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| 2. |
- Bates, William P., et al.
(författare)
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Properties Augmentation of Cast Hypereutectic Al-Si Alloy Through Friction Stir Processing
- 2022
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Ingår i: Metals and Materials International. - : KOREAN INST METALS MATERIALS. - 1598-9623 .- 2005-4149.
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Tidskriftsartikel (refereegranskat)abstract
- The present endeavour is to augment mechanical attributes via friction stir processing (FSP) in hypereutectic aluminium-silicon castings by the means of microstructural modifications and defects reduction. Wherein, the study proceeds with mainly two approaches namely, alteration in tool revolution (TR) and the number of FSP passes. The prepared specimens were evaluated investigating volume fraction of porosities, microstructural characterizations and microhardness. Therefrom, the specimen with highest number of passes delivered most uniform properties resulting from the reduction in casting porosities and refined silicon particle uniform distribution throughout friction stir processed zone. This endeavour may be considered as a footstep towards more industrial readied material transformation.
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| 3. |
- Bolmsjö, Gunnar, 1955-, et al.
(författare)
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Robotic Friction Stir Welding of complex geometry and mixed materials
- 2018
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Ingår i: 50th International Symposium on Robotics, ISR 2018. - : VDE Verlag GmbH. - 9783800746996 - 9781510870314 ; , s. 35-41
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Konferensbidrag (refereegranskat)abstract
- 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
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| 4. |
- De Backer, Jeroen, 1987-, et al.
(författare)
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Deflection model for robotic friction stir welding
- 2014
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Ingår i: Industrial robot. - Bingley : Emerald Group Publishing Limited. - 0143-991X .- 1758-5791. ; 41:4, s. 365-372
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Tidskriftsartikel (refereegranskat)abstract
- This paper aims to present a deflection model to improve positional accuracy of industrial robots. Earlier studies have demonstrated the lack of accuracy of heavy-duty robots when exposed to high external forces. One application where the robot is pushed to its limits in terms of forces is friction stir welding (FSW). This process requires the robot to deliver forces of several kilonewtons causing deflections in the robot joints. Especially for robots with serial kinematics, these deflections will result in significant tool deviations, leading to inferior weld quality.This paper presents a kinematic deflection model, assuming a rigid link and flexible joint serial kinematics robot. As robotic FSW is a process which involves high external loads and a constant welding speed of usually below 50 mm/s, many of the dynamic effects are negligible. The model uses force feedback from a force sensor, embedded on the robot, and predicts the tool deviation, based on the measured external forces. The deviation is fed back to the robot controller and used for online path compensation.The model is verified by subjecting an FSW tool to an external load and moving it along a path, with and without deviation compensation. The measured tool deviation with compensation was within the allowable tolerance for FSW.The model can be applied to other robots with a force sensor.The presented deflection model is based on force feedback and can predict and compensate tool deviations online.
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| 5. |
- De Backer, Jeroen, 1987-
(författare)
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Feedback Control of Robotic Friction Stir Welding
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Friction Stir Welding (FSW) process has been under constant developmentsince its invention, more than 20 years ago. Whereas most industrial applicationsuse a gantry machine to weld linear joints, there are applications which consistof complex three-dimensional joints, requiring more degrees of freedom fromthe machines. The use of industrial robots allows FSW of materials alongcomplex joint lines. There is however one major drawback when using robotsfor FSW: the robot compliance. This results in vibrations and insufficient pathaccuracy. For FSW, path accuracy is important as it can cause the welding toolto miss the joint line and thereby cause welding defects.The first part of this research is focused on understanding how welding forcesaffect the FSW robot accuracy. This was first studied by measuring pathdeviation post-welded and later by using a computer vision system and laserdistance sensor to measure deviations online. Based on that knowledge, a robotdeflection model has been developed. The model is able to estimate thedeviation of the tool from the programmed path during welding, based on thelocation and measured tool forces. This model can be used for online pathcompensation, improving path accuracy and reducing welding defects.A second challenge related to robotic FSW on complex geometries is thevariable heat dissipation in the workpiece, causing great variations in the weldingtemperature. Especially for force-controlled robots, this can lead to severewelding defects, fixture- and machine damage when the material overheats.First, a new temperature method was developed which measures thetemperature at the interface of the tool and the workpiece, based on the thermoelectriceffect. The temperature information is used as input to a closed-looptemperature controller. This modifies primarily the rotational speed of the tooland secondarily the axial force. The controller is able to maintain a stablewelding temperature and thereby improve the weld quality and allow joining ofgeometries which were impossible to weld without temperature control.Implementation of the deflection model and temperature controller are twoimportant additions to a FSW system, improving the process robustness,reducing the risk of welding defects and allowing FSW of parts with highlyvarying heat dissipation.
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| 6. |
- De Backer, Jeroen, 1987-, et al.
(författare)
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Friction stir welding with robot for light vehicle design
- 2010
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Ingår i: Proceedings from the 8<sup>th</sup> International Friction Stir Welding Symposium. - : The Welding Institute. - 1903761085 - 9781903761083
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Reducing weight is one of the enablers to design more environmentally friendly vehicles. Friction Stir Welding (FSW) supports low weight design through its capability to join different combinations of light weight materials, e.g. different aluminium alloys, but also through its possibilities in producing continuous joints. StiRoLight is a recently started project for robotised FSW for joining of light weight materials emphasising on the vehicle industry, an industry with a long-time experience of robotic welding. The first task involves investigation of force feedback for maintaining the desired contact force. Another important aspect in robotised FSW is the compliance of the robot, which may result in deviations from the pre-programmed path as a result of the high process forces experienced during the welding operation. The further exploration of three-dimensional FSW seams and definition of the process windows will be part of further research within this project.
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| 7. |
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| 8. |
- De Backer, Jeroen, 1987-, et al.
(författare)
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Investigation of path compensation methods for robotic friction stir welding
- 2012
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Ingår i: Industrial robot. - : Emerald Group Publishing Limited. - 0143-991X .- 1758-5791. ; 39:6, s. 601-608
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Tidskriftsartikel (refereegranskat)abstract
- Purpose – Friction stir welding (FSW) is a novel method for joining materials without using consumables and without melting the materials. The purpose of this paper is to present the state of the art in robotic FSW and outline important steps for its implementation in industry and specifically the automotive industry.Design/methodology/approach – This study focuses on the robot deflections during FSW, by relating process forces to the deviations from the programmed robot path and to the strength of the obtained joint. A robot adapted for the FSW process has been used in the experimental study. Two sensor-based methods are implemented to determine path deviations during test runs and the resulting welds were examined with respect to tensile strength and path deviation.Findings – It can be concluded that deflections must be compensated for in high strengths alloys. Several strategies can be applied including online sensing or compensation of the deflection in the robot program. The welding process was proven to be insensitive for small deviations and the presented path compensation methods are sufficient to obtain a strong and defect-free welding joint.Originality/value – This paper demonstrates the effect of FSW process forces on the robot, which is not found in literature. This is expected to contribute to the use of robots for FSW. The experiments were performed in a demonstrator facility which clearly showed the possibility of applying robotic FSW as a flexible industrial manufacturing process.
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| 9. |
- De Backer, Jeroen, 1987-
(författare)
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Robotic Friction Stir Welding for Flexible Production
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Friction Stir Welding (FSW) is a modern welding process that joins materials by frictional heat, generated by a rotating tool. Unlike other welding processes, the material never melts, which is beneficial for the weld properties. FSW is already widely adopted in several industries but the applications are limited to simple geometries like straight lines or circular welds, mostly in aluminium. The welding operation is performed by rigid FSW machines, which deliver excellent welds but puts limitations on the system in terms of flexibility and joint geometries. Therefore, several research groups are working on the implementation of the FSW process on industrial robots. A robot allows welding of three-dimensional geometries and increases the flexibility of the whole system. The high process forces required for FSW, in combination with the limited stiffness of the robot brings some extra complexity to the system. The limitations of the robot system are addressed in this licentiate thesis.One part of the thesis studies the effect of robot deflections on the weld quality. A sensor-based solution is presented that measures the path deviation and compensates this deviation by modifying the robot trajectory. The tool deviation is reduced to an acceptable tolerance and root defects in the weld are hereby eliminated. The sensor-based method provided better process understanding, leading to a new strategy that uses existing force-feedback for path compensations of the tool. This method avoids extra sensors and makes the system less complex. Another part of this work focuses on the extra complexity to maintain a stable welding process on more advanced geometries. A model is presented that allows control of the heat input in the process by control of the downforce. Finally, the robot’s limitations in terms of maximal hardness of the materials to be welded are investigated. Parameter tuning and implementation of preheating are proposed to allow robotic FSW of superalloys.
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