Clarification of material flow and defect formation during friction stir welding

Morisada, Yoshiaki; Imaizumi, Tsutomu; Fujii, Hidetoshi

doi:10.1179/1362171814y.0000000266

Cited by 85 publications

(39 citation statements)

References 29 publications

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“…a Tracing particle distribution in the observation plane after moving through the tool area (Sim-1.1-1.5), b Sim-2.1-2.5, c wormhole defect distribution in the nugget area after the experiment. Reprinted from Zhu et al [68], Copyright (2016), with permission from Elsevier by Morisada et al [94], in which the tilt of horizontal material flow and the decrease in material velocity on the advancing side were correlated to the formation of defects.…”

Section: Materials Flow Behaviormentioning

confidence: 99%

Thermo-mechanical Analysis of Friction Stir Welding: A Review on Recent Advances

Chen

Zhang

Zhu

et al. 2019

Acta Metall. Sin. (Engl. Lett.)

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In recent studies, critical research interest exists in the thermo-mechanical analysis of the friction stir welding (FSW) process by numerical simulation. In this review, the thermo-mechanical analysis for FSW is overviewed regarding the computational approaches, the heat generation, the temperature, and the material flow behavior. Current concerns, challenges, and opportunities in current studies are discussed considering the application of the thermo-mechanical analysis. Generally, larger computational scale and better computational efficiency are required to allow better spatial resolution in future analysis. The concepts and approaches demonstrated in the thermo-mechanical analysis for FSW open up quantitative prospects for the design of the FSW process.

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Section: Materials Flow Behaviormentioning

confidence: 99%

Thermo-mechanical Analysis of Friction Stir Welding: A Review on Recent Advances

Chen

Zhang

Zhu

et al. 2019

Acta Metall. Sin. (Engl. Lett.)

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“…The travel rate of the tool and the tool 90 tilt angle were 400 mm/min and 3°, respectively. The observed X-ray transmission images, and the shape of the material flow zone are described in detail elsewhere [13][14][15]. Figure 1 shows the three-dimensional graph of the material flow and its two-dimensional graph on the WD-TD plane.…”

mentioning

confidence: 99%

“…The material flow during the FSW was observed by the three-dimensional visualization process [13][14][15]. The material flow has been studied using various approaches such as the tracer method [16][17][18][19][20], analysis of the crystallographic texture in a weld [21], measuring the eutectic Si distribution [22].…”

mentioning

confidence: 99%

Determination of strain rate in Friction Stir Welding by three-dimensional visualization of material flow using X-ray radiography

2015

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Recrystallization, which is mainly caused by the induced strain, is one of the most important factors of Friction Stir Welding. In this study, strain and strain rate are directly obtained by the change in the material flow velocity which is observed by three-dimensional visualization of the material flow. The grain size of the pure aluminum in the stir zone estimated by the Zener-Hollomon parameter using the obtained strain rate shows good agreement with that observed by Electron Back-Scatter Diffraction mapping.Much attention has recently been paid to Friction Stir Welding (FSW) because of the low distortion and 20 excellent mechanical properties of the joint [1][2][3][4]. A rotating tool is inserted into the interface at the butt line of the metal plates and produces a highly plastically deformed zone. The metal plates are joined by the traveling of the rotating tool along the interface. Sever plastic deformation occurs and strain is induced in the stir zone (SZ). The interface of the two metal plates disappears by the material flow, and it is the main bonding mechanism of FSW. Generally, the SZ consists of recrystallized fine and equiaxed grains which are formed by the induced strain during the FSW 30 [5][6][7]. Therefore, the recrystallization is one of the most important factors of FSW. It is well known that the recrystallized grain size can be estimated by the strain rate [8,9]. However, it is difficult to measure the strain rate accurately during the FSW because the various changes in the SZ cannot be observed directly using conventional methods. Therefore, determination of the strain rate is very important for estimating the microstructure in the SZ.There are several reports related to the strain rate in the FSW. Chen et al. showed that the strain was $3.5 and the 40 strain rate was $85 s À1 before entering into the thread space during the FSW with a simple threaded pin at 740 rpm [10]. Arora et al. indicated that the computed strains and strain rates were in ranges of À10 to 5 and À9 to 9 s À1 , respectively [11]. However, the obtained results are computed values based on a three-dimensional coupled viscoplastic flow and heat transfer model. The strain rate of 34.8 ± 5.2 s À1 was estimated for magnesium alloy (AZ31) during FSW by the experimentally verified finite element model [12]. If it can be obtained these values by a direct 50 observation of the phenomenon, it should be very valuable to compare the other results.In this study, the strain rate was directly calculated by the change in the material flow velocity. The material flow during the FSW was observed by the three-dimensional visualization process [13][14][15]. The material flow has been studied using various approaches such as the tracer method [16][17][18][19][20], analysis of the crystallographic texture in a weld [21], measuring the eutectic Si distribution [22]. However, it is impossible to know the material flow velocity using 60 these approaches because the obtained results show only one part of the process. In this study, the material f...

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“…However, information regarding any discontinuity formed during FSW was missing. Morisada et al (2015) used a real-time X-ray imaging system to obtain three-dimensional flow patterns during FSW of Aluminum 1050 plates. The tungsten tracer was used to track the material movement.…”

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confidence: 99%

Force measurement-based discontinuity detection during friction stir welding

Shrivastava

Zinn

Duffie

et al. 2017

Journal of Manufacturing Processes

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The objective of this work is to develop a method for detecting the creation of discontinuities (i.e., voids, volume defects) during friction stir welding. Friction stir welding is inherently cost effective, however, the need for significant weld inspection can make the process cost prohibitive. A new approach to weld inspection is required in which an in-situ characterization of weld quality can be obtained, reducing the need for post-process inspection. To this end, friction stir welds with subsurface voids and without voids were created. The subsurface voids were generated by reducing the friction stir tool rotation frequency and increasing the tool traverse speed to create "colder" welds. Process forces were measured during welding, and the void sizes were measured post-process by computerized tomography (i.e., 3D X-ray imaging). Two parameters, based on frequency domain content and timedomain average of the force signals, were found to be correlated with void size. Criteria for subsurface void detection and size prediction were developed and shown to be in good agreement with experimental observations. With the proper choice of data acquisition system and frequency analyzer the occurrence of subsurface voids can be detected in real time.

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Clarification of material flow and defect formation during friction stir welding

Cited by 85 publications

References 29 publications

Thermo-mechanical Analysis of Friction Stir Welding: A Review on Recent Advances

Thermo-mechanical Analysis of Friction Stir Welding: A Review on Recent Advances

Determination of strain rate in Friction Stir Welding by three-dimensional visualization of material flow using X-ray radiography

Force measurement-based discontinuity detection during friction stir welding

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