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

Wednesday 2:00 PM
March 22, 2023
Room: 29A
Location: SDCC

Session Chair: Kevin Colligan, Concurrent Technologies Corporation; Darrell Herling, Pacific Northwest National Laboratory


2:00 PM  Invited
Linking Tool Features to Process Forces: Samuel Merritt1; Yuri Hovanski1; Kenneth Ross2; 1Brigham Young University; 2Pacific Northwest National Laboratory
    Tool design in linear friction stir welding has been largely Edisonian with organizations having favorite tools and features that have been used without clear data showing cause and effect. Previous studies evaluating features have elucidated certain trends with respect to reducing reactionary forces on the tools, although most of these studies focused on fixed tool diameters with few variations based on the complexity associated with machining or grinding new tool geometries. The present work focuses on FSW tools that have been produced using direct laser sintering to enable rapid evaluation of numerous tool features and designs. Tools were produced showing the effects of variation in shoulder convexity, shoulder features, probe features and probe geometry. Analysis of how each feature influences the transverse and axial forces are presented, as a means of demonstrating low-force tool designs.

2:20 PM  
Next Generation Tooling for Friction Stir Technologies: Supreeth Gaddam1; Amit Behera2; Qiaofu Zhang2; Noriaki Arai2; James Male2; Rajiv Mishra1; 1University of North Texas; 2QuesTek Innovations LLC
    The success of friction stir welding (FSW) and related technologies on materials such as aluminum and magnesium alloys is owed to the superior properties of the processed material that are associated with the absence of melting and solidification during the solid-state processes. However, the commercial application of these technologies on steels and other non-ferrous high-strength, high-temperature materials is limited due to the high cost and short lifetimes of the available tool materials. To overcome this, Integrated Computational Materials Engineering (ICME) combined with experimental prototyping validation has been adopted to design next-generation tools specific to workpiece materials. Cermet tools with tungsten carbide or niobium carbide as the hard phase with a high entropy alloy binder are processed via mechanical alloying and spark plasma sintering and their feasibility and effectiveness are evaluated for FSW and related technologies. Results from the experimental prototyping and testing effort will be presented and discussed in-depth.

2:40 PM  
Hybrid FSW Tools for Electromobile Applications: Michael Grätzel1; Markus Weigl2; Michael Hasieber1; Jean Pierre Bergmann1; 1Technische Universität Ilmenau; 2Grenzebach Maschinenbau GmbH
    Joining of battery cases for elcetro mobiles require high demands on the installed joining technologies. Therefore, FSW is increasingly used due to high joint quality and the mechanical properties similar to the base material. However, these properties are significantly influenced by the tool concepts. Using monolitic FSW tools high heat inputs can be achieved by comparative higher frictional surface. However, there are limitations in terms of surface quality and fatigue. With stationary shoulder tools, excellent weld seam surfaces can be produced. However, the stationary shoulder has a lower heat input compared to under consideration of the same process condition. Consequently the reduced heat input leads to restrictions regarding the welding speed and the maximum penetration depth. Thus present article deals with the application of hybrid FSW tools in industrial application, which combines monolithic and stationary shoulder tools whereby the advantages of those two variants can be concentrated.

3:00 PM  
Measurement of Heat Transfer Coefficient between a Friction Stir Welding Tool and Workpiece during Plunge Using a 3ω Sensor: Matthew Goodson1; Ryan Melander1; Troy Munro1; Michael Miles1; 1Brigham Young University
    When simulating friction stir welding (FSW) to understand weld quality, there are two key factors that have yet to be experimentally measured: the friction coefficient (µ) and the heat transfer coefficient (h) [W/m2K] between the workpiece and the rapidly rotating tool. The current practice when simulating the FSW process is to tune µ after selecting approximate h values based on two often cited papers. The current research presents h measurements conducted during the plunge step of a friction stir weld, including the h value for the tool/workpiece interface. Validation and integration of a 3ω measurement system will be presented. The 3ω measurement systems works by introducing a periodic temperature variation that leads to the measurement of the thermal contact resistance between two layers. Thermal contact resistance is the inverse of h. Future work will extend the newly developed approach to measurements of h for other FSW processes.

3:20 PM Break

3:40 PM  Invited
Friction Stir Welding Operating Window for Aluminum Alloy Obtained by Temperature Measurement: Moura Abboud1; Laurent Dubourg2; Adrien Leygue3; Guillaume Racineux3; Olivier Kerbrat4; 1Ecole Normale Supérieure de Rennes / Stirweld; 2Stirweld; 3Institut de Recherche en Génie Civil et Mécanique (GeM); 4Ecole Normale Supérieure de Rennes
     Finding the process parameters (advancing and rotational speed) in FSW is the key to construct an operating window based on a type of material and a tool geometry. Literature shows different process methods carried out by researchers and engineers to obtain the data needed to select suitable parameters. These methods can be divided into “destructive”, based on macrostructures analyses, and “non-destructive” with temperature measurement. This article describes a continuous temperature measurement method of the nugget zone using a thermocouple embedded in the tool for aluminum alloy. The results show that the FSW window obtained by temperature measurement is wider than the one obtained by analyzing the macrostructures. It is then possible to quickly acquire the technological window of operating parameters adapted to the tool-material couple.The aim of this study is to reduce time of the welding process, number of trials, cost and guarantee a good quality.

4:00 PM  
The Performance of a Force-based General Defect Detection Method Outside of Calibration: Johnathon Hunt1; Yuri Hovanski1; 1Brigham Young University
    Friction stir welding (FSW) is an advantageous joining process that is suitable for many engineering designs. The need for economical non-destructive evaluation (NDE) for welding is imperative for high volume industries. This need has led the development of many different inline force-based NDE methods. This work introduces the performance of a generalized NDE method that is applied to friction stir welds where the process parameters were not included in the NDE calibration. When this NDE method is applied to welds within calibration the process spatially detects defects with 94% accuracy with 4% false positives. In addition, the methodology proved 100% effective at positive detection when defects were present with zero scrap rate as a Go, No-Go test.

4:20 PM  Invited
Material Flow Visualization and Comparison in Different Aluminum Alloys during Friction Stir Welding using High-Speed X-ray Imaging: Hemant Agiwal1; Daniel Franke1; Mohammad Ansari1; Patrick Faue1; Samuel Clark2; Kamel Fezzaa2; Michael Zinn1; Shiva Rudraraju1; Frank Pfefferkorn1; 1University of Wisconsin-Madison; 2Argonne National Laboratory
    The intricacies of material flow dynamics during friction stir welding for different aluminum alloys have been a long hypothesized phenomenon in the literature, with studies predicting the material flow using post-factum microstructural characterization and numerical simulations. This study employs high-speed X-ray imaging performed at the Advanced Photon Source facility in Argonne National Laboratory to capture the process dynamics during friction stir welding. A high-intensity X-ray beam was used to image a 2 mm x 2 mm area at 20,000 frames per second. The friction stir tool made of H13 tool steel with threads and 3-flats on the probe was used to compare material flow in aluminum 6061-T6 and aluminum 7075 workpieces. The density changes captured by the high-intensity X-ray beam show the formation and filling of cavities in the wake of the tool. The difference in material flow and visco-plastic shearing is also observed in the two alloys.

4:40 PM  
The Role of Fracture Properties on Lap Joint Strength of Friction Stir Welded AA 7055-T6 Sheets: Kranthi Balusu1; Hrishikesh Das1; Xiao Li1; Timothy Roosendaal1; Robert Seffens1; Ayoub Soulami1; Piyush Upadhyay1; 1Pacific Northwest National Laboratory
     Friction stir lap welded (FSLW) joints have weight-saving potential in Aluminum intensive automotive assembly. However, FSLW also modifies the microstructure close to the joint. Optimizing the FSLW process requires understanding the relationship between the strength and the joint’s microstructure. In previous studies, efforts have been dedicated to determining the effects of local softening, the shape of the oxide line, and porosity. However, the impact of changes to the fracture properties on the joint’s strength has not been studied. In this work, strength testing, and simulations, aided by microstructural characterization, were used to determine the role of fracture properties on the shear strength of a 3-sheet (alloys 7055-7055-6011) lap joint. Characterization involved testing for fracture properties and hardness within different regions of the weld. This data was then implemented into finite element simulations. As a result, the joint strength was predicted with a deviation less than 10% from the experimental value.

5:00 PM  
Simulation and Realization of Friction Stir Welding of Aluminum Joints Using Additively Manufactured Ceramic Bobbin Tools: Toni Sprigode1; Andreas Gester1; Guntram Wagner1; Murat Demirtas2; Nadja Kratz2; Anna Foit3; Gerald Ochse3; Angelika Brückner-Foit3; Adrian Rienäcker3; Marcus Emmel4; 1Chemnitz University of Technology; 2Forschungsinstitut für Glas - Keramik GmbH; 3University of Kassel; 4Product Area Ceramics (GROW/PAC), grow platform GmbH
    A huge disadvantage of conventional friction stir welding (FSW) tools is that if the welding depth is insufficient, root defects can occur, which have a negative effect on the joint strength and especially on the fatigue behavior. Bobbin tools are used to counteract this weak point. These special tools have an additional second shoulder at the welding probe, which enables welding over the entire thickness of the workpiece. The possibility of producing tools from ceramic materials by means of additive manufacturing allows direct adaptation to the respective welding task. In this investigation, aluminum joints were produced by FSW using additive manufactured ceramic bobbin tools. Thereby, the running-in process in particular proved to be a critical stress for the ceramic tools. As a consequence, the process was investigated through simulation including shape optimization of the tool. This contributed to improve the joint formation in the simulation as well as the process.