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Thermal dissipation effect on temperature-controlled friction stir welding: [Efeito da dissipação térmica inducida durante soldadura por friçcão linear sob controlo de temperatura]
University West, Department of Engineering Science, Division of Production Systems. University West, Department of Engineering Science, Division of Welding Technology. (PTW)ORCID iD: 0000-0003-3261-9097
University West, Department of Engineering Science, Division of Production Systems. (PTW)ORCID iD: 0000-0001-9553-7131
Linnaeus University, Växjö, Sweden.ORCID iD: 0000-0002-1869-232X
2019 (English)In: Soldagem & Inspeção, ISSN 0104-9224, E-ISSN 1980-6973, Vol. 24, article id e2428Article in journal (Refereed) Published
Abstract [en]

During Friction Stir Welding (FSW) of complex geometries, the thermal dissipation, induced by geometric features or the surrounding environment, may strongly affect the final weld quality. In order to guarantee a consistent weld quality for different conditions, in-process welding parameter adaptation is needed. This paper studies the effect of thermal dissipation, induced by the backing bar thermal conductivity, on the weld temperature and the temperature controller response to it. A new temperature sensor solution, the Tool-Workpiece Thermocouple (TWT) method, was applied to acquire online temperature measurements during welding. An FSW-robot equipped with temperature control, achieved by rotation speed adaptation, was used. AA7075-T6 lap joints were performed with and without temperature control. The cooling rate during welding was register plus macrographs and tensile tests were assessed. The controller demonstrated a fast response promoting the heat input necessary to maintain the set welding temperature. The results demonstrated that temperature control using the TWT method is suitable to achieve higher joint performance and provides a fast setup of optimal parameters for different environments. © 2019, Universidade Federal de Uberlandia. All rights reserved.

Place, publisher, year, edition, pages
2019. Vol. 24, article id e2428
Keywords [en]
Aluminum alloys; Controllers; Cooling; Friction; Research laboratories; Temperature control; Temperature measurement; Temperature sensors; Tensile testing; Thermal conductivity; Thermoanalysis; Thermocouples; Welds, Cooling rates; Friction stir welding(FSW); Online temperature measurement; Surrounding environment; Temperature controllers; Thermal dissipation; TWT method; Welding temperatures, Friction stir welding
National Category
Manufacturing, Surface and Joining Technology
Identifiers
URN: urn:nbn:se:hv:diva-14999DOI: 10.1590/0104-9224/SI24.28ISI: 000510209200001Scopus ID: 2-s2.0-85078163111OAI: oai:DiVA.org:hv-14999DiVA, id: diva2:1395484
Funder
Region Västra Götaland, RUN 612-0254-15European Regional Development Fund (ERDF), No. 20200328Available from: 2020-02-22 Created: 2020-02-22 Last updated: 2020-02-26
In thesis
1. Thermoelectric Measurements for Temperature Control of Robotic Friction Stir Welding
Open this publication in new window or tab >>Thermoelectric Measurements for Temperature Control of Robotic Friction Stir Welding
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Friction stir welding (FSW) has undergone a rapid expansion in several industrial sectors such as in the aerospace, marine, railway and automotive sectors. Current industrial applications are mainly simple long straight welds, but there is a growth of interest in components with higher geometric complexity. However, welding of geometrically complex components represents a challenging task due to the resulting uneven induced thermal dissipation along the weld, but especially due to the need for suitable equipment, able to accurately follow a complex 3D path under high mechanical loads, while managing the machine deflection. This is the case for robots, where the high process forces result in deflections, which affects robots' compliance, leading to weld failures and poor consistency in mechanical properties.

In the presented approach, the rotational speed is controlled during welding in order to maintain the set temperature value along the weld. An innovative method to measure the process temperature, the tool-workpiece thermocouple (TWT), which offers a temperature estimation from the whole tool-workpiece interface (TWT-data), is set as the controlled variable. The overall aim of this thesis is then to demonstrate the industrial applicability of TWT temperature control for joining geometrically complex components using robotic friction stir welding.

The TWT-data signal is demonstrated to be fast, repeatable and representative of the welding temperature. Moreover, TWT-data supplies online information during the whole weld procedure, especially during plunging. The shoulder contact with the workpiece is identified by TWT-data, providing for an improved plunging operation, which was demonstrated to significantly improve the use of robotic FSW, overcoming the lack of stiffness inherent to this equipment type at this welding stage.

Improved joint performance, low tensile strength variation along the weld path and a reduced number of failed welds were achieved by welding under temperature control. As a result, such a welding approach simplifies the development of a welding procedure, allowing for a decrease in time and material. The concept was successfully validated by performing two welds consisting of two dissimilar materials in a two-dimensional weld path on a geometrically complex component by using robotic equipment. The temperature control approach is not limited to robotic equipment, but also suitable for standard FSW equipment, being of interest to a various range of applications where quality and/or time is an important factor.

Abstract [sv]

Friktionsomrörningssvetsning (FSW) genomgår en snabb industriell utveckling inom bland andra flyg-, marin-, järnvägs- och fordonssektorn, speciellt i aluminium. Aktuella industriella tillämpningar har hittills huvudsakligen varit enkla långa raka svetsar, men intresset för komponenter med högre geometrisk komplexitet ökar. Sådana komponenter utgör en utmanande uppgift på grund avvarierande inducerad termisk spridning längs med fogen, och särskilt på grund av behovet av lämplig utrustning, som kan följa en 3D-svetsbana. Detta gäller speciellt när verktyget monteras på en industrirobot, där höga processkrafter resulterar i böjning, vilka kan leda till svetsfel och sämre mekaniska egenskaper. Utgångspunkten i detta arbete är att temperaturen i verktygets kontakt med materialet har störst betydelse för fogkvaliteten.

I det presenterade tillvägagångssättet styrs rotationshastigheten under svetsningen för att bibehålla önskad temperatur längs svetsen. En innovativ temperaturmätmetod baserad på termoelektrisk effekt mellan verktyg och arbetsstycke (TWT) erbjuder en skattning av temperaturen från hela gränssnittet mellan verktyg och arbetsstycke (TWT-data). Denna temperaturskattning används som den styrda variabeln. Det övergripande syftet med denna avhandling är att visa att styrning baserad på TWT-data är industriellt användbar för att bibehålla fogegenskaper vid fogning av geometriskt komplexa komponenter med hjälp av friktionsomröringssvetsning.

TWT-data visar sig vara ett snabbt, repeterbart och genomförbart sätt att få en representativ realtidsskattning av fogens temperatur under hela processen. Som sådan är den lämplig för skattning av processtemperaturen och styrning av processen. TWT-data tillhandahåller information även under startskedet och identifierar när verktyget pressas mot arbetsstycket, och speciellt när verktygets skuldra får kontakt med arbetsstycket. Denna information ger en förbättrad startprocedur, vilket är viktigt speciellt vid robotisering, eftersom robotens vekhet påverkar verktygets z-position.

Svetsning under temperaturreglering gav förbättrad fogprestanda, låg draghållfasthetsvariation längs fogen och ett reducerat antal misslyckade svetsar, och förväntas förenkla utvecklingen av en svetsprocedur, vilket möjliggör en minskning av tid och material.

Konceptet validerades framgångsrikt genom att svetsa en komponent bestående av två olika fogar med en tvådimensionell svetsbana i en geometriskt komplexkomponent med hjälp av robotutrustning. Tillvägagångssättet för temperaturstyrning är inte begränsat till robotutrustning, utan också lämpligt för standard FSW-utrustning, vilket är av intresse för olika applikationer där kvalitet och tid är viktiga faktor.

Place, publisher, year, edition, pages
Trollhättan: University West, 2020. p. 110
Series
PhD Thesis: University West ; 33
Keywords
Friction stir welding, Aluminium, Temperature measurements, Process control, Robotics, Geometrically complex components, Friktionsomrörningssvetsning, Aluminium, temperaturmätning, Processstyrning, Robotik, Geometriskt komplexa komponenter
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14982 (URN)978-91-88847-48-5 (ISBN)978-91-88847-47-8 (ISBN)
Public defence
2020-02-25, Albertssalen, 09:00 (English)
Opponent
Supervisors
Available from: 2020-02-26 Created: 2020-02-26 Last updated: 2020-02-26Bibliographically approved

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Ferreira Magalhães, Ana CatarinaDe Backer, Jeroen

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