In the electroslag remelting(ESR)process,it mainly relies on thermal experiments or analysis via mechanistic models to realize the physical fields simulation of the electromagnetic field and temperature field coupled ...In the electroslag remelting(ESR)process,it mainly relies on thermal experiments or analysis via mechanistic models to realize the physical fields simulation of the electromagnetic field and temperature field coupled transfer,which has the limitations of high cost,a large amount of calculating data and high computing power requirements.A novel network based on physics-informed neural network(PINN)was designed to realize the fast and high-fidelity prediction of the distribution of electromagnetic field and temperature field in ESR process.The physical laws were combined with the deep learning network through PINN,and physical constraints were embedded to achieve effective solution of partial differential equations(PDEs).PINN was used to minimize the loss function consisting of data error,physical information error and boundary condition error.The physical laws and boundary condition constraints in the ESR process were considered to maintain high PDE solution accuracy under different spatial and temporal resolutions.Automatic differentiation(Autodiff)technique and gradient descent algorithm were used to optimize the network parameters.The experimental results show that compared with the mechanistic models,PINN can effectively replace thermal experiments to realize the physical field simulation of ESR process with only a few experimental data,which can avoid the disadvantages of pure data-driven network simulation that requires a large amount of training data.Moreover,the solution of PINN has good physical interpretability and reliability of simulation results.For simulating electromagnetic field and temperature field distribution,the training time of the network is only 140 and 203 s,and the regression indicators of root mean square error can reach 12.65 and 13.76,respectively.展开更多
With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher ...With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher and higher.The importance of fast and accurate electromagnetic thermal coupling analysis of such motors becomes more and more prominent.In view of this,the surfacemounted PMSM(SPMSM)equipped with unequally thick magnetic poles is taken as the main object and its electromagnetic thermal coupling analytical model(ETc AM)is investigated.First,the electromagnetic analytical model(EAM)is studied based on the modified subdomain method.It realizes the fast calculation of key electromagnetic characteristics.Subsequently,the 3D thermal analytical model(TAM)is developed by combining the EAM,the lumped parameter thermal network method(LPTNM),and the partial differential equation of heat flux.It realizes the fast calculation of key thermal characteristics in 3D space.Further,the information transfer channel between EAM and TAM is built with reference to the intrinsic connection between electromagnetic field and temperature field.Thereby,the novel ETcAM is proposed to realize the fast and accurate prediction of electromagnetic and temperature fields.Besides,ETcAM has a lot to commend it.One is that it well accounts for the complex structure,saturation,and heat exchange behavior.Second,it saves a lot of computer resources.It offers boundless possibilities for initial design,scheme evaluation,and optimization of motors.Finally,the validity,accuracy,and practicality of this study are verified by simulation and experiment.展开更多
This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plas...This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plasma to calculate the temperature and flow field of the reactor as well as the generator. The algorithm is based on the solutions of the two-dimensional continuity, momentum, and energy equations in term of vorticity, stream function and enthalpy. An upwind finite-difference scheme was adopted to solve those equations with appropriate boundary conditions. The computed results show that there is a flat region with little parameter change in the reactor, that the diameter of the region is not much larger than that of the generator and that a deep change of parameter exists in the outer side of the region.展开更多
Interaction between high-intensity pulsed ion beam （HIPIB） and a double-layer target with titanium film on top of aluminum substrate was simulated. The two-dimensional nonlinear thermal conduction equations, with th...Interaction between high-intensity pulsed ion beam （HIPIB） and a double-layer target with titanium film on top of aluminum substrate was simulated. The two-dimensional nonlinear thermal conduction equations, with the deposited energy in the target taken as source term, were derived and solved by finite differential method. As a result, the two-dimensional spatial and temporal evolution profiles of temperature were obtained for a titanium/aluminum double-layer target irradiated by a pulse of HIPIB. The effects of ion beam current density on the phase state of the target materials near the film and substrate interface were analyzed. Both titanium and aluminum were melted near the interface after a shot when the ion beam current density fell in the range of 100 A/cm2 to 200 A/cm2.展开更多
By using the monthly data from 1951 through 1984, empirical orthogonal expansion is performed for the 500 hPa geopotential height north of 65°N and the canonical fields are clustered by fuzzy classification. It i...By using the monthly data from 1951 through 1984, empirical orthogonal expansion is performed for the 500 hPa geopotential height north of 65°N and the canonical fields are clustered by fuzzy classification. It is noted that both the mean monthly polar vortex fields and the large-scale anomaly fields fall into three regimes, with those of the January mean field and th April anomaly field having characteristic features. In addition, the relationship between the time weigthing coefficients of the canonical fields and El Nino / SO is examined, showing significant anomalies in the large-scale polar anomaly fields during April and October of the year when El Nino occurs. These polar circulation anomalies have considerably influenced the temperature fields in China during April and October. Thus, we may conclude that this is one of the most important reasons for a relatively cool April and a warm October in China during the El Nino year.展开更多
the temperature distributions in th metallic foils induced by spatially cyindricallong-pulsed laser is examined inorder to aalyse the neoly-discovered reverse-plugging effet(RPE).An exact solution for the temperature...the temperature distributions in th metallic foils induced by spatially cyindricallong-pulsed laser is examined inorder to aalyse the neoly-discovered reverse-plugging effet(RPE).An exact solution for the temperature fields is derived by using the Hankel transform and Laplace transform.Numerical results are obtained for bothspatial distributions with Gaussian and eylindrical types.The results show that thespatially eylindrieal distribution fo laser offers a formidable potential for the RPk.展开更多
The temperature distributions in the metallic foils induced by spatially cylindrical long-pulsed laser is examined in order to analyse the newly-discovered reverse-pluggingeffect ( RPE).An exact solution for the tempe...The temperature distributions in the metallic foils induced by spatially cylindrical long-pulsed laser is examined in order to analyse the newly-discovered reverse-pluggingeffect ( RPE).An exact solution for the temperature fields is derived by using the Hankel transform and Laplace transform.Numerical results are obtained for bothspatial distributions with Gaussian and cylindrical types.The results show that thespatially cylindrical distribution of laser offers a formidable potential for the RPE.展开更多
The temperature field of stainless steel during twin-roll strip casting was simulated by experiment and a finite element （FE） model. By comparing the measured result with the simulated values, it is found that they ...The temperature field of stainless steel during twin-roll strip casting was simulated by experiment and a finite element （FE） model. By comparing the measured result with the simulated values, it is found that they fit close to each other, which indicates this FE model is effective. Based on this model, the effects of roll gap （t） and roll radius （R） on solidification were simulated. The simulated results give the relationship between t or R and the position of the freezing point. The larger the t is and the smaller the R is, the closer the position of the freezing point is to the exit.展开更多
The multi-piped freezing method is usually applied in artificial ground freezing （AGF） projects to fulfill special construction requirements, such as two-, three-, or four-piped freezing. Based on potential superpos...The multi-piped freezing method is usually applied in artificial ground freezing （AGF） projects to fulfill special construction requirements, such as two-, three-, or four-piped freezing. Based on potential superposition theory, this paper gives analytical solutions to steady-state frozen temperature for two, three, and four freezing pipes with different temperatures and arranged at random. Specific solutions are derived for some particular arrangements, such as three freezing pipes in a linear arrangement with equal or unequal spacing, right and isosceles triangle arrangements, four freezing pipes in a linear arrangement with equal spacing, and rhombus and rectangle arrangements. A comparison between the analytical solutions and numerical thermal analysis shows that the analytical solutions are sufficiently precise. As a part of the theory of AGF, the analytical solutions of temperature fields for multi-piped freezing with arbitrary layouts and different temperatures of freezing pipes are approached for the first time.展开更多
Pipe cooling is an effective method of mass concrete temperature control, but its accurate and convenient numerical simulation is still a cumbersome problem. An improved embedded model, considering the water temperatu...Pipe cooling is an effective method of mass concrete temperature control, but its accurate and convenient numerical simulation is still a cumbersome problem. An improved embedded model, considering the water temperature variation along the pipe, was proposed for simulating the temperature field of early-age concrete structures containing cooling pipes. The improved model was verified with an engineering example. Then, the p-version self-adaption algorithm for the improved embedded model was deduced, and the initial values and boundary conditions were examined. Comparison of some numerical samples shows that the proposed model can provide satisfying precision and a higher efficiency. The analysis efficiency can be doubled at the same precision, even for a large-scale element. The p-version algorithm can fit grids of different sizes for the temperature field simulation. The convenience of the proposed algorithm lies in the possibility of locating more pipe segments in one element without the need of so regular a shape as in the explicit model.展开更多
Three kinds of mathematical models representing welding heat sources are presented. Among them, Gaussian model and double ellipsoidal model are used to analyze the thermal distributions with finite element method. At ...Three kinds of mathematical models representing welding heat sources are presented. Among them, Gaussian model and double ellipsoidal model are used to analyze the thermal distributions with finite element method. At the same time, this paper analyzed the influences of the heat source models, the latent heat and the welding parameters on the temperature distributions. The comparisons between the simulated results and the experiments show double ellipsoidal model is good for three-dimensional numerical simulations. Furthermore, the adaptive mesh technique is applied in the three-dimensional model which greatly reduces the number of nodes and elements in the simulation.展开更多
Three-dimensional finite element model was established to simulate temperature fields of T-joint titanium sheets during TIG welding with finite element method （FEM） software. Temperature dependent material propertie...Three-dimensional finite element model was established to simulate temperature fields of T-joint titanium sheets during TIG welding with finite element method （FEM） software. Temperature dependent material properties and the effect of latent heat were considered. A technique of element birth and death was used to simulate the process of welded metal filling. Dynamic variation process of temperature fields during T1G welding was achieved. The simulated results agreed well with the measured results.展开更多
This paper has analyzed the influences of the heat input of welding arc, the latent heat of solidifica- tion,fluid flow of liquid metal on the heat conductivity pertaining to welding solidification crack of stainles...This paper has analyzed the influences of the heat input of welding arc, the latent heat of solidifica- tion,fluid flow of liquid metal on the heat conductivity pertaining to welding solidification crack of stainless steels. As a result,two - dimensional heat conduction models with prescribed heat flux mov- ing along the the have been developed that can simulate welding arc, convection and radiation heat loss from top and bottom surfaces of the workpiece. Finally, the finite element model was used to ana- lyze and calculate the temperature field.展开更多
Temperature curves reflect geothermal gradients and local temperature anomalies, thus providing a new understanding of the underground reservoir conditions. When encountering caverns or fractures and fissures during d...Temperature curves reflect geothermal gradients and local temperature anomalies, thus providing a new understanding of the underground reservoir conditions. When encountering caverns or fractures and fissures during drilling, lost circulation may occur and result in a change to the original formation temperature field, and in severe cases, even the conventional open hole well logging data cannot be obtained. This paper uses finite element analysis software COMSOL to establish a heat transfer model for the wellbore/reservoir formation system during drilling and shut-in in the presence of lost circulation, and a case study is made in a carbonate reservoir in the Tahe oilfield. On the basis of the above, we analyze the temperature distribution in the leakage zone, and the studies have shown that the leakage and petrophysical properties have an impact on the temperature of the wellbore and formation, hence we can estimate the reservoir permeability using the temperature data. In addition, the determination of the temperature recovery time after some drilling fluids have leaked into the formation will help in recognizing the subsurface temperature field of the carbonate formation correctly, thus enhancing production logging interpretation accuracy and improving the understanding of later measurements.展开更多
With the finite difference method to calculate the temperature distribution in mass concrete structures, the solution precision will increase with a smaller step size, at the cost of computational time. In view of the...With the finite difference method to calculate the temperature distribution in mass concrete structures, the solution precision will increase with a smaller step size, at the cost of computational time. In view of the basic characteristics of the finite difference method, a simple yet powerful improvement is introduced. By multiplying the adiabatic temperature function with a correction factor, the precision of the solution can be assured without an increase in the computation time. In addition, the correction rules for three types of commonly used concrete hydration formulas are investigated.展开更多
Plastic wrinkling predictions and shear enforced wrinkling characteristics of Ti-alloy thin-walled tubes under combination die constraints have become key problems urgently in need of solutions in order to improve for...Plastic wrinkling predictions and shear enforced wrinkling characteristics of Ti-alloy thin-walled tubes under combination die constraints have become key problems urgently in need of solutions in order to improve forming quality in their shear bending processes under differential temperature fields. To address this, a wrinkling wave function was developed by considering their shear bend deformation characteristics. Based on this wave function and the thin shell theory, an energy prediction model for this type of wrinkling was established. This model enables consideration of the effects of shear deformation zone ranges, material parameters, loading modes, and friction coefficients between tube and dies on the minimum wrinkling energy. Tube wrinkling sensitive zones(WSZs) can be revealed by combining this wrinkling prediction model with a thermalmechanical coupled finite element model for simulating these bending processes. The reliability of this wrinkling prediction model was verified, and an investigation into the tube wrinkling characteristics was carried out based on the experimental conditions. This found that the WSZs are located on either a single side or both sides of the maximum shear stress zone. When the friction coefficients between the tube and the various dies coincide, the WSZs are located on both sides.The larger the value of the tube inner corner radius and/or the smaller the value of the outer cornerradius, the smaller the wrinkling probability. With an increase in the value of the moving die displacement, the wrinkling probability increases at first, and then decreases.展开更多
In order to develop super-board and super-thick slabs, the flow and temperatur fields were studied in slab continuous casting molds under different practical conditions, such as slab dimensions, with-drawing slab spee...In order to develop super-board and super-thick slabs, the flow and temperatur fields were studied in slab continuous casting molds under different practical conditions, such as slab dimensions, with-drawing slab speed, design of nozzles, and superheat tempera-ture. The results showed that it is preferred to incline nozzle bores downwards and the submerged depth of the nozzles is best kept be-tween 250-300 mm. In addition, the solidified shell is thicker at the wide face than that at the narrow face, while the thin points alongthe wide face ekist both in the center and in the some area toward each respective end.展开更多
This paper has analyzed the influences of the heat input of the welding arc, the latent heat of solidification, the fluid flow of liquid metal on the heat conductivity pertaining to the welding solidification crack of...This paper has analyzed the influences of the heat input of the welding arc, the latent heat of solidification, the fluid flow of liquid metal on the heat conductivity pertaining to the welding solidification crack of stainless steels. As a result, two dimensional heat conduction models with the prescribed heat flux moving along the weld have been developed that can simulate welding arc, convection and radiation heat loss from top and bottom surfaces of the workpiece. Finally, the finite element model was used to analyze and calculate the temperature fields.展开更多
Usually, it is very difficult to find out an analytical solution to thermal conduction problems during high temperature welding. Therefore, as an important numerical approach, the method of lines （MOLs） is introduce...Usually, it is very difficult to find out an analytical solution to thermal conduction problems during high temperature welding. Therefore, as an important numerical approach, the method of lines （MOLs） is introduced to solve the temperature field characterized by high gradients. The basic idea of the method is to semi-discretize the governing equation of the problem into a system of ordinary differential equations （ODEs） defined on discrete lines by means of the finite difference method, by which the thermal boundary condition with high gradients are directly embodied in formulation. Thus the temperature field can be obtained by solving the ODEs. As a numerical example, the variation of an axisymmetrical temperature field along the plate thickness can be obtained.展开更多
Based oil the fundamental principles of meteorology and thermodynamics, the calculation theory of the nonlinear unstable pavement temperature fields of two-dimension layered system by analytic theory is established an...Based oil the fundamental principles of meteorology and thermodynamics, the calculation theory of the nonlinear unstable pavement temperature fields of two-dimension layered system by analytic theory is established and the calculation methods of surface temperature, ground temperature distribution along the thickness under different climate conditions are put forward respectively.展开更多
基金supported by National Natural Science Foundation of China(52274323 and 524743495)the Postdoctoral Fellowship Program of CPSF under Grant Number GZC20240231.
文摘In the electroslag remelting(ESR)process,it mainly relies on thermal experiments or analysis via mechanistic models to realize the physical fields simulation of the electromagnetic field and temperature field coupled transfer,which has the limitations of high cost,a large amount of calculating data and high computing power requirements.A novel network based on physics-informed neural network(PINN)was designed to realize the fast and high-fidelity prediction of the distribution of electromagnetic field and temperature field in ESR process.The physical laws were combined with the deep learning network through PINN,and physical constraints were embedded to achieve effective solution of partial differential equations(PDEs).PINN was used to minimize the loss function consisting of data error,physical information error and boundary condition error.The physical laws and boundary condition constraints in the ESR process were considered to maintain high PDE solution accuracy under different spatial and temporal resolutions.Automatic differentiation(Autodiff)technique and gradient descent algorithm were used to optimize the network parameters.The experimental results show that compared with the mechanistic models,PINN can effectively replace thermal experiments to realize the physical field simulation of ESR process with only a few experimental data,which can avoid the disadvantages of pure data-driven network simulation that requires a large amount of training data.Moreover,the solution of PINN has good physical interpretability and reliability of simulation results.For simulating electromagnetic field and temperature field distribution,the training time of the network is only 140 and 203 s,and the regression indicators of root mean square error can reach 12.65 and 13.76,respectively.
基金supported by the Project of National Natural Science Foundation of China under Grant 52077122。
文摘With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher and higher.The importance of fast and accurate electromagnetic thermal coupling analysis of such motors becomes more and more prominent.In view of this,the surfacemounted PMSM(SPMSM)equipped with unequally thick magnetic poles is taken as the main object and its electromagnetic thermal coupling analytical model(ETc AM)is investigated.First,the electromagnetic analytical model(EAM)is studied based on the modified subdomain method.It realizes the fast calculation of key electromagnetic characteristics.Subsequently,the 3D thermal analytical model(TAM)is developed by combining the EAM,the lumped parameter thermal network method(LPTNM),and the partial differential equation of heat flux.It realizes the fast calculation of key thermal characteristics in 3D space.Further,the information transfer channel between EAM and TAM is built with reference to the intrinsic connection between electromagnetic field and temperature field.Thereby,the novel ETcAM is proposed to realize the fast and accurate prediction of electromagnetic and temperature fields.Besides,ETcAM has a lot to commend it.One is that it well accounts for the complex structure,saturation,and heat exchange behavior.Second,it saves a lot of computer resources.It offers boundless possibilities for initial design,scheme evaluation,and optimization of motors.Finally,the validity,accuracy,and practicality of this study are verified by simulation and experiment.
文摘This paper gives a numerical study on the flow and temperature fields in an induced plasma reactor, which worked in 0.5 ATM with air as a working gas. We employed a two-dimensional mode of an inductively coupled plasma to calculate the temperature and flow field of the reactor as well as the generator. The algorithm is based on the solutions of the two-dimensional continuity, momentum, and energy equations in term of vorticity, stream function and enthalpy. An upwind finite-difference scheme was adopted to solve those equations with appropriate boundary conditions. The computed results show that there is a flat region with little parameter change in the reactor, that the diameter of the region is not much larger than that of the generator and that a deep change of parameter exists in the outer side of the region.
基金supported by National Natural Science Foundation of China (No.10975026)
文摘Interaction between high-intensity pulsed ion beam （HIPIB） and a double-layer target with titanium film on top of aluminum substrate was simulated. The two-dimensional nonlinear thermal conduction equations, with the deposited energy in the target taken as source term, were derived and solved by finite differential method. As a result, the two-dimensional spatial and temporal evolution profiles of temperature were obtained for a titanium/aluminum double-layer target irradiated by a pulse of HIPIB. The effects of ion beam current density on the phase state of the target materials near the film and substrate interface were analyzed. Both titanium and aluminum were melted near the interface after a shot when the ion beam current density fell in the range of 100 A/cm2 to 200 A/cm2.
文摘By using the monthly data from 1951 through 1984, empirical orthogonal expansion is performed for the 500 hPa geopotential height north of 65°N and the canonical fields are clustered by fuzzy classification. It is noted that both the mean monthly polar vortex fields and the large-scale anomaly fields fall into three regimes, with those of the January mean field and th April anomaly field having characteristic features. In addition, the relationship between the time weigthing coefficients of the canonical fields and El Nino / SO is examined, showing significant anomalies in the large-scale polar anomaly fields during April and October of the year when El Nino occurs. These polar circulation anomalies have considerably influenced the temperature fields in China during April and October. Thus, we may conclude that this is one of the most important reasons for a relatively cool April and a warm October in China during the El Nino year.
文摘the temperature distributions in th metallic foils induced by spatially cyindricallong-pulsed laser is examined inorder to aalyse the neoly-discovered reverse-plugging effet(RPE).An exact solution for the temperature fields is derived by using the Hankel transform and Laplace transform.Numerical results are obtained for bothspatial distributions with Gaussian and eylindrical types.The results show that thespatially eylindrieal distribution fo laser offers a formidable potential for the RPk.
文摘The temperature distributions in the metallic foils induced by spatially cylindrical long-pulsed laser is examined in order to analyse the newly-discovered reverse-pluggingeffect ( RPE).An exact solution for the temperature fields is derived by using the Hankel transform and Laplace transform.Numerical results are obtained for bothspatial distributions with Gaussian and cylindrical types.The results show that thespatially cylindrical distribution of laser offers a formidable potential for the RPE.
文摘The temperature field of stainless steel during twin-roll strip casting was simulated by experiment and a finite element （FE） model. By comparing the measured result with the simulated values, it is found that they fit close to each other, which indicates this FE model is effective. Based on this model, the effects of roll gap （t） and roll radius （R） on solidification were simulated. The simulated results give the relationship between t or R and the position of the freezing point. The larger the t is and the smaller the R is, the closer the position of the freezing point is to the exit.
基金Project supported by the National Natural Science Foundation of China （Nos. 51178336 and 51478340）, the Natural Science Foundation of Zhejiang Province, China （No. LZ13E080002）, and the China Ministry of Communications Construction Science ＆ Technology Projects （No. 2013318R11300）
文摘The multi-piped freezing method is usually applied in artificial ground freezing （AGF） projects to fulfill special construction requirements, such as two-, three-, or four-piped freezing. Based on potential superposition theory, this paper gives analytical solutions to steady-state frozen temperature for two, three, and four freezing pipes with different temperatures and arranged at random. Specific solutions are derived for some particular arrangements, such as three freezing pipes in a linear arrangement with equal or unequal spacing, right and isosceles triangle arrangements, four freezing pipes in a linear arrangement with equal spacing, and rhombus and rectangle arrangements. A comparison between the analytical solutions and numerical thermal analysis shows that the analytical solutions are sufficiently precise. As a part of the theory of AGF, the analytical solutions of temperature fields for multi-piped freezing with arbitrary layouts and different temperatures of freezing pipes are approached for the first time.
基金supported by the National Natural Science Foundation of China(Grant No.51109071)
文摘Pipe cooling is an effective method of mass concrete temperature control, but its accurate and convenient numerical simulation is still a cumbersome problem. An improved embedded model, considering the water temperature variation along the pipe, was proposed for simulating the temperature field of early-age concrete structures containing cooling pipes. The improved model was verified with an engineering example. Then, the p-version self-adaption algorithm for the improved embedded model was deduced, and the initial values and boundary conditions were examined. Comparison of some numerical samples shows that the proposed model can provide satisfying precision and a higher efficiency. The analysis efficiency can be doubled at the same precision, even for a large-scale element. The p-version algorithm can fit grids of different sizes for the temperature field simulation. The convenience of the proposed algorithm lies in the possibility of locating more pipe segments in one element without the need of so regular a shape as in the explicit model.
文摘Three kinds of mathematical models representing welding heat sources are presented. Among them, Gaussian model and double ellipsoidal model are used to analyze the thermal distributions with finite element method. At the same time, this paper analyzed the influences of the heat source models, the latent heat and the welding parameters on the temperature distributions. The comparisons between the simulated results and the experiments show double ellipsoidal model is good for three-dimensional numerical simulations. Furthermore, the adaptive mesh technique is applied in the three-dimensional model which greatly reduces the number of nodes and elements in the simulation.
基金China Postdoctoral Science Foundation (No 20080430129)
文摘Three-dimensional finite element model was established to simulate temperature fields of T-joint titanium sheets during TIG welding with finite element method （FEM） software. Temperature dependent material properties and the effect of latent heat were considered. A technique of element birth and death was used to simulate the process of welded metal filling. Dynamic variation process of temperature fields during T1G welding was achieved. The simulated results agreed well with the measured results.
文摘This paper has analyzed the influences of the heat input of welding arc, the latent heat of solidifica- tion,fluid flow of liquid metal on the heat conductivity pertaining to welding solidification crack of stainless steels. As a result,two - dimensional heat conduction models with prescribed heat flux mov- ing along the the have been developed that can simulate welding arc, convection and radiation heat loss from top and bottom surfaces of the workpiece. Finally, the finite element model was used to ana- lyze and calculate the temperature field.
文摘Temperature curves reflect geothermal gradients and local temperature anomalies, thus providing a new understanding of the underground reservoir conditions. When encountering caverns or fractures and fissures during drilling, lost circulation may occur and result in a change to the original formation temperature field, and in severe cases, even the conventional open hole well logging data cannot be obtained. This paper uses finite element analysis software COMSOL to establish a heat transfer model for the wellbore/reservoir formation system during drilling and shut-in in the presence of lost circulation, and a case study is made in a carbonate reservoir in the Tahe oilfield. On the basis of the above, we analyze the temperature distribution in the leakage zone, and the studies have shown that the leakage and petrophysical properties have an impact on the temperature of the wellbore and formation, hence we can estimate the reservoir permeability using the temperature data. In addition, the determination of the temperature recovery time after some drilling fluids have leaked into the formation will help in recognizing the subsurface temperature field of the carbonate formation correctly, thus enhancing production logging interpretation accuracy and improving the understanding of later measurements.
基金the Shanghai Excellent Young Professor Candidate Program (Grant No.04YQHB139)
文摘With the finite difference method to calculate the temperature distribution in mass concrete structures, the solution precision will increase with a smaller step size, at the cost of computational time. In view of the basic characteristics of the finite difference method, a simple yet powerful improvement is introduced. By multiplying the adiabatic temperature function with a correction factor, the precision of the solution can be assured without an increase in the computation time. In addition, the correction rules for three types of commonly used concrete hydration formulas are investigated.
基金support of National Natural Science Foundation of China (No. 51305415)
文摘Plastic wrinkling predictions and shear enforced wrinkling characteristics of Ti-alloy thin-walled tubes under combination die constraints have become key problems urgently in need of solutions in order to improve forming quality in their shear bending processes under differential temperature fields. To address this, a wrinkling wave function was developed by considering their shear bend deformation characteristics. Based on this wave function and the thin shell theory, an energy prediction model for this type of wrinkling was established. This model enables consideration of the effects of shear deformation zone ranges, material parameters, loading modes, and friction coefficients between tube and dies on the minimum wrinkling energy. Tube wrinkling sensitive zones(WSZs) can be revealed by combining this wrinkling prediction model with a thermalmechanical coupled finite element model for simulating these bending processes. The reliability of this wrinkling prediction model was verified, and an investigation into the tube wrinkling characteristics was carried out based on the experimental conditions. This found that the WSZs are located on either a single side or both sides of the maximum shear stress zone. When the friction coefficients between the tube and the various dies coincide, the WSZs are located on both sides.The larger the value of the tube inner corner radius and/or the smaller the value of the outer cornerradius, the smaller the wrinkling probability. With an increase in the value of the moving die displacement, the wrinkling probability increases at first, and then decreases.
文摘In order to develop super-board and super-thick slabs, the flow and temperatur fields were studied in slab continuous casting molds under different practical conditions, such as slab dimensions, with-drawing slab speed, design of nozzles, and superheat tempera-ture. The results showed that it is preferred to incline nozzle bores downwards and the submerged depth of the nozzles is best kept be-tween 250-300 mm. In addition, the solidified shell is thicker at the wide face than that at the narrow face, while the thin points alongthe wide face ekist both in the center and in the some area toward each respective end.
文摘This paper has analyzed the influences of the heat input of the welding arc, the latent heat of solidification, the fluid flow of liquid metal on the heat conductivity pertaining to the welding solidification crack of stainless steels. As a result, two dimensional heat conduction models with the prescribed heat flux moving along the weld have been developed that can simulate welding arc, convection and radiation heat loss from top and bottom surfaces of the workpiece. Finally, the finite element model was used to analyze and calculate the temperature fields.
基金National Natural Science Foundation of China (50574097 90305023)
文摘Usually, it is very difficult to find out an analytical solution to thermal conduction problems during high temperature welding. Therefore, as an important numerical approach, the method of lines （MOLs） is introduced to solve the temperature field characterized by high gradients. The basic idea of the method is to semi-discretize the governing equation of the problem into a system of ordinary differential equations （ODEs） defined on discrete lines by means of the finite difference method, by which the thermal boundary condition with high gradients are directly embodied in formulation. Thus the temperature field can be obtained by solving the ODEs. As a numerical example, the variation of an axisymmetrical temperature field along the plate thickness can be obtained.
文摘Based oil the fundamental principles of meteorology and thermodynamics, the calculation theory of the nonlinear unstable pavement temperature fields of two-dimension layered system by analytic theory is established and the calculation methods of surface temperature, ground temperature distribution along the thickness under different climate conditions are put forward respectively.
