Friction Stir Welding

Shear localisation modelling of friction stir weld formation process

“…As a case in point, an orderly banded structure (see Fig. 1) typically seen in quality friction stir welds by various researchers [3][4][5][6] coincides with an incremental distance travelled by stir pin per revolution, suggesting that an essentially displacement controlled weld formation process is at play, or more precisely, through a local shear deformation process.…”

“…A review summary on various modelling approaches is given by Nandan et al 12 Although a plenty of numerical models for FSW have been proposed or attempted over the last two decades, a modelling capability for process parameter window estimation 1 in terms of friction stir pin rotational and translational speed for a given material of interest remains elusive today. Recognising the dominance of local plastic deformation characteristics discussed in aforementioned work, [3][4][5][6] this paper presents a rather different approach to friction stir weld formation modelling by focusing on shear localisation process dynamics which should be directly applicable to the SB formation process shown in Fig. 1 as reported elsewhere.…”

“…Friction stir welding (FSW) is a relatively new solid state joining process, as first reported by Dawes and Thomas, 1 and has many advantages over traditional welding and joining processes as recently reviewed by Nandan et al 2 It can be used either to join advanced high strength materials deemed not weldable or modify material surface conditions for improved fracture and fatigue resistance of a structure that may be subjected to a hostile service environment, such as space vehicle launch and operation, as discussed by Nandan et al 2 and Nunes. 3 Recognising the needs for an improved understanding of weld formation process associated with FSW, there have been numerous investigations into various aspects of FSW process over the last decade, which resulted in many important findings as recently discussed elsewhere. 2 One significant finding that is of a particular interest to the authors of this paper is that plastic flow phenomena in form of shear banding seem 1 to govern weld development process as shown experimentally by Schneider and Nunes 4 and, Yang et al 5 for high strength aluminium alloys, by Knipling and Fonda 6 and Pilchak et al 7 for titanium alloys.…”

Liquid film formation and cracking during friction stir welding

“…9 To date, a clear connection between partial melting and defect formation or cracking in friction stir welds has not been established. In a recent book chapter, 10 Nunes has suggested that the formation of tears or galling near the surface of the weld directly below tool shoulder is related to low melting point phases present in the base material. In a discussion regarding the role of processing parameters on defect formation, Arbegast 11 argued that surface galling defects, or tears, may be expected when relatively high rotation speeds are used in combination with low travels speeds.…”

Principles and Thermo-Mechanical Model of Friction Stir Welding

“…Though, the most important innovation in the process itself is its variations; (1) high speed FSW (HS-FSW), (2) ultrasonic stir welding (USW), (3) thermal stir welding (TSW), (4) friction stir spot welding (FSSW), (5) friction stir joining (FSJ), (6) friction stir processing (FSP), (7) friction bonding (FB) [37].…”