The formed characteristics of thin-wall part is studied when it is in the process of MPAW. Finite element method is used to sinmlate the temperature field coupling flow field in the welding of thin-wall part. It is fo...The formed characteristics of thin-wall part is studied when it is in the process of MPAW. Finite element method is used to sinmlate the temperature field coupling flow field in the welding of thin-wall part. It is found that because of the obvious effect of heat accumution in cross-section, where the distribution of temperature field area presents trapezoidal inverted approximately in the molten pool and the non-molten pool area presents level. The surface tension, the electromagnetic force and buoyancy are considered for analyzing the effects on the fluid flow of welding-pool. It can be obtained that the surface tension is the main driving force in the welding pool, which is far greater than electromagnetic force and buoyancy.展开更多
A mathematical model is presented to describe transient behavior of heat transfer and fluid flow in stationary pulsed current tungsten inert gas (PC-TIG) weld pool, which considers three kinds of driving, forces for w...A mathematical model is presented to describe transient behavior of heat transfer and fluid flow in stationary pulsed current tungsten inert gas (PC-TIG) weld pool, which considers three kinds of driving, forces for weld pool convection, i,e. buoyancyforce, electromagnetic force and surface tension force. furthermore. the effect of vaporization heat flux at the free surface of weld pool and the temperature coefficient of surface tenston which is a function of temperatuer and composition are considered in the model In order to accelerate the convergence of iteration the AST(additive source term)method which concerns with the thermal energv boundary conditions is extended successfully to deal with the momentum boundary conditions by which the transient momentum equation and energy equation are mutually coupled. At the same time. ADI (Alternating direction implicit) method and DBC (double blocks correction) technque are employed to solve the finite difference equations. The results of numerical simulation demonstrate the transient behavior of PC-TIG weld pool, as well as the periodic variation of fluid flow and heat transfer with the periodic variation of welding current in stationary PC-TIG weld pool. The theoretical predictions based on this model are, shown to be in good accordance with the experimental measurements.展开更多
In order to investigate the process of laser cladding(LC)Inconel 625 alloy powder on Q235 steel plate,this paper focuses on analyzing the effects of different process parameters on the temperature field,stress field a...In order to investigate the process of laser cladding(LC)Inconel 625 alloy powder on Q235 steel plate,this paper focuses on analyzing the effects of different process parameters on the temperature field,stress field and flow behavior of the molten pool through a combination of finite element simulation and experiment.The simulation part established a geometric model,applied the Goldak double el-lipsoid heat source model,and simulated the LC process by varying the laser power and scanning speed.For the experimental part,LC equipment was used,parameters such as laser power and scanning speed were adjusted,and the molten pool dynamics were observed by in-frared temperature measurement and high-speed photography.The results show that the laser power and scanning speed are the key factors affecting the quality of cladding,and the experimental observation coincides with the simulation results,which verifies the validity of the simulation method and provides theoretical basis and experimental support for the optimization of the LC process.展开更多
A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpi...A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpieees,takes the are pressure as the drivingforce of the pool surface deformation,and determines the surface configuration of weldpool based on the dynamic balance of arc pressure,pool gravity and surface tension atdeformed weld pool surface. The SIMPLER algorithm is used to calculate the fluid flowfield and temperature distribution in TIG weld pools of stainless steel workpieces.TIGwelding experiments are made to verify the validity of the model.It shows the calculatedresults by the model are in good agreement with experimental measurements. professor,Dept of Welding Engineering,Harbin Institute of Technology,Harbin 150006,China展开更多
This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow...This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios,which is defined as the ratio of the layer thickness to the gap width. The flow domain is divided into the core region away from the cylinder walls and two end regions near each cylinder wall. Asymptotic solutions are obtained in the core region by solving the core and end flows separately and then joining them through matched asymptotic expansions. For the system of silicon melt,the asymptotic solutions are compared with the results of numerical simulations. It is found that the two kinds of solutions have a good agreement in the core region for a small aspect ratio. With the increase of aspect ratio,the applicability of the present asymptotic solutions decreases gradually.展开更多
This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are...This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are solved using an asymptotic theory for the aspect ratios ε→ 0.Asymptotic solutions of the velocity and temperature fields are obtained in the core region away from the cylinder walls.In order to validate the asymptotic solutions,numerical simulations are also carried out and the results are compared to each other.It is found that the present asymptotic solutions are valid in most of the core region.And the applicability of the obtained asymptotic solutions decreases with the increase of the aspect ratio and the thickness ratio of the two layers.For a system of gallium arsenide （lower layer） and boron oxide （upper layer）,the buoyancy slightly weakens the thermocapillary convection in the upper layer and strengthens it in the lower layer.展开更多
Submerged arc welding process has been simulated to investigate the molten pool features of EH36 shipbuilding steel.One case only involved the surface tension model,and another one involved both the surface tension mo...Submerged arc welding process has been simulated to investigate the molten pool features of EH36 shipbuilding steel.One case only involved the surface tension model,and another one involved both the surface tension model and the interface tension model.The role of interface tension during welding is revealed,and the evolution of molten pool morphology is understood by comparing the surface temperature distribution,surface tension and interface tension distribution,and the streamline of the molten pool for the two cases.When the interface tension model is disregarded,a flow conducive to the outward expansion is formed in the surface area of the molten pool,resulting in a small weld depth-to-width ratio.After applying the interface tension model,the expanding outward flow is restrained,which leads to a deep penetration morphology with a large weld depth-to-width ratio due to the inward flow governed by the Marangoni forces.The simulation results involving the interface tension model have been verified with satisfactory predictability.展开更多
A mathematical model was established to simulate the weld pool development and dynamic process in stationary iaser-MlG hybrid welding. Surface tension and buoyancy were considered to calculate liquid metal flow patter...A mathematical model was established to simulate the weld pool development and dynamic process in stationary iaser-MlG hybrid welding. Surface tension and buoyancy were considered to calculate liquid metal flow patter, moreover, typical phenomena of MIG welding, such as filler droplets impinging weld pool, electromagnetic force in the weld pool, and typical phenomena of laser beam welding, such as recoil pressure, Inverse Bremsstrahlung absorption, Fresnel absorption were all considered in the model. The laser beam and arc couple effect were introduced into this model by the plasma width during hybrid welding. The role of recoil pressure in the weld formation was discussed. Transient weld pool shape and complicated liquid metal velocity distribution from two kinds weld pool to an unified weld pool were calculated. The simulated weld bead geometry with consideration recoil pressure was in good agreement with experimental measurement.展开更多
Effects of welding current on temperature and velocity fields during gas metal arc welding(GMAW) of commercially pure aluminum were simulated. Equations of conservation of mass, energy and momentum were solved in a th...Effects of welding current on temperature and velocity fields during gas metal arc welding(GMAW) of commercially pure aluminum were simulated. Equations of conservation of mass, energy and momentum were solved in a three-dimensional transient model using FLOW-3 D software. The mathematical model considered buoyancy and surface tension driving forces. Further, effects of droplet heat content and impact force on weld pool surface deformation were added to the model. The results of simulation showed that an increase in the welding current could increase peak temperature and the maximum velocity in the weld pool. The weld pool dimensions and width of the heat-affected zone(HAZ) were enlarged by increasing the welding current. In addition, dimensionless Peclet, Grashof and surface tension Reynolds numbers were calculated to understand the importance of heat transfer by convection and the roles of various driving forces in the weld pool. In order to validate the model, welding experiments were conducted under several welding currents. The predicted weld pool dimensions were compared with the corresponding experimental results, and good agreement between simulation and preliminary test results was achieved.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.U1333128,U1733125)Science and Technology Project of Tianjin(Grant No.14ZCDZGX00802,17JCZDJC38700)
文摘The formed characteristics of thin-wall part is studied when it is in the process of MPAW. Finite element method is used to sinmlate the temperature field coupling flow field in the welding of thin-wall part. It is found that because of the obvious effect of heat accumution in cross-section, where the distribution of temperature field area presents trapezoidal inverted approximately in the molten pool and the non-molten pool area presents level. The surface tension, the electromagnetic force and buoyancy are considered for analyzing the effects on the fluid flow of welding-pool. It can be obtained that the surface tension is the main driving force in the welding pool, which is far greater than electromagnetic force and buoyancy.
文摘A mathematical model is presented to describe transient behavior of heat transfer and fluid flow in stationary pulsed current tungsten inert gas (PC-TIG) weld pool, which considers three kinds of driving, forces for weld pool convection, i,e. buoyancyforce, electromagnetic force and surface tension force. furthermore. the effect of vaporization heat flux at the free surface of weld pool and the temperature coefficient of surface tenston which is a function of temperatuer and composition are considered in the model In order to accelerate the convergence of iteration the AST(additive source term)method which concerns with the thermal energv boundary conditions is extended successfully to deal with the momentum boundary conditions by which the transient momentum equation and energy equation are mutually coupled. At the same time. ADI (Alternating direction implicit) method and DBC (double blocks correction) technque are employed to solve the finite difference equations. The results of numerical simulation demonstrate the transient behavior of PC-TIG weld pool, as well as the periodic variation of fluid flow and heat transfer with the periodic variation of welding current in stationary PC-TIG weld pool. The theoretical predictions based on this model are, shown to be in good accordance with the experimental measurements.
基金supported by Natural Science Foundation of Shandong Province of China(Grant No.ZR2023ME201)Qingdao Key Technology Research and Industrialization Demonstration Project(23-1-2-qljh-17-gx).
文摘In order to investigate the process of laser cladding(LC)Inconel 625 alloy powder on Q235 steel plate,this paper focuses on analyzing the effects of different process parameters on the temperature field,stress field and flow behavior of the molten pool through a combination of finite element simulation and experiment.The simulation part established a geometric model,applied the Goldak double el-lipsoid heat source model,and simulated the LC process by varying the laser power and scanning speed.For the experimental part,LC equipment was used,parameters such as laser power and scanning speed were adjusted,and the molten pool dynamics were observed by in-frared temperature measurement and high-speed photography.The results show that the laser power and scanning speed are the key factors affecting the quality of cladding,and the experimental observation coincides with the simulation results,which verifies the validity of the simulation method and provides theoretical basis and experimental support for the optimization of the LC process.
基金The research work was surpported by the National Natural Science Foundation of China.
文摘A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpieees,takes the are pressure as the drivingforce of the pool surface deformation,and determines the surface configuration of weldpool based on the dynamic balance of arc pressure,pool gravity and surface tension atdeformed weld pool surface. The SIMPLER algorithm is used to calculate the fluid flowfield and temperature distribution in TIG weld pools of stainless steel workpieces.TIGwelding experiments are made to verify the validity of the model.It shows the calculatedresults by the model are in good agreement with experimental measurements. professor,Dept of Welding Engineering,Harbin Institute of Technology,Harbin 150006,China
基金supported by the National Natural Science Foundation of China (50776102)the Fundamental Research Funds for the Central Universities (CDJXS10142248)
文摘This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios,which is defined as the ratio of the layer thickness to the gap width. The flow domain is divided into the core region away from the cylinder walls and two end regions near each cylinder wall. Asymptotic solutions are obtained in the core region by solving the core and end flows separately and then joining them through matched asymptotic expansions. For the system of silicon melt,the asymptotic solutions are compared with the results of numerical simulations. It is found that the two kinds of solutions have a good agreement in the core region for a small aspect ratio. With the increase of aspect ratio,the applicability of the present asymptotic solutions decreases gradually.
基金supported by the National Natural Science Foundation of China (50776102)the Fundamental Research Funds for the Central Universities (CDJXS1041148)
文摘This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are solved using an asymptotic theory for the aspect ratios ε→ 0.Asymptotic solutions of the velocity and temperature fields are obtained in the core region away from the cylinder walls.In order to validate the asymptotic solutions,numerical simulations are also carried out and the results are compared to each other.It is found that the present asymptotic solutions are valid in most of the core region.And the applicability of the obtained asymptotic solutions decreases with the increase of the aspect ratio and the thickness ratio of the two layers.For a system of gallium arsenide （lower layer） and boron oxide （upper layer）,the buoyancy slightly weakens the thermocapillary convection in the upper layer and strengthens it in the lower layer.
基金The authors sincerely thank the National Natural Science Foundation of China(Grant Nos.U20A20277,52150610494,52104295,52011530180 and 52050410341)Research Fund for Central Universities(Grant Nos.N2125016 and N2025025)Young Elite Scientists Sponsorship Program by CAST(YESS)(Grant No.2021-2023QNRC001).
文摘Submerged arc welding process has been simulated to investigate the molten pool features of EH36 shipbuilding steel.One case only involved the surface tension model,and another one involved both the surface tension model and the interface tension model.The role of interface tension during welding is revealed,and the evolution of molten pool morphology is understood by comparing the surface temperature distribution,surface tension and interface tension distribution,and the streamline of the molten pool for the two cases.When the interface tension model is disregarded,a flow conducive to the outward expansion is formed in the surface area of the molten pool,resulting in a small weld depth-to-width ratio.After applying the interface tension model,the expanding outward flow is restrained,which leads to a deep penetration morphology with a large weld depth-to-width ratio due to the inward flow governed by the Marangoni forces.The simulation results involving the interface tension model have been verified with satisfactory predictability.
文摘A mathematical model was established to simulate the weld pool development and dynamic process in stationary iaser-MlG hybrid welding. Surface tension and buoyancy were considered to calculate liquid metal flow patter, moreover, typical phenomena of MIG welding, such as filler droplets impinging weld pool, electromagnetic force in the weld pool, and typical phenomena of laser beam welding, such as recoil pressure, Inverse Bremsstrahlung absorption, Fresnel absorption were all considered in the model. The laser beam and arc couple effect were introduced into this model by the plasma width during hybrid welding. The role of recoil pressure in the weld formation was discussed. Transient weld pool shape and complicated liquid metal velocity distribution from two kinds weld pool to an unified weld pool were calculated. The simulated weld bead geometry with consideration recoil pressure was in good agreement with experimental measurement.
文摘Effects of welding current on temperature and velocity fields during gas metal arc welding(GMAW) of commercially pure aluminum were simulated. Equations of conservation of mass, energy and momentum were solved in a three-dimensional transient model using FLOW-3 D software. The mathematical model considered buoyancy and surface tension driving forces. Further, effects of droplet heat content and impact force on weld pool surface deformation were added to the model. The results of simulation showed that an increase in the welding current could increase peak temperature and the maximum velocity in the weld pool. The weld pool dimensions and width of the heat-affected zone(HAZ) were enlarged by increasing the welding current. In addition, dimensionless Peclet, Grashof and surface tension Reynolds numbers were calculated to understand the importance of heat transfer by convection and the roles of various driving forces in the weld pool. In order to validate the model, welding experiments were conducted under several welding currents. The predicted weld pool dimensions were compared with the corresponding experimental results, and good agreement between simulation and preliminary test results was achieved.
