Friction Stir Welding and Processing XI: Control & Non-Destructive Examination
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Shaping and Forming Committee
Program Organizers: Yuri Hovanski, Brigham Young University; Piyush Upadhyay, Pacific Northwest National Laboratory; Yutaka Sato, Tohoku University; Nilesh Kumar, University of Alabama, Tuscaloosa; Anton Naumov, Peter The Great St. Petersburg Polytechnic University

Tuesday 2:00 PM
March 16, 2021
Room: RM 39
Location: TMS2021 Virtual


2:00 PM  
Real-time Measurement of Friction Stir Tool Motion during Defect Interaction in Aluminum Alloy 6061-T6: Daniel Franke1; Frank Pfefferkorn1; Shiva Rudraraju1; Michael Zinn1; 1University of Wisconsin Madison
    The objective of this research is to develop a fundamental understanding of the interaction between features on the friction stir tool probe and volumetric sub-surface defects formed during welding. This will guide the development of real-time defect monitoring methods that will promote process adoption in high volume and high-reliability applications. A single-head laser doppler vibrometer system was used to produce a non-contact measurement of the eccentric motion of a friction stir tool during welding. When features on the tool probe interact with voided volumes, the tool is momentarily deflected into the voided volume. The distortions in the tool position signals measured with the laser vibrometer are correlated with distortions in measured process forces and defect size. The results add understanding to the changes in forces signals that hold potential for defect monitoring and also suggest that monitoring may be possible through a position-based measurement (accelerometer) from the tool side.

2:20 PM  
Development of Automatic Quality Control Techniques for Friction Stir Welding Processes: Egoitz Aldanondo1; 1LORTEK
     Friction Stir Welding (FSW) processes have been shown to be very attractive not only for high-value added structure manufacturing such as aerospace structures but also for high-volume manufacturing of many other components. For example, the emerging applications for e-mobility have promoted the industrialization of the FSW technology due to advantages such as high productivity, low cost, high quality, energy efficiency, etc. The mass production of some components present very short cycle times and the quality control or inspection techniques can be very time consuming and expensive. Thus, it is necessary to develop new quality control techniques to improve the global manufacturing chain of the newly developed components.Several quality control techniques with automation potential and applicable for components manufactured by FSW will be discussed in this work, such as infrared thermography for root defect detection or laser profilometry for surface defect detection.

2:40 PM  
Preliminary Investigation of the Effect of Temperature Control in Friction Stir Welding: Johnathon Hunt1; David Pearl2; Carter Hamilton2; Yuri Hovanski1; 1Brigham Young University; 2Miami University
    Friction stir welding (FSW) is an advantageous solid-state joining process, suitable for many hard to weld materials in the energy, aerospace, naval and automotive industries. Precipitation strengthened alloys, specifically 2XXX and 7XXX series aluminum alloys, are often joined by FSW to protect the strength of the materials and to avoid cracking. To maximize the strength of FSW joints in these precipitation hardened alloys, the thermal input affect must be better understood. The authors hypothesised that controlling the welding temperature under the dissolution temperature would result in stronger joints. To test the main hypothesis single alloy friction stir “butt” welds were produced, from aluminum 2024-T351 and 7075-T651 alloys, and tensile tested. Spindle speed proportional–integral–derivative (PID) temperature control was implemented to achieve sub-dissolution welding temperatures. This preliminary study will supply additional research to better understand the resulting microstructure, weld properties of sub-dissolution FSW. In addition, a numerical simulation to represent the temperature distribution will be built. Then optimized FSW temperatures could be predicted and tested in these alloys.

3:00 PM  
Transitioning FSW to a Controlled Production Process: Arnold Wright1; Devry Smith1; Brandon Taysom2; Yuri Hovanski1; 1Brigham Young University; 2Pacific Northwest National Laboratory
    Systematic investigation of the Friction Stir Welding (FSW) process shows that a fixed rotational velocity and feed rate may not yield uniform mechanical properties along the length of a weldment. Nevertheless, correlations between process parameters and post-weld material properties have successfully demonstrated that peak temperature and cooling rate drive post-weld properties. We review the reported methodologies reported for controlling friction stir welding with a detailed look at how temperature control has been used. We compare data from uncontrolled FSW of AA 6111-T4 sheet with controlled FSW at temperatures ranging from 375 °C to 450 °C, as a means of demonstrating that a simplified methodology of a single-loop PID controlling with spindle speed may be used to effectively control temperature. This methodology can be simply used with any machine that already has the ability to actively control spindle speed, and has been previously shown to be able to be auto-tuned with a single weld.

3:20 PM  
Removing Rotational Variations from Shoulder Thermocouples in Friction Stir Welding: Brandon Taysom1; Kenneth Ross1; Woongjo Choi1; 1Pacific Northwest National Laboratory
    Thick plate and colder temperature friction stir welding results in good post weld properties by welding at very low tool rotational speeds. At low speeds, large variations in the measured shoulder temperature occur which makes controlling temperature difficult. This paper describes a computationally light method to compensate for oscillating measured temperatures. Data is collected over the previous two revolutions and used to calculate a derivative and build a compensation table. In simulation, measured temperature variations are reduced by a factor of about ten with zero added delay. When implemented on a PLC in an actual weld showed dramatic reductions of measured oscillation at rotational speeds between 30 and 120 rpm.