Fatigue Behaviour of Friction Stir Spot Welded Al-Mg-Si Alloy

美彦, 植松; 惠郎, 戸梶; 瞬亮, 村田; 康成, 戸崎; 達夫, 栗田

doi:10.2472/jsms.56.537

Cited by 13 publications

(9 citation statements)

References 12 publications

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“…However, it should be noted that the amount of scatter is very small. The test results of the friction stir spot welds fabricated by a conventional concave tool with probe are also included in the figure for comparison 17,19 . The fatigue strengths of the similar welds made by the scroll tool are higher than those of the welds by the conventional tool with probe.…”

Section: Resultsmentioning

confidence: 99%

Fatigue behaviour of dissimilar friction stir spot welds between A6061-T6 and low carbon steel sheets welded by a scroll grooved tool without probe

Uematsu

Tokaji

Tozaki

et al. 2011

Fatigue &Amp; Fracture of Engineering Materials &Amp; Structures

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A B S T R A C T A6061 and low carbon steel sheets, whose thicknesses were 2 mm, were welded by a friction stir spot welding (FSSW) technique using a scroll grooved tool without probe (scroll tool). Tensile-shear fatigue tests were performed using lap-shear specimens at a stress ratio R = 0.1, and the fatigue behaviour of dissimilar welds was discussed. Tensile-shear force of the dissimilar welds was higher than that of the A6061 similar ones. Furthermore, the dissimilar welds exhibited nearly the same fatigue strengths as the A6061 similar ones, indicating FSSW by a scroll tool was effective technique for joining aluminium to steel sheet. Fatigue fracture modes of the dissimilar welds were dependent on load levels, where shear fracture through the interface between A6061 and steel occurred at high load levels, while crack grew through A6061 sheet at low load level.A = nugget size (mm 2 ) HV = vickers hardness N f = number of cycles to failure P max = maximum load (N) R = stress ratio I N T R O D U C T I O NThe application of lightweight metals such as aluminium alloys in transportation industries, especially in automotive industry, is rapidly developed in order to reduce CO 2 exhaust gas and fuel consumption. However, steels are still widely used for structural components because of the lower absolute strength and higher material cost of aluminium alloys. Therefore, assembling both aluminium alloys and steels is necessary to develop hybrid body structures. It is known that fusion welding between aluminium alloy and steel are not reliable because brittle intermetallic compounds are formed along the interface, 1 and results in the lower strength of welds. Recently, joining aluminium alloys to steels are tried by a friction stir welding (FSW) technique, which is a solid state welding process, and successfully achieved high strength welds. 2-6 A spot welding process using FSW technique has been newly developed, which is called friction stir spot weldCorrespondence: Yoshihiko Uematsu.

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Section: Resultsmentioning

confidence: 99%

Fatigue behaviour of dissimilar friction stir spot welds between A6061-T6 and low carbon steel sheets welded by a scroll grooved tool without probe

Uematsu

Tokaji

Tozaki

et al. 2011

Fatigue &Amp; Fracture of Engineering Materials &Amp; Structures

View full text Add to dashboard Cite

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“…Figure 6 represents the relationship between maximum load, P max , and number of cycles to failure, N f , for the dissimilar and similar welds. The test results of the friction stir spot welds fabricated by a conventional concave tool with probe are also included in the figure for comparison [17,19]. The fatigue strengths of the similar welds made by the newly designed scroll tool are higher than those of the welds by the conventional tool with probe.…”

Section: Tensile-shear Strengthmentioning

confidence: 98%

“…Figure 11 reveals the relationship between normalized maximum load and N f , in which the results of the similar welds made by FSSW using a conventional concave tool with a probe are also included. The fatigue strengths of the similar welds by conventional FSSW were normalized by the actual nugget size measured on the fatigue fracture surface [17,19]. Furthermore, the fatigue strengths of the dissimilar welds were normalized by both the nugget size measured on the fracture surface and the area of residual aluminium on the tensile fracture surface of the steel sheet.…”

Section: Tensile-shear Strengthmentioning

confidence: 99%

“…The authors investigated the fatigue behaviour of T4 treated Al-Mg-Si aluminium alloy welds made by FSSW [16][17][18][19][20] and pointed out the transition behaviour of fracture mechanism depending on load levels. Pan et al investigated the fatigue behaviour of A6111-T4 [21][22][23][24] and A5754-O [25] welds and proposed a fatigue life estimation procedure.…”

Section: Introductionmentioning

confidence: 99%

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Fatigue behaviour of dissimilar friction stir spot weld between A6061 and SPCC welded by a scrolled groove shoulder tool

Uematsu

Tokaji

Tozaki

et al. 2010

Procedia Engineering

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A6061 and low carbon steel sheets, SPCC, whose thicknesses were 2 mm, were welded by a friction stir spot welding (FSSW) technique using a scrolled groove shoulder tool without a probe (scroll tool). Tensile-shear fatigue tests were performed using lap-shear specimens at a stress ratio R = 0.1 in order to figure out fatigue behaviour of dissimilar welds. The tensile-shear strength of the dissimilar welds was higher than that of the A6061 similar ones. Furthermore, the dissimilar welds exhibited nearly the same fatigue strengths as the A6061 similar ones, indicating that FSSW by a scroll tool was effective technique for joining aluminium to steel sheet. The fatigue fracture modes of the dissimilar welds were dependent on load levels, where shear fracture through the interface between A6061 and steel occurred at high load levels, while a fatigue crack grew through A6061 sheet at low load levels.

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“…For future applications of FSSpW to joining of load-bearing components, it is significant to elucidate the tensile [5,[11][12][13][14][15][16][17][18][19][20] and fatigue strengths and the fracture mechanism of FSSpW joint. In previous reports, the authors investigated the static fracture [20,21] and fatigue behavior of FSSpW joints welded by a conventional concave tool and reported that the fracture modes under tensile and fatigue loading were strongly affected by the macroscopic weld structure depending on welding conditions [21,22]. However, the main limitation of FSSpW joint is that the probe hole inevitably remains at weld nugget resulting corrosion at the probe hole because of rainwater remains in the hole, where body paint barely reaches the bottom.…”

Section: Introductionmentioning

confidence: 94%

Refilling Probe Hole of Friction Spot Joints by Friction Forming

Prakash

Muthukumaran

2011

Materials and Manufacturing Processes

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Friction stir spot welding (FSSpW) is a variant of friction stir welding (FSW) that has wider industrial application. However, Probe hole left after the welding is the main limitation of their process. In this present study, modified FSSpW has been developed and the refilling is achieved by friction forming process. This process has been called Friction Stir Spot Welding with refilling by Friction Forming Process (FSSpW-FFP). The Aluminum alloy (AA 6061-T6) plates are welded in two stages. Welding and refilling are achieved in first and second stages, respectively. Mechanical and metallurgical properties of the joints are studied and compared with welds made by FSSpW. The mechanical properties studied in the present work are tensile shear strength and microhardness. Macro-and microstructures of weld joints are compared and analyzed. The mechanical and metallurgical properties of the joints made by FSSpW-FFP are found to be better than the joints made by FSSpW. The tensile shear strength of the joint with refilled hole is higher than that of the joint with probe hole. The refilling process increases effective cross-sectional area of the nugget, resulting in higher tensile shear strength and joint efficiency at medium and high tool rotational speeds. After experiment, fracture surfaces are analyzed in detail using scanning electron microscope (SEM). The pull out of the nugget, i.e., plug type fracture, occurs in the joint with refilled probe hole, while shear fracture through the nugget is observed in the joint with probe hole. IntroductionFriction stir spot welding with refilling by friction forming process (FSSpW-FFP) is achieved in two stages. In the first stage, a backing plate with hole is prepared. The hole-axis is matched with the tool axis. The metal plates to be welded are fixed on the backing plate, and the tool is lowered under rotation. The tool is withdrawn after a predetermined time. During the first stage, the metal gets extruded into the hole in the backing plate [ Figs. 2(a) and (b)]. In the second stage, the joint obtained is tilted 180 and fixed on the solid backing plate [Figs. 2(c) and (e)]. A friction forming tool is lowered to touch the joint under rotation. During this stage, refilling of the probe-hole occurs through desired downward metal flow of extruded material on the surface of the plate made of ductile materials using a friction forming tool.Recently, lightweight metals such as aluminum alloys and magnesium alloys are increasingly used, especially in the automotive and aerospace industry, in which weight saving is extremely important. Resistance spot welding (RSW) has been widely used for decades in the automotive and other industries for fabricating sheet metal assemblies. However, the conventional RSW technique is unsuitable for joining lightweight metals because of its demerits such as high operating and investment cost due to high thermal and electrical conductivity of lightweight metals, consumption of RSW probe during joining, large heat distortion, and poor weld strength in jo...

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Fatigue Behaviour of Friction Stir Spot Welded Al-Mg-Si Alloy

Cited by 13 publications

References 12 publications

Fatigue behaviour of dissimilar friction stir spot welds between A6061-T6 and low carbon steel sheets welded by a scroll grooved tool without probe

Fatigue behaviour of dissimilar friction stir spot welds between A6061-T6 and low carbon steel sheets welded by a scroll grooved tool without probe

Fatigue behaviour of dissimilar friction stir spot weld between A6061 and SPCC welded by a scrolled groove shoulder tool

Refilling Probe Hole of Friction Spot Joints by Friction Forming

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