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Cooling rate effect on temperature controlled FSW process
University West, Department of Engineering Science, Division of Automation Systems. (PTW)ORCID iD: 0000-0003-3261-9097
University West, Department of Engineering Science, Division of Automation Systems. (PTW)ORCID iD: 0000-0001-9553-7131
University West, Department of Engineering Science, Division of Automation Systems. (PTW)ORCID iD: 0000-0002-1869-232X
2015 (English)Conference paper, Presentation (Refereed)
Abstract [en]

A continuous trend towards more demanding jointgeometries is imposed across various manufacturingindustries. During Friction Stir Welding (FSW) of suchcomplex geometries, the surrounding environment playsan important role on the final weld quality, especially inthermal aspects. In order to guarantee a consistent weldquality for different conditions, in-process weldingparameter adaptation is needed.This paper studies the effect of the cooling rate onmechanical properties for temperature controlled FSW byusing different backing bar materials. A new temperaturesensor solution, the Tool-Workpiece Thermocouple(TWT) method [1], was applied to measure thetemperature during welding. A FSW-robot equipped withtemperature and force feedback control was used, whererotation speed was varied to maintain a constant weldingtemperature. AA7075-T6 lap joints were performed withand without temperature control. The cooling rate duringwelding was acquired and macrographs and mechanicalproperties were evaluated for each weld. The rotationspeed offered a fast response promoting the heat inputnecessary to weld at the set temperature. Temperaturecontrolled welds presented a better behaviour undertensile loads. The results prove that temperature controlusing the TWT method is suitable to achieve higher jointquality and provides a fast setup of optimal parameters fordifferent environments.The work presented is an important step in the processoptimization through feedback control which willconsider not only the operational parameters of theprocess as such but also the resulting quality of the joint.

Place, publisher, year, edition, pages
Helsinki, Finland, 2015. 1-5 p.
Keyword [en]
Friction Stir weld, Cooling rate, TWT method, Temperature control, Aluminium alloy
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
URN: urn:nbn:se:hv:diva-9120OAI: oai:DiVA.org:hv-9120DiVA: diva2:906831
Conference
IIW International Conference High-Strength Materials - Challenges and Applications, 2-3 July 2015, Helsinki, Finland, Helsingfors, 2015
Available from: 2016-02-25 Created: 2016-02-25 Last updated: 2016-10-14Bibliographically approved
In thesis
1. Thermo-electric temperature measurements in friction stir welding: Towards feedback control of temperature
Open this publication in new window or tab >>Thermo-electric temperature measurements in friction stir welding: Towards feedback control of temperature
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Friction Stir Welding has seen a fast uptake in many industry segments. Mechanical properties superior to fusion welding, the ability to weld "unweldable" aluminium alloys and low distortion are often described as the main reasons for the fast industrial implementation of FSW. Most existing applications consist of long straight welding joints. Applications with complex weld geometries, however, are rarely produced by FSW. These geometries can induce thermal variations during the welding process, thus making it challenging to maintain a consistent weld quality. In-process adaptation of weld parameters to respond to geometrical variations and other environmental variants allow new design opportunities for FSW. Weld quality has been shown to be reliant on the welding temperature. However, the optimal methodology to control the temperature is still under development.The research work presented in this thesis focuses on some steps to take in order to reach the improvement of the FSW temperature controller, thus reach a better and consistent weld quality. In the present work different temperature methods were evaluated. Temperature measurements acquired by the tool-workpiece thermocouple (TWT) method were accurate and fast, and thereby enhanced suitable for the controller. Different environmental conditions influencing the material heat dissipation were imposed in order to verify the controller effect on the joint quality. In comparison with no controlled weld, the use of the controller enabled a fast optimization of welding parameters for the different conditions, leading to an improvement of the mechanical properties of the joint.For short weld lengths, such as stitch welds, the initial plunge and dwell stages occupy a large part of the total process time. In this work temperature control was applied during these stages. This approach makes the plunge and dwell stages more robust by preventing local material overheating, which could lead to a tool meltdown. The TWT method was demonstrated to allow a good process control during plunging and continuous welding. The approach proposed for control offers weld quality consistency and improvement. Also, it allows a reduction of the time required for the development of optimal parameters, providing a fast adaptation to disturbances during welding and, by decreasing the plunge time, provides a significant decrease on the process time for short welds.

Place, publisher, year, edition, pages
Trollhättan: University West, 2016. 62 p.
Keyword
FSW, Robotic, Temperature, TWT, Plunge, Control
National Category
Robotics
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-9982 (URN)978-91-87531-43-9 (ISBN)978-91-87531-42-2 (ISBN)
Supervisors
Available from: 2016-11-09 Created: 2016-10-12 Last updated: 2016-11-10Bibliographically approved

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