBSD)and transmission electron microscopy(TEM).The processing maps were constructed with strains of0.1,0.3,0.5and0.7.The results showed that the instability domain was more inclined to occur at strain rates higher than0.1s-1and manifested in theform of local non-uniform deformation.At the strain of0.7,the processing map showed two stability domains:domain I(350-430°C,0.005-0.1s-1)and domain II(450-480°C,0.001-0.05s-1).The predominant softening mechanisms in both of the twodomains were dynamic recovery.Uniform microstructures were obtained in domain I,and an extended recovery occurred in domainII,which would lead to the potential sub-grain boundaries progressively transforming into new high-angle grain boundaries.Theoptimum hot working parameters for the AA2014forging aluminum alloy were determined to be370-420°C and0.008-0.08s-1.
基金Project(51375502)supported by the National Natural Science Foundation of ChinaProject(2015CX002)supported by the Innovation-driven Plan in Central South University,China+2 种基金Project(2016RS2006)supported by the Science and Technology Leading Talent in Hunan Province,ChinaProject(Q2015140)supported by the Program of Chang Jiang Scholars of Ministry of Education,ChinaProject(2016JJ1017)supported by the Natural Science Foundation for Distinguished Young Scholars of Hunan Province,China
文摘Isothermal compression experiments were conducted to study the hot deformation behaviors of a Sr-modified Al-Si-Mg alloy in the temperature range of 300-420°C and strain rate range of 0.01-10 s-1.A physically-based model was developed to accurately predict the flow stress.Meanwhile,processing maps were established to optimize hot working parameters.It is found that decreasing the strain rate or increasing the deformation temperature reduces the flow stress.The high activation energy is closely related to the pinning of dislocations from Si-containing dispersoids.Moreover,the deformed grains and the Si-containing dispersoids in the matrix are elongated perpendicular to the compression direction,and incomplete dynamic recrystallization(DRX)is discovered on the elongated boundaries in domain with peak efficiency.The flow instability is mainly attributed to the flow localization,brittle fracture of eutectic Si phase,and formation of adiabatic shear band.The optimum hot working window is 380-420°C and 0.03-0.28 s-1.
基金Project(2020JC-17)supported by the Science Fund for Distinguished Young Scholars from Shaanxi Province,ChinaProject(51705425)+4 种基金supported by the National Natural Science Foundation of ChinaProject(2019-QZ-04)supported by the Research Fund of the State Key Laboratory of Solidification Processing(NWPU),ChinaProjects(3102019PY007,3102019MS0403)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The apparent activation energy for deformation(Q)and strain rate sensitivity(m)of GH4586 superalloy are calculated and the variation trend is reasonably explained by the microstructure observations.Constitutive modelling of this superalloy is established and the processing maps at different strains are constructed.The results show that the Q value is in the range of 751.22−878.29 kJ/mol.At a temperature of 1060°C,strain rate of 0.001 s^(−1),and strain of 0.65,the m value of GH4586 superalloy reaches a maximum of 0.42.The optimal processing parameter of GH4586 superalloy is at a deformation temperature of 1050°C and a strain rate of 0.001 s^(−1).The domains of flow instability notably expand with increasing strain during high temperature deformation of GH4586 superalloy.
基金Project(51322405)supported by the National Natural Science Foundation of China
文摘The hot deformation behaviors of Cr5 steel were investigated.The hot compression tests were conducted in the temperature range of 900-1150 °C under strain rates of 0.01,0.1 and 1 s^(-1).The constitutive equation and material constants(Q,n,α ln A) are obtained according to the hyperbolic sine function and Zener-Hollomon parameter.Besides,dynamic recrystallization(DRX) grain size model and critical strain model are acquired.The processing maps with the strain of 0.1,0.3 and 0.5 are obtained on the basis of dynamic materials model.It has been observed that DRX occurs at high temperature and low strain rate.According to the processing map,the safety region exists in the temperature range of 920-1150 °C with strain rate of 0.01-0.20 s^(-1).
基金Supported by the Forestry Public Welfare Industry Research Special Fund Project of China(201304708)
文摘[Objective] The aims was to construct peak sweet processing suitability evaluation model and determine the suitable varieties of peak sweet processing in chestnut. [Method] "Zaofeng", "Yah Long" etc. 15 chestnut varieties in Yan Shan area were taken as research objects and investigated the sensory, physicochemical nutrition and processing indexes. The correlation analysis, principal component analysis and cluster analysis were adopted to simplify and calculate the evaluation index, and set up the mathematical model. [Result] Obvious differences in different varieties of raw materials and products of each index and some indicators existed significant correlation relationship; principal component analysis determined the five principal components: hardness, b value, moisture content, total sugar, browning degree and edible rate or the core indicators of quality evaluation in peak sweet chestnut, and the establishment of products comprehensive value scoring model: Y=0.033 509 hardness +0.033 509 b value +0.f85 1'73 moisture content +0.208 983 total sugar +0.108 499 browning degree +0.430 327 ratio of feed, peak sweet chestnut quality and raw material associated model: Y=-1.109+0.015 ratio of good fruit -0.018 kernel hardness +0.008 starch, [Conclusion] Peak sweet chestnut processing suitability evaluation model can provide the basis for chestnut processing and the suitable processing of the chestnut breeding; "Yanguang", "Yan Long", "Yankui", are very suitable, and "Zibo", "Yah Ping" are more appropriate for peak sweet processing.
文摘This research paper describes an SEE (Structural Engineering Encounter) Lab project. The paper reports on the development of a single-story, single-bay portal frame model as part of the AIMS2 (attract, inspire, mentor and support students) grant supported through the US DOE (Department of Education) summer research program at California State University, Northridge. This research effort is part of a comprehensive program to develop laboratory models of structures commonly encountered in civil engineering practice, which can serve the dual purpose of accomplishing engineering education and research in the areas of structural and earthquake engineering. The objective of the present study was to construct a physical model of the aforementioned frame to experimentally collect data due to the application of vertical and lateral loadings through instrumentation such as strain gages and an LVDT (linear variable differential transformer) displacement transducer, and also to make comparisons with theoretical and numerical predictions.
基金supported by the National Basic Research Program of China ("973"Project)(Grant No. 2007CB714104)
文摘Gravity dam is a typical structure that has been frequently used in the fields of water conservancy engineering, and the safety of the structure has received widespread attention recently. Due to earthquakes or other reasons, gravity dams normally have damage such as cracks in practical service. Damage in the structures can alter the structural dynamic behavior and seriously affect structural performance. Maintaining safety and integrity of the gravity dam structures requires a better understanding of dynamic response of structure with damage and associated damage detection method. In order to study thoroughly the dynamic behavior of gravity dam with damage, the sweep vibration responses of the gravity dam with and without damage are investigated. The experimental results show that the peak-peak acceleration responses all increase for the structure is with crack. At the same time, a structural damage detection method, i.e., the local damage factor (LDF) method, is considered in the study of gravity dam damage detection when the dam is subjected to the base excitation. It is shown that the LDF method can be used as a damage index and is capable of evaluating both the presence and relative severity of structural damage, and it can be used as a viable condition assessment and damage identification technique to detect and quantify the damage in the gravity dam.