Effects of tool–workpiece interface temperature on weld quality and quality improvements through temperature control in friction stir welding

2013 ◽  
Vol 71 (1-4) ◽  
pp. 165-179 ◽  
Author(s):  
Axel Fehrenbacher ◽  
Neil A. Duffie ◽  
Nicola J. Ferrier ◽  
Frank E. Pfefferkorn ◽  
Michael R. Zinn
Keyword(s):  
Friction Stir Welding ◽  
Temperature Control ◽  
Interface Temperature ◽  
Weld Quality ◽  
Quality Improvements ◽  
Friction Stir

scholarly journals Thermal Dissipation Effect on Temperature-controlled Friction Stir Welding

2019 ◽  
Vol 24 ◽  
Author(s):  
Ana Magalhães ◽  
Jeroen De Backer ◽  
Gunnar Bolmsjö
Keyword(s):  
Friction Stir Welding ◽  
Temperature Control ◽  
Tensile Tests ◽  
Fast Response ◽  
Lap Joints ◽  
Thermal Dissipation ◽  
Welding Parameter ◽  
Weld Quality ◽  
Welding Temperature ◽  
Friction Stir

Abstract 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.

Application of Fuzzy Logic Control Strategy for Temperature Control in Friction Stir Welding

2013 ◽  
Author(s):  
R. R. Varun Das ◽  
V. Kalaichelvi ◽  
R. Karthikeyan
Keyword(s):  
Fuzzy Logic ◽  
Friction Stir Welding ◽  
Dynamic Modeling ◽  
Temperature Control ◽  
Control Strategy ◽  
Welding Process ◽  
Weld Quality ◽  
Production Environment ◽  
Welding Temperature ◽  
Friction Stir

Friction Stir welding is a solid state joining process that utilizes a rotating non-consumable tool to plastically deform and forge together parent metals. Welding can be controlled either by using Force, Temperature and Traverse or Seam Control methods. The presence of numerous parameters and conditional variations in FSW production environment can adversely affect weld quality making extensive automation processes impossible till date. The weld quality of FSW is closely related to the stability of the welding temperature. For such a non-linear complex process conventional control theory is not an appropriate choice. A fuzzy logic controller with a specially chosen triangular membership function has been suggested as an effective alternative approach. The aim of the present work includes dynamic modeling of a friction stir welding process and the use of a suitable Fuzzy tuned Control Strategy for temperature control. The Temperature at stir zone is measured using a K type Thermocouple. It has a sensitivity of 41μV/°C and also a wide variety of probes are available within its −200° C to +1250 °C range. The thermocouple is used by drilling a hole in the shank of the tool and letting it pass through it. The spindle speed is used as an appropriate variable to control temperature variations. The dynamic modeling and simulations were performed using Matlab whereas the variable values were derived during friction stir welding of aluminum.

Combined Temperature and Force Control for Robotic Friction Stir Welding

2013 ◽  
Author(s):  
Axel Fehrenbacher ◽  
Christopher B. Smith ◽  
Neil A. Duffie ◽  
Nicola J. Ferrier ◽  
Frank E. Pfefferkorn ◽  
...  
Keyword(s):  
Control System ◽  
Force Control ◽  
Closed Loop ◽  
Interface Temperature ◽  
Closed Loop Control ◽  
Weld Quality ◽  
Loop Control ◽  
Friction Stir ◽  
Tool Position ◽  
Robotic Friction Stir Welding

The objective of this research is to develop a closed-loop control system for robotic friction stir welding (FSW) that simultaneously controls force and temperature in order to maintain weld quality under various process disturbances. FSW is a solid-state joining process enabling welds with excellent metallurgical and mechanical properties, as well as significant energy consumption and cost savings compared to traditional fusion welding processes. During FSW, several process parameter and condition variations (thermal constraints, material properties, geometry, etc.) are present. The FSW process can be sensitive to these variations, which are commonly present in a production environment; hence, there is a significant need to control the process to assure high weld quality. Reliable FSW for a wide range of applications will require closed-loop control of certain process parameters. A linear multi-input-multi-output process model has been developed that captures the dynamic relations between two process inputs (commanded spindle speed and commanded vertical tool position) and two process outputs (interface temperature and axial force). A closed-loop controller was implemented that combines temperature and force control on an industrial robotic FSW system. The performance of the combined control system was demonstrated with successful command tracking and disturbance rejection. Within a certain range, desired axial forces and interface temperatures are achieved by automatically adjusting the spindle speed and the vertical tool position at the same time. The axial force and interface temperature is maintained during both thermal and geometric disturbances and thus weld quality can be maintained for a variety of conditions in which each control strategy applied independently could fail.

scholarly journals Study on Quality Prediction of 2219 Aluminum Alloy Friction Stir Welding Based on Real-Time Temperature Signal

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3496
Author(s):  
Haijun Wang ◽  
Diqiu He ◽  
Mingjian Liao ◽  
Peng Liu ◽  
Ruilin Lai
Keyword(s):  
Aluminum Alloy ◽  
Friction Stir Welding ◽  
Prediction Model ◽  
Real Time ◽  
Support Vector ◽  
Weld Quality ◽  
Prediction Ability ◽  
Friction Stir ◽  
Temperature Signal ◽  
2219 Aluminum Alloy

The online prediction of friction stir welding quality is an important part of intelligent welding. In this paper, a new method for the online evaluation of weld quality is proposed, which takes the real-time temperature signal as the main research variable. We conducted a welding experiment with 2219 aluminum alloy of 6 mm thickness. The temperature signal is decomposed into components of different frequency bands by wavelet packet method and the energy of component signals is used as the characteristic parameter to evaluate the weld quality. A prediction model of weld performance based on least squares support vector machine and genetic algorithm was established. The experimental results showed that, when welding defects are caused by a sudden perturbation during welding, the amplitude of the temperature signal near the tool rotation frequency will change significantly. When improper process parameters are used, the frequency band component of the temperature signal in the range of 0~11 Hz increases significantly, and the statistical mean value of the temperature signal will also be different. The accuracy of the prediction model reached 90.6%, and the AUC value was 0.939, which reflects the good prediction ability of the model.

scholarly journals Physics-based interpretation of tool-workpiece interface temperature signals for detection of defect formation during friction stir welding

2015 ◽  
Vol 5 ◽  
pp. 7-11 ◽  
Author(s):  
Amber Shrivastava ◽  
Clemens Dingler ◽  
Michael Zinn ◽  
Frank E. Pfefferkorn
Keyword(s):  
Friction Stir Welding ◽  
Defect Formation ◽  
Interface Temperature ◽  
Friction Stir

Combined Temperature and Force Control for Robotic Friction Stir Welding

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Axel Fehrenbacher ◽  
Christopher B. Smith ◽  
Neil A. Duffie ◽  
Nicola J. Ferrier ◽  
Frank E. Pfefferkorn ◽  
...  
Keyword(s):  
Control System ◽  
Friction Stir Welding ◽  
Force Control ◽  
Process Model ◽  
Closed Loop ◽  
Interface Temperature ◽  
Friction Stir ◽  
Tool Position ◽  
Robotic Friction Stir Welding ◽  
Robotic Fsw

Use of robotic friction stir welding (FSW) has gained in popularity as robotic systems can accommodate more complex part geometries while providing high applied tool forces required for proper weld formation. However, even the largest robotic FSW systems suffer from high compliance as compared to most custom engineered FSW machines or modified computer numerical control (CNC) mills. The increased compliance of robotic FSW systems can significantly alter the process dynamics such that control of traditional weld parameters, including plunge depth, is more difficult. To address this, closed-loop control of plunge force has been proposed and implemented on a number of systems. However, due to process parameter and condition variations commonly found in a production environment, force control can lead to oscillatory or unstable conditions and can, in extreme cases, cause the tool to plunge through the workpiece. To address the issues associated with robotic force control, the use of simultaneous tool interface temperature control has been proposed. In this paper, we describe the development and evaluation of a closed-loop control system for robotic friction stir welding that simultaneously controls plunge force and tool interface temperature by varying spindle speed and commanded vertical tool position. The controller was implemented on an industrial robotic FSW system. The system is equipped with a custom real-time wireless temperature measurement system and a force dynamometer. In support of controller development, a linear process model has been developed that captures the dynamic relations between the process inputs and outputs. Process validation identification experiments were performed and it was found that the interface temperature is affected by both spindle speed and commanded vertical tool position while axial force is affected primarily by commanded vertical tool position. The combined control system was shown to possess good command tracking and disturbance rejection characteristics. Axial force and interface temperature was successfully maintained during both thermal and geometric disturbances, and thus weld quality can be maintained for a variety of conditions in which each control strategy applied independently could fail. Finally, it was shown through the use of the control process model, that the attainable closed-loop bandwidth is primarily limited by the inherent compliance of the robotic system, as compared to most custom engineered FSW machines, where instrumentation delay is the primary limiting factor. These limitations did not prevent the implementation of the control system, but are merely observations that we were able to work around.

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