• Journal of Welding and Joining
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• v.34 no.3
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• pp.12-16
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• 2016

Friction stir welding(FSW) was studied using commercial tool, FLOW-3D. The purpose of this study is to suggest a method to apply frictional heat in Computational fluid dynamics(CFD) analysis. Cylindrical tool shape was used, and the interface cells between tool surface and workpiece were tracked by its geometrical relations in order to consider the frictional heat in FSW. After tracking the interface cells, average area concept was used to calculate the frictional heat, which is related to interface area. Also three-dimensional heat source and visco-plastic flow were modeled. The frictional heat generation rate calculated numerically from the suggested algorithm was validated with the analytical solution. The numerical solution was well matched with the analytical solution, and the maximum percentage of error was around 3%.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.499-504
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• 2002

The microstructural change associated with the hardness profile in friction stir welded, age-hardenable 6005 Al alloy had been evaluated. Frictional heat and plastic flow during friction stir welding created the fine recrystallized grain (Stir Zone, SZ), the elongated and recovered grain (Thermo-Mechanical Affected Zone, TMAZ) in the weld zone. Heat affected zone (HAZ), which could be only identified by hardness test because there is no difference in the grain structure compared with that of the base metal, was formed beside the weld zone. A softened region had been formed near the weld zone during friction stir welding process. The softened region was characterized by the dissolution and coarsening of the strengthening precipitate during the friction stir welding. The sound joints of 6005 Al alloys were successfully formed under a wide range of the friction stir welding conditions.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.22-28
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• 2008

Friction stir welding(FSW) is an relatively new solid state joining process. A1606l-T6 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process(FSP) uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile playa major role in deciding FSP zone formation in A16061-T6 aluminium alloy. Tow different tool pin profiles have been used to fabricate the joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.3
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• pp.270-278
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• 2009

Friction stir welding is a relatively new solid state joining process. A6061-T6 and A5052-H32 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength to weight ratio and good corrosion resistance. This friction stir process uses a non-consumable tool to generate frictional heat in the abutting surfaces. The welding parameters such as tool rotational speed, welding speed, etc., and tool pin profile play a major role in deciding FSP zone formation in A6061-T6 and A5052-H32 aluminium alloy. Three different tool pin profiles have been used to fabricate the dissimilar butt joints. The formation of friction stir processed zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the friction stir processed zone formation.

• Journal of Welding and Joining
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• v.29 no.5
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• pp.63-71
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• 2011

Three-dimensional finite element analysis is performed to study the temperature distribution phenomenon of TIG assisted friction stir welding (TAFSW) between dissimilar plates (Al 6061-T6 and stainless steel 304). TAFSW is a solid-state welding process that integrates TIG (Tungsten Inert Gas) into a friction stir welding (FSW), to preheat the harder material ahead of FSW tool during welding. In order to facilitate the industrial application of welding, 3D numerical modeling of heat transfer has been carried out applying Finite Element Method (FEM). The temperature distribution due to heat generation during TAFSW on dissimilar materials joint is analysed using in-house solver. Moving heat source along with frictional heat between the work specimens and tool surface is considered to calculate the heat input. The analytical model used predicts successfully the maximum welding temperatures that occur on the dissimilar materials during TAFSW. Comparison with the infra red camera and thermocouple measurement results shows that the results from the current numerical simulation have good agreement with the measured data.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.458-461
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• 2009

Thermo-mechanical simulation of the Friction Stir Spot Welding (FSSW) processes was performed for the AA5083-H18 sheets, utilizing commercial Finite Element Method (FEM) and Finite Volume Method (FVM) which are based on Lagrangian and Eulerian formulations, respectively. The Lagrangian explicit dynamic FEM code, PAM-CRASH, and the Eulerian Computational Fluid Dynamics (CFD) FVM code, STAR-CD, were utilized to understand the effect of pin geometry on weld strength and material flow under the unsteady state condition. Using FVM code, material flow pattern near the tool boundary was analyzed to explain the weld strength difference between the weld by cylindrical pin and the weld by triangular pin, while the frictional energy concept using the FEM code had limitation to explain the weld strength difference.

• Tribology and Lubricants
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• v.39 no.3
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• pp.118-122
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• 2023

In our study, we develop a finite element model based on Archard's wear law to predict the cumulative wear and the evolution of the tool profile in friction stir welding (FSW) applications. Our model considers the rotational and translational behaviors of the tool, providing a comprehensive description of the wear process. We validate the accuracy of our model by comparing it against experimental results, examining both the predicted cumulative wear and the resulting changes to the tool profile caused by wear. We perform a detailed comparison between the predictions of the model and experimental data by manipulating non-dimensional coefficients comprising model parameters, such as element sizes and time increments. This comparison facilitates the identification of a specific non-dimensional coefficient condition that best replicates the experimentally observed cumulative wear. We also directly compare the worn tool profiles predicted by the model using this specific non-dimensional coefficient condition with the profiles obtained from wear experiments. Through this process, we identify the model settings that yield a tool wear profile closely aligning with the experimental results. Our research demonstrates that carefully selecting non-dimensional coefficients can significantly enhance the predictive accuracy of finite element models for tool wear in FSW processes. The results from our study hold potential implications for enhancing tool longevity and welding quality in industrial applications.

• Korean Journal of Materials Research
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• v.27 no.6
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• pp.331-338
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• 2017

This study was carried out to investigate the optimum condition of a friction stir welding process for a joint of AA2219-T87 and AA2195-T8 dissimilar aluminum alloys. These alloys are known to have good cryogenic properties, and as such to be suitable for use in fuel tanks of space vehicles. The welding parameters include the travelling speed, rotation speed and rotation direction of the tool. The experiment was conducted under conditions in which the travelling speed of the tool was 120-300 mm/min and the rotation speed of the tool was 400-800 rpm. To investigate the effect of the rotation direction of the tool, the joining was performed by switching the positions of the two dissimilar alloys. After welding, the microstructure was observed and the micro-hardness were measured; non-destructive evaluation was carried out to perform tensile tests on defect-free specimens. The result was that the microstructure of the weld joint underwent dynamic recrystallization due to sufficient deformation and frictional heat. The travelling speed of the tool had little effect on the properties of the joint, but the properties of the joint varied with the rotation speed of the tool. The conditions for the best joining properties were 600 rpm and 180-240 mm/min when the AA2219-T8 alloy was on the retreating side(RS).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.434-441
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• 2016

Friction Stir Welding (FSW) is a solid-state joining process involving the frictional heat between the materials and tools. The amount of heat conducted into the workpiece determines the quality of the welded zone. Excessive heat input is the cause of oxides and porosity defects, and insufficient heat input can cause problems, such as tunnel defects. Therefore, analyzing the temperature history and distribution at the center of the Friction Stir Welded zone is very important. In this study, the temperature distribution of the friction stir welding region of an AZ61 magnesium alloy was investigated. To achieve this goal, the temperature and metal flow was predicted using the finite element method. In FE analysis, the welding tool was simplified and the friction condition was optimized. Moreover, the temperature measuring test at the center of the welding region was performed to verify the FE results. In this study, the tool rotation speed was a more dominant factor than the welding speed. In addition, the predicted temperature at the center of the welding region showed good agreement with the measurement results within the error range of 5.4% - 7.7%.