Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occtLrring on the run-out table （ROT） in a hot strip mill. A variational method is utilized for the discretizati...Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occtLrring on the run-out table （ROT） in a hot strip mill. A variational method is utilized for the discretization of the governing transient conduction-convection equation, with heat transfer coefficients adaptively determined by the actual mill data. To consider the thermal effect of phase transformation during cooling, a constitutive equation for describing austenite decomposition kinetics of steel in air and water cooling zones is coupled with the heat transfer model. As the basic required inputs in the numerical simulations, thermal material properties are experimentally measured for three carbon steels and the least squares method is used to statistically derive regression models for the properties, including specific heat and thermal conductivity. The numerical simulation and experimental results show that the setup accuracy of the temperature prediction system of ROT is effectively improved.展开更多
Non-uniformity of temperature distribution across strip width direction is the ultimate reason why the flatness defect occurs on the strip after cooling process although the strip is flat at the exit of finishing mill...Non-uniformity of temperature distribution across strip width direction is the ultimate reason why the flatness defect occurs on the strip after cooling process although the strip is flat at the exit of finishing mill.One thermal , microstructural and mechanical coupling analysis model for predicting flatness change of steel strip during the run-out table cooling process was established using ABAQUS finite element software.K Esaka phase transformation kinetics model was employed to calculate the phase transformation , and coupled with temperature calculation using the user subroutine program HETVAL.Elasto-plasticity constitutive equations of steel material , in which conventional elastic and plastic strains , thermal strain , phase transformation strain and transformation induced plastic strain were considered , were derived and programmed in the user subroutine program UMAT.The conclusion that flatness of steel strip will develop to edge wave defect under the functions of the differential thermal and microstructural behaviors across strip width during the run-out table cooling procedure was acquired through the analysis results of this model.Calculation results of this analysis model agree well with the actual measurements and observation.展开更多
Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic leve...Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic level is a key concept to understand where connections occur and how far molecules aggregate. A periodic table for liquids with saturation levels is proposed, in agreement with the even-odd rule, for both organic and inorganic elements. With the aim at reaching the most stable complexes, meaning no other chemical reactions can occur in the liquid phase, the structure of complexes resulting from liquefaction of about 30 molecules is devised. The article concludes that complexes in liquids generally assume rounded shapes of an intermediate size between gas and solid structures. It shows that saturation and covalent bonds alone can explain the specific properties of liquids. While it is generally acknowledged that molecular energy in gases and solids are respectively linear kinetic and vibratory, we suggest that rotatory energy dominates in liquids.展开更多
Physical modelling of cantilever retaining walls with and without backfill reinforcement was conducted on a 1g shaking table to evaluate the mitigation effect of reinforcement on system dynamics(g denotes the accelera...Physical modelling of cantilever retaining walls with and without backfill reinforcement was conducted on a 1g shaking table to evaluate the mitigation effect of reinforcement on system dynamics(g denotes the acceleration of gravity).The model wall has a height of 1.5 m with a scale ratio of 1/4 and retains dry sand throughout.The input motions are amplified to three levels of input peak base acceleration,0.11g,0.24g,and 0.39g,corresponding to minor,moderate,and major earthquakes,respectively.Investigation of the seismic response of the retaining walls focuses on acceleration and lateral displacement of the wall and backfill,dynamic earth pressures,and tensile load in the reinforcements(modeled by phosphor-bronze strips welded into a mesh).The inclusion of reinforcement has been observed to improve the integrity of the wall-soil system,mitigate vibration-related damage,and reduce the fundamental frequency of a reinforced system.Propagation of acceleration from the base to the upper portion is accompanied by time delay and nonlinear amplification.A reinforced system with a lower acceleration amplification factor than the unreinforced one indicates that reinforcement can reduce the amplification effect of input motion.Under minor and moderate earthquake loadings,reinforcement allows the inertia force and seismic earth pressure to be asynchronous and decreases the seismic earth pressure when inertia forces peak.During major earthquake loading,the wall is displaced horizontally less than the backfill,with soil pushing the wall substantially;the effect of backfill reinforcement has not been fully mobilized.The dynamic earth pressure is large at the top and diminishes toward the bottom.展开更多
基金the National Basic Research Program (973) of China (No. 2006CB705400)the National Natural Science Foundation of China (No. 50575200)
文摘Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occtLrring on the run-out table （ROT） in a hot strip mill. A variational method is utilized for the discretization of the governing transient conduction-convection equation, with heat transfer coefficients adaptively determined by the actual mill data. To consider the thermal effect of phase transformation during cooling, a constitutive equation for describing austenite decomposition kinetics of steel in air and water cooling zones is coupled with the heat transfer model. As the basic required inputs in the numerical simulations, thermal material properties are experimentally measured for three carbon steels and the least squares method is used to statistically derive regression models for the properties, including specific heat and thermal conductivity. The numerical simulation and experimental results show that the setup accuracy of the temperature prediction system of ROT is effectively improved.
文摘Non-uniformity of temperature distribution across strip width direction is the ultimate reason why the flatness defect occurs on the strip after cooling process although the strip is flat at the exit of finishing mill.One thermal , microstructural and mechanical coupling analysis model for predicting flatness change of steel strip during the run-out table cooling process was established using ABAQUS finite element software.K Esaka phase transformation kinetics model was employed to calculate the phase transformation , and coupled with temperature calculation using the user subroutine program HETVAL.Elasto-plasticity constitutive equations of steel material , in which conventional elastic and plastic strains , thermal strain , phase transformation strain and transformation induced plastic strain were considered , were derived and programmed in the user subroutine program UMAT.The conclusion that flatness of steel strip will develop to edge wave defect under the functions of the differential thermal and microstructural behaviors across strip width during the run-out table cooling procedure was acquired through the analysis results of this model.Calculation results of this analysis model agree well with the actual measurements and observation.
文摘Building on the idea that molecules in liquid phase associate into multi-molecular complexes through covalent bonds, the present article focuses on the possible structures of these complexes. Saturation at atomic level is a key concept to understand where connections occur and how far molecules aggregate. A periodic table for liquids with saturation levels is proposed, in agreement with the even-odd rule, for both organic and inorganic elements. With the aim at reaching the most stable complexes, meaning no other chemical reactions can occur in the liquid phase, the structure of complexes resulting from liquefaction of about 30 molecules is devised. The article concludes that complexes in liquids generally assume rounded shapes of an intermediate size between gas and solid structures. It shows that saturation and covalent bonds alone can explain the specific properties of liquids. While it is generally acknowledged that molecular energy in gases and solids are respectively linear kinetic and vibratory, we suggest that rotatory energy dominates in liquids.
基金the National Natural Science Foundation of China(Nos.41901073 and 52078435)the Sichuan Science and Technology Program of China(No.2021YJ0001)。
文摘Physical modelling of cantilever retaining walls with and without backfill reinforcement was conducted on a 1g shaking table to evaluate the mitigation effect of reinforcement on system dynamics(g denotes the acceleration of gravity).The model wall has a height of 1.5 m with a scale ratio of 1/4 and retains dry sand throughout.The input motions are amplified to three levels of input peak base acceleration,0.11g,0.24g,and 0.39g,corresponding to minor,moderate,and major earthquakes,respectively.Investigation of the seismic response of the retaining walls focuses on acceleration and lateral displacement of the wall and backfill,dynamic earth pressures,and tensile load in the reinforcements(modeled by phosphor-bronze strips welded into a mesh).The inclusion of reinforcement has been observed to improve the integrity of the wall-soil system,mitigate vibration-related damage,and reduce the fundamental frequency of a reinforced system.Propagation of acceleration from the base to the upper portion is accompanied by time delay and nonlinear amplification.A reinforced system with a lower acceleration amplification factor than the unreinforced one indicates that reinforcement can reduce the amplification effect of input motion.Under minor and moderate earthquake loadings,reinforcement allows the inertia force and seismic earth pressure to be asynchronous and decreases the seismic earth pressure when inertia forces peak.During major earthquake loading,the wall is displaced horizontally less than the backfill,with soil pushing the wall substantially;the effect of backfill reinforcement has not been fully mobilized.The dynamic earth pressure is large at the top and diminishes toward the bottom.
