The hot flow behaviors,microstructure evolution and fractographs were studied to optimize the hot forming process of the TA32 titanium alloy thin-walled part.A set of microstructure-based constitutive equations were d...The hot flow behaviors,microstructure evolution and fractographs were studied to optimize the hot forming process of the TA32 titanium alloy thin-walled part.A set of microstructure-based constitutive equations were developed based on the experimental data,which described the relationships among the hot flow stresses and the evolution of phase volume fraction,dislocation density,grain size and damage.The constitutive model was imported into ABAQUS 6.14 to simulate the hot forming process for a typical thin-walled part.The effective strain,dislocation density and damage distribution as well as forming defects of formed parts under different process parameters were predicted.A qualified part without wrinkling and fracture defects was produced at a loading speed of 5 mm/s at 800℃ by the modified blank shape,where the maximum damage value was only 18.3%.The accuracy of constitutive model and finite element(FE)simulation was verified by the microhardness tests,which indicates that the FE model based on physical internal-state variables can well optimize the hot forming process of TA32 titanium alloy complex parts.展开更多
The sensitive second derivative waves of Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ),Ni(Ⅱ),Zn(Ⅱ),Fe(Ⅱ)and Mn(Ⅱ),forming in the substrate solution(pH=9.26)consisting of ammonia,ammonium chlorid,gelatin and ascorbic acid were researched.T...The sensitive second derivative waves of Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ),Ni(Ⅱ),Zn(Ⅱ),Fe(Ⅱ)and Mn(Ⅱ),forming in the substrate solution(pH=9.26)consisting of ammonia,ammonium chlorid,gelatin and ascorbic acid were researched.The peak potentials of the polarographic waves of the seven ions are at about 0.48,0.63,0.79,1.04,1.28,1.44 and 1.60 V respectively.Combining with microwave technique,a new method for the simultaneous determination of the seven trace elements in Chinese traditional medicine was developed.The method is easy to operate,rapid,simple and convenient.When the signal-to-noise rate equals 3,the detection limits of Cu,Pb,Cd,Ni,Zn,Fe and Mn are 4.2×10 3,5.3×10 3,2.1×10 3,5.8×10 4,3.0×10 3,7.7×10 4 and 1.1×10 3 μg/mL respectively.Well linear relationships exist between the concentrations and the peak currents when Cu,Pb,Cd,Ni,Zn,Fe and Mn concentrations are within 8.5×10 3 10,9.7×10 3 10,4.5×10 3 10,1.2×10 3 10,6.4×10 3 10,1.5×10 3 10 and 2.8×10 3 10 μg/mL,respectively.The method has been used to the simultaneous determination of the seven trace elements in Salvia Miltiorrhiza Root and compound Salvia Miltiorrhiza Root injection,the relative standard deviations(RSDs)of the Cu,Pb,Cd,Ni,Zn,Fe and Mn in the two medicines are 3.9% and 5.8%,4.0% and 4.1%,4.3% and 5.7%,4.9% and 5.3%,4.4% and 4.7%,3.5% and 4.0%,0.51% and 2.8%,respectively;the comparisons of the determination results with the values obtained by the standard method indicate that the presented method has very well veracity.展开更多
The effects of forging parameters on the deformation and microstructure distributions of as-forged straight spur gears wereinvestigated by finite element(FE)simulation and statistical analysis method.Spur gear forging...The effects of forging parameters on the deformation and microstructure distributions of as-forged straight spur gears wereinvestigated by finite element(FE)simulation and statistical analysis method.Spur gear forging using the movable cavity die designwas investigated by integrating the FE method with the microstructure evolution models for AZ31B magnesium alloys.The requiredinputs such as flow stress curves and microstructure evolution models,were obtained through the Gleeble thermal mechanical testingand quantitative metallography analysis method.Numerical simulation and experimental examination confirm that both thedeformation and microstructure are non-uniformly distributed in the as-forged gears.Decreasing deformation temperature orincreasing strain rate is beneficial to obtaining fine-grained microstructure but is harmful to the uniformity in deformation ormicrostructure.The level of the non-uniformity results from the complex shape of gear and the friction between the billet and dies,which is closely associated with the characteristics of flow stress curve.展开更多
Trace element analysis on hair samples has been widely used to assess wildlife and human exposure to different contaminants present in the environment or at the workplace. Pollutants due to the presence of toxic metal...Trace element analysis on hair samples has been widely used to assess wildlife and human exposure to different contaminants present in the environment or at the workplace. Pollutants due to the presence of toxic metals in environment not only enter the body by breading, water, and foodstuff accumulates in hair, but they could be adsorbed directly on the hair from environment. In order to remove adsorbed elements and thus determine the internally bound elements correctly, hair sample must be washed. In the present work, we propose uncertainty estimation for the analytical results that are obtained from determination of cadmium, lead, copper, iron, manganese and nickel in human hair by flame and electrothermal atomic absorption spectrometry （FAAS and ETAAS）. To estimate the uncertainty of analytical result obtained, two types of bias are calculated in the assessment of trueness： a proportional bias and a constant bias. Nested design was applied for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked samples. In this case, the concentration found is plotted against the concentration added and the slop of standard addition curve is an estimate of the method recovery. Estimated method of average recovery in human hair is： （1.019 ±0.026）, （0.918 ±0.014）, （1.073±0.016）, （1.0597± 0.017）, （1.073± 0.020） and （0.934± 0.117） for Cd, Pb, Mn, Ni, Fe and Cu respectively.展开更多
With the aim of simulating the blow-up solutions, a moving finite element method, based on nonuni- form meshes both in time and in space, is proposed in this paper to solve time fractional partial differential equatio...With the aim of simulating the blow-up solutions, a moving finite element method, based on nonuni- form meshes both in time and in space, is proposed in this paper to solve time fractional partial differential equations （FPDEs）. The unconditional stability and convergence rates of 2 -a for time and r for space are proved when the method is used for the linear time FPDEs with a-th order time derivatives. Numerical exam-ples are provided to support the theoretical findings, and the blow-up solutions for the nonlinear FPDEs are simulated by the method.展开更多
The approach of nonconforming finite element method admits users to solve the partial differential equations with lower complexity,but the accuracy is usually low.In this paper,we present a family of highaccuracy nonc...The approach of nonconforming finite element method admits users to solve the partial differential equations with lower complexity,but the accuracy is usually low.In this paper,we present a family of highaccuracy nonconforming finite element methods for fourth order problems in arbitrary dimensions.The finite element methods are given in a unified way with respect to the dimension.This is an effort to reveal the balance between the accuracy and the complexity of finite element methods.展开更多
We analyze an h-p version Petrov-Galerkin finite element method for linear Volterra integrodifferential equations. We prove optimal a priori error bounds in the L2- and H1-norm that are explicit in the time steps,the ...We analyze an h-p version Petrov-Galerkin finite element method for linear Volterra integrodifferential equations. We prove optimal a priori error bounds in the L2- and H1-norm that are explicit in the time steps,the approximation orders and in the regularity of the exact solution. Numerical experiments confirm the theoretical results. Moreover,we observe that the numerical scheme superconverges at the nodal points of the time partition.展开更多
H1-Galerkin nonconforming mixed finite element methods are analyzed for integro-differential equation of parabolic type.By use of the typical characteristic of the elements,we obtain that the Galerkin mixed approximat...H1-Galerkin nonconforming mixed finite element methods are analyzed for integro-differential equation of parabolic type.By use of the typical characteristic of the elements,we obtain that the Galerkin mixed approximations have the same rates of convergence as in the classical mixed method,but without LBB stability condition.展开更多
A numerical analysis was performed to study the influence of process parameters on the microstructure evolution of IN718 alloy in rotary forging using the finite element method （FEM）. For this purpose, a constitutiv...A numerical analysis was performed to study the influence of process parameters on the microstructure evolution of IN718 alloy in rotary forging using the finite element method （FEM）. For this purpose, a constitutive equation considering the effects of strain hardening and dynamic softening of IN718 alloy was built. The constitutive equation and microstructure models were implemented into the finite element code to investigate the microstructure evolution during rotary forging subject to large deformations. The simulations were carried out in the ratio of initial height to diameter range 0.2-0.8, the angle of the rocker 3°-7° and the relative feed per revolution range 0.01-0.1 r^-1. The research results revealed the deformation mechanism and the correlation of process parameters with the grain size evolution of IN718 alloy during rotary forging. These provide evidence for the selection of rotary forging parameters.展开更多
Seawater intrusion problem is considered in this paper.Its mathematical model is anonlinear coupled system of partial differential equations with initial boundary problem.It consistsof the water head equation and the ...Seawater intrusion problem is considered in this paper.Its mathematical model is anonlinear coupled system of partial differential equations with initial boundary problem.It consistsof the water head equation and the salt concentration equation.A combined method is developedto approximate the water head equation by mixed finite element method and concentration equationby discontinuous Galerkin method.The scheme is continuous in time and optimal order estimates inH^1-norm and L^2-norm are derived for the errors.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51805256)。
文摘The hot flow behaviors,microstructure evolution and fractographs were studied to optimize the hot forming process of the TA32 titanium alloy thin-walled part.A set of microstructure-based constitutive equations were developed based on the experimental data,which described the relationships among the hot flow stresses and the evolution of phase volume fraction,dislocation density,grain size and damage.The constitutive model was imported into ABAQUS 6.14 to simulate the hot forming process for a typical thin-walled part.The effective strain,dislocation density and damage distribution as well as forming defects of formed parts under different process parameters were predicted.A qualified part without wrinkling and fracture defects was produced at a loading speed of 5 mm/s at 800℃ by the modified blank shape,where the maximum damage value was only 18.3%.The accuracy of constitutive model and finite element(FE)simulation was verified by the microhardness tests,which indicates that the FE model based on physical internal-state variables can well optimize the hot forming process of TA32 titanium alloy complex parts.
基金Proejcr(20235020) supported by the National Natural Science Foundation of China
文摘The sensitive second derivative waves of Cu(Ⅱ),Pb(Ⅱ),Cd(Ⅱ),Ni(Ⅱ),Zn(Ⅱ),Fe(Ⅱ)and Mn(Ⅱ),forming in the substrate solution(pH=9.26)consisting of ammonia,ammonium chlorid,gelatin and ascorbic acid were researched.The peak potentials of the polarographic waves of the seven ions are at about 0.48,0.63,0.79,1.04,1.28,1.44 and 1.60 V respectively.Combining with microwave technique,a new method for the simultaneous determination of the seven trace elements in Chinese traditional medicine was developed.The method is easy to operate,rapid,simple and convenient.When the signal-to-noise rate equals 3,the detection limits of Cu,Pb,Cd,Ni,Zn,Fe and Mn are 4.2×10 3,5.3×10 3,2.1×10 3,5.8×10 4,3.0×10 3,7.7×10 4 and 1.1×10 3 μg/mL respectively.Well linear relationships exist between the concentrations and the peak currents when Cu,Pb,Cd,Ni,Zn,Fe and Mn concentrations are within 8.5×10 3 10,9.7×10 3 10,4.5×10 3 10,1.2×10 3 10,6.4×10 3 10,1.5×10 3 10 and 2.8×10 3 10 μg/mL,respectively.The method has been used to the simultaneous determination of the seven trace elements in Salvia Miltiorrhiza Root and compound Salvia Miltiorrhiza Root injection,the relative standard deviations(RSDs)of the Cu,Pb,Cd,Ni,Zn,Fe and Mn in the two medicines are 3.9% and 5.8%,4.0% and 4.1%,4.3% and 5.7%,4.9% and 5.3%,4.4% and 4.7%,3.5% and 4.0%,0.51% and 2.8%,respectively;the comparisons of the determination results with the values obtained by the standard method indicate that the presented method has very well veracity.
基金Project(51675335)supported by the National Natural Science Foundation of ChinaProject(BK20130447)supported by the Natural Science Foundation of Jiangsu Province,China
文摘The effects of forging parameters on the deformation and microstructure distributions of as-forged straight spur gears wereinvestigated by finite element(FE)simulation and statistical analysis method.Spur gear forging using the movable cavity die designwas investigated by integrating the FE method with the microstructure evolution models for AZ31B magnesium alloys.The requiredinputs such as flow stress curves and microstructure evolution models,were obtained through the Gleeble thermal mechanical testingand quantitative metallography analysis method.Numerical simulation and experimental examination confirm that both thedeformation and microstructure are non-uniformly distributed in the as-forged gears.Decreasing deformation temperature orincreasing strain rate is beneficial to obtaining fine-grained microstructure but is harmful to the uniformity in deformation ormicrostructure.The level of the non-uniformity results from the complex shape of gear and the friction between the billet and dies,which is closely associated with the characteristics of flow stress curve.
文摘Trace element analysis on hair samples has been widely used to assess wildlife and human exposure to different contaminants present in the environment or at the workplace. Pollutants due to the presence of toxic metals in environment not only enter the body by breading, water, and foodstuff accumulates in hair, but they could be adsorbed directly on the hair from environment. In order to remove adsorbed elements and thus determine the internally bound elements correctly, hair sample must be washed. In the present work, we propose uncertainty estimation for the analytical results that are obtained from determination of cadmium, lead, copper, iron, manganese and nickel in human hair by flame and electrothermal atomic absorption spectrometry （FAAS and ETAAS）. To estimate the uncertainty of analytical result obtained, two types of bias are calculated in the assessment of trueness： a proportional bias and a constant bias. Nested design was applied for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked samples. In this case, the concentration found is plotted against the concentration added and the slop of standard addition curve is an estimate of the method recovery. Estimated method of average recovery in human hair is： （1.019 ±0.026）, （0.918 ±0.014）, （1.073±0.016）, （1.0597± 0.017）, （1.073± 0.020） and （0.934± 0.117） for Cd, Pb, Mn, Ni, Fe and Cu respectively.
基金supported by National Natural Science Foundation of China (Grant Nos.10901027 and 11171274)Foundation of Hunan Educational Committee (Grant No. 10C0370)
文摘With the aim of simulating the blow-up solutions, a moving finite element method, based on nonuni- form meshes both in time and in space, is proposed in this paper to solve time fractional partial differential equations （FPDEs）. The unconditional stability and convergence rates of 2 -a for time and r for space are proved when the method is used for the linear time FPDEs with a-th order time derivatives. Numerical exam-ples are provided to support the theoretical findings, and the blow-up solutions for the nonlinear FPDEs are simulated by the method.
基金supported by National Natural Science Foundation of China (Grant No.11101415)the National Center for Mathematics and Interdisciplinary Sciences,CAS
文摘The approach of nonconforming finite element method admits users to solve the partial differential equations with lower complexity,but the accuracy is usually low.In this paper,we present a family of highaccuracy nonconforming finite element methods for fourth order problems in arbitrary dimensions.The finite element methods are given in a unified way with respect to the dimension.This is an effort to reveal the balance between the accuracy and the complexity of finite element methods.
基金supported by National Natural Science Foundation of China(Grant Nos.11226330 and 11301343)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20113127120002)+3 种基金the Research Fund for Young Teachers Program in Shanghai(GrantNo.shsf018)the Fund for E-institute of Shanghai Universities(Grant No.E03004)supported by the Natural Sciences and Engineering Research Council of Canada(Grant No.OGP0046726)Shanghai University under Leading Academic Discipline Project of Shanghai MunicipalEducation Commission(Grant No.J50101)
文摘We analyze an h-p version Petrov-Galerkin finite element method for linear Volterra integrodifferential equations. We prove optimal a priori error bounds in the L2- and H1-norm that are explicit in the time steps,the approximation orders and in the regularity of the exact solution. Numerical experiments confirm the theoretical results. Moreover,we observe that the numerical scheme superconverges at the nodal points of the time partition.
基金Foundation item： the National Natural Science Foundation of China （Nos. 10671184 10371113）.
文摘H1-Galerkin nonconforming mixed finite element methods are analyzed for integro-differential equation of parabolic type.By use of the typical characteristic of the elements,we obtain that the Galerkin mixed approximations have the same rates of convergence as in the classical mixed method,but without LBB stability condition.
基金the National Basic Research Program(973) of China (No. 2006CB705400).
文摘A numerical analysis was performed to study the influence of process parameters on the microstructure evolution of IN718 alloy in rotary forging using the finite element method （FEM）. For this purpose, a constitutive equation considering the effects of strain hardening and dynamic softening of IN718 alloy was built. The constitutive equation and microstructure models were implemented into the finite element code to investigate the microstructure evolution during rotary forging subject to large deformations. The simulations were carried out in the ratio of initial height to diameter range 0.2-0.8, the angle of the rocker 3°-7° and the relative feed per revolution range 0.01-0.1 r^-1. The research results revealed the deformation mechanism and the correlation of process parameters with the grain size evolution of IN718 alloy during rotary forging. These provide evidence for the selection of rotary forging parameters.
基金supported by the National Natural Science Foundation of China under Grant No. 10771124
文摘Seawater intrusion problem is considered in this paper.Its mathematical model is anonlinear coupled system of partial differential equations with initial boundary problem.It consistsof the water head equation and the salt concentration equation.A combined method is developedto approximate the water head equation by mixed finite element method and concentration equationby discontinuous Galerkin method.The scheme is continuous in time and optimal order estimates inH^1-norm and L^2-norm are derived for the errors.
