Friction Stir Welding and Processing XII: Spot Technologies
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 8:30 AM
March 22, 2023
Room: 29A
Location: SDCC
Session Chair: Axel Meyer, RIFTEC GmbH; Josef Cobb, NASA Marshall Space Flight Center
8:30 AM
Joining of High Strength Low Ductility AA7055 by Friction Self-piercing Rivet: Yong Chae Lim1; Hui Huang1; Yiyu Wang1; Yuan Li1; Zhili Feng1; 1Oak Ridge National Laboratory
High strength aluminum (Al) alloy is one of higher specific strength materials for decarbonization in transportation industries. Because of low ductility at room temperature, conventional mechanical fastening such as self-piercing riveting produces cracks at the joint. In this work, we applied friction self-piercing riveting to join Al alloy (AA) 7055. No cracks were observed in the joints because of the improved local ductility of Al alloy by the generated frictional heat during joining step. Mechanical integrity of the AA7055 joints was assessed by lap shear tensile and cross-tension testing. Metallurgical characterizations revealed solid-state bonding formed not only between the rivet and surround Al materials, but also upper and lower Al sheets at the joint interface. Both solid-state bonding and mechanical interlocking between the flared rivet and bottom AA7055 sheet were the major joint mechanisms.
8:50 AM
2D Axisymmetric Modeling of RFSSW Repair and Experimental Validation: Evan Berger1; Michael Miles1; Yuri Hovanski1; Paul Blackhurst1; Andrew Curtis1; Ruth Belnap1; 1Brigham Young University
Refill friction stir spot welding (RFSSW) is a solid-state spot joining technique that can be used to weld aluminum alloys in various thickness and alloy combinations. It is critical to identify the unique conditions that yield excellent bonded properties and the ability to repair a joint that was interrupted during the welding process. Qualified repair techniques are critical for successful implementation of a welding process for use on large weldments with a significant number of spot joints. The focus of this work is to demonstrate a repair technique for RFSSW that can be validated both numerically and experimentally. Modeling is performed in Transvalor’s Forge NxT 3.2 as a 2-D axisymmetric, thermo-mechanically coupled model, which has previously been validated for the RFSSW joining process. Repaired properties are shown to exceed 90% of the original mechanical properties of the RFSSW process.
9:10 AM
Production Evaluation of Refill Friction Stir Spot Welding: Ruth Belnap1; Paul Blackhurst1; Andrew Curtis1; Heath Misak2; Josef Cobb3; Yuri Hovanski1; 1Brigham Young University; 2Spirit AeroSystems, Inc.; 3NASA - MSFC
Since the introduction of refill friction stir spot welding (RFSSW) in the early 2000s numerous evaluations of properties, performance and prototypes have been documented. RFSSW is a solid-state spot joining technique that is being evaluated as a rivet replacement technology for aerospace structures and fuselage fabrication. A production evaluation of overlapping wing skin assembly was completed with both bare metal and sealant at the skin interface. The production consisted of 105 spots per panel in a three-spot wide configuration on a 3” overlap. Weld properties were evaluated for spots produced on bare sheet as well as for sections with sealant applied. Furthermore, evaluations of the performance of repaired spots using the RFSSW process is demonstrated. Characterization of the weld interface, heat-affected zone, and complete through-thickness consolidation via computed tomography is presented.
9:30 AM
Numerical Simulation of the FSSW Process for Aluminum Alloys 5082-O, 6082-T6 and 7075-T6: Mikhail Ozhegov1; Mark Belousov1; Pavel Uporov1; Karolina Vladova1; 1St. Petersburg Polytechical University
The aim оf the present research is to analyze the distribution of temperature fields in the welded joints of thin sheets of aluminum alloys 5082-O, 6082-T6, 7075-T6, produced by friction stir spot welding (FSSW), as well as to determine the mechanical characteristics of the obtained joints. The process of temperatures data acquisition was done by means of thermocouples for different FSW modes, the rotation speed and the speed of penetration of the tool were varied. For aluminum alloy 6082-T6, stress-strain curves were obtained using high-speed torsion tests on the Gleeble-3800 system with Torsion MCU. Data on temperature fields and stress-strain curves are used to validate the 3D numerical model of the FSSW process.
9:50 AM Break
10:10 AM
Embedded Anchoring of Multi-material Assemblies by Friction Riveting Process: Hrishikesh Das1; Keerti Kappagantula1; Abhinav Srivastava1; Piyush Upadhyay1; Jorge F Dos Santos1; Md Reza-E-Rabby1; 1Pacific Northwest National Laboratory
We are reporting on the capability development and broaden the applicability of friction-riveting process for a wide range of multi-layer stacking of polymer to metal, similar and dissimilar metal to metal joining. We present first direct experimental evidence of aluminum to steel dissimilar joining using steel rivet by this process. We have manifested for the first time, magnesium as a rivet material for carbon fiber reinforced polymer (CFRP) stacking, aluminum as a rivet material to laminate magnesium to CFRP, and aluminum to aluminum similar joining and aluminum to steel using steel rivet during the Friction-riveting process. Shed light on detail process parameter optimization and corresponding process response behavior to understand this complex joining method for a wide range of material combinations.
10:30 AM Invited
Effect of Welding Parameters on Microstructure and Mechanical Properties of Friction Stir Lap Welds of an Ultrahigh Strength Steel: Yutaka Sato1; Shunsuke Mimura1; Shun Tokita1; Yusuke Yasuda2; Akihiro Sato2; Satoshi Hirano2; 1Tohoku University; 2Hitachi
In this study, effect of welding parameters on microstructure and mechanical properties of an ultrahigh strength steel (UHSS) friction-stir-lap-welded with Co-based alloy tool was examined. Friction stir lap welding of the UHSS was successfully done at various welding parameters. Tensile shear load of the lap welds was higher at the lower rotational speed. In the lap welds produced at the high rotational speed, crack was initiated from the tip of the lapped interface and then propagated into the stir zone having high fraction of martensite, possibly resulting from the stress concentration. On the other hand, the lap welds produced at the low rotational speed failed in the softened region of the heat affected zone. This study showed that the reduced brittleness of the stir zone arising from the low rotational speed was an effective strategy for the higher mechanical properties of the lap welds of the UHSS.