Material flow in butt friction stir welds in AA2024-T3
TL;DR: In this article, the average velocities for material flowing through the shear layer are estimated based on the configuration of marker material relative to the welding direction, i.e. longitudinal and transverse.
About: This article is published in Acta Materialia.The article was published on 2006-02-01. It has received 326 citations till now. The article focuses on the topics: Friction welding & Welding.
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TL;DR: In this article, the authors deal with the fundamental understanding of the process and its metallurgical consequences, focusing on heat generation, heat transfer and plastic flow during welding, elements of tool design, understanding defect formation and the structure and properties of the welded materials.
1,811 citations
Cites background from "Material flow in butt friction stir..."
...[75] estimated the average velocity of material flow through shear layers during FSW of aluminium alloy based on experimental investigation of tracer flow....
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25 Jun 2008-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, an attempt has been made to understand the mechanism of friction stir weld formation and the role of the friction stir welding tool in it by understanding the material flow pattern in the weld produced in a special experiment.
Abstract: In this investigation an attempt has been made to understand the mechanism of friction stir weld formation and the role of friction stir welding tool in it. This has been done by understanding the material flow pattern in the weld produced in a special experiment, where the interaction of the friction stir welding tool with the base material is continuously increased. The results show that there are two different modes of material flow regimes involved in the friction stir weld formation; namely “pin-driven flow” and “shoulder-driven flow”. These material flow regimes merge together to form a defect-free weld. The etching contrast in these regimes gives rise to onion ring pattern in friction stir welds. In addition to that based on the material flow characteristics a mechanism of weld formation is proposed.
418 citations
TL;DR: In this article, the authors review the latest developments in the numerical analysis of friction stir welding processes, microstructures of friction-stir welded joints and the properties of friction spat welded structures.
397 citations
TL;DR: In this paper, a review of the control strategies for back support, weld thinning, and keyhole defects in friction stir welding (FSW) is presented, which are basically divided into self-supported FSW, non-weld-thinning FSW and friction stir-based remanufacturing.
350 citations
TL;DR: In this paper, the microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature are discussed in detail in order to highlight the correlations between weld parameters used during FSW and the micro-structures evolved in the weld region and thus mechanical properties.
Abstract: The diversity and never-ending desire for a better life standard result in a continuous development of the existing manufacturing technologies. In line with these developments in the existing production technologies the demand for more complex products increases, which also stimulates new approaches in production routes of such products, e.g., novel welding procedures. For instance, the friction stir welding (FSW) technology, developed for joining difficult-to-weld Al-alloys, has been implemented by industry in manufacturing of several products. There are also numerous attempts to apply this method to other materials beyond Al-alloys. However, the process has not yet been implemented by industry for joining these materials with the exception of some limited applications. The microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature will be discussed in detail in this review. The correlations between weld parameters used during FSW and the microstructures evolved in the weld region and thus mechanical properties of the joints produced will be highlighted. However, the modeling studies, material flow, texture formation and developments in tool design are out of the scope of this work as well as the other variants of this technology, such as friction stir spot welding (FSSW).
325 citations
References
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TL;DR: In this article, the authors established an analytical model for heat generation by friction stir welding (FSW), based on different assumptions of the contact condition between the rotating tool surface and the weld piece.
Abstract: The objective of this work is to establish an analytical model for heat generation by friction stir welding (FSW), based on different assumptions of the contact condition between the rotating tool surface and the weld piece. The material flow and heat generation are characterized by the contact conditions at the interface, and are described as sliding, sticking or partial sliding/sticking. Different mechanisms of heat generation are behind each contact condition, making this study important for further understanding of the real FSW process. The analytical expression for the heat generation is a modification of previous analytical models known from the literature and accounts for both conical surfaces and different contact conditions. Experimental results on plunge force and torque are used to determine the contact condition. The sliding condition yields a proportional relationship between the plunge force and heat generation. This is not demonstrated in the experiment, which suggests that the sticking contact condition is present at the tool/matrix interface.
686 citations
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07 Aug 2013TL;DR: In this article, the flow of metal during friction stir welding is investigated using a faying surface tracer and a nib frozen in place during welding, showing that material is transported by two processes: a wiping of material from the advancing front side of the nib onto a zone of material that rotates and advances with the nib.
Abstract: Friction Stir Welding is a relatively new technique for welding that uses a cylindrical pin or nib inserted along the weld seam. The nib (usually threaded) and the shoulder in which it is mounted are rapidly rotated and advanced along the seam. Extreme deformation takes place leaving a fine equiaxed structure in the weld region., The flow of metal during Friction Stir Welding is investigated using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes. The first is a wiping of material from the advancing front side of the nib onto a zone of material that rotates and advances with the nib. The material undergoes a helical motion within the rotational zone that both rotates and advances and descends in the wash of the threads on the nib and rises on the outer part of the rotational zone. After one or more rotations, this material is sloughed off in its wake of the nib, primarily on the advancing side. The second process is an entrainment of material from the front retreating side of the nib that fills in between the sloughed off pieces from the advancing side.
396 citations
TL;DR: In this paper, the Coulomb's Law of friction was used to model the contact forces at the tool/matrix interface and the material flow at the interface was modeled as boundary conditions.
Abstract: The conditions under which the deposition process in friction stir welding is successful are not fully understood. However, it is known that only under specific thermomechanical conditions does a weld formation occur. If these conditions are not present, void formation will occur leading to a faulty weld. The objective of the present work is to analyse the primary conditions under which the cavity behind the tool is filled. For this, a fully coupled thermomechanical three-dimensional FE model has been developed in ABAQUS/Explicit using the arbitrary Lagrangian–Eulerian formulation and the Johnson–Cook material law. The model accounts for the compressibility by including the elastic response of the aluminium matrix. The contact forces are modelled by Coulomb's Law of friction, making the contact condition highly solution dependent. Furthermore, separation between the workpiece and the tool is allowed. This is often neglected in other models. Once non-recoverable separation is estimated by the model, a void develops. This is suggested as a preliminary criterion for evaluating the success of the deposition process. Of special interest is the contact condition along the tool/matrix interface, which controls the efficiency of the deposition process. In most models presented previously in the literature, the material flow at the tool interface is prescribed as boundary conditions. In all other contact models, the material is forced to keep contact with the tool. Therefore, the models are unable to predict when the suitable thermomechanical conditions and welding parameters are present. In the present work, the quasi-stationary thermomechanical state in the workpiece is established by modelling the dwell and weld periods. The different thermomechanical states in the colder, stiffer far-field matrix and the hotter, softer near-field matrix (under the tool) result in contact at the tool/matrix interface, thus, no void formation is observed. The steady-state model results are compared to the plunge force and heat generation observed in experimental welds in AA2024-T3.
395 citations
Journal Article•
TL;DR: In this paper, material movement within friction stir welds is either simple extrusion or chaotic mixing, depending on where within the weld zone the material originates, and two new techniques for visualizing material flow patterns are presented.
Abstract: Friction stir welding (FSW) is a new technique for joining aluminum alloys. Invented in 1991 at The Welding Institute (Ref. 1), this technique results in low distortion and high joint strength compared with other techniques, and is capable of joining all aluminum alloys. To date, the majority of research has concentrated on developing the tools and procedures for making reliable welds in a variety of alloys, on characterizing the properties of welds and on developing design allowables (Refs. 2-7). However, very little is known about material flow behavior during welding. The purpose of the current study is to document the movement of material during friction stir welding as a means of developing a conceptual model of the deformation process. In this paper, two new techniques for visualizing material flow patterns in friction stir welds are presented. Based on measured results in welds of 6061 and 7075 aluminum, material movement within friction stir welds is by either simple extrusion or chaotic mixing, depending on where within the weld zone the material originates. These results impact the development of welding procedures and suggest ways to model the process for predicting welding tool performance.
306 citations
01 Jan 2004
26 citations