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  • 1.
    Bolmsjö, Gunnar
    et al.
    Linnaeus University, Växjö, Sweden.
    Ferreira Magalhães, Ana Catarina
    University West, Department of Engineering Science, Division of Production Systems. University West, Department of Engineering Science, Division of Welding Technology.
    Cederqvist, L.
    SKB AB, Oskarshamn, Sweden.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production Systems.
    Robotic Friction Stir Welding of complex geometry and mixed materials2018In: 50th International Symposium on Robotics, ISR 2018, VDE Verlag GmbH , 2018, p. 35-41Conference paper (Refereed)
    Abstract [en]

    Friction stir welding (FSW) is a solid state process for joining materials which has demonstrated advantages compares with other methods which include joining of mixed materials, hard to weld alloys and consistent and high quality. This paper presents a study of robotic FSW initiated by Volvo Skövde plant to join an insert workpiece of extruded aluminium with a cylinder block of aluminium casting. A three-stage procedure was decided to determine the feasibility to apply robotic FSW. The stages included study of welding the mixed materials, weld along the complex joint line with holes and channels close to the joint, and finally welding the cylinder block. The results based on preliminary analysis indicate that the final tests were successful and the process is feasible for the challenging case study. However, further studies are recommended in order to identify the operating parameters window, tool design, and control of the process in order to optimize productivity and quality. © VDE VERLAG GMBH

  • 2.
    Ferreira Magalhães, Ana Catarina
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Cederqvist, Lars
    SKB AB, Oskarshamn, Sweden.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production Systems.
    Håkansson, Emil
    Volvo Cars, Göteborg, Sweden.
    Ossiansson, Bruno
    Volvo Cars, Skövde, Sweden.
    Bolmsjö, Gunnar
    Linnaeus University, Växjö, Sweden.
    A Friction Stir Welding case study using Temperature Controlled Robotics with a HPDC Cylinder Block and dissimilar materials joining2019In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 46, p. 177-184Article in journal (Refereed)
    Abstract [en]

    The automotive industry is going through a radical transformation from combustion engines to fully electric propulsion, aiming at improving key performance indicators related to efficiency, environmental sustainability and economic competitiveness. In this transition period, it is important to continue the innovation of combustion engines for e.g. plug-in hybrid vehicles. This led Volvo Cars to pursue radically new manufacturing processes such as Friction Stir Welding (FSW). The work presented in this paper is a case study whereby feasibility of using FSW to join a reinforcement element into the aluminium casted Cylinder Block was studied. The complex geometry of the joint required a flexible five-axis manipulator, i.e. an industrial robot, as well as advanced process control, i.e. temperature feedback control, in order to maintain a consistent weld quality throughout the whole component. The process was successfully demonstrated in a lab environment and offers a cost-efficient solution while maintaining the durability and higher efficiency. The outcome of this study shows the great potential of implementing the FSW process in combination with High Pressure Die Casted components, such a Cylinder Block. © 2019 The Society of Manufacturing Engineers

  • 3.
    Ferreira Magalhães, Ana Catarina
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production Systems. TWI Ltd. Cambridge, UK.
    Martin, Jonathan Peter
    TWI Ltd. Cambridge, UK.
    Bolmsjö, Gunnar
    Linnaeus University, Växjö, Sweden.
    In-situ temperature measurement in friction stir welding of thick section aluminium alloys2019In: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 39, p. 12-17Article in journal (Refereed)
    Abstract [en]

    Friction stir welding (FSW) is a reliable joining technology with a wide industrial uptake. However, several fundamentals of the process such as the temperature inside the stirred zone of the weld and its influence on mechanical properties, are not yet fully understood. This paper shows a method for accurate temperature measurements in multiple locations around the tool, to identify the location of the peak temperature, the temperature variations between the advancing and the retreating side of the tool and its relation to the tool geometry. Both standardised thermocouples in the FSW tool and the novel "tool-workpiece thermocouple" method were used to record temperatures.Bead-on-plate welds in 20 mm thickness AA6082-T6 were produced while the temperatures were measured in three locations on the FSW tool: at the shoulder outer diameter, at the transition from shoulder to probe and at the probe tip. It was found that the hottest point in the stirred zone was 607 °C and was located at the transition between the shoulder and probe, on the retreating-trailing side of the tool. The lowest temperature was found at the probe tip on the retreating-leading side of the tool.The results offer a better understanding of the temperature distribution around a FSW tool. The method presented can be applied to verification of thermal simulation models, tool design optimization, quality assurance and temperature feedback control.

  • 4.
    Magalhães, Ana
    University West, Department of Engineering Science, Division of Production Systems.
    Thermo-electric temperature measurements in friction stir welding: Towards feedback control of temperature2016Licentiate 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.

  • 5.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Production System.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production System.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Production System.
    Analysis of Plunge and Dwell Parameters of Robotic FSW Using TWT Temperature Feedback Control2016In: Proceedings of 11th International Symposium on Friction Stir Welding, Cambridge, UK, 2016, p. 1-11Conference paper (Other academic)
    Abstract [en]

    Friction stir welding (FSW) and variants of the process have generated high interest in many industries due to its several advantages such as low distortion, superior mechanical properties over arc welding and the possibility of joining dissimilar materials. Increased complexity of industrial applications require a better control of the welding process in order to guarantee a consistent weld quality. This can be achieved by implementing feedback control based on sensor measurements. Previous studies have demonstrated a direct effect of weld temperature on the mechanical properties of FSW joints, [1], and therefore, temperature is chosen as primary process variable in this study.A new method for temperature measurement in FSW referred to as the Tool-WorkpieceThermocouple (TWT) method has recently been developed by De Backer. The TWT method is based on thermoelectric effect and allows accurate, fast and industrially suitable temperature monitoring during welding, without the need for thermocouples inside the tool [2].This paper presents an application of the TWT method for optimisation of the initial weld phases, plunge and dwell, operation in conventional FSW, which can also be applied to friction stir spot welding (FSSW). An analysis of the operation parameters by using feedback temperature control is presented aiming to better control of the initial weld phases through temperature feedback.

    The introduction of the TWT temperature sensor provides additional process information during welding. Fast data acquisition gives opportunity to differentiate different process phases: contact of probe tip with workpiece surface; plunge phase; dwell phase. This would be followed by tool retraction for FSSW or tool traverse phase for FSW.The effect of the plunge parameters on weld temperature and duration of each phase were studied for the purpose of optimising the process with respect to process (i) robustness, (ii)time, (iii) robot deflection and (iv) quality. By using temperature feedback, it is possible to control the plunge phase to reach a predefined weld temperature, avoiding overheating of the material, which is known to have a detrimental influence on mechanical properties. The work presented in this paper is an important step in the optimization of robotic FSSW and FSW.

  • 6.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Automation Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation Systems.
    Cooling rate effect on temperature controlled FSW process2015Conference paper (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.

  • 7.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Production Systems.
    Temperature measurements during friction stir welding2017In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 88, no 9-12, p. 2899-2908Article in journal (Refereed)
    Abstract [en]

    The increasing industrial demand for lighter, more complex and multi-material components supports the development of novel joining processes with increased automation and process control. Friction stir welding (FSW) is such a process and has seen a fast development in several industries.This welding technique gives the opportunity of automation and online feedback control, allowing automatic adaptation to environmental and geometrical variations of the component.Weld temperature is related to the weld quality and therefore proposed to be used for feedback control. For this purpose, accurate temperature measurements are required. This paper presents an overview of temperature measurement methods applied to the FSW process. Three methods were evaluated in this work: thermocouples embedded in the tool, thermocouples embedded in the workpiece and the tool-workpiece thermocouple(TWT) method. The results show that TWT is an accurate and fast method suitable for feedback control of FSW.

  • 8.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Automation Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation Systems.
    TWT method for temperature measurement during FSW process2015In: The 4th international Conference on scientific and technical advances on friction stir welding & processing, San Sebastian, Spain, 2015, p. 95-98Conference paper (Refereed)
    Abstract [en]

    Friction stir weld (FSW) has generated a high interest in many industry segments in the past 20 years. Along with new industrial challenges, more complex geometries and high quality demands, a better control of the welding process is required. New approaches using temperature controlled welding have been proposed and revealed good results. However, few temperature measurement methods exist which are accurate, fast and industrially suitable. A new and simple sensor solution, the Tool-Workpiece Thermocouple (TWT) method, based on the thermoelectric effect was recently developed.This paper presents a calibration solution for the TWT method where the TWT temperature is compared to calibrated thermocouples inside the tool. The correspondence between both methods is shown. Furthermore, a calibration strategy in different aluminium alloys is proposed, which is based on plunge iterations. This allows accurate temperature monitoring during welding, without the need for thermocouples inside the tool.

  • 9.
    Silva, Ana
    et al.
    University West, Department of Engineering Science, Division of Production Systems.
    De Backer, Jeroen
    University West, Department of Engineering Science, Division of Production Systems.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Production Systems.
    Welding Temperature during FSW of 5 mm thickness AA6082-T62017In: 5th international conference on scientific and technical advances on friction stir welding & processing, Metz, France, 11-13 October 2017., 2017Conference paper (Other academic)
1 - 9 of 9
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