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Tozaki Y.,Gifu Prefectural Research Institute For Machinery And Material | Uematsu Y.,Gifu University | Tokaji K.,Gifu University
Journal of Materials Processing Technology | Year: 2010

A newly developed tool for friction stir spot welding (FSSW) has been proposed, which has no probe, but a scroll groove on its shoulder surface (scroll tool). By use of this tool, FSSW has been performed on aluminium alloy 6061-T4 sheets and the potential of the tool was discussed in terms of weld structure and static strength of welds. The experimental observations showed that the scroll tool had comparable or superior performance to a conventional probe tool. It was confirmed that sound welding could be achieved without a probe hole, in which the scroll groove played significant roles in the stirring of the material and the shoulder plunge depth was the important processing variable. The maximum tensile-shear strength of the welds made by the scroll tool was found to be 4.6 kN that was higher than that of the welds made by the probe tool and two different fracture modes, shear fracture and plug fracture, appeared depending on processing condition. The shear fracture took place at smaller shoulder plunge depths or at shorter tool holding times, while the plug fracture occurred at larger shoulder plunge depths or at longer tool holding times. It was indicated that the tensile-shear strength and associated fracture modes were determined by two geometrical parameters in the weld zone. © 2010 Elsevier B.V. All rights reserved.


Uematsu Y.,Gifu University | Tokaji K.,Gifu University | Tozaki Y.,Gifu Prefectural Research Institute For Machinery And Material | Nakashima Y.,ADVICS Co | Shimizu T.,Toyota National College of Technology
Fatigue and Fracture of Engineering Materials and Structures | Year: 2011

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. © 2011 Blackwell Publishing Ltd.


Kakiuchi T.,Gifu University | Uematsu Y.,Gifu University | Tozaki Y.,Gifu Prefectural Research Institute For Machinery And Material
Key Engineering Materials | Year: 2012

The fatigue behavior of cast aluminum alloy, A356-T6, microstructurally modified by the friction stir processing (FSP) was investigated. The FSP conditions were set to be the tool rotational speed of 500 rpm and traveling speed of 200 mm/min, in which the strain rate was relatively low. Plane bending fatigue tests have been performed using the as-cast and friction stir processed (FSPed) specimens. Fatigue strengths in the finite life region and the fatigue limit of the FSPed specimens were highly improved compared with the as-cast ones resulting from the elimination of casting defects by the FSP. However, the crack growth rates of the FSPed specimens were faster than those of the as-cast ones due to the softening of the material by heat input during the FSP. The effects of FSP with low stain rate were discussed based on the microstructural consideration.


Uematsu Y.,Gifu University | Tokaji K.,Gifu University | Tozaki Y.,Gifu Prefectural Research Institute For Machinery And Material | Nakashimac Y.,ADVICS Co
Procedia Engineering | Year: 2010

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. © 2010 Published by Elsevier Ltd.


Uematsu Y.,Gifu University | Kakiuchi T.,Gifu University | Tozaki Y.,Gifu Prefectural Research Institute For Machinery And Material | Kojin H.,Sumitomo Wiring Systems Ltd.
Science and Technology of Welding and Joining | Year: 2012

Aluminium alloy A6061-T6 or magnesium alloy AZ31 sheet was welded to steel sheet by a friction stir spot welding technique using a scroll grooved tool without a probe. The material flow in the nugget of the Mg/steel weld was less than that in the Al/steel one. The Al/steel weld exhibited higher static tensile-shear strength than the Al/Al weld, while the strengths of Mg/steel and Mg/Mg welds were comparable. Tensile-shear fatigue tests were performed using lap shear specimens of both dissimilar and similar welds. The dissimilar welds exhibited nearly the same fatigue strengths as the similar ones. The effective nugget size in the dissimilar welds was defined as the area where Al or Mg alloy remained on the steel side after static fracture. When the fatigue strengths of dissimilar welds were evaluated based on the effective nugget size, the normalised fatigue strengths of Al/steel and Mg/steel welds were comparable. © 2012 Institute of Materials, Minerals and Mining.

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