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Melt convection in welding and crystal growth
KTH, Superseded Departments, Mechanics.ORCID iD: 0000-0003-2830-0454
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

A parallel finite element code with adaptive meshing was developed and used to study three dimensional, time-dependent fluid flows caused by thermocapillary convection as well as temperature and dopant distribution in fusion welding and floating zone crystal growth.

A comprehensive numerical model of the three dimensional time-dependent fluid flows in a weld pool had been developed. This model considered most of the physical mechanisms involved in gas tungsten arc welding. The model helped obtaining the actual chaotic time-dependent melt flow. It was found that the fluid flow in the weld pool was highly complex and influenced the weld pool’s depth and width. The physicochemical model had also been studied and applied numerically in order to simulate the surfactant adsorption onto the surface effect to the surface tension of the metal liquid in a weld pool.

Another model, a three dimensional time-dependent, with adaptive mesh refinement and coarsening was applied for simulating the effect of weak flow on the radial segregation in floating zone crystal growth. The phase change equation was also included in this model in order to simulate the real interface shape of floating zone.

In the new parallel code, a scheme that keeps the level of node and face instead of the complete history of refinements was utilized to facilitate derefinement. The information was now local and the exchange of information between each and every processor during the derefinement process was minimized. This scheme helped to improve the efficiency of the parallel adaptive solver.

Place, publisher, year, edition, pages
Stockholm: KTH , 2004. , 36 p.
Series
Trita-MEK, ISSN 0348-467X ; 2004:15
Keyword [en]
Engineering physics, thermocapillary convection, gas-tungsten arc welding, floating zone, parallel computing, finite element method
Keyword [sv]
Teknisk fysik
National Category
Other Engineering and Technologies
Identifiers
URN: urn:nbn:se:kth:diva-83OAI: oai:DiVA.org:kth-83DiVA: diva2:14813
Public defence
2004-12-15, kollegiesalen, Valhallavägen 79, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20100527Available from: 2004-12-15 Created: 2004-12-15 Last updated: 2010-05-27Bibliographically approved
List of papers
1. Modeling of Time-Dependent 3D Weld Pool Flow Due to a Moving Arc
Open this publication in new window or tab >>Modeling of Time-Dependent 3D Weld Pool Flow Due to a Moving Arc
2003 (English)In: Proceedings of High Performance Scientific Computing, 2003Conference paper, Published paper (Other academic)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-13092 (URN)
Conference
International Conference on High Performance Scientific Computing
Note
QC 20100527Available from: 2010-05-27 Created: 2010-05-27 Last updated: 2010-05-27Bibliographically approved
2. Modelling of time-dependent 3D weld pool flow
Open this publication in new window or tab >>Modelling of time-dependent 3D weld pool flow
2003 (English)In: Mathematical modelling of weld Phenomena 7 / [ed] Cerjak, H, 2003, 91-112 p.Conference paper, Published paper (Refereed)
Abstract [en]

The fluid flows in molten pools during arc welding are important factors. These in turn influence in overall heat and mass transfer, which determine the mechanical properties and quality of the weld fusion zone. Here, modelling results are presented concerning the time dependent weld pool flow and temperature in gas tungsten arc welding (GTA) of the difference type of stainless steels. It is proved that the temperature fields are strongly affected by the convection at the weld pool’s surfaces. With the stainless steel type 304 (low sulfur content 0.0005 weight % and high sulfur content 0.0139 weight %), the actual chaotic time dependent melt flow is obtained with a fully time dependent model. In those cases, the fluid flow in the weld pool is highly complex and it influenced the weld pool`s depth and width. For the 645 SMO steel, which has an extremely low sulfur content and low conductivity, the chaotic fluid flows did not appear. The calculated geometry of the weld fusion zone and heat affected zone were in good agreement with the experimental results, both with or without chaotic fluid flows.

National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-13093 (URN)3-901351-99-X (ISBN)
Conference
International Seminar on the 'Numerical Analysis of Weldability'
Note
QC 20100527Available from: 2010-05-27 Created: 2010-05-27 Last updated: 2010-05-27Bibliographically approved
3. Experimental and Numerical study of the influence of sulfur redistributation in welding of SAF-2507 stainless steel.
Open this publication in new window or tab >>Experimental and Numerical study of the influence of sulfur redistributation in welding of SAF-2507 stainless steel.
2004 (English)In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936Article in journal (Other academic) Published
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-13103 (URN)
Note
QC 20100527Available from: 2010-05-27 Created: 2010-05-27 Last updated: 2017-12-12Bibliographically approved
4. Modellingof the adsorption kinetics and the convection of surfactants in GTA welding
Open this publication in new window or tab >>Modellingof the adsorption kinetics and the convection of surfactants in GTA welding
2004 (English)Article in journal (Other academic) Submitted
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-13105 (URN)
Note
QC 20100527Available from: 2010-05-27 Created: 2010-05-27 Last updated: 2010-05-27Bibliographically approved
5. Three-dimensional modelling of radial segregation due to weak convection
Open this publication in new window or tab >>Three-dimensional modelling of radial segregation due to weak convection
2004 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 269, 454-463 p.Article in journal (Refereed) Published
Abstract [en]

A comprehensive three-dimensional, time-dependent model of heat, momentum and solute transfer during solidification is carried out to illustrate the influence of weak convection, caused by surface tension forces, on radial dopant segregation occurring in crystal growth under micro-gravity conditions. 3D adaptive finite element method is used in order to simulate the motion and deformation of the solidification interface. The geometry studied is a Bridgman configuration with a partly coated surface. The small slots in the coating gives a free surface in a controlled way, and is varied in order to alter the Marangoni flow. In this study, A comparison is made between the numerical results and the experimental results. A good agreement has been observed for the effective distribution coefficient keff and for the radial segregation [Delta]c’. The radial dopant segregation is affected by weak convection.

Keyword
3D numerical simulation, Adaptive finite element, Automated code generation, Radial segregation, Floating zone technique, Microgravity conditions
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-13094 (URN)10.1016/j.jcrysgro.2004.05.076 (DOI)000223813300039 ()2-s2.0-4344633801 (Scopus ID)
Note
QC 20100527Available from: 2010-05-27 Created: 2010-05-27 Last updated: 2017-12-12Bibliographically approved
6. Problem Solving Environment for Parallel Adaptive Computation
Open this publication in new window or tab >>Problem Solving Environment for Parallel Adaptive Computation
2004 (English)In: Mathematics and Computers in Simulation, ISSN 0378-4754, E-ISSN 1872-7166Article in journal (Other academic) Submitted
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-13106 (URN)
Note

QCR 20160722

Available from: 2010-05-27 Created: 2010-05-27 Last updated: 2017-12-12Bibliographically approved

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