This document presents a dynamic welding heat source model for pulsed current gas tungsten arc welding (PCGTAW). The model uses two different heat source distributions over time - a Gaussian model during peak times due to the bell-shaped temperature contour, and a parabolic model during background times. An experiment was conducted to validate the model by comparing simulated and measured temperature values. The results show that the dynamic model using a parabolic distribution during background times is more realistic and accurate for PCGTAW under the given welding conditions.
Solidification Simulation of Aluminum Alloy Casting – A Theoretical and Exper...IJMER
Aluminium alloy castings are extensively used in general engineering, automotive and
aerospace industries due to their excellent castability, machinability and high strength-to-weight ratio.
The major problem with aluminium castings is relatively high shrinkage of between 3.5 to 8.5% that
occurs during solidification. This study aims to theoretically analyze shrinkage behavior of cast
aluminium alloy and to conduct solidification simulation of casting using finite element technique based
on the experimental findings. A detailed finite element solidification simulation of A356 aluminum alloy
casting in sand mould is performed, and numerical simulations are carried out considering interface
resistance and with out interface resistance. Few test castings are poured with ordinary riser and
insulated riser, and time - temperature history is plotted with the help of thermocouples to verify the
results. It is observed that the results obtained by the solidification simulation are helpful in optimizing
casting yield, predicting shrinkage, reducing number of trials and rejections.
International Journal of Engineering Research and Applications (IJERA) aims to cover the latest outstanding developments in the field of all Engineering Technologies & science.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
The weld pool dynamics in the tandem weldingeSAT Journals
Abstract
The tandem welding process establishes a means for increasing both the travel speed and deposition rate. Electromagnetic force
models of the tandem weld pool are developed. Thermal fields and flow fields under tandem heat sources are simulated. Simulation
results show that flow characteristics of the weld puddle are affected by source process parameters.
Key words: Temperature field; Flow field; Welded pool; Model; Tandem welding
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Solidification Simulation of Aluminum Alloy Casting – A Theoretical and Exper...IJMER
Aluminium alloy castings are extensively used in general engineering, automotive and
aerospace industries due to their excellent castability, machinability and high strength-to-weight ratio.
The major problem with aluminium castings is relatively high shrinkage of between 3.5 to 8.5% that
occurs during solidification. This study aims to theoretically analyze shrinkage behavior of cast
aluminium alloy and to conduct solidification simulation of casting using finite element technique based
on the experimental findings. A detailed finite element solidification simulation of A356 aluminum alloy
casting in sand mould is performed, and numerical simulations are carried out considering interface
resistance and with out interface resistance. Few test castings are poured with ordinary riser and
insulated riser, and time - temperature history is plotted with the help of thermocouples to verify the
results. It is observed that the results obtained by the solidification simulation are helpful in optimizing
casting yield, predicting shrinkage, reducing number of trials and rejections.
International Journal of Engineering Research and Applications (IJERA) aims to cover the latest outstanding developments in the field of all Engineering Technologies & science.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
The weld pool dynamics in the tandem weldingeSAT Journals
Abstract
The tandem welding process establishes a means for increasing both the travel speed and deposition rate. Electromagnetic force
models of the tandem weld pool are developed. Thermal fields and flow fields under tandem heat sources are simulated. Simulation
results show that flow characteristics of the weld puddle are affected by source process parameters.
Key words: Temperature field; Flow field; Welded pool; Model; Tandem welding
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Enhancement of Heat Transfer Analysis and Optimization of Engine Fins of Vary...ijtsrd
The Engine cylinder is one of the major automobile components, which is subjected to high temperature variations and thermal stresses. In order to cool the cylinder, fins are provided on the cylinder to increase the rate of heat transfer. By doing thermal analysis on the engine cylinder fins, it is helpful to know the heat dissipation inside the cylinder. The principle implemented in this project is to increase the heat dissipation rate by using the invisible working fluid, nothing but air. As know, by increasing the surface area we can increase the heat dissipation rate, so designing such a large complex engine is very difficult. The main purpose of using these cooling fins is to cool the engine cylinder by air. The main aim of the project is to analyse the thermal properties by varying geometry, material, distance between the fins and thickness of cylinder fins. Parametric models of cylinder with fins have been developed to predict the transient thermal behaviour. The models are created by varying the geometry circular and also by varying thickness of the fins for both geometries. The 3D modelling software used is Pro/Engineer. Thermal analysis is done on the cylinder fins to determine variation temperature distribution over time. The analysis is done using ANSYS. Thermal analysis determines temperatures and other thermal quantities. In this thesis, using materials cast iron, Copper and Aluminium alloy 6082 are also for cylinder fin body. Thermal analysis is done using all the three materials by changing geometries, distance between the fins and thickness of the fins for the actual model of the cylinder fin body. K. Karthikeyan | C. Saravanan | Dr. T. Senthil Kumar"Enhancement of Heat Transfer Analysis and Optimization of Engine Fins of Varying Geometry" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd14327.pdf http://www.ijtsrd.com/engineering/mechanical-engineering/14327/enhancement-of-heat-transfer-analysis-and-optimization-of-engine-fins-of-varying-geometry/k-karthikeyan
MODELLING FOR CROSS IGNITION TIME OF A TURBULENT COLD MIXTURE IN A MULTI BURN...ijcsa
The impact of Cross Ignition process (CI) in the gas turbine operation and environmental issue is still
investigated for extending the efficiency of gas turbine engines and meanwhile decreasing the environment
pollution.This paper presents various constructive influential parameters and analysis of their related
interaction during CI. A developed computational model for determination of cross-ignition time (CIT) is
proposed, based on previous relevant models for thermal analysis and for distinguishing of heat fluxes in
combustion processes.
Due to the first analysis of theoretical results, experimental investigation for various operating conditions
were essential to validate the developed computational model of the CIT. Thus, a simple experimental test
rig is designed for this purpose, and for validation of certain conditions of the computational model.
Meanwhile, for expanding the investigations in higher energy conversion and reducing expensive testprocedures,
that are conducted during critical test running, a new strategy is proposed for simulating the
thermal heat fluxes throughout the burners compartment model by implementation of Computational Fluid
Dynamic (CFD).
Finally, new constructive criteria based on the validated investigations will enable the future generation of
gas turbine combustors to operate in critical conditions.
Heat Transfer Analysis of Refrigerant Flow in an Evaporator TubeIJMER
the paper aim is to presenting the heat transfer analysis of refrigerant flow in an evaporator
tube is done. The main objective of this paper is to find the length of the evaporator tube for a pre-defined
refrigerant inlet state such that the refrigerant at the tube outlet is superheated. The problem involves
refrigerant flowing inside a straight, horizontal copper tube over which water is in cross flow. Inlet
condition of the both fluids and evaporator tube detail except its length are specified. here pressure and
enthalpy at discrete points along the tube are calculated by using two-phase frictional pressure drop model.
Predicted values were compared using another different pressure drop model. A computer-code using
Turbo C has been developed for performing the entire calculation
Natural convection heat transfer flow visualization of perforated fin arrays ...eSAT Journals
Abstract
The present paper reports, the validation of results of modeling and simulation in CFD by experiment on the fluid flow and heat
transfer characteristics of a fin arrays with lateral circular perforation and its external dimensionally equivalent solid fin arrays
equipped on horizontal flat surface a problem of natural convection. The simulation is carried out using the fluid flow (CFX)
workbench of ANSYS 12.0. In this study, results shows that formation of the stagnant layer around the solid fin array which slowdowns
the heat dissipation rate. Increase in the fluid flow movement around the fin results increase in the heat dissipation rate. It can
be achieved by adding perforation to the fins. Natural convection is a buoyancy driven phenomenon; the state of the art of CFX was
used to carry the study of fluid flow separation and velocity field over a fin array. New designed perforated fins have an improvement
in average Nusselt number, over its external dimensionally equivalent solid fin arrays.
Keywords: CFD simulation, perforated fins, Natural convection, Heat sink, Nusselt number, Flow Visualization
EXPERIMENTAL STUDY OF HEAT TRANSFER FROM PLATE FIN ARRAY IN MIXED CONVECTION ...ijiert bestjournal
The work summarized in this paper presents an exper imental study of heat transfer from plate fin in mixed convection mode enhancement by the us e of plate fins is presented. After a brief review of the basic methods used to enhance the hea t transfer by simultaneous increase of heat transfer surface area as well as the heat tran sfer coefficient,a simple experimental method to assess the heat transfer enhancement is p resented. The method is demonstrated on plate fins as elements for the heat transfer enhanc ement,but it can in principle be applied also to other fin forms. That is varying various paramet ers (height,spacing). The order of the magnitude of heat transfer enhancement obtained exp erimentally,it was found that by a direct comparison of Nu and Re no conclusion regarding the relative performances could be made. This is because the dimensionless variables are int roduced for the scaling of heat transfer and pressure drop results from laboratory to large scal e but not for the performance comparison. Therefore a literature survey of the performance co mparison methods used in the past was also performed. Experiments will carried out on mix ed convection heat transfer from plate fin heat sinks subject to the influence of its geometry and heat flux. A total of 9 plate fins were pasted into the upper surface of the base plate. Th e area of the base plate is 150mm by 150mm. The base plate and the fins were made of alu minum. For all tested plate fin heat sinks,however,the heat transfer performance for h eat sinks with plate fins was better than that of solid pins.
The Elevated Temperature Deformation of G115 Steel and the Associated Deforma...IJAMSE Journal
The next Generation-IV reactors need to be stand for a very high temperature. Structural materials have to resist that temperature; otherwise, damages could appear. G115 steel is a candidate structural material which has been considered in this work. The hot deformation behavior of G115 steel was carried out at elevated temperatures 500, 550 and 600°C with different strain rates ranging from 1x10-5 to 1x10-3 s-1. To derive the hot deformation constitutive equation, the universal hyperbolic-sine Arrhenius-type equation was utilized considering the ultimate stresses values for each condition. As a result, the activation energy of G115, which will assess the high-temperature deformation mechanism, was obtained to be 331 KJ/mol.
Theoretical investigations on standing wave thermoacoustic prime mover using ...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
CFD Analysis of Plate Fin Tube Heat Exchanger for Various Fin InclinationsIJERA Editor
ANSYS Fluent software is used for three dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of six different fin angles with plain fin tube heat exchangers. The numerical simulation of the fin tube heat exchanger was performed by using a three dimensional numerical computation technique. Geometry of model is created and meshed by using ANSYS Workbench software. To solve the equation for the fluid flow and heat transfer analysis ANSYS FLUENT was used in the fin-tube heat exchanger. The fluid flow and heat transfer are simulated and result compared for both laminar and turbulent flow models k-epsilon and SST k-omega, with steady state solvers to calculate heat transfer, flow velocity and temperature fields of variable inclined fin angles (Ɵ = 00,100 , 200, 300, 400,500). Model is validate by comparing the simulated value of velocity, temperature and colburn factor with experimental and numerical results investigated by WANG [1] and GHORI KIRAR [10]. Reasonable agreement is found between the simulations and other results, and the ANSYS Fluent software is sufficient for simulating the flow fields in tube fin heat exchanger.
L'agence Jed Voras s'ouvre à la customisation de meubles de récupération. L'idée, créer un marché artistique et une nouvelle démarche de création pour les artistes.
Enhancement of Heat Transfer Analysis and Optimization of Engine Fins of Vary...ijtsrd
The Engine cylinder is one of the major automobile components, which is subjected to high temperature variations and thermal stresses. In order to cool the cylinder, fins are provided on the cylinder to increase the rate of heat transfer. By doing thermal analysis on the engine cylinder fins, it is helpful to know the heat dissipation inside the cylinder. The principle implemented in this project is to increase the heat dissipation rate by using the invisible working fluid, nothing but air. As know, by increasing the surface area we can increase the heat dissipation rate, so designing such a large complex engine is very difficult. The main purpose of using these cooling fins is to cool the engine cylinder by air. The main aim of the project is to analyse the thermal properties by varying geometry, material, distance between the fins and thickness of cylinder fins. Parametric models of cylinder with fins have been developed to predict the transient thermal behaviour. The models are created by varying the geometry circular and also by varying thickness of the fins for both geometries. The 3D modelling software used is Pro/Engineer. Thermal analysis is done on the cylinder fins to determine variation temperature distribution over time. The analysis is done using ANSYS. Thermal analysis determines temperatures and other thermal quantities. In this thesis, using materials cast iron, Copper and Aluminium alloy 6082 are also for cylinder fin body. Thermal analysis is done using all the three materials by changing geometries, distance between the fins and thickness of the fins for the actual model of the cylinder fin body. K. Karthikeyan | C. Saravanan | Dr. T. Senthil Kumar"Enhancement of Heat Transfer Analysis and Optimization of Engine Fins of Varying Geometry" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-4 , June 2018, URL: http://www.ijtsrd.com/papers/ijtsrd14327.pdf http://www.ijtsrd.com/engineering/mechanical-engineering/14327/enhancement-of-heat-transfer-analysis-and-optimization-of-engine-fins-of-varying-geometry/k-karthikeyan
MODELLING FOR CROSS IGNITION TIME OF A TURBULENT COLD MIXTURE IN A MULTI BURN...ijcsa
The impact of Cross Ignition process (CI) in the gas turbine operation and environmental issue is still
investigated for extending the efficiency of gas turbine engines and meanwhile decreasing the environment
pollution.This paper presents various constructive influential parameters and analysis of their related
interaction during CI. A developed computational model for determination of cross-ignition time (CIT) is
proposed, based on previous relevant models for thermal analysis and for distinguishing of heat fluxes in
combustion processes.
Due to the first analysis of theoretical results, experimental investigation for various operating conditions
were essential to validate the developed computational model of the CIT. Thus, a simple experimental test
rig is designed for this purpose, and for validation of certain conditions of the computational model.
Meanwhile, for expanding the investigations in higher energy conversion and reducing expensive testprocedures,
that are conducted during critical test running, a new strategy is proposed for simulating the
thermal heat fluxes throughout the burners compartment model by implementation of Computational Fluid
Dynamic (CFD).
Finally, new constructive criteria based on the validated investigations will enable the future generation of
gas turbine combustors to operate in critical conditions.
Heat Transfer Analysis of Refrigerant Flow in an Evaporator TubeIJMER
the paper aim is to presenting the heat transfer analysis of refrigerant flow in an evaporator
tube is done. The main objective of this paper is to find the length of the evaporator tube for a pre-defined
refrigerant inlet state such that the refrigerant at the tube outlet is superheated. The problem involves
refrigerant flowing inside a straight, horizontal copper tube over which water is in cross flow. Inlet
condition of the both fluids and evaporator tube detail except its length are specified. here pressure and
enthalpy at discrete points along the tube are calculated by using two-phase frictional pressure drop model.
Predicted values were compared using another different pressure drop model. A computer-code using
Turbo C has been developed for performing the entire calculation
Natural convection heat transfer flow visualization of perforated fin arrays ...eSAT Journals
Abstract
The present paper reports, the validation of results of modeling and simulation in CFD by experiment on the fluid flow and heat
transfer characteristics of a fin arrays with lateral circular perforation and its external dimensionally equivalent solid fin arrays
equipped on horizontal flat surface a problem of natural convection. The simulation is carried out using the fluid flow (CFX)
workbench of ANSYS 12.0. In this study, results shows that formation of the stagnant layer around the solid fin array which slowdowns
the heat dissipation rate. Increase in the fluid flow movement around the fin results increase in the heat dissipation rate. It can
be achieved by adding perforation to the fins. Natural convection is a buoyancy driven phenomenon; the state of the art of CFX was
used to carry the study of fluid flow separation and velocity field over a fin array. New designed perforated fins have an improvement
in average Nusselt number, over its external dimensionally equivalent solid fin arrays.
Keywords: CFD simulation, perforated fins, Natural convection, Heat sink, Nusselt number, Flow Visualization
EXPERIMENTAL STUDY OF HEAT TRANSFER FROM PLATE FIN ARRAY IN MIXED CONVECTION ...ijiert bestjournal
The work summarized in this paper presents an exper imental study of heat transfer from plate fin in mixed convection mode enhancement by the us e of plate fins is presented. After a brief review of the basic methods used to enhance the hea t transfer by simultaneous increase of heat transfer surface area as well as the heat tran sfer coefficient,a simple experimental method to assess the heat transfer enhancement is p resented. The method is demonstrated on plate fins as elements for the heat transfer enhanc ement,but it can in principle be applied also to other fin forms. That is varying various paramet ers (height,spacing). The order of the magnitude of heat transfer enhancement obtained exp erimentally,it was found that by a direct comparison of Nu and Re no conclusion regarding the relative performances could be made. This is because the dimensionless variables are int roduced for the scaling of heat transfer and pressure drop results from laboratory to large scal e but not for the performance comparison. Therefore a literature survey of the performance co mparison methods used in the past was also performed. Experiments will carried out on mix ed convection heat transfer from plate fin heat sinks subject to the influence of its geometry and heat flux. A total of 9 plate fins were pasted into the upper surface of the base plate. Th e area of the base plate is 150mm by 150mm. The base plate and the fins were made of alu minum. For all tested plate fin heat sinks,however,the heat transfer performance for h eat sinks with plate fins was better than that of solid pins.
The Elevated Temperature Deformation of G115 Steel and the Associated Deforma...IJAMSE Journal
The next Generation-IV reactors need to be stand for a very high temperature. Structural materials have to resist that temperature; otherwise, damages could appear. G115 steel is a candidate structural material which has been considered in this work. The hot deformation behavior of G115 steel was carried out at elevated temperatures 500, 550 and 600°C with different strain rates ranging from 1x10-5 to 1x10-3 s-1. To derive the hot deformation constitutive equation, the universal hyperbolic-sine Arrhenius-type equation was utilized considering the ultimate stresses values for each condition. As a result, the activation energy of G115, which will assess the high-temperature deformation mechanism, was obtained to be 331 KJ/mol.
Theoretical investigations on standing wave thermoacoustic prime mover using ...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
CFD Analysis of Plate Fin Tube Heat Exchanger for Various Fin InclinationsIJERA Editor
ANSYS Fluent software is used for three dimensional CFD simulations to investigate heat transfer and fluid flow characteristics of six different fin angles with plain fin tube heat exchangers. The numerical simulation of the fin tube heat exchanger was performed by using a three dimensional numerical computation technique. Geometry of model is created and meshed by using ANSYS Workbench software. To solve the equation for the fluid flow and heat transfer analysis ANSYS FLUENT was used in the fin-tube heat exchanger. The fluid flow and heat transfer are simulated and result compared for both laminar and turbulent flow models k-epsilon and SST k-omega, with steady state solvers to calculate heat transfer, flow velocity and temperature fields of variable inclined fin angles (Ɵ = 00,100 , 200, 300, 400,500). Model is validate by comparing the simulated value of velocity, temperature and colburn factor with experimental and numerical results investigated by WANG [1] and GHORI KIRAR [10]. Reasonable agreement is found between the simulations and other results, and the ANSYS Fluent software is sufficient for simulating the flow fields in tube fin heat exchanger.
L'agence Jed Voras s'ouvre à la customisation de meubles de récupération. L'idée, créer un marché artistique et une nouvelle démarche de création pour les artistes.
Finite Element Simulation of Plasma Transferred ARC Welding [PTAW] of Structu...IJERA Editor
Plasma transferred Arc welding is one of the most widely used welding process, in which the metals are fused just above the melting point, and makes the metal to fuse. It is employed in many applications like tool die and metal casting, strip metal welding etc. This investigation is to analyze temperature distribution residual stress and distortion by varying the heat source parameter in SYSWELD, and compared the results with ANSYS. The simulation of Plasma Transferred Arc welding was of structural steel plate performed using a non-linear transient heat transfer analysis. Heat losses due to convection and variation of material properties with temperature were considered in this analysis. To incorporate the heat developed the Gaussian distribution was considered. Finite element simulations were performed using ANSYS Parametric Design Language (APDL) code and using SYSWELD. The temperatures obtained were compared with experimental results for validation. It was found that the predicted values of temperature agree very well with the experimental values. Residual Stress and Distortion were also predicted for various heat Input. The effect of heat input on residual stress and distortion was investigated.
Computational model for multi alloy casting of aluminum rolling ingotsLOKESH BAVISKAR
The present model is useful in providing the insight on the thermo-fluid and solidification profile that can help in identifying appropriate process parameters. The development and validation of a steady-state computational fluid dynamics (CFD) model which appropriately treats heat transfer, fluid flow and solidification during multi alloy casting. Due to solidification shrinkage (density difference between the solid and liquid phase), the ingot contracts leading to the formation of an air gap between the ingot surface and the mold wall (air gap zone). In this zone, air gap gives rise to additional resistance to heat transfer from the ingot surface to the mold wall. To capture this phenomenon proposed a simplified approach for air gap predictions which is a combination of a one-dimensional air gap model with two dimensional CFD simulation for contact heat transfer coefficient when metal is in perfect contact with the mold surface.
An Analytical Lumped Thermal Circuit for the Determination of Fast Warm up and Steady State Characteristics Of Heater/Cathode Packages for TWT’s.
The challenge of determining fast warm up rates in small heater/cathode packages is critical to many tube development programs, but suffused with difficulties. An over voltage is applied to the heater during the warm up time and current and hence power in the heater is determined by the resistance of
the wire at any point in time. The heater
wire usually consists of 97%
tungsten/3% rhenium alloy and this has
the property of resistivity variation with
temperature of over an order of
magnitude. This wire will also not be at
a uniform temperature at any time. In
addition, power is lost by a complex
combination of conductions and
radiation exchanges, with thermal
conductivities, expansivities,
emissivities, and specific heats for all
materials varying markedly with
temperature.
FINITE ELEMENT SIMULATION OF WELDING IN STEEL PIPES AND PLATESIjorat1
Welding is a common joint type in the fabrication of structural members in aerospace, aeronautical and
pressure vessel industries. Welding is highly reliable and efficient metal joining process. The thermal response of
materials to a welding heat source sometimes causes mechanical problems, e.g. residual stresses and distortion and
changes in mechanical properties due to changes in the microstructure. The Finite Element Method (FEM) is the most
commonly used numerical technique, which provides accurate estimates of thermal parameters for this analysis. Finite
Element Analysis (FEA) is a tool used especially in determining the thermal stresses and temperature distribution of
the welded models, which are difficult to analyze by hand calculations. The objective of the current work is to study
transient temperature in both arc welded pipe and welded plate of 304L stainless steel. The object is modeled in 3D and
analyzed using FEA with an element type of SOLID70 and heat density of the moving circular area heat source is used.
Knowledge of temperature distribution patterns is useful in any welding process to predict microstructure and
distortion. In the current work a model has been developed to predict the thermal cycles during welding of 304L
pipeline steel
Comparison of Shell and Tube Heat Exchanger using Theoretical Methods, HTRI, ...IJERA Editor
The aim of this article is to compare the design of Shell and Tube Heat Exchanger with baffles. Baffles used in
shell and tube heat exchanger improve heat transfer and also result in increased pressure drop. Shell and tube
heat exchanger with single segmental baffles was designed with same input parameters using 1) Kern’s
theoretical method; 2) ASPEN simulation software and 3) HTRI simulation software 4) SOLIDWORKS
simulation software. Shell side pressure drop and heat transfer coefficient are predicted. The results of all the
three methods indicated the results in a close range. The proven theoretical methods are in good agreement with
the simulation results
Heat transfer enhancement_fusion reactor.pdfSandeepRimza1
jet impingement technique with a sectorial extended surface (SES) concept for the modular heliumcooled
divertor has been studied within the framework of the post ITER tokamak, at the Institute for
plasma research (IPR), INDIA. Experimental and numerical studies have been conducted to predict the
thermal-hydraulic performance of a finger-type divertor design with proposed SES. Critical thermal
hydraulic parameters, effective heat transfer coefficient and pressure loss have been measured in the
experiment for the reference divertor as well as for a divertor with SES. The experimental mock-ups are
made to full scale respecting Reynolds and Prandtl number similarities. Air is used as the simulant to
represent helium, which is used as the coolant in prototype. A novel heat concentrator has been
developed to simulate the high heat flux, by electrical heating.
Numerical Modeling and Simulation of a Double Tube Heat Exchanger Adopting a ...IJERA Editor
The double tube heat exchangers are commonly used in industry due to their simplicity in design and also their
operation at high temperatures and pressures. As the inlet parameters like temperatures and mass flow rates
change during operation, the outlet temperatures will also change. In the present paper, a simple approximate
linear model has been proposed to predict the outlet temperatures of a double tube heat exchanger, considering it
as a black box. The simulation of the heat exchanger has been carried out first using the commercial CFD
software FLUENT. Next the linear model of the double tube heat exchanger based on lumped parameters has
been developed using the basic governing equations, considering it as a black box. Results have been generated
for outlet temperatures for different inlet temperatures and mass flow rates of the cold and hot fluids. The results
obtained using the above two methods have then been discussed and compared with the numerical results
available in the literature to justify the basis for the assumption of a linear approximation. Comparisons of the
predicted results from the present model show a good agreement with the experimental results published in the
literature. The assumptions of linear variation of outlet temperatures with the inlet temperature of one fluid
(keeping other inlet parameters fixed) is very well justified and hence the model can be employed for the
analysis of double tube heat exchangers.
2. 2330 Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338
Table 1
The classification of current welding heat source models.
One-dimension Two-dimension Three-dimension
Uniform distribution mode
Point heat source Plane heat source Columnar heat source
Line heat source Circular mode –
– Tripped heat source –
– Square heat source –
Gaussian mode
– Circular mode Circular disk heat source
– Oval-shaped heat source Columnar heat source
– Double oval-shaped heat source Cuboid heat source
– Tripped heat source Rotary body heat source
– – Conic heat source
– – Hemispherical heat source
– – Semi-ellipsoidal heat source
– – Ellipsoidal heat source
– – Double ellipsoidal heat source
Exponential decay mode – – Exponential decay heat source
developed on the geometrical shape and distribution in space, but
time as an important factor, which has rarely been considered, in
the model design. In fact, the heat source is varied with time in some
dynamic process, e.g. in the PCGTAW. Therefore, a time-dependent
heat source model, which is available for the dynamic process, is
necessary to be developed.
In this paper, a dynamic finite element model of welding heat
source under PCGTAW is established. Then the moving, time-
dependent heat source was attempted to load onto the structure,
and the FEM was used to compute the temperature field through
the software ANSYS.
2. Theoretical formulations
2.1. Model consideration
With the help of high speed CCD, Traidia and Roger (2011) used
an infra-red camera to capture the characteristic of a welding arc
under PCGTAW, and some good images were obtained which at the
background and peak times (see Fig. 2).
It is easy to see that there is significant difference between the
peak time and the background time, and the arc is bell-shaped
during the peak duration, but not during the background duration.
Fig. 1. Pulsed current GTAW process parameters (Madadi et al., 2012).
In contrast to constant current welding, the heat input in
PCGTAW is supplied mainly during the peak times, and the heating
is halted periodically during the background times. Xu et al. (2009)
pointed out that the characteristic of discontinuity during heating
under PCGTAW is more obvious when the frequency is low. So, two
heat source models must be proposed which will be available in
the peak times and background times. Considering the bell-shaped
temperature contour, the recommended Gaussian model was used
during the peak times; the big problem at present is to propose a
good heat source model which is available during the background
times.
Some good experience can be obtained from the proposed
process of the Gaussian heat source model. The design of the exper-
iment was made to investigate the heat and current distribution of
GTAW, which consists of splitting a water cooled copper anode.
Measure the heat flux to one of the sections as a function of the arc
position relative to the splitting plane. The radial heat distribution
can then be derived by an Abel transformation of the measured heat
flux on the anode. The distribution of heat on the anode is a result
of a series of collisions of electrons with ionized atoms as electrons
travel from the cathode to the anode. The energy released on the
anode surface carried by the electrons constitutes most of the heat,
and Tsai and Eagar (1985) considered that the distribution of the
heat flux on the water cooled anodes should closely approximate
to the distribution across the weld pool.
Similarly, regarding the PCGTAW in this paper, it can be also con-
sidered that the anodic heat flux distribution is closely approximate
to the heat distribution across the weld pool.
2.2. Mathematical model
Traidia and Roger (2011) obtained the numerical simulation
result of the radial heat flux distribution at the anode between the
pulsed current – background time and peak time – and the mean
current, which are shown in Fig. 3a. The third curve which the arrow
points to is the radial heat flux distribution during the background
time.
To simplify the problem, it can be assumed that the radial
heat flux at the background time is parabolic shape, which passes
through three points (0, q(0)), (Rb, 0), (−Rb, 0) in the coordinate
–x plane. The function of radial heat flux distribution at the back-
ground time can be written as:
q(x, ) = q(0) 1 −
x2
R2
b
, − Rb ≤ x ≤ Rb (1)
where q(0) is the maximum value of heat flux and Rb is the radius
of the power density.
3. Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338 2331
Fig. 2. Infra-red camera images at the background and peak times for both first and last periods.
Substituting q(0) = 43 W/mm2 and R ≈ 2.8 mm which is corre-
sponded with the third curve in Fig. 3a into Eq. (1):
q(x, ) = 43 1 −
x2
2.82
, − Rb ≤ x ≤ Rb (2)
The function image of Eq. (2) is shown in Fig. 3b, which approxi-
mates to the third curve in Fig. 3a that represents the radial heat flux
distribution at the background time, which can be clearly observed
in Fig. 3c which combined Fig. 3a with Fig. 3b in the same scale. So
it can be considered that the radial heat flux distribution at back-
ground time is approximate to parabolic shape, and the welding
heat source is a spinning parabolic shape distribution as shown in
Fig. 4.
The spinning parabolic shape model of welding heat source with
the center at (0, 0, 0) to coordinate axes x, y, can be written as:
q(x, y, ) = q(0) 1 −
x2 + y2
R2
b
(3)
where q(x, y, ) is the power density (W/m2).
For r = x2 + y2 which is the radial distance from the center of
the heat source, then Eq. (3) can be written as:
q(r) = q(0) 1 −
r2
R2
b
, r ≤ Rb (4)
Conservation of energy requires that:
Q = ÁUI = q(r)r dr d =
Rb
0
q(0) 1 −
r2
R2
b
r dr
2
0
d (5)
and produces the following:
Q = ÁUI = q(0)
R2
b
2
(6)
q(0) =
2ÁUI
R2
b
(7)
Substituting q(0) from Eq. (7) into Eq. (4) gives:
q(r) =
2ÁUI
R2
b
1 −
r2
R2
b
, r ≤ Rb (8)
So the dynamic welding heat source model of PCGTAW in one
pulse cycle can be written as:
q(r) =
3ÁpUIp
R2
p
exp −3
r2
R2
p
, t ∈ [0, tp] (at peak times)
or q(r) =
2ÁbUIb
R2
b
1−
r2
R2
b
, t ∈ (tp, tT ] and r ≤ Rb (at background times)
(9)
where q(r) is the power density (W/m2), Áp the heat source effi-
ciency at the peak time, Áb the heat source efficiency at the
background time, U the arc voltage (V), Ip the peak current (A), Ib
the background current (A), r = (x2 + y2)1/2 which is the radial dis-
tance from the center of the heat source (m), Rb the radius of the
heat source at the background time (m), Rp the radius of the heat
source at the peak time (m), tT = 1 pulse cycle time = 1/f (s), f the
pulse frequency, tp the peak time (s), tb the background time (s)
and tp + tb = tT.
3. Evaluation of the dynamic model of welding heat source
in PCGTAW
One experiment was conducted in which the pulsed current
gas tungsten arc was deposited on the plate. The thermocouple
was used to measure the temperature field at the given points,
then the experimental values were compared with the simulated
values to assess the validity of the dynamic welding heat source
model.
Due to the lack of data on material properties, material mod-
eling has always been a critical issue in the welding simulation.
4. 2332 Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338
Table 2
The chemical composition of AA7075.
Elements Zn Mg Cu Cr Mn Fe Si Ti Al Impurities
wt.% 5.1–6.1 2.1–2.9 1.2–2.0 0.18–0.28 0.30 0.50 0.40 0.20 Bal. 0.15
Sattari-Far and Javadi (2008) reported that some simplifications
and approximations are usually introduced to deal with this prob-
lem, which are necessary because of the scarcity of material
data and numerical problems when trying to model the actual
high-temperature behaviors of the material. Here we select the
Aluminum Alloy 7075 as the base metal; the chemical composi-
tion is shown in Table 2. The thermal properties of AA7075 shown
Fig. 3. The establishment of the parabolic distribution (a is referred to Traidia and
Roger, 2011).
in Fig. 5 were reported by Guo et al. (2006) which are temperature-
dependent, the emissivity is assumed to be 0.6, and the fusion
temperature range is 477–638 ◦C.
3.1. Experimental procedure
3.1.1. Experiment preparation
The plate of Aluminum Alloy 7075 was cut to the required size of
80 mm × 80 mm × 8 mm. To measure the temperature in the weld-
ing process, the K type NiCr–NiSi thermocouple was used. The
positions of the thermocouples in the plate were shown in Fig. 6.
The thermocouples were glued to a depth of 4 mm, through the
blind holes which were drilled from the bottom of the plate; the hot
end diameter of the thermocouple was 1.5 mm, the cold end was
connected to a multichannel temperature measuring instrument
to acquire the thermal cycle, and the same method was introduced
by Karunakaran and Balasubramanian (2011).
3.1.2. Welding
Bead-on-plate welds were made using the PCGTAW on the sur-
face of the plate along with the center line. The welding parameters
are shown in Table 3.
3.2. FEM calculation
3.2.1. Finite element model
Only half of the plate was selected to analysis for its symmetry.
To reduce the calculation time, the zone near the welding bead has
been modeled with a finer mesh, while the zone further away from
the welding bead has been modeled with a coarser one. Solid70
and Surf152 were used to mesh the model; the surface has been
Fig. 4. Heat source configuration for the spinning parabolic shape.
5. Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338 2333
Fig. 5. Thermal physical properties of AA7075: (a) specific heat and density and (b)
conductivity.
Fig. 6. Schematic diagram of welded plate used in the experiment.
Table 3
Welding parameter.
Process parameter Actual Simulated
Welding current
Peak current 180 A 180 A
Background current 60 A 60 A
Arc voltage 14 V 14 V
Welding speed 1.96–2.03 mm/s 2 mm/s
Pulse frequency 1 Hz 1 Hz
% Pulse on time 50% 50%
Electrode W–2%Th –
Electrode diameter 3.2 mm –
Arc length 2 mm –
Torch angle 60◦
–
Shielding gas Argon 99.9% –
Flow rate 15 L/min –
“coated” with Surf152 to represent the convective heat exchange.
The FEM model is shown in Fig. 7.
3.2.2. Welding heat source
In this research, the APDL programming languages of ANSYS
were applied to realize the moving load of the heat source. A
local coordinate system was established, and the center of the heat
source coincided with the original point of the local coordinate,
then the heat source moved gradually under the control of the loop
command in APDL.
To evaluate the validity of the dynamic heat source model, two
simulation tests were implemented under the same welding con-
ditions, which are described in Table 4. The parameters in the
dynamic welding heat source model are not easy to decide, so a
further study is needed.
3.2.3. Initial condition and boundary conditions
The ambient temperature is 28 ◦C. Considering the moving heat
source, heat losses due to convention and radiation are taken into
account in the finite element models. Heat loss due to convection
(qc) is taken into account using Newton’s law:
qc = hc(Ts − T0)
where hc is the heat transfer coefficient, Ts the surface temperature
of the weldment and T0 is the ambient temperature which is 28 ◦C.
Heat loss due to radiation is modeled using Stefan–Boltzmann’s
law:
qr = −ε · [(Ts + 273)4
− (T0 + 273)4
]
where ε is emissivity which is 0.6 and = 5.67 × 10−8 W/m2 ◦C−4 is
defined as the Stefan–Boltzmann constant.
3.2.4. Latent heat of phase transition
During the welding process, melting and solidifying will occur
in the welding pool, it will absorb or release latent heat in the
phase transition, which is defined as “latent heat of phase tran-
sition”. Lei et al. (2006) use the enthalpy method to deal with the
Fig. 7. FEM model.
6. 2334 Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338
Table 4
List of the simulation test.
Simulation test 1 Simulation test 2
Heat source model Dynamic Model 1 Dynamic Model 2
Model description Use Gaussian model at peak times; use parabolic model at
background times
Use Gaussian model both at peak times and background times, but
different values of parameters were used, respectively
Parameters in model
Ip = 180 A, Ib = 60 A, U = 14 V, f = 1 Hz Ip = 180 A, Ib = 60 A, U = 14 V, f = 1 Hz,
Pulse on time = 50%, Rp ≈ 5.0 mm, Rb ≈ 2.8 mm, Áp ≈ 0.68, Áb ≈ 0.62. Pulse on time = 50%, Rp ≈ 5.0 mm, Rb ≈ 2.8 mm, Áp ≈ 0.68, Áb ≈ 0.62.
Notes: The parameters in heat source models are difficult to decide. To simplify the problems, the same parameters in Traidia and Roger (2011) were used for test 1 and test
2 under the same welding condition.
latent heat, and define the material’s enthalpy which varies with
the temperature:
H(T) =
T
0
(T)c(T) dT
where (T) is the density of the material varying with temperature
(kg/m3) and c(T) is the specific heat of the material varying with
temperature (J/(kg K)).
Murugan et al. (2000) reported that the release or absorption of
latent heat can also be considered in the numerical analysis by an
artificial increase in the value of the specific heat over the melting
temperature range.
3.2.5. Others
In the meshed finite element model, the number of the Solid70
element is 848,000, the number of the Surf152 element is 46,640,
and the number of nodes is 887,814 in total.
The heat source defined in a local coordinate system moves with
time, the former load step is deleted when the heat source moves to
the next step. Considering both the calculation time and the com-
puter’s capacity, the minimum size of element is 0.2 mm, and the
cooling time is fixed to 20 s.
Fig. 8. Top view of temperature distribution: (a) at 20.3 s (peak time) and (b) at 20.8 s (background time) computed by the Dynamic Model 1.
7. Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338 2335
Fig. 9. Top view of temperature distribution: (a) at 20.3 s (peak time) and (b) at 20.8 s (background time) computed by the Dynamic Model 2.
Fig. 10. Longitudinal cross-section of temperature distribution: (a) at 20.3 s (peak time) and (b) at 20.8 s (background time) computed by the Dynamic Model 1.
8. 2336 Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338
Fig. 11. Longitudinal cross-section of temperature distribution: (a) at 20.3 s (peak time) and (b) at 20.8 s (background time) computed by the Dynamic Model 2.
4. Results and discussion
4.1. Temperature field
4.1.1. Top view of temperature distribution
Figs. 8 and 9 which are in the same scale, show the temperature
field computed by the Dynamic Model 1 and the Dynamic Model
2, respectively, and including the time 20.3 s (peak time) and 20.8 s
(background time) for each. To illustrate the difference of the tem-
perature field between the peak time and the background time in
the welding process, the same area region near the weld pool was
magnified in the same scale.
Comparing the two temperature fields in Fig. 8a and b, it can
be seen that the high temperature region at 20.3 s is larger than
that at 20.8 s. Due to the cyclic variation of the heat input, there is
a thermal fluctuation in the temperature field, which corresponds
to the real dynamic welding process. From Fig. 9a and b, the same
conclusion above can be obtained.
Table 5
Peak temperature comparison of the experimental and simulated results.
Measuring
point
Methodsa
Peak
temperature (◦
C)
Differenceb
(%)
Point Ac
Experimental 402.5 –
FEM (Dynamic Model 1) 397.6 −1.2
FEM (Dynamic Model 2) 393.9 −2.1
Point Bc
Experimental 285.8 –
FEM (Dynamic Model 1) 276.7 −3.2
FEM (Dynamic Model 2) 272.5 −4.7
Point Cc
Experimental 327.2 –
FEM (Dynamic Model 1) 317.2 −3.1
FEM (Dynamic Model 2) 312.3 −4.6
a
Experimental: use PCGTAW – welding parameter is shown in Table 3; base metal
– AA7075, chemical composition is shown in Table 2. The description of the Dynamic
Model 1 and Dynamic Model 2 are listed in Table 4.
b .
Difference (%) = (Calculated value − Experimental value)/Experimental value.
c .
The position of the measuring points is depicted in Fig. 6.
In Fig. 8a and b, the maximum temperatures are 892 ◦C and
779 ◦C, respectively. It was found that the maximum temperature
at 20.3 s (peak time) is higher than the value at 20.8 s (background
time). In Fig. 9a and b, the maximum temperatures are 887 ◦C and
849 ◦C, respectively. The maximum temperature appears in the
center of the heat source model for both Figs. 8 and 9.
Comparing Fig. 8a with Fig. 9a, it can be seen that there is small
difference of the maximum temperature between them, which
implies that the maximum temperature is nearly the same at 20.3 s
when using the Dynamic Model 1 and the Dynamic Model 2. How-
ever, the maximum temperature in Fig. 8b is much lower than that
in Fig. 9b, which implies that there is much difference in the max-
imum temperature at 20.8 s (background time) when using the
Dynamic Model 1 and the Dynamic Model 2.
Supplementary Video 1 is available for readers to show the tem-
perature field computed by the Dynamic Model 1 in PCGTAW.
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.jmatprotec.2013.07.007.
4.1.2. Longitudinal cross-section of temperature distribution
Along with the midline of the plate in the longitudinal direc-
tion, the cross-sections of temperature distribution which are in
the same scale were obtained, as shown in Figs. 10 and 11. To
demonstrate clearly, the same area region near the heat source was
magnified in the same scale. From Figs. 10 and 11, the same conclu-
sions in Section 4.1.1 can also be obtained. The difference between
the calculated results by the Dynamic Model 1 and the Dynamic
Model 2 is demonstrated in some extent.
4.2. Welding thermal cycles
The comparison of the experimental and simulated welding
thermal cycles at Point A, Point B and Point C are shown in
Fig. 12a–c, respectively.
As can be seen from the figures, the temperatures computed by
the Dynamic Model 1 and the Dynamic Model 2 are slightly lower
9. Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338 2337
Fig. 12. Comparison of the experimental and simulated welding thermal cycles: (a)
Point A, (b) Point B and (c) Point C.
than the experimental values. Table 4 shows the peak temperature
comparison of the experimental and the simulated values. The dif-
ference value listed in Table 5 indicated that the Dynamic Model 1
is more accurate than the Dynamic Model 2, and it implies that the
dynamic model which uses the parabolic model at the background
time is more realistic and accurate.
From Fig. 12a and b, it can be noted that the temperature
is increased slightly during the cooling time while it cannot be
observed in Fig. 12c. The reason for that could be attributed to the
latent heat in the solidifying process. Many experiments show that
Fig. 13. The welding thermal cycle during 5–20 s at point A.
the energy released during solidifying for aluminum alloy is much
bigger than the carbon steel due to the thermal physical properties
of the material in or near the weld pool. However, the latent heat
become less and can be neglected for the areas far away from the
weld pool.
4.3. The characteristic of the pulsed current
Fig. 13 is part of Fig. 12a that magnified with a proper scale.
It is clearly seen that there are some fluctuations in the welding
thermal cycle computed by the Dynamic Model 1 and the Dynamic
Model 2, which can be attributed to the influence of pulsed current.
Wang (2003) used the finite element method to compute the tem-
perature field in molybdenum alloy under PCGTAW, the fluctuation
was observed in the computed welding thermal cycle. Zheng et al.
(1997) developed a three-dimensional model to demonstrate the
transient behavior of temperature field and weld pool in PCGTAW,
and verified that the fluctuations in the thermal cycle curve are
characteristic of the pulsed current welding. Therefore, it can be
concluded that the Dynamic Model 1 and the Dynamic Model 2 can
successfully demonstrate the dynamic process of temperature field
in pulsed current welding.
However, the experiment in this paper failed to capture the
characteristic of the pulsed current. This may be due to the sensi-
tivity of the temperature measuring instrument. The thermocouple
is widely used as temperature sensor for measuring instrument,
which can convert a temperature gradient into electricity. For the
dynamic welding process of PCGTAW, the heat input is varied
periodically in a very short time, which leads to the dynamic char-
acteristic of the process that cannot be obtained easily. This requires
the thermocouples to be sensitive enough to the short-term varia-
tion and the measuring instrument immediately responsive to deal
with the electronic signals from thermocouples at different mea-
sured points. Maybe an improved measuring instrument or a better
measuring method is needed to be developed. Although the exper-
iment failed to capture the temperature fluctuations in PCGTAW,
the temperature values measured by the calibrated instrument are
accurate and convincing.
The peak temperature is obtained when the heat source sur-
passes the measured point. As seen from Fig. 11, the pulsing effect
is more obvious for the pulses closed to the measured point, while it
becomes less for the pulses further away from the measured point.
It can be seen that the region in or near the welded joint has expe-
rienced several heating and cooling processes due to the pulsing
current, and that the soaking time at the high temperature is shorter
10. 2338 Z. Tong et al. / Journal of Materials Processing Technology 213 (2013) 2329–2338
compared with CCGTAW. That is why the grain is refined under the
PCGTAW process.
Compared with the welding thermal cycle at different points
in Fig. 12a–c, it can be concluded that the pulsed current has an
significant effect on the points in or near the welded joint, but less
effect on the points far away from the welded joint.
5. Conclusions
(1) Most of the current heat source models are static models that do
not vary with time and cannot represent the heat flux distribu-
tion in some dynamic welding processes; so a good heat source
model for the dynamic welding process must be developed.
(2) The FEM dynamic heat source model was used to simulate the
low frequency PCGTAW, which has successfully demonstrated
the dynamic temperature field in the welding process.
(3) From the comparisons of the experimental and the simulated
values, it can be concluded that the dynamic heat source model
which uses the parabolic model at the background time is more
accurate under the same welding conditions.
(4) In some welding process simulation, especially for those whose
dynamic characteristic is more obvious, the dynamic welding
heat source model has more advantages over the static models.
The static heat source model is the special case of the dynamic
heat source model, which is not varied with time.
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